METHODS FOR SYNTHESIZING SILVER NANOWIRES

FIELD OF THE INVENTION

The present invention pertains to methods for synthesizing silver nanowires.

BACKGROUND

With the emergence of new flexible transparent conductive film (TCF) to replace the indium tin oxide (ITO), scientists have paid great attention to new transparent conductors, such as conductive polymers, carbon nanotubes, graphene, metal grids, and the random networks of metallic nanomaterials including nanowires (See, e.g., Cheng I. C. et al, Vol. 11, Springer, (2009), Crawford G.P., Flexible Flat Panel Displays, Ed: P. C. Gregory (2005); Fehse K. et al, Adv. Mat. 19:

441(2007); Taylor P. G. et al, Adv. Mat. 21 : 2314(2009); Jung Y. C. et al, Adv. Mat. 20:4509 (2008). Gu H. et al, Adv. Mat. 20: 4433 (2008); Wu Z.C., et al, Science 305: 1273 (2004); Lee J.H. et al, Adv. Mat. 21 : 4383 (2009). Kim K.S. et al, Nature 457:706 (2009). Kang M. G. et al, Adv. Mat. 20:4408(2008). With regard to nanomaterials, it is known that nanomaterials can differ markedly from their analogous bulk counterparts. For example, nanomaterial's physical and chemical properties often correlate strongly with their size, shape, and morphology. Hence, material scientists pay great attention to developing simple and effective methods for synthesizing nanomaterials with controllable shapes and sizes to tailor their chemical and physical properties. For example, several studies indicate that transparent electrodes having solution-processed CNT films with smaller bundles and longer CNTs improve electrode performance, and it is also thought that the same idea can be applied to silver nanowire electrodes. (See e.g., Hecht D. et al, Appl. Phys. Lett. 89, 133122(2006)).

Because of its excellent electrical and thermal conductivity, silver and various silver

nanostructures are widely used in the electronic industry to fabricate conductive adhesives, inks, electrodes, etc. For example, several recent reports have been directed to adaptations of the polyol process for the production of various selected nanostructures, including multiply twinned particles, silver nanopyramids, silver nanocubes, silver nanowires, etc. (See, for example: Sun et al, Nano Letters, 3(7): 955-960 (2003); Wiley et al, Langmuir, 21(18): 8077-8080 (2005); Wiley et al, Chem. Eur. J., 11 : 454-463 (2005); and Wiley et al, Acc. Chem. Res., 40: 1067-1076 (2007)). In certain instances, it is thought that longer and thinner nanowires can potentially decrease percolation threshold in surface conductance (Hu, L. et al., Nano. Lett. 4, 2513-2517(2004)).

Benjamin J. Wiley and Jonathan N Coleman groups have systematically researched the diameter and length effect on the conductivity and transmittance of silver nanowires films (Stephen M.

Bergin et al, Nanoscale 4, 1996-2004(2012). Sophie S. et al, Nanotechnology 23: 185201(2012).). Consequently, the effective and reproducible preparation of silver nanowires with high purity and high aspect ratios are of great importance for their potential application in the flexible transparent conductive film.

Furthermore, Xia and co-workers have successfully synthesized high-quality silver nanowires in a "polyol" process by adding ethylene glycol (EG) solutions of AgN0 ₃ and

poly(vinylpyrrolidone) (PVP) at a specific temperature in a dropwise manner. In the typical polyol synthesis, silver atoms (which produce metal that forms nanostructures) may be obtained by reducing AgN0 ₃ with ethylene glycol (EG) through the following reactions:

2HOCH ₂ CH ₂ OH→2CH ₃ CHO+2H20 (1)

2Ag ⁺ +2CH ₃ CHO→CH3CHO— OHCCH ₃ +2Ag+2H ⁺ (2) In general, the polyol serves as a solvent for the silver compound as well as a solvent for the reaction. According to several reports, the polyol is also the reducing agent that reduces the silver compound to silver metal. Silver production is controlled by the rate of Ag(I) reduction, which increases with temperature (Ducamp-Sanguesa et al, Journal of Solid State Chemistry, 100: 272-280 (1992) at page 274, col. 2). Thus, the polyol process is typically practiced at elevated temperatures. (See: Carotenuto et al, Eur. Phys. J. B, 16: 11-17 (2000) at page 12, col. 2 and US Published Patent Application No. US 2007/0034052 Al to Vanheusden et al. published on Feb. 15, 2007 at paragraph 38).

When using this method, Xia and co-workers also found that low reagent concentrations and slow addition rates can control silver nanowire quality; otherwise, seed crystals or metal salt seasoning agents would be necessary. See, e.g., Sun, Y. et al, Science, 298, 2176(2002); Sun, Y. et al, Nano Lett. 2, 165(2002); Sun, Y. et al, Adv. Mater. 14, 833(2002); Kim, F. et al, Angew. Chem. Int. Ed. 116, 3759(2004); and U.S. Published Application 2005/0056118, Wiley, B. et al, Nano Lett. 4(9), 1733-1739(2004), Sun, Y. et al, Chem. Mater. 14, 4736-4745(2002). Recently, US patent 7,922,787 disclosed a process for the production of silver nanowires by using Fe(II) and/or Fe(III) compounds at low temperatures and/or at high concentrations (e.g., a ratio of total moles of silver (either as an ion or as metal) to a total volume of polyol or polyols (in liters) in the product solution is greater than or equal to 0.1 molar).

Recently, another report disclosed a modified polyol method of synthesis silver nanowires using AgCl. (See, e.g., Hu L. B. et al, ACS Nano 4 (5): 2955-2963(2010) and Erik C. Garnett et al, Nature Materials (2012) doi: 10.1038/nmat3238). The reactions disclosed in this report occurred at a relatively high reaction temperature (e.g., above 170°C) with addition of high amounts of AgCl, which resulted in silver nanowires with 50-100 nm (average 70nm) in diameter and 10 microns in length. To synthesize longer and thinner nanowires, excess amounts of KBr were added. The excessive amount of KBr led numerous large silver particles in the final yield, which required additional processing to purify the silver nanowires. It has been suggested that reaction

temperature can affect silver nanowire production. In particular, several reports suggest that higher temperatures (e.g., above 160° C) tend to improve nanowire formation when compared to the production of other silver nanostructures. (See: Sun et al, Crystalline Silver Nanowires by Soft Solution Processing, Nano Letters, 2(2): 165-168 (2002) at page 167, col. 2 and Sun et

al., Uniform Silver Nanowires Synthesis by Reducing AgN03 with Ethylene Glycol in the Presence of Seeds and Poly(Vinyl Pyrrolidone), Chem, Mater. 14: 4736-4745 (2002) at page 4742, col. 2). Contrary to these reports and as disclosed herein, temperatures ranging from about 100° C to less than 160° C can be selected to produce silver nanowires. In addition, the processes further described herein can utilize decreased temperatures. These decreased temperatures can aid in obtaining longer silver nanowires with consistent lengths, diameters, and aspect ratios.

In addition, other reports suggest that silver nanowires can also be formed by using

polyquaternium instead of PVP as capping agent in the polyol process, but to date, very little data has been reported regarding these processes. (See, e.g., U.S. Patent Application Publication No. 2006/0115536: Glycerin based synthesis of silver nanoparticles and nanowires.) However, described further herein are methods for synthesizing silver nanowires using various

polyquaterniums and silver salts.

References:

All literature and similar materials cited in this application, including but not limited to patents, patent applications, articles, books and treatises, regardless of the format of such literature or similar material, are expressly incorporated by reference herein in their entirety for any and all purposes.

US Patent References:

Other References:

1. E. Majidi and B.D. Gates, Optimizing Growth Rates and Thermal Stability of Silver Nanowires, Mater. Res. Soc. Symp. Proc, vol. 1017, ID: 1017-DD18-12, 6 pages total(2007).

2. Y. Sun et al. Uniform Silver Nanowires Synthesis by Reducing AgN03 with Ethylene Glycol in the Presence of Seeds and Poly(Vinyl Pyrrolidone), Chem. Mater., , vol. 14, pp.

4736-4745(2002).

3. Fievet et al., "Homogeneous and Heterogeneous Nucleations In The Polyol Process For The Preparation of Micron and Submicron Size Metal Particles", Solid State Ionics, 32/33: 198-205 (1989).

4. Ducamp-Sanguesa et al., "Synthesis and Characterization of Fine Monodisperse Silver Particles of Uniform Shape", Journal of Solid State Chemistry, 100: 272-280 (1992).

5. Sun et al, "Crystalline Silver Nanowires by Soft Solution Processing", Nano Letters, 2(2):

165-168 (2002).

6. Sun et al, "Large-Scale Synthesis of Uniform Silver Nanowires Through a Soft, Self-Seeding, Polyol Process", Adv. Mater., 14(11): 833-837 (2002).

7. Sun et al, "Uniform Silver Nanowires Synthesis by Reducing AgN03 with Ethylene Glycol in the Presence of Seeds and Poly(Vinyl Pyrrolidone", Chem. Mater., 14: 4736-4745 (2002). 8. Sun et al, Shape-Controlled Synthesis of Gold and Silver Nanoparticles, Science, 298: 2176-2179 (2002).

9. Sun et al., "Polyol Synthesis of Uniform Silver Nanowires: A Plausible Growth Mechanism and the Supporting Evidence", Nano Letters, 3(7): 955-960 (2003).

10. Wiley et al, "Polyol Synthesis of Silver Nanostructures: Control of Product Morphology with Fe(II) or Fe (III) Species", Langmuir, 21(18): 8077-8080 (2005).

11. Wiley et al, "Shape-Controlled Synthesis of Metal Nanostructures: The Case of Silver", Chem.

Eur. J., 11 : 454-463 (2005).

12. Wiley et al., "Maneuvering the Surface Plasmon Resonance of Silver Nanostructures Through Shape-Controlled Synthesis", J. Phys. Chem. B, 110: 15666-15675 (2006).

13. Wiley, B et al. Synthesis and Electrical Characterization of Silver Nanobeams. Nano Lett. 6, 2273(2007).

14. Xia Y. N. et al One-Dimensional Nanostructures: Synthesis, Characterization, and Applications.

Adv. Mater. 15 :353(2003).

15. Reyes-Gasga et al., On the Structure of Nanorods and Nanowires with Pentagonal

Cross-sections", Journal of Crystal Growth, 286: 162-172 (2006).

16. Chen C. et al, "Study on the synthesis of silver nanowires with adjustable diameters through the polyol process", Nanotechnology 17: 3933-3938 (2006).

17. Wiley et al, "Synthesis of Silver Nanostructures with Controlled Shape Properties", Acc. Chem.

Res., 40: 1067-1076 (2007).

18. Chen J. Y. et al., "One-Dimensional Nanostructures of Metals: Large-Scale Synthesis and Some Potential Applications", Langmuir, 23: 4120-4129 (2007).

19. Zhang et al., "High-Concentration Preparation of Silver Nanowires: Restraining in Situ Nitric Acidic Etching by Steel-Assisted Polyol Method", Chem. Mater., 20: 1699-1704 (2008).

20. Korte et al, Rapid Synthesis of silver nanowires through a CuCI- or CuCI2-mediated polyol process, Journal of Materials Chemistry 18: 437-441 (2008).

21. Hu L. B. et al. "Scalable Coating and Properties of Transparent, Flexible, Silver Nanowire

Electrodes" ,ACS Nano, 4(5), 2955-2963 (2010).

22. Erik C. Garnett et al., "Self-limited plasmonic welding of silver nanowire junctions", Nature Materials (2012) doi: 10.1038/nmat3238.

SUMMARY

Described herein are polyol methods for large-scale synthesis of silver nanowires at (i) lower reaction temperatures (less than 160°C) with longer reaction times, (II) lower amounts of AgCl or acid compound addition, and/or (iii) lower amounts of soluble halide addition. In certain aspects, lowering the reaction temperatures (less than 160°C) and extending reaction times or adding acid compound can improve silver nanowire aspect ratios. For example, the processing and reaction conditions described herein not only improve nanowire aspect ratios but also aid in controlling nanowire shape or morphology. For example, either by lowering the reaction temperature and extending reaction times or by adding an acid compound, one can obtain longer nanowires. In certain aspects, one can obtain silver nanowires with fewer nanoparticles by lowering the addition of halide. By lowering the amount of halide addition and/or lowering amount of AgCl addition, impurities can be significantly decreased.

Also as described herein are methods for synthesizing silver nanowires by using various polyquaterniums and silver salts. In certain aspects, synthesizing silver nanowires by using various polyquaterniums and silver salts can result in more efficient, cheaper, and environmentally friendly production of silver nano wires than other known methods.

BRIEF DESCRIPTION OF THE DRAWINGS

The skilled artisan will understand that the drawings, described below, are for illustration purposes only. The drawings are not intended to limit the scope of the present teaching in any way.

In the drawings, the sizes and relative positions of elements in the drawings are not necessarily drawn to scale. For example, the shapes of various elements and angles may not be drawn to scale, and some of these elements may be arbitrarily enlarged and positioned to improve drawing legibility. Further, the particular shapes of the elements as drawn may not be intended to convey any information regarding the actual shape of the particular elements, and may have been selected solely for ease of recognition in the drawings.

FIG. 1(A) shows a low magnification and FIG. 1(B) shows a high magnification scanning electronic microscope (SEM) image of silver nanowires as prepared in Example 1.

FIG. 2(A) shows a low magnification and FIG. 2(B) shows a high magnification scanning electronic microscope (SEM) image of silver nanowires as prepared in Example 2.

FIG. 3(A) shows a low magnification and FIG. 3(B) shows a high magnification scanning electronic microscope (SEM) image of silver nanowires as prepared in Example 3.

FIG. 4(A) shows a low magnification and FIG. 4(B) shows a high magnification scanning electronic microscope (SEM) image of silver nanowires as prepared in Example 4.

FIG. 5(A) shows a low magnification and FIG. 5(B) shows a high magnification scanning electronic microscope (SEM) image of silver nanowires as prepared in Example 5.

FIG. 6 shows a scanning electronic microscope (SEM) image of silver nanowires as prepared in Comparative Example 1.

FIG. 7 shows a scanning electronic microscope (SEM) image of silver nanoparticles as prepared in Comparative Example 2.

FIG. 8 shows an x-ray diffraction pattern of silver nanowires as obtained in Example 1.

FIG. 9 shows an EDX (Energy Dispersive X-Ray Fluorescence Spectrometer) of silver nanowires as obtained in Example 1.

FIG. 10 shows a high magnification of scanning electronic microscope (SEM) image of silver nanowires as prepared in Example 19.

FIGS. 11 shows a high magnification of scanning electronic microscope (SEM) image of silver nanowires as prepared in Example 20.

DETAILED DESCRIPTION

Definitions

For the purposes of interpreting this specification, the following definitions will apply and whenever appropriate, terms used in the singular will also include the plural and vice versa. In the event that any definition set forth below conflicts with the usage of that word in any other document, the definition set forth below shall always control for purposes of interpreting the scope and intent of this specification and its associated claims.

As used herein, the use of "or" means "and/or" unless stated otherwise or where the use of "and/or" is clearly inappropriate. The use of "a" means "one or more" unless stated otherwise or where the use of "one or more" is clearly in appropriate.

As used herein, the use of "comprise", "comprises", "comprising", "include", "includes", and "including" are interchangeable and not intended to be limiting. Furthermore, where the description of one or more embodiments uses the term "comprising" those skilled in the art would understand that in some specific instances, the embodiment or embodiments can be alternatively described using language "consisting essentially of and/or "consisting of.

As used herein, 'aspect ratio' should be interpreted differently depending on whether it is being used with reference to an individual nanostructure or to the general characteristics of bulk material. With respect to an individual nanostructure, 'aspect ratio', as used herein, refers to the length divided by diameter of the individual nanostructure. For example, a nanowire having a length of 30,000 nanometers (30 um) and a diameter of 50 nanometers would have an aspect ratio of 600 (30,000/50=600). With respect to bulk material, 'aspect ratio' refers to the averaged aspect ratio that is characterized based on the average length and diameter dimensions obtained by sampling individual nanostructures contained in the bulk material. For example, the "aspect ratio" of bulk product silver nano wires can be determined as follows: This method is based upon collecting measurement data from individual nanostructures in a population using electron microscopy (FIG. 2). The lengths are obtained using low magnification electron microscopy (although other methods such as optical microscopy could also be used), and the diameters are determined using electron microscopy (although other methods could be used). The diameters and lengths are determined from a sampling taken from the bulk material, which contains the produced

nanostructures. In certain aspects, nanorods have a width of ~1±500 nm and aspect ratios greater than 5 but less than 20; and we call nanowires analogous materials that have aspect ratios greater than 20. In certain aspects, "silver nanowires with high aspect ratio" have a value of individual or bulk samples not less than 100. Using this process, approximately 100 nanostructures are measured to determine the lengths, and more than 50 nanostructures are measured to determine the diameters. An average length and average diameter is determined for the nanostructures examined. It is also to be understood that the selection of 100 and 50 nanostructures, respectively, referred to above is arbitrary and not intended to be a limitation. Rather, the number of nanostructures selected for analysis can depend on the characteristics (e.g. homogeneity) of the bulk material and the accuracy desired for estimating the properties of the bulk material. With reference to Table 1, the average length column (the 'Average Length') is the average length of the

measured nanowire population. With reference to Table 1 , the average diameter column (the 'Average Diameter') is the average diameter of the measured nanowire population. With reference to aspect ratio of bulk samples, the aspect ratio is determined by dividing the average length of the nanowires to the average diameter of the nanowires (average length, average diameter and aspect ratio are listed in Table 1).

As used herein, 'nanoparticle' refers to a nanostructure or a collection of nanostructures with an aspect ratio of less than or equal to 5, such as nanopyramids, or nanocubes, but except nanowires.

As used herein, "nanorods" generally refers to materials that have aspect ratios greater than 5 but less than 20.

As used herein, "nanowires" refer to materials that have aspect ratios greater than 20.

As used herein, 'weight percent' or 'wgt %' refers to percent by weight or mass. For example, the phrase 'at least 20 weight percent (20 wgt %) silver nanowires as compared with a weight percent of all other silver nanostructures in the product solution' refers to calculating, as a percentage, a fraction represented by the weight or mass of all silver nanowires present in the product solution divided by the weight or mass of all other silver nanostructures present in the product solution. Although real-time monitoring of the reaction may permit this analysis (See: Reyes-Gasga et al, On the structure of nanorods and nanowires with pentagonal cross-sections, Journal of Crystal Growth, 286: 162-172 (2006); Wiley et al., Maneuvering the Surface Plasmon Resonance of Silver Nanostructures through Shape-Controlled Synthesis, J. Phys. Chem. B., 110: 15666-15675 (2006); or Wiley et al, Synthesis of Silver Nanostructures with Controlled Shapes and Properties, Acc. Chem. Res., 40: 1067-1076 (2007)), in practice this can also (more practically) be determined by calculating (determining) the weight of silver nanowires isolated from the reaction divided by the theoretical weight of all silver metal that could be produced (and thereby exist as silver nanostructures) by the reaction.

As used herein with respect to practice of the methods, the terms "added", "mixed" or

"combined" are generally interchangeable and refer to the act of adding, mixing or combining one or more of the reactants with one or more other reactants. This can occur by adding reactants to, or mixing or combining the reactants in, the reaction vessel and/or with each other.

As used herein, 'soluble halide' refers to soluble fluoride, chloride, bromide or iodide, which is soluble in polyols, and 'halide ion' refers to fluoride ion, chloride ion, bromide ion or iodide ion produced by the halide being dissolved in the polyol.

As used herein, 'reactant' refers to a compound or solution comprising a compound that reacts in the reaction or that is capable of influencing the abundance of nanowires (or nanostructures). In certain aspects, reactants include, but are not necessarily limited to, the polyol (or polyols), AgCl powder or dispersion, the silver compound(s), the capping agent(s), an acid compound (or compounds), and/or the compound(s) that comprise halide ion (e.g. NaCl) either as solids, liquids, gases or in solution.

As used herein, 'mixture of reactants' refers to the mixture including the entirety of all the reactants before reaction is finished or artificially stopped. The mixture can be solutions or dispersion. In some cases, 'mixture of reactants' refers to both the mixture of reactants as fully combined as well as to a mixture to which one or more of the reactants is being added but to which at least a portion of all the reactants has been added such that the reaction can begin. For example, in the polyol process, it is common to add dropwisely the silver solution and a solution comprising the capping agent into a vessel comprising polyol. From the time the first drops of silver solution and solution comprising the protective agent mix with the polyol in the vessel, the reaction has begun despite the fact that not all of each of the reactants has yet been combined. Thus, according to this definition, the vessel comprising the drops of silver solution, solution comprising the capping agent and the polyol is a reaction mixture.

As used herein, 'product mixture' or 'product solution' refers to the mixture comprising the entirety of all the reactants. In certain aspects, product mixture or product solution can refer to after the reaction is finished or artificially stopped but before any dilution or concentration is performed. The mixture can be solutions or dispersion. For example, product solution can refer to a solution mixture comprising silver nanowires. There are generally no limitations on the weight or weight percentage of silver nanowires in the product solution/mixture. Generally, if the reactions are finished or partially finished, there may be silver particles, silver nanowires, and silver nanorods in the solution/mixture.

As used herein 'reaction temperature' refers to the temperature of the heat source applied to the reaction vessel or the actual temperature of the reaction mixture during the reaction as determined by direct monitoring. For example, the reaction temperature can be the temperature of an oil bath used to heat the vessel containing all the reactants of a polyol reaction or could be the temperature of the reaction mixture as determined by a thermometer or thermocouple inserted into said reaction mixture. As used herein 'large scale synthesis of silver nanowires' refers to obtaining 0.2 g or more of silver nanowires when utilizing any method or process described herein. For example, if one wants to obtain 0.2 g of silver nanowires, one should input about more than 0.002 mol of silver compound in any method or process described herein.

Production Of Silver Nanowires

As disclosed herein, it is desirable to produce silver nanowires with a scalable process and high manufacturing efficiency. The methods described herein disclose various polyol methods for large-scale synthesis of silver nanowires, which utilize, for example, low reaction temperatures (less than 160°C), long reaction times, low acid compound addition, and/or low amounts of halide addition. Based on the reaction conditions described herein, silver nanowires with lower impurities, thinner diameters and/or higher aspect ratio can be obtained. Such silver nanowires are especially suitable for the application in the flexible transparent electrodes, as they can

simultaneously improve the electrical conductivity and transparency.

In certain aspects, silver nanowires can be synthesized by combining: a) at least one polyol; b) at least one silver compound capable of producing silver metal when reduced; c) at least one capping agent; and d) at least one silver halide in a reactant mixture and reacting at a reaction temperature less than 160°C and under conditions that produce a product mixture comprising at least 20 weight percent (20 wgt %) silver nanowires as compared with a weight percent of all other silver nanostructures in the product mixture

i. wherein a ratio of total moles of silver compound to a total volume of polyol or polyols (in liters) in the mixture of reactants is greater than or equal to 0.02 mol/L;

ii. wherein a ratio of a molar concentration of the capping agent to a molar concentration of the silver compound in the total reactants mixture is between 15 : 1 to 0.1 : 1 ; and

iii. wherein the molar ratio of silver halide to silver compound in the mixture of reactants is less than or equal to 1 :5.

In certain aspects, the above method can further include the following steps:

Step 1 : Preparing a silver compound solution and capping agent solution by mixing the silver compound into the polyols and capping agent into the polyols, respectively;

Step 2: Heating the capping agent solution to a first temperature and then adding the silver halide into solution. Alternatively, silver halide powder can also be firstly dispersed into the polyols to form a dispersion and then the dispersion can be added into the capping agent solution;

Step 3 : After silver halide addition to the capping agent solution, the mixture can be heated to a second temperature and then the silver compound solution can be added;

Step 4: After addition of the silver compound solution, the whole product mixture can be heated to a third temperature and maintained for a certain time period to ensure that the reactions is complete or partially complete and yields at least 20 weight percent (20 wgt %) silver nanowires as compared with a weight percent of all other silver nanostructures in the product mixture;

Step 5 : Silver nanowires can be isolated from the product mixture by centrifugation or filtration. After isolating the silver nanowires, the silver nanowires can be re-dispersed in solvents.

In another aspect, silver nanowires having high aspect ratios can be synthesize by combining: a) at least one polyol; b) at least one silver compound capable of producing silver metal when reduced; c) at least one capping agent; d) at least one silver halide powder; and e) halide capable of producing halide ion in the polyols in a reactant mixture and reacting at a reaction temperature less than 160°C and under conditions that produce a product mixture having at least 50 weight percent (50 wgt %) silver nanowires as compared with a weight percent of all other silver nanostructures in the product mixture;

i. wherein a ratio of total moles of silver compound to a total volume of polyol or polyols (in liters) in the mixture of reactants is greater than or equal to 0.02 mol/L;

ii. wherein a ratio of a molar concentration of the capping agent to a molar concentration of the silver compound in the total reactants mixture is between 15:1 to 0.1 : 1 ;

iii. wherein a ratio of total moles of silver halide to a total volume of silver compound in the mixture of reactants is less than or equal to 1 :5; and

iv. wherein a ratio of total moles of halide to a total volume of silver compound in the mixture of reactants is less than 1 :20.

In certain aspects, the above method can further include the following steps:

Step 1 : Preparing a silver compound solution and a capping agent solution by mixing the silver compound into the polyols and capping agent into the polyols, respectively;

Step 2: Heating the capping agent solution to a first temperature and then adding the soluble halide, and silver halide into the solution. Alternatively, the halide, and silver halide powder can also be firstly dispersed into the polyols to form a dispersion or solution and then added into the capping agent solution;

Step 3: After Step 2, the mixture can be heated to a second temperature and then the silver compound solution can be added;

Step 4: After addition of the silver compound solution, the whole product mixture can be heated to a third temperature and maintained for a time period to ensure that the reactions is complete or partially complete and yields at least 50 weight percent (50 wgt %) silver nanowires as compared with a weight percent of all other silver nanostructures in the product mixture;

Step 5 : Silver nanowires can be isolated from the product mixture by centrifugation or filtration. After isolating the silver nanowires, the silver nanowires can be re-dispersed in solvents.

In another aspect, silver nanowires having high aspect ratios can be synthesized by reacting: a) at least one polyol; b) at least one silver compound capable of producing silver metal when reduced; c) at least one capping agent; d) at least one silver halide; and e) at least one acid compound in a reactant mixture and reacting at a reaction temperature less than 160°C and under conditions that produce a product mixture comprising at least 20 weight percent (20 wgt %) silver nanowires as compared with a weight percent of all other silver nanostructures in the product mixture;

i. wherein a ratio of total moles of silver compound to a total volume of polyol or polyols (in liters) in the total reactants mixture is greater than or equal to 0.02 mol/L;

ii. wherein a ratio of a molar concentration of the capping agent to a molar concentration of the silver compound in the total reactants mixture is between 15 : 1 to 0.1 : 1 ; and

iii. wherein the molar ratio of silver halide to silver compound in the mixture of reactants is less than or equal to 1 :5.

In certain aspects, the above method can further include the following steps:

Step 1 : Preparing a silver compound solution and a capping agent solution by mixing the silver compound into the polyols and capping agent into the polyols, respectively;

Step 2: Heating the capping agent solution to a first temperature and then adding the silver halide and acid compound into solution. Alternatively, the silver halide powder and acid compound can also be firstly dispersed into the polyols to form a dispersion or solution and then added into the capping agent solution;

Step 3: After Step 2, the mixture can be heated to a second temperature and then the silver compound solution can be added;

Step 4: After addition of the silver compound solution, the whole product mixture can be heated to a third temperature and maintained for a certain time period to ensure that the reactions is complete or partially complete and yields at least 20 weight percent (20 wgt %) silver nanowires as compared with a weight percent of all other silver nanostructures in the product mixture;

Step 5 : Silver nanowires can be isolated from the product mixture by centrifugation or filtration. After isolating the silver nanowires, the silver nanowires can be re-dispersed in solvents.

In another aspect, silver nanowires having high aspect ratios can be synthesized by reacting: a) at least one polyol; b) at least one silver compound capable of producing silver metal when reduced; c) at least one capping agent; d) at least one silver halide; e) at least one soluble halide capable of producing halide ion in the polyols; and f) at least one acid compound in a reactant mixture and reacting at a reaction temperature less than 160°C and under conditions that produce a product mixture comprising at least 50 weight percent (50 wgt %) silver nanowires as compared with a weight percent of all other silver nanostructures in the product mixture;

i. wherein a ratio of total moles of silver compound to a total volume of polyol or polyols (in liters) in the mixture of reactants is greater than or equal to 0.02 mol/L;

ii. wherein a ratio of a molar concentration of the capping agent to a molar concentration of the silver compound in the total reactants mixture is between 15:1 to 0.1 : 1 ;

iii. wherein a ratio of total moles of silver halide to a total volume of silver compound in the mixture of reactants is less than or equal to 1 :5; and

iv. wherein a ratio of total moles of halide to a total volume of silver compound in the mixture of reactants is less than 1 :20.

In certain aspects, the above method can further include the following steps:

Step 1 : Preparing a silver compound solution and a capping agent solution by mixing the silver compound into the polyols and capping agent into the polyols, respectively;

Step 2: Heating the capping agent solution to a first temperature and then adding the halide, silver halide and acid compound into the solution. Alternatively, the halide, silver halide powder and acid compound can also be firstly dispersed into the polyols to form a dispersion or solution and then added into the capping agent solution;

Step 3: After Step 2, the mixture can be heated to a second temperature and then the silver compound solution can be added;

Step 4: After addition of the silver compound solution, the whole product mixture can be heated to a third temperature and maintained for a certain time period to ensure that the reactions is complete or partially complete and at least 50 weight percent (50 wgt %) silver nanowires as compared with a weight percent of all other silver nanostructures in the product mixture;

Step 5 : Silver nanowires can be isolated from the product mixture by centrifugation or filtration. After isolating the silver nanowires, the silver nanowires can be re-dispersed in solvents.

Production Of Silver Nanowires With Polyquaterniums

In certain aspects, the silver nanowires described herein can be synthesized using various polyquaterniums and silver salts. These methods can result in high yields of silver nanowires with very few impurities. Furthermore, these methods can result in a more efficient, cheaper, and environmentally friendly production of silver nanowires than other known methods.

In certain aspects, halides and/or acid compounds are used with the polyquaternium to synthesize silver nanowires. In certain aspects, these halides and/or acid compounds can influence the initial nucleation process and promote selectivity among different nanostructures. For example, in this process, these halides and/or acid compounds enhance selectivity for silver nanowires formation under certain reaction conditions by the "seed oxidative etching mechanism." Thus, in certain aspects and when synthesizing silver nanowires with polyquaternium, the addition of halide and/or acid compound can lower impurities in the reaction, enhance the yield of silver nanowires, and improve the aspect ratio of silver nanowires.

For example, in certain aspects, silver nanowires can be synthesized by:

Step 1 : Preparing the following polyols solutions:

A: at least one silver compound dissolved in at least one polyol;

B: at least one polyquaternium dissolved in at least one polyol;

Step 2: Mixing the above two solutions and stirring the mixture to obtain a homogenous solution; Step 3: Adding a halide and/or acid compound to the solution of Step 2, and stirring to obtain a homogenous solution.

Step 4: Heating the solution of Step 3 to a temperature below the boiling point of the polyol(s) and maintaining the temperature for a certain period of time to obtain a complete or partially complete reaction that yields silver nanowires.

Step 5: Obtaining silver nanowires from the product solution in Step 4. Conducting solid- liquid separation or centrifugation to remove the polyquaternium and impurities including silver nanoparticles.

In certain aspects, silver nanowires can be synthesized by:

Step 1 : Preparing the following polyols solutions:

A: at least one silver compound dissolved in at least one polyol;

B: at least one polyquaternium dissolved in at least one polyol;

Step 2: Simultaneously, heating and stirring the polyquaternium solution. Then adding at least one halide and/or at least one acid compound to the polyquaternium solution at a temperature below the boiling point of the polyol.

Step 3 : Adding the silver compound solution dropwisely to the solution of Step 2 at a temperature below the boiling point of the polyols and maintaining the temperature for a time period to obtain a complete or partially complete reaction.

Step 4: Obtaining silver nanowires from the product solution in Step 3. Conducting solid- liquid separation or centrifugation to remove the polyquaternium and impurities including silver nanoparticles.

In another aspect, silver nanowires can be synthesized by:

Step 1 : Preparing the following polyols solutions:

A: at least one silver compound dissolved in at least one polyol;

B: at least one polyquaternium dissolved in at least one polyol;

C: at least one halide and/or at least one acid compound dissolved in at least one polyol;

Step 2: Getting the above three solutions proportionally and stirring to obtain a homogenous solution

Step 3 : Simultaneously, heating and stirring the solution of Step 2 at a temperature below the boiling point of the polyols, and then maintaining the temperature for a time period to obtain a complete or partially complete reaction.

Step 4: Obtaining silver nanowires from the product solution in Step 3. Conducting so lid- liquid separation or centrifugation to remove the polyquaternium and impurities including silver nanoparticles. In yet another aspect, silver nanowires can be synthesized by:

Step 1 : Preparing the following polyols solutions:

A: at least one silver compound dissolved in at least one polyol;

B: at least one polyquaterniums dissolved in at least one polyol;

C: at least one halide and/or at least one acid compound dissolved in at least one polyol;

Step 2: Simultaneously, heating and stirring the halide and/or acid compound solutions;

Step 3 : Simultaneously adding the silver compound solution and polyquaternium solution dropwisely to the solution of step 2 at a temperature below the boiling point of the polyols, and then maintaining the temperature for a time period to obtain a complete or partially complete reaction. Step 4: Obtaining silver nanowires from the product solution in Step 3. Conducting so lid- liquid separation or centrifugation to remove the polyquaternium and impurities including silver nanoparticles.

Reactants And Conditions

As used herein, the polyol(s), silver compound, capping agent, acid compound, halide and other reaction conditions that preferentially produce silver nanowires according to the processes described above are further explained below.

(1) Polyol(s)

The polyols described herein can be used as both a solvent (e.g., to dissolve the silver compound to form the silver solution) and a reducing agent (e.g., capable of reducing the silver compound to silver metal at the reaction temperature when present in the reaction mixture). In certain aspects, the polyols can include, but are not limited to, ethylene glycol, glycerol, glucose, diethylene glycol, tri-ethylene glycol, propylene glycol, a butanediol, a dipropylene glycol, a polyethylene glycol, or any combination thereof. In certain aspects, the polyol can be a single polyol or a mixture of two or more polyols (e.g. three, four, five or more polyols).

(2) Silver Compound

The silver compounds described herein are the source of the silver metal that produces the silver nanostructures according to the polyol methods described herein. Silver compound refers to a neutral compound having a positively charged silver ion and a negatively charged counterion. The counterion may be inorganic or organic. Exemplary metal salts include, but are not limited to, silver nitrate (AgN0 ₃ ), silver acetate ((CH ₃ COO) ₂ Ag), silver perchlorate (AgC10 ₄ ) and the like. In certain aspects, the silver compound can be soluble to at least some extent in the polyol (other solvents or mixture of polyols and other solvent(s)) at room temperature and at a reaction temperature that dissociates the silver compound into oppositely charged Ag ⁺ ion and counterion. Typically, the solubility of the metal salt in the polyols is at least 0.001 g/ml, at least 0.05 g/ml, or at least 0.1 g/ml. In certain aspects, the solubility of the metal salt in the polyol ranges from at least 0.001 g/ml to 0.5 g/ml, from at least 0.001 g/ml to 0.3 g/ml, from at least 0.001 g/ml to at least 0.1 g/m., from 0.05 g/ml to at least 0.3 g/ml, from at least 0.05 g/ml to at least 0.2 g/ml, from at least 0.1 g/ml to 0.3 g/ml, or from 0.1 g/ml to 0.2 g/ml. Whenever the term

'silver compound' is used herein, this term is meant to include either a single silver compound or a mixture of two or more silver compounds unless use of the singular term is clearly intended or required.

Silver compounds suitable for use in the process of the present invention can further include, but are not limited to, silver nitrate, silver nitrite, silver oxide, silver fluoride, silver hydrogen fluoride, silver carbonate, silver oxalate, silver azide, silvertetrafluoroborate, silver acetate, silver propionate, silver butanoate, silver ethylbutanoate, silver pivalate, silvercyclohexanebutanoate, silver ethylhexanoate, silver neodecanoate, silver decanoate, silver trifluoroacetate,

silverpentafluoropropionate, silver heptafluorobutyrate, silver trichloroacetate, silver 6,6,7,7,8,8,8 heptafluoro-2,2-dimethyl-3,5-octanedioate, silver lactate, silver citrate, silver glycolate, silver glyconate, silver benzoate, silver salicylate, silverphenylacetate, silver nitrophenylacetate, silver dinitrophenylacetate, silver difluorophenylacetate, silver 2-fluoro-5-nitrobenzoate, silver acetylacetonate, silver hexafluoroacetylacetonate, silver trifluoroacetylacetonate, silver tosylate, silvertriflate, silver trispyrazolylborate, silver tris(dimethylpyrazolyl)borate, silver beta-diketonate olefin complexes and silvercyclopentadienides. In certain aspects, the silver compound can be added to the reaction in solution form, solid form (i.e., as a solid powder), or as a suspension.

According to certain embodiments, the silver compound and the associated reaction conditions are selected to preferentially produce silver nanowires as compared with other nanostructures. (3) Capping agent

Without wishing to be bound by theory, the capping agents described herein are believed to preferentially interact and adhere to a lateral surface of a growth nanowire such that the capping agent confines the lateral surface from growing and encourages a cross-section surface of the nanowire to crystallize. The growing nanowire includes the lateral surface and the cross-section surface. In certain aspects, the capping agent interacts with the lateral surface of the growing nanowire more strongly than it does with the cross-section surface of the growing nanowire. The lateral surface of the growing nanowire is thus passivated while the cross-section surface of the growing nanowire is available for further crystallization to produce the nanowire.

Capping agents are generally selected to be able to dissolve but not react with the polyol or any other solvent to any significant extent, even at various reaction temperatures.

Examples of the capping agent include, but are not limited to, poly( vinyl pyrrolidone), polyarylamide, polyacrylic, poly (dimethyldiallylammoniumchloride) (PDADMAC) and any of the copolymers thereof.

Some non-limiting examples of capping agents that can be used alone or as mixtures include poly( vinyl alcohol), polyarylamide, polyacrylic, and any of the copolymers, and surfactants such as sodium dodecyl sulfate (SDS), laurylamine and hydroxypropyl cellulose.

It is not a requirement that the capping agent be added to the reaction in solution as it may be added in solid form (a solid powder).

Whenever the term 'capping agent' is used herein, this term is meant to include either a single capping agent or a mixture of two or more capping agents unless use of the singular term is clearly intended or required.

Non-limiting specific examples of vinyllactam polymers that can be used as a capping agent include, but are not limited to, homo- and copolymers of vinylpyrrolidone, which are commercially available from, e.g., International Specialty Products (www.ispcorp.com). In particular, these polymers may include:

(a) vinylpyrrolidone homopolymers such as, e.g., grades K-15 and K-30 with K-value ranges of from 13-19 and 26-35, respectively, corresponding to average molecular weights (determined by GPC/MALLS) of about 10,000 and about 67,000;

(b) alkylated polyvinylpyrrolidones such as, e.g., those commercially available under the trade mark GANEX® which are vinylpyrrolidone-alpha-olefin copolymers that contain most of the

alpha-olefm (e.g., about 80% and more) grafted onto the pyrrolidone ring, mainly in the 3-position thereof; the alpha-olefins may comprise those having from about 4 to about 30 carbon atoms; the alphaolefm content of these copolymers may, for example, be from about 10% to about 80% by weight;

(c) vinylpyrrolidone-vinylacetate copolymers such as, e.g., random copolymers produced by a free-radical polymerization of the monomers in a molar ratio of from about 70/30 to about 30/70 and having weight average molecular weights of from about 14,000 to about 58,000;

(d) vinylpyrrolidone-dimethylaminoethylmethacrylate copolymers;

(e) vinylpyrrolidone-methacrylamidopropyl trimethylammonium chloride copolymers such as, e.g., those commercially available under the trade mark GAFQUAT®;

(f) vinylpyrrolidone-vinylcaprolactam-dimethylaminoethyl methacrylate terpolymers such as, e.g., those commercially available under the trade mark GAFFIX®;

(g) vinylpyrrolidone-styrene copolymers such as, e.g., those commercially available under the trade mark POLECTRON®; a specific example thereof is a graft emulsion copolymer of about 70% vinylpyrrolidone and about 30% styrene polymerized in the presence of an anionic surfactant; or

(h) vinylpyrrolidone-acrylic acid copolymers such as, e.g., those commercially available under the trade mark ACRYLIDONE® which are produced in the molecular weight range of from about 80,000 to about 250,000.

In certain aspects the capping agents described herein can include various polyquaterniums. Examples of polyquaterniums can include but are not limited to a copolymer of acrylamide and diallyldimethylammonium chloride, Poly(diallyldimethylammonium chloride), a copolymer of acrylamide and quaternized dimethylammoniumethyl methacrylate, acrylamide-dimethylaminoethyl methacrylate methyl chloride copolymer, a copolymer of acrylic acid and

diallyldimethylammonium chloride, a copolymer of vinylpyrrolidone and methacrylamidopropyl trimethylammonium, poly(2-methacryloxyethyltrimethylammonium chloride), a terpolymer of acrylic acid, acrylamide and diallyldimethylammonium chloride, hydroxyethyl cellulose dimethyl diallylammonium chloride copolymer, and a diallyldimethylammonium chloride -hydroxyethyl cellulose copolymer.

Accordingly, using the disclosure provided herein and routine experimentation, one having ordinary skill in the art can select appropriate capping agents to preferentially

produce silver nanowires as compared with other nanostructures.

(4) Ratios of Silver Compound to Capping Agent

Certain reports discussing selective production of nanostructures have suggested that the ratio between the concentrations of the capping agent to the concentration of the silver solution can affect the types of nanostructures formed. (See: Sun et al, Uniform Silver Nanowires Synthesis by Reducing AgN0 ₃ with Ethylene Glycol in the Presence of Seeds and Poly(Vinyl

Pyrrolidone), Chem, Mater. 14: 4736-4745 (2002) at page 4739, paragraph bridging col. 1 to col. 2).

While generally maintaining certain ratios of capping agent to silver solution have been found suitable for silver nanowire formation, it is possible to increase the concentrations of these solutions, sometimes substantially. Thus, in certain aspects, the silver solution and/or capping solution can be prepared at significantly higher concentrations than those typically used. Moreover, in certain aspects, the entire reaction can be run at significantly higher concentrations such that the product solution is significantly more concentrated than has been previously disclosed. Thus, with reference to the product solution, in certain aspects, the ratio of the molar concentration of the capping agent to the molar concentration of the silver (either as an ion or as metal) used in the reaction ranges from about 15: 1 to about 0.1 : 1, from about 12: 1 to about 0.1 : 1, from about 9: 1 to about 0.1 :1 , from about 6: 1 to about 0.1 :1 , from about 3: 1 to about 0.1 : 1, about 15: 1 to about 0.5: 1, from about 12: 1 to about 0.5: 1, from about 9: 1 to about 0.5: 1, from about 6: 1 to about 0.5: 1, from about 3: 1 to about 0.5 :1, about 15: 1 to about 1 : 1, from about 12:1 to about 1 : 1, from about 9: 1 to about 1 : 1, from about 6: 1 to about 1 : 1, and from about 3 : 1 to about 1 : 1.

(5) Acid Compound

The acid compounds referred to herein can have a pKa lower than 7. In some embodiments, the acid compound has a pKa less than 3.5. In some embodiments, the acid compound has a pKa less than 2. In some embodiments, the acid compound has a pKa less than 1. The acid compound can be any acid that does not appreciably interfere with the reduction of the silver nitrate to silver metal or otherwise interfere with the reaction. In some embodiments, the acid compound may also be selected to avoid halide ion or iron. In some embodiments, the acid compound is intended to refer to a mixture of two or more compounds have a pKa less than 7, less than 3.5, less than 2 or less than 1. For the avoidance of any doubt however, the 'acid compound' is not intended to refer to a 'silver compound' as discussed and defined below.

In certain aspects, an acid compound can be used as a reactant. As with the other reactants, there is no limitation on the order of mixing so long as the reaction produces the desired

nanostructure, such as silver nano wires. The acid compound can be a liquid, solid, or gas. If the acid compound is a liquid, it can be mixed directly in solution either dropwise or portionwise. If the acid compound is a solid, the acid compound can be mixed in solid form or in solution either dropwise or portionwise. If the acid compound is a gas, it can be bubbled into (through) the reaction.

Examples of the acid compound include, but are not limited to, hydrochloric acid (HC1), nitric acid (FIN0 ₃ ), sulfuric acid (H ₂ S0 ₄ ). With reference to the mixture of reactants, in certain aspects, the ratio of total moles of acid compound to total moles of the silver (either as an ion or as metal) used in the reaction ranges from about 1 : 10 to about 1 : 10,000, from about 1 :20 to about 1 :8000, from about 1 :20 to about 1 :6000, from about 1 :20 to about 1 :2000, from about 1 :50 to about 1 :8000, from about 1 :50 to about 1 :6000, from about 1 :50 to about 1 :2000, about 1 : 100 to about 1 :8000, from about 1 : 100 to about 1 : 5000, about 1 : 100 to about 1 :2000,from about 1 :200 to about 1 :8000, from about 1 :200 to about 1 :5000, from about 1 :200 to about 1 :2000, about 1 :400 to about 1 :8000, from about 1 :400 to about 1 : 5000, from about 1 :400 to about 1 : 2000, from about 1 :800 to about 1 : 10000, from about 1 :800 to about 1 :5000, from about 1 :800 to about 1 :2500, and from about 1 :800 to about 1 : 1000.

(6) Soluble halide

"Halide" refers to a salt additive comprising a cation and an anion, such as F ^~ , CI , Br , and I . The cation and anion are associated by ionic interaction and dissociate in polar solvents such as water, alcohol, diols and polyols (including ethylene glycol, 1 ,2-propylene glycol, 1,3-propylene glycol, glycerin, glycerol, and glucose). The cation can be organic or inorganic.

The soluble halide refers to halide that can produce halide ions after dissolved in the polyols.

In certain embodiments, the halide is a quaternary ammonium halide. As used herein,

"quaternary ammonium chloride" refers to ammonium halide (NH ₄ F , NH ₄ CI , NH ₄ Br , NH ₄ T ) in which all four hydrogens have been replaced by an organic group. Thus, the quaternary ammonium halide can be typically represented by formula NR ₄ F , NR ₄ CI , NR ₄ ⁺ Br , NR ₄ I , wherein each R is the same or different and independently an alkyl, alkenyl, alkynyl, aryl, or aralkyl.

In certain embodiments, the halide is a quaternary phosphonium halide. The quaternary phosphonium halide can be typically represented by formula PR ₄ ⁺ F , PR ₄ ⁺ Cr, PR ₄ ⁺ Br , PR ₄ ⁺ F„ wherein each R is the same or different and independently an alkyl, alkenyl, alkynyl, aryl, or aralkyl. They are soluble in the reducing solvent, as defined herein. Moreover, they are compatible with PVP due to the organic moieties present.

"Alkyl" refers to monovalent saturated hydrocarbon structure of between 1 and 20 carbons, in which the carbons are arranged in either a linear or branched manner. Lower alkyl refers to alkyl groups of 1 to 5 carbon atoms. Examples of lower alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, s- and t-butyl and the like. Examples of alkyl groups of longer chains include octyl(C8), decyl(ClO), dodecyl(C12), cetyl(C16), and the like. When an alkyl residue having a specific number of carbons is named, all geometric isomers having that number of carbons are contemplated; thus, for example, "butyl" is meant to include n-butyl, sec-butyl, isobutyl and t-butyl; propyl includes n-propyl and isopropyl.

Unless specified otherwise, the alkyl can be optionally substituted with a halogen (F, Br, CI or I), alkoxy, amine, and the like.

"Alkenyl" refers to a monovalent hydrocarbon structure of between 2 and 20 carbon atoms with at least one double bond. Examples include, without limitation: ethenyl, propenyl, butenyl, pentenyl, hexenyl, butadienyl, pentadienyl, and the like. Unless specified otherwise, the alkyl can be optionally substituted with a CI, alkoxy, amine, or the like.

"Alkynyl" refers to a monovalent hydrocarbon structure of between 2 and 20 carbon atoms with at least one triple bond. Examples include, without limitation: ethynyl, propynyl, butynyl, pentynyl, hexynyl, methylpropynyl, 4-methyl-l -butynyl, 4-propyl-2-pentynyl, and the like.

"Alkoxy" refers to a radical of the formula— O-alkyl. Examples include methoxy, ethoxy, propoxy, isopropoxy, and the like. Lower-alkoxy refers to groups containing one to five carbons.

"Aryl" refers to optionally substituted phenyl or naphthyl. Exemplary substituents for aryl include one or more of halogen, hydroxy, alkoxy, amino, mercapto, or the like.

"Aralkyl" refers to an alkyl residue substituted with at least an aryl group. The aralkyl can be typically represented by the formula aryl-alkyl-. Exemplary aralkyls include, without limitation, phenylmethyl (i.e., benzyl), or phenylethyl group.

Exemplary halide therefore include, without limitation: Tetraphenylphosphonium bromide, Tetrapropylammonium bromide, Tetrabutylammonium fluoride, Tetrabutylammonium iodide, Benzyl triphenyl phosphonium chloride (BTPC), Ethyltripheny phosphonium Chloride

(ETPC), Tetrabutylphosphonium Chloride (TBPC), Diphenyl phosphinic chloride, Tributyl

Tetradecyl Phosphonium Chloride (TTPC), Tetrakis(hydroxymethyl)phosphonium chloride

(THPC), Methyltripheny phosphonium Chloride, Tetramethylammonium chloride (TMAC),

Tetrabutylammonium chloride (TBAC), Cetyl trimethylammonium chloride (CTAC), C8-C18 alkyl dimethyl benzyl ammonium chloride, methyl trioctylammonium chloride (i.e., Aliquat 336®), and the like.

(7) Silver halide

In certain aspects, the silver halide can include compounds formed between silver and one of the halogens, which include, but are not limited to bromine, chlorine, and iodine. For example, these compounds, can include silver bromide (AgBr), silver chloride (AgCl), and

silver iodide (Agl).

(8) "Solvent Temperature below the boiling point of the polyol(s)"

"Solvent Temperature below the boiling point of the polyol(s)" refers to the lowest boiling point of the reactants. In certain aspects, the solutions described herein can be heat with a microwave, an oven, an oil bath, a heating mantle, or the combination thereof. (9) Other Reaction Conditions

The reaction conditions selected for the polyol process are those which preferentially produce the desired silver nanowires. Thus, according to various aspects described herein, reactants are selected, combined, and then reacted under conditions that are selected to preferentially

produce silver nanowires.

In certain aspects, temperatures in the range, for example, of 60°C to 160°C, 0°C to 155°, 80° to 145°, 90° to 135° can be selected to produce the silver nanowires. Thus, in certain aspects, reaction temperatures described herein are at or below 160° C.

In certain aspects, multiple temperature ranges may be used depending on which reactants are being combined. For example, when producing the silver nanowires described herein, the reaction may utilize multiple temperatures, which can include, for example, a first temperature, a second temperature, and a third temperature. In certain aspects, the first temperature, the second temperature, and the third temperature are very important reaction conditions that influence silver nanowire yields in the final product. For example, the first temperature can range from 60°C to 160°C, 60°C to 130°C, 70°C to 150°C, 70°C to 120°C, 80°C to 140°C, 80°C to 110°C, and 90°C to 110°C. In certain aspects, the second temperature is in the range from 80°C to 160°C, from 90°C to 150°C, from 100°C to 140°C from 110°C to 130°C and from 120°C to 130°C. In certain aspects, the third temperature is in the range from 100°C to 160°C, from 110°C to 150°C, from 120°C to 140°C, and from 130°C to 140°C.

It has been observed that the concentrations of the constituents in the reaction mixture have an impact on the formation of the nanostructures and their yields. For example, the concentration of the silver compound in the solution is greater than or equal to 0.02 mol/L, for an optimal yield of nanowires.

It has been observed that the addition rate of AgN0 ₃ solution to the reaction mixture have an impact on the formation of the nanostructures and their yields. For example, the addition rate of the silver compound in the solution is in the range of 5-500 ml/min, more preferably 10-300 ml/min, for an optimal yield of nanowires.

In addition, the ratio of the mass concentration of the capping agent to the mass concentration of the silver compound in the reaction mixture is in the range of about 15:1 to 0.1 : 1 , more preferably 10: 1 to 1 : 1. In certain aspects, the ratio of the mass concentration of the capping agent to the mass concentration of the silver compound in the reaction mixture is in the range from about 12: 1 to about 0.1 : 1 , from about 9: 1 to about 0.1 : 1, from about 6: 1 to about 0.1 :1, from about 3 : 1 to about 0.1 :1, about 15: 1 to about 0.5: 1, from about 12: 1 to about 0.5: 1, from about 9: 1 to about 0.5: 1, from about 6: 1 to about 0.5 : 1, from about 3: 1 to about 0.5: 1, about 15: 1 to about 1 : 1, from about 12: 1 to about 1 : 1, from about 9: 1 to about 1 : 1, from about 6: 1 to about 1 :1 , and from about 3 : 1 to about 1 : 1.

In some aspects, the concentration ratio of the acid compounds in the reaction mixture is in the range of 0.00005-0.5mol/L, more preferably, the concentration is in the range of 0.00005-0.3mol/L, more preferably, the concentration is in the range of 0.000 l~0.2mol/L, more preferably, the concentration is in the range of 0.0001-0. lmol/L, more preferably, the concentration is in the range of 0.00025-0. lmol/L, more preferably, the concentration is in the range of 0.0005-0.05mol/L, more preferably, the concentration is in the range of 0.001-0. Olmol/L.

In some aspects, the ratio of total moles of halide to a total volume of silver compound in the mixture of reactants is less than or equal to 1 :20. More preferably, the ratio of total moles of halide to a total volume of silver compound in the mixture of reactants is less than or equal to 1 :50. More preferably, the ratio of total moles of halide to a total volume of silver compound in the mixture of reactants is less than or equal to 1 : 100. More preferably, the ratio of total moles of halide to a total volume of silver compound in the mixture of reactants is less than or equal to 1 :200.

More preferably, the ratio of total moles of halide to a total volume of silver compound in the mixture of reactants is less than or equal to 1 :500. More preferably, the ratio of total moles of halide to a total volume of silver compound in the mixture of reactants is less than or equal to 1 :800. More preferably, the ratio of total moles of halide to a total volume of silver compound in the mixture of reactants is less than or equal to 1 : 1200. More preferably, the ratio of total moles of halide to a total volume of silver compound in the mixture of reactants is less than or equal to 1 :2000. More preferably, the ratio of total moles of halide to a total volume of silver compound in the mixture of reactants is less than or equal to 1 :5000. More preferably, the ratio of total moles of halide to a total volume of silver compound in the mixture of reactants is less than or equal to 1 : 10000.

In some embodiments, the ratio of total moles of silver halide to a total volume of silver compound in the mixture of reactants is less than or equal to 1 :5. More preferably, the ratio of total moles of silver halide to a total volume of silver compound in the mixture of reactants is less than or equal to 1 : 10. More preferably, the ratio of total moles of silver halide to a total volume of silver compound in the mixture of reactants is less than or equal to 1 :50. More preferably, the ratio of total moles of silver halide to a total volume of silver compound in the mixture of reactants is less than or equal to 1 : 100. More preferably, the ratio of total moles of silver halide to a total volume of silver compound in the mixture of reactants is less than or equal to 1 :200. More preferably, the ratio of total moles of silver halide to a total volume of silver compound in the mixture of reactants is less than or equal to 1 :500. More preferably, the ratio of total moles of silver halide to a total volume of silver compound in the mixture of reactants is less than or equal to 1 : 1000. More preferably, the ratio of total moles of silver halide to a total volume of silver compound in the mixture of reactants is less than or equal to 1 :2000.

In some embodiments, the times maintained at the third temperature is above 30 minutes, 35 minutes, 40 minutes, 50 minutes, 1 hour, 2 hours, 3 hours, or above 3 hours.

EXAMPLES

Aspects of the present teachings can be further understood in light of the following examples, which should not be construed as limiting the scope of the present teachings in any way.

The chemicals used are listed here:

a) Purified ethylene glycol ( "EG" from "aladdin-reagent" )

b) Purified glycerol ( from "aladdin-reagent")

c) Purified 1 ,2-propylene glycol ( from "aladdin-reagent")

d) Purified 1,3 -propylene glycol ( from "aladdin-reagent")

e) Silver nitrate ('AgN03', from "aladdin-reagent")

f) Silver acetate ('C ₂ H ₃ 0 ₂ Ag', from "aladdin-reagent")

g) AgCl powder (from "Colonial Metals Inc")

h) AgBr powder (from "Colonial Metals Inc")

i) Silver acetylacetonate from "meryer")

j) Poly (vinyl pyrrolidone) ('PVP', K30, "ISP")

k) Poly (vinyl pyrrolidone) ('PVP', K85, "ISP")

1) Poly (vinyl pyrrolidone) ('PVP', K 90, "ISP")

m) Sodium dodecyl sulfate (from "aladdin-reagent")

n) Standard HC1 solution (1.0mol/L from "aladdin-reagent") o) TBAC powder (TBAC from "aladdin-reagent")

p) Nitrate Acid ( HNO ₃ ) solution (HNO ₃ weight percent 70% , from "aladdin-reagent" ) q) Manganese chloride (MnCl ₂ ) powder (MnCl ₂ , from "aladdin-reagent")

r) Tetrabutylphosphonium chloride powder (TBPC from "aladdin-reagent")

s) Poly (dimethyldiallylammoniumchloride) (PDADMAC from "Hangzhou Yinhu chemical") Example 1

Step 1 : Preparing the following solution or dispersion:

Silver nitrate solution: 0.04mol AgN0 ₃ in 300ml glycerol

PVP solution: 0.12mol PVP (K85) in 500ml 1 ,2-propylene glycol

HNO ₃ solution: 0.04 mmol HN0 ₃ in 50ml 1 ,2-propylene glycol

NaBr solution: 0.001 mol NaBr in 50ml 1 ,2-propylene glycol

AgCl dispersion: O.Olmol AgCl in 100ml 1 ,2-propylene glycol

Step 2: Heating the PVP solution to 140°C and then adding the above AgCl dispersion and NaBr solution into the PVP solution;

Step 3: After that, the mixture was heated to 120°C and HN0 ₃ solution was added , subsequently the silver nitrate solution was dropwisely added at an addition rate of 50 ml/min;

Step 4: After addition of the silver nitrate solution, the whole mixture was heated to 145°C for 60 minutes under vigorous stirring to ensure that the reactions is partially complete.

Step 5: The silver nanowire product mixture was poured into 2500 mL of methanol.

Centrifugalization and filtration was used to remove unnecessary solvent and PVP and nanoparticles. Figs. 1 A and IB is the SEM picture of the sample synthesized under low and high magnification. The average length, average diameter, aspect ratio and weight percentage of silver nanowires as compared with all other silver nanostructures in the product mixture is listed in Table 1. It was determined that this product mixture contained i at least 75 weight percent (75 wgt %) silver nanowires as compared with a weight percent of all other silver nanostructures in the product mixture.

Example 2

Step 1 : Preparing the following solution or dispersion:

Silver nitrate solution: 0.06mol AgN0 ₃ in 300ml glycerol

PVP solution: 0.3mol PVP (K85) in 500ml glycerol

HN0 ₃ solution: 0.04 mmol HN0 ₃ in 50ml glycerol

MgCl ₂ solution: 0.5 mmol NaBr in 50ml glycerol

AgCl dispersion: 0.005 mol AgCl in 100ml 1 ,2-propylene glycol

Step 2: Heating the PVP solution to 80°C and then adding the above AgCl dispersion and MgCl ₂ solution into the PVP solution;

Step 3: After that, the mixture was heated to 120°C and HN0 ₃ solution was added , subsequently the silver nitrate solution was dropwisely added at an addition rate of 20 ml/min;

Step 4: After addition of the silver nitrate solution, the whole mixture was heated to 135°C for 90 minutes under vigorous stirring to ensure that the reactions is partially complete.

Step 5: The silver nanowire product mixture was poured into 2500 mL of methanol.

Centrifugalization and filtration was used to remove unnecessary solvent and PVP and nanoparticles. Figs. 2A and 2B is the SEM picture of the sample synthesized under low and high magnification. The average length, average diameter, aspect ratio and weight percentage of silver nanowires as compared with all other silver nanostructures in the product mixture is listed in Table 1. It was determined that this product mixture contained at least 65 weight percent (65 wgt %) silver nanowires as compared with a weight percent of all other silver nanostructures in the product mixture.

Example 3

Step 1 : Preparing the following solution or dispersion:

Silver nitrate solution: 0.06mol AgN0 ₃ in 600ml glycerol

PVP solution: 0.18mol PVP (K85) in 1000ml glycerol

HCl solution: 0.4 mmol HN0 ₃ in 100ml glycerol

AgCl dispersion: 0.005 mol AgCl in 100ml 1 ,2-propylene glycol

Step 2: Heating the PVP solution to 100°C and then adding the above AgCl dispersion into the PVP solution;

Step 3: After that, the mixture was heated to 120°C and HCl solution was added , subsequently the silver nitrate solution was dropwisely added at an addition rate of 40 ml/min;

Step 4: After addition of the silver nitrate solution, the whole mixture was heated to 125°C for 180 minutes under vigorous stirring to ensure that the reactions is partially complete.

Step 5: The silver nanowire product mixture was poured into 2500 mL of methanol.

Centrifugalization and filtration was used to remove unnecessary solvent and PVP and nanoparticles. Figs. 3A and 3B is the SEM picture of the sample synthesized under low and high magnification. The average length, average diameter, aspect ratio and weight percentage of silver nanowires as compared with all other silver nanostructures in the product mixture is listed in Table 1. It was determined that this product mixture contained at least 60 weight percent (60 wgt %) silver nanowires as compared with a weight percent of all other silver nanostructures in the product mixture.

Example 4

Step 1 : Preparing the following solution or dispersion:

Silver nitrate solution: 0.08mol AgN0 ₃ in 300ml EG

PVP solution: O.lOmol PVP (K90) and O. lmol PVP (K30) in 500ml EG

HN0 ₃ solution: 0.04 mmol HN0 ₃ in 50ml EG

TBAC and KBr solution: 0. 1 mmol TBAC and O.lmmol KBr in 50ml EG

AgCl dispersion: 0.00 lmol AgCl in 100ml 1 ,2-propylene glycol

Step 2: Heating the PVP solution to 140°C and then adding the above AgCl dispersion and HN0 ₃ solution, TBAC and KBr solution into the PVP solution;

Step 3: After that , the mixture was heated to 130°C and then the silver nitrate solution was

dropwisely added at an addition rate of 35ml/min ;

Step 4: After addition of the silver nitrate solution, the whole mixture was heated to 125°C for 60 minutes under vigorous stirring to ensure that the reactions is partially complete.

Step 5: The silver nanowire product mixture was poured into 2500 mL of methanol.

Centrifugalization and filtration was used to remove unnecessary solvent and PVP and nanoparticles. Figs. 4A and 4B is the SEM picture of the sample synthesized under low and high magnification. The average length, average diameter, aspect ratio and weight percentage of silver nanowires as compared with all other silver nanostructures in the product mixture is listed in Table 1. It was determined that this product mixture contained at least 80 weight percent (80 wgt %) silver nanowires as compared with a weight percent of all other silver nanostructures in the product mixture.

Example 5 Step 1 : Preparing the following solution or dispersion:

Silver nitrate solution: 0.1 mol AgN0 ₃ in 900ml EG

PVP solution: 0.5 mol PVP (K85) in 1800ml 1 ,2-propylene glycol

HN0 ₃ solution: O.Olmol HN0 ₃ in 50ml 1,2-propylene glycol

TBAC solution: 0.001 mol TBAC in 50ml 1,2-propylene glycol

AgCl dispersion: 0.003 mol AgCl in 100ml 1,2-propylene glycol

Step 2: Heating the mixture of PVP solution and TBAC solution to 140°C and then adding the above AgCl dispersion and HN0 ₃ solution into the PVP solution;

Step 3: After AgCl and HN0 ₃ solution addition , the mixture was heated to 130°C and then the silver nitrate solution was dropwisely added at an addition rate of 55ml/min ;

Step 4: After addition of the silver nitrate solution, the whole mixture was heated to 135°C for 120 minutes under vigorous stirring to ensure that the reactions was partially complete.

Step 5: The silver nanowire product mixture was poured into 6500 mL of methanol.

Centrifugalization and filtration was used to remove unnecessary solvent and PVP and nanoparticles. It was determined that this product mixture contained at least 90 weight percent (90 wgt %) silver nanowires as compared with a weight percent of all other silver nanostructures in the product mixture.

Example 6

Step 1 : Preparing the following solution or dispersion:

Silver nitrate solution: O. lmol AgN0 ₃ in 300ml glycerol

PVP solution: 0.05 mol PVP in 400ml 1,2-propylene glycol

HN0 ₃ solution: 0.008mol HN0 ₃ in 50ml 1,2-propylene glycol

MnCl ₂ solution: 0.005 mol TBAB in 50ml 1,2-propylene glycol

AgCl dispersion: 0.02 mol AgCl in 200ml 1,2-propylene glycol

Step 2: Heating the PVP solution to 100°C and then adding the above AgCl dispersion, TBAB solution and HN0 ₃ solution into the PVP solution;

Step 3: After that, the mixture were heated to 160°C and then the silver nitrate solution was

dropwisely added at an addition rate of 120ml/min;

Step 4: After addition of the silver nitrate solution, the whole mixture was heated to 145°C for 60 minutes under vigorous stirring to ensure that the reactions was partially complete.

Step 5: The silver nanowire product mixture was poured into 2500 mL of methanol.

Centrifugalization and filtration was used to remove unnecessary solvent and PVP and nanoparticles. It was determined that this product mixture contained at least 50 weight percent (50 wgt %) silver nanowires as compared with a weight percent of all other silver nanostructures in the product mixture.

Example 7

Step 1 : Preparing the following solution or dispersion:

Silver nitrate solution: 0.02 mol AgN0 ₃ in 300ml glycerol

PVP solution: 0.06 mol PVP in 300ml 1,2-propylene glycol

HN0 ₃ solution: 0.00 lmol HN0 ₃ in 50ml 1,2-propylene glycol

TBAB solution: 0.1 mmol TBAB in 50ml 1,2-propylene glycol

AgCl dispersion: 0.002 mol AgCl in 300ml 1,2-propylene glycol

Step 2: Heating the PVP solution to 100°C and then adding the above AgCl dispersion, TBAB solution and HN0 ₃ solution into the PVP solution;

Step 3: After that, the mixture were heated to 120°C and then the silver nitrate solution was dropwisely added at an addition rate of 5ml/min;

Step 4: After addition of the silver nitrate solution, the whole mixture was heated to 145°C for 60 minutes under vigorous stirring to ensure that the reactions was partially complete.

Step 5: The silver nanowire product mixture was poured into 2500 mL of methanol.

Centrifugalization and filtration was used to remove unnecessary solvent and PVP and nanoparticles. It was determined that this product mixture contained at least 50 weight percent (50 wgt %) silver nano wires as compared with a weight percent of all

other silver nanostructures in the product mixture.

Example 8

Step 1 : Preparing the following silver nitrate solution and PVP solution by mixing the silver nitrate into the ethylene glycol and PVP (K30) into the ethylene glycol, respectively:

Silver nitrate solution: 0. 1 mol AgN0 ₃ in 2000ml EG

PVP solution: 0. 5 mol PVP in 2000ml EG

Step 2: Heating the PVP solution to 100°C and then adding 0.015 mol of finely ground AgCl powder into solution;

Step 3: After AgCl addition, the mixture was heated to 120°C and then the silver nitrate solution was dropwisely added at an addition rate of 70 ml/min;

Step 4: After addition of the silver compound solution, the whole mixture was heated to 130°C for 30 minutes under vigorous stirring to ensure that the reactions was partially complete.

Step 5: The silver nanowire product mixture was poured into 250 mL of ethanol. Centrifugalization was used to remove unnecessary solvent and PVP. It was determined that this product mixture contained at least 35 weight percent (35wgt%) silver nano wires as compared with a weight percent of all other silver nanostructures in the product mixture.

Example 9

Step 1 : Preparing the following solutions:

Silver nitrate solution: 0.05mol AgN0 ₃ in 600ml 1 ,2-propylene glycol

PVP solution: 0.5 mol PVP (K30) in 800ml 1 ,2-propylene glycol

MgCl ₂ solution: 0.00 lmol MgCl ₂ in 100ml 1 ,2-propylene glycol

Step 2: Heating the PVP solution to 100°C and then adding 0.001 mol of finely ground AgCl powder and O.lmmol HC1 solution into the above solution;

Step 3: After AgCl and MgCl ₂ solution addition , the mixture was heated to 120°C and then the silver nitrate solution was dropwisely added at an addition rate of lOml/min;

Step 4: After addition of the silver nitrate solution, the whole mixture was heated to 130°C for 60 minutes under vigorous stirring to ensure that the reactions was partially complete.

Step 5: The silver nanowire product mixture was poured into 2500 mL of methanol.

Centrifugalization and filtration was used to remove unnecessary solvent and PVP and nanoparticles. It was determined that this product mixture contained at least 45 weight percent (45wgt %) silver nanowires as compared with a weight percent of all

other silver nanostructures in the product mixture.

Example 10

Step 1 : Preparing the following solutions:

Silver nitrate solution: 0.02 mol AgN0 ₃ in 200ml 1,3-propylene glycol

PVP solution: 0.01 mol PVP (K90) in 200ml 1,3-propylene glycol

HC1 solution: 0.00 lmol HC1 in 100ml 1,3-propylene glycol Step 2: Heating the PVP solution to 100°C and then adding 0.002 mol of finely ground AgCl powder and HC1 solution into the above solution;

Step 3: After AgCl and HC1 solution addition, the mixture was heated to 120°C and then the silver nitrate solution was dropwisely added at an addition rate of 50ml/min;

Step 4: After addition of the silver nitrate solution, the whole mixture was heated to 130°C for 60 minutes under vigorous stirring to ensure that the reactions partially complete.

Step 5: The silver nanowire product mixture was poured into 2500 mL of methanol.

Centrifugalization and filtration was used to remove unnecessary solvent and PVP and nanoparticles. It was determined that this product mixture contained at least 50 weight percent (50 wgt %) silver nano wires as compared with a weight percent of all

other silver nanostructures in the product mixture.

Example 11

Step 1 : Preparing the following solution or dispersion:

Silver nitrate solution: 0.03 mol AgN0 ₃ in 300ml glycerol

PVP solution: 0.1 mol PVP in 300ml 1 ,2-propylene glycol

HN0 ₃ solution: 0.00 lmol HN0 ₃ in 50ml 1 ,2-propylene glycol

TBPC solution: 0.5 mmol TBPC in 50ml 1 ,2-propylene glycol

AgCl dispersion: 0.001 mol AgCl in 300ml 1 ,2-propylene glycol

Step 2: Heating the mixture of PVP solution and TBPC solution to 140°C and then adding the above

AgCl dispersion and HN0 ₃ solution into the PVP solution;

Step 3: After AgCl and HN0 ₃ solution addition , the mixture was heated to 120°C and then the silver nitrate solution was dropwisely added at an addition rate of 200ml/min;

Step 4: After addition of the silver nitrate solution, the whole mixture was heated to 145°C for 60 minutes under vigorous stirring to ensure that the reactions is partially complete.

Step 5: The silver nanowire product mixture was poured into 2500 mL of methanol.

Centrifugalization and filtration was used to remove unnecessary solvent and PVP and nanoparticles. It was determined that this product mixture contained at least 35 weight percent (35 wgt %) silver nano wires as compared with a weight percent of all

other silver nanostructures in the product mixture.

Example 12

Step 1 : Preparing the following solution or dispersion:

Silver nitrate solution: 0.05 mol AgN0 ₃ in 1200ml glycerol

PVP solution: 0.15 mol PVP in 200ml 1 ,2-propylene glycol

HN0 ₃ solution: 0.00 lmol HC1 in 50ml 1,3-propylene glycol

NaBr solution: 0.001 mol NaBr in 50ml 1 ,2-propylene glycol

AgCl dispersion: 0.002 mol AgCl in 100ml 1,3-propylene glycol

Step 2: Mixing the mixture of PVP and NaBr solution and then heating the mixed solution to 160°C and then adding the above AgCl dispersion and HN0 ₃ solution into it. For temperature and chemical composition homogeneities, mechanical stirring was used in the whole process.

Step 3: After AgCl and HN0 ₃ solution addition, the mixture was heated to 140°C and then the silver nitrate solution was dropwisely added at an addition rate of 500ml/min;

Step 4: After addition of the silver nitrate solution, the whole mixture was heated to 140°C and maintained for 60 minutes under vigorous stirring.

Step 5: The silver nanowire product mixture was poured into 5000 mL of water. Centrifugalization and filtration was used to remove unnecessary solvent and PVP and nanoparticles. It was determined that this product mixture contained at least 20 weight percent (20

wgt %) silver nanowires as compared with a weight percent of all other silver nanostructures in the product mixture.

Example 13

Step 1 : Preparing the following solution or dispersion:

Silver nitrate solution: 0.06 mol AgN0 ₃ in 1200ml glycerol

PVP-SDS solution: 0.04 mol PVP and 0.04 mol SDS in 600ml EG

HC1 solution: 0.00 lmol HC1 in 50ml glycerol

NaBr solution: 0.001 mol NaBr in 50ml 1,3-propylene glycol

AgCl dispersion: 0.002 mol AgCl in 200ml 1,3-propylene glycol

Step 2: Mixing the mixture of PVP-SDS and NaBr solution and then heating the mixed solution to 60°C and then adding the above AgCl dispersion and HC1 solution into it. For temperature and chemical composition homogeneities, mechanical stirring is used in the whole process.

Step 3: After AgCl and HC1 solution addition, the mixture was heated to 80°C and then the silver nitrate solution was dropwisely added at an addition rate of 360ml/min;

Step 4: After addition of the silver nitrate solution, the whole mixture was heated to 160°C and maintained for 40 minutes under vigorous stirring.

Step 5: The silver nanowire product mixture was poured into 5000 mL of water. Centrifugalization and filtration was used to remove unnecessary solvent and PVP and nanoparticles. It was determined that this product mixture contained at least 30 weight percent (30

wgt %) silver nanowires as compared with a weight percent of all

other silver nanostructures in the product mixture.

Example 14

Step 1 : Preparing the following solution or dispersion:

Silver acetate solution: 0.04 mol silver acetate in 600ml glycerol

PVP-Ganex P-904LC solution: 0.04 mol PVP and 0.02 mol Ganex P-904LC in 400ml glycerol

HNO ₃ solution: 0.00 lmol HN0 ₃ in 50ml glycerol

TBPC solution: 0.001 mol TBPC in 50ml 1,3-propylene glycol

AgCl dispersion: 0.005 mol AgCl in 200ml 1,3-propylene glycol

Step 2: Mixing the PVP- Ganex P-904LC and TBPC solution and then heating the mixed solution to 80°C and then adding the above AgCl dispersion and FIN0 ₃ solution into it. For temperature and chemical composition homogeneities, mechanical stirring is used in the whole process.

Step 3: After AgCl and FIN0 ₃ solution addition , the mixture was heated to 80°C and then the silver acetate solution was dropwisely added at an addition rate of 300ml/min;

Step 4: After addition of the silver acetate solution, the whole mixture was heated to 160°C and maintained for 0.5 hours under vigorous stirring.

Step 5: The silver nanowires product mixture was poured into 5000 mL of water. Centrifugalization and filtration was used to remove unnecessary solvent and PVP, Ganex P-904LC and nanoparticles. It was determined that this product mixture contained at least 40 weight percent (40 wgt %) silver nanowires as compared with a weight percent of all

other silver nanostructures in the product mixture. Example 15

Step 1 : Preparing the following solution or dispersion:

Silver nitrate and silver acetate solution: 0.05 mol silver acetate and 0.1 mol silver nitrate in 3000ml glycerol

PVP and PVP-VA S630 solution: 0.3 mol PVP and 0.05 mol PVP-VA S630 in 6000ml glycerol

HNO ₃ solution: 0.005mol HNO ₃ in 50ml glycerol

THPC solution: 0.01 mol TMPC in 50ml 1,3-propylene glycol

AgCl dispersion: 1.5 mmol AgCl in 2000ml 1,3-propylene glycol

Step 2: Mixing the PVP and PVP-VA S630 solution and THPC solution and then heating the mixed solution to 60°C and then adding the above AgCl dispersion and HNO ₃ solution into it.

For temperature and chemical composition homogeneities, mechanical stirring is used in the whole process.

Step 3: After AgCl and HNO ₃ solution addition, the mixture was heated to 60°C and then the Silver nitrate and silver acetate solution was dropwisely added at an addition rate of 400ml/min;

Step 4: After addition of the silver nitrate and silver acetate solution, the whole mixture was heated to 100°C and maintained for 24 hours under vigorous stirring.

Step 5: The silver nanowire product mixture was poured into 50000 mL of water.

Centrifugalization and filtration was used to remove unnecessary solvent and capping agent and nanoparticles. It was determined that this product mixture yielded at least 60 weight percent (60wgt%) silver nanowires as compared with a weight percent of all other silver nanostructures in the product mixture.

Example 16

Step 1 : Preparing the following solution or dispersion:

AgN0 ₃ and AgC10 ₄ solution: 0. 1 mol AgC10 ₄ and 0.2 mol AgN0 ₃ in 0.8L glycerol

PVP solution: 0.3 mol PVP in 2.0L glycerol

HBr solution: 0.001 mol HBr in 100ml 1,3-propylene glycol

AgCl and Agl dispersion: O.OOlmol AgCl and O.OOlmol Agl in 100ml EG

Step 2: Heating the PVP solution to 100°C and then adding the above AgCl and Agl dispersion and HBr solution into it. For temperature and chemical composition homogeneities, mechanical stirring was used in the whole process.

Step 3 : After the above addition , the mixture was heated to 100°C and then the AgNC>3 and AgC10 ₄ solution was dropwisely added at an addition rate of 60ml/min;

Step 4: After addition of the silver nitrate and silver acetate solution, the whole mixture was heated to 155°C and maintained for 40 minutes under vigorous stirring.

Step 5: The silver nanowire product mixture was poured into 5000 mL of water. Centrifugalization and filtration was used to remove unnecessary solvent and PVP and nanoparticles. It was determined that this product mixture contained at least 35 weight percent

(35wgt %) silver nanowires as compared with a weight percent of all

other silver nanostructures in the product mixture.

Example 17

Step 1 : Preparing the following solution or dispersion:

AgN0 ₃ solution: 0.03molAgNO ₃ in 300ml glycerol

PVP solution: 0.45 mol PVP (K30) in 600ml glycerol

HC1 solution: 0.001 mol TBPC in 50ml 1,3-propylene glycol AgBr dispersion: 0.001 mol AgCl in 200ml 1,3-propylene glycol

Step 2: Heating the PVP solution to 100°C and then adding the above AgBr dispersion and HC1 solution into it. For temperature and chemical composition homogeneities, mechanical stirring is used in the whole process.

Step 3: After AgBr and HC1 solution addition , the mixture was heated to 100°C and then the

AgN0 ₃ solution was dropwisely added at an addition rate of 45ml/min;

Step 4: After addition of the silver nitrate and silver acetate solution, the whole mixture was heated to 160°C and maintained for 20 minutes under vigorous stirring.

Step 5: The silver nanowire product mixture was poured into 5000 mL of water. Centrifugalization and filtration was used to remove unnecessary solvent and PVP and nanoparticles. It was determined that this product mixture contained at least 25 weight percent

(25wgt %) silver nanowires as compared with a weight percent of all

other silver nanostructures in the product mixture.

Example 18

Step 1 : Preparing the following solution or dispersion:

Silver nitrate solution: 0.06mol AgN0 ₃ in 300ml glycerol

PDADMAC solution: 0.02mol PDADMAC in 500ml glycerol

HN0 ₃ solution: 0.04 mmol HN0 ₃ in 50ml glycerol

MgCl ₂ solution: 0.5 mmol NaBr in 50ml glycerol

AgCl dispersion: 0.005 mol AgCl in 100ml 1 ,2-propylene glycol

Step 2: Heating the PDADMAC solution to 80°C and then adding the above AgCl dispersion and

MgCl ₂ solution into the PDADMAC solution;

Step 3: After that, the mixture was heated to 120°C and HN0 ₃ solution was added , subsequently the silver nitrate solution was dropwisely added at an addition rate of 20 ml/min;

Step 4: After addition of the silver nitrate solution, the whole mixture was heated to 135°C for 90 minutes under vigorous stirring to ensure that the reactions was partially complete.

Step 5: The silver nanowire product mixture was poured into 2500 mL of methanol.

Centrifugalization and filtration was used to remove unnecessary solvent and PDADMAC and nanoparticles. It was determined that this product mixture contained at least 20 weight percent (20 wgt %) silver nanowires as compared with a weight percent of all other silver nanostructures in the product mixture.

Example 19

Step 1 : Prepared the following polyol solutions:

A: O.lmol/L silver nitrate dissolved in the Ethylene glycol;

B: O. lmol/L PDADMAC dissolved in the Ethylene glycol;

Step 2: Mixed the above silver nitrate solution 1000ml and 1000ml PDADMAC solution and stirred to obtain a homogenous solution;

Step 3: Added 0.02g of highly concentrated HC1 solution (with 37.5% mass

concentration) and O.lg of highly concentrated HN0 ₃ (with 65% mass

concentration), and homogenously mix the product solution.

Step 4: Heated the above product solution to 160°C and maintain this temperature for 1 hour to fully or partially react the solution to obtain silver nanowires.

Step 5: Obtained silver nanowires in the product solution. Centrifuge to remove the

polyquaternium and impurities including silver nanoparticles. Figure 10 shows a sample prepared according to Example 19. Example 20

Step 1 : Prepared the following polyol solutions:

A: 0.06mol/L silver nitrate dissolved in the Ethylene glycol;

B: 0.05 mol/L PDADMAC dissolved in the Ethylene glycol;

Step 2: Added 0.05g MnCl ₂ and 0.05g highly concentrated HC1 solution (with 37.5% mass concentration) to 1000ml PDADMAC solution, and stirred to obtain a homogeneous solution. Step 3: Heated the above solution in oil bath to 120°C and then added 800ml silver nitrate solutions dropwisely;

Step 4: Heated the product solution of step 3 to 140°C and maintained this

temperature for 1 hour to fully or partially react the solution to obtain silver nano wires.

Step 5 : Obtained silver nanowires in the product solution. Centrifuge to remove the

polyquaternium and impurities including silver nanoparticles. Figure 11 shows a sample prepared according to example 20.

Example 21

Step 1 : Prepared the following polyol solutions:

A: 0.12mol/L silver acetate dissolved in the glycerol;

B: 0.14 mol/L PDADMAC dissolved in the Ethylene glycol;

C: 0.01 mol/L Hexadecyl trimethyl ammonium chloride (HTAC) in

glycerol;

Step 2: Mixed the 1000ml PDADMAC solution, 1000ml silver acetate solution and 25ml HTAC solution, and stirred to obtain a homogeneous solution.

Step 3: Heated the above solution by microwave irradiation to 140°C and then move the reaction mixture into oven and maintaining the temperature for 2 hours;

Step 4: Obtained silver nanowires in the product solution after heating for 2 hours.

Centrifuge to remove the polyquaternium and impurities including silver nanoparticles.

Example 22

Step 1 : Prepared the following polyol solutions:

A: 0.2mol/L silver nitrate dissolved in the ethylene glycol;

B: 0.4 mol/L PDADMAC dissolved in the ethylene glycol;

C: 0.01 mol/L HC1 in glycerol;

Step 2: Mixed the 1000ml silver nitrate solution, 1000ml silver PDADMAC

solution and 25ml HC1 solution, and stirred to obtain a homogeneous solution.

Step 3: Heated the above solution by jacketed pilot plant reactor to 140°C and then

maintained the temperature for 2 hours;

Step 4: Obtained silver nanowires in the product solution after heating for 2 hours.

Centrifuge to remove the polyquaternium and impurities including silver nanoparticles.

Example 23

Step 1 : Prepared the following polyol solutions:

A: 0.02mol/L silver nitrate dissolved in the glycerol;

B: 0.01 mol/L PDADMAC dissolved in the glycerol;

C: 0.01 mol/L Tetramethylphosphonium chloride in ethylene glycol (TMPC);

D: 0.01 mol/L HN0 ₃ in glycerol;

Step 2: Mixed the 500 mL silver nitrate solution, 1000 mL PDADMAC

solution, 5 mL TMPC solution and 1 mL HN0 ₃ solution, and stirred to obtain a homogeneous solution. Step 3: Heated the above solution by oven to 160°C and then maintained the

temperature for lhour;

Step 4: Obtained silver nano wires in the product solution after the above step.

Centrifuge to remove the polyquaternium and impurities including silver nanoparticles. Example 24

Step 1 : Prepared the following polyols solutions:

A: O.lmol/L silver acetate dissolved in the propylene glycol;

B: 0.14 mol/L PDADMAC dissolved in the propylene glycol ;

C: 0.001 mol/L HC1 in glycerol;

Step 2: Mixed the 200 mL silver acetate solution, 250 mL PDADMAC solution, 25 mL HC1 solution, and then stirred to obtain homogeneous solution.

Step 3: Heated the above solution by oven to 130°C and then maintained the

temperature for 2.5 hours;

Step 4: Obtained silver nano wires in the product solution after the above step.

Centrifuge to remove the polyquaternium and impurities including silver

nanoparticles.

Example 25

Step 1 : Prepared the following polyols solutions:

A: 0.08mol/L silver acetate dissolved in the propylene glycol;

B: 0.04 mol/L PDADMAC dissolved in the ethylene glycol ;

C: 0.01 mol/L ZnCl ₂ in glycerol;

D: 0.01 mol/L HN0 ₃ in glycerol;

Step 2: Mixed the 500 mL silver acetate solution, 500 mL PDADMAC

solution, 20 volume ZnCl ₂ solution and 1 volume HN0 ₃ solution, and then stirred to obtain a homogeneous solution.

Step 3: Heated the above solutions by microwave to 145°C and maintained the

temperature in an oven for 2 hours;

Step 4: Obtained silver nano wires in the product solution after the above step.

Centrifuge to remove the polyquaternium and impurities including silver

nanoparticles.

Example 26

Step 1 : Prepared the following polyols solutions:

A: 0.06mol/L silver nitrate dissolved in the propylene glycol;

B: 0.02 mol L PDADMAC dissolved in the ethylene glycol ;

C: 0.01 mol/L MgCl ₂ in glycerol;

D: 0.01 mol/L HN0 ₃ in glycerol;

Step 2: Mixed the 500 mL PDADMAC solution, 10 mL MgCl ₂ solution and 1 mL HN0 ₃ solution, and then stirred to obtain a homogenous solution.

Step 3: Heated the above solutions by microwave to 125°C and then added 500 volume silver nitrate solution within 15 minutes and maintained the 125°C temperature in oven for 4 hours;

Step 4: Obtained silver nano wires in the product solution after the above step.

Centrifuge to remove the polyquaternium and impurities including silver

nanoparticles.

Example 27

Step 1 : Prepared the following polyols solutions: A: O.lmol/L silver nitrate dissolved in the propylene glycol;

B: 0.05 mol/L PDADMAC dissolved in the ethylene glycol ;

C: 0.01 mol/L Tetrabutylammonium Chloride ( TBAC) in glycerol;

D: 0.01 mol/L HN0 ₃ in glycerol;

Step 2: Mixed 10 mL TBAC solution and 1 mL HN0 ₃ solution in 1000 volume propylene glycol, and then stirred to obtain a homogeneous solution.

Step 3: Heated the above solution by microwave to 150°C and then added 1000 mL silver nitrate solution and 1500 mL PDADMAC solutions simultaneously within 15 minutes and then maintained the 150°C temperature in oven for 3 hours;

Step 4: Obtained silver nano wires in the product solution after the above step.

Centrifuge to remove the polyquaternium and impurities including silver

nanoparticles.

Com arative Example 1

Higher concentration of both halide and AgCl and higher reaction temperature

Step 1 : Preparing the following solution or dispersion:

Silver nitrate solution: 0.04mol AgN0 ₃ in 300ml glycerol

PVP solution: 0.12mol PVP (K85) in 500ml 1 ,2-propylene glycol

KBr solution: 0.02 mol NaBr in 50ml 1 ,2-propylene glycol

AgCl dispersion: 0.04 mol AgCl in 300ml 1 ,2-propylene glycol

Step 2: Heating the mixture of PVP solution and KBr solution to 170°C and then adding the above

AgCl dispersion into the PVP solution;

Step 3: After that, the mixture was heated to 170°C and the silver nitrate solution was subsequently dropwisely added at an addition rate of 1000 mL/min ;

Step 4: After addition of the silver nitrate solution, the whole mixture were heated to 170°C for 30 minutes under vigorous stirring to ensure that the reactions was partially complete.

Step 5: The silver nanowires product mixture was poured into 2500 mL of methanol.

Centrifugalization was used to remove unnecessary solvent and PVP. Fig.6 is the SEM picture of the sample synthesized. It was determined that this product mixture contained less than 5% weight percent (5% wgt %) silver nanowires as compared with a weight percent of all other silver nanostructures in the product mixture.

Com arative Example 2

No addition of AgCl

Step 1 : Preparing the following solution or dispersion:

Silver nitrate solution: 0.04mol AgN0 ₃ in 300ml glycerol

PVP solution: 0.12mol PVP (K85) in 500ml 1 ,2-propylene glycol

NaBr solution: 0.001 mol NaBr in 50ml 1 ,2-propylene glycol

Step 2: Heating the PVP solution to 140°C and then adding the above NaBr solution into the PVP solution;

Step 3: After that, the mixture was heated to 120°C, subsequently the silver nitrate solution was dropwisely added at an addition rate of 50 ml/min;

Step 4: After addition of the silver nitrate solution, the whole mixture was heated to 145°C for 60 minutes under vigorous stirring to ensure that the reactions was partially complete.

Step 5: The silver nanowires product mixture was poured into 2500 mL of methanol.

Centrifugalization was used to remove unnecessary solvent and PVP. Fig. 7 is the SEM picture of the sample synthesized. It was determined that this product mixture contained less than 5% weight percent (5% wgt %) silver nanowires as compared with a weight percent of all other silver nanostructures in the product mixture.

Com arative Example 3

Higher addition rate (1000 ml/min) of AgN0 ₃

Step 1 : Preparing the following solution or dispersion:

Silver nitrate solution: 0.04mol AgN0 ₃ in 300ml glycerol

PVP solution: 0.12mol PVP (K85) in 500ml 1 ,2-propylene glycol

KBr solution: 0.001 mol NaBr in 50ml 1 ,2-propylene glycol

AgCl dispersion: 0.002 mol AgCl in 300ml 1 ,2-propylene glycol

Step 2: Heating the mixture of PVP solution and KBr solution to 140°C and then adding the above

AgCl dispersion into the PVP solution;

Step 3: After that, the mixture was heated to 120°C and the silver nitrate solution was subsequently dropwisely added at an addition rate of 1000 ml/min;

Step 4: After addition of the silver nitrate solution, the whole mixture was heated to 145°C for 60 minutes under vigorous stirring to ensure that the reactions was partially complete.

Step 5: The silver nanowires product mixture was poured into 250 mL of methanol.

Centrifugalization was used to remove unnecessary solvent and PVP. It was determined that this product mixture contained less than 5% weight percent (5%

wgt %) silver nanowires as compared with a weight percent of all

other silver nanostructures in the product mixture.

Com arative Example 4

Ultralow addition rate (2ml/min) of AgN0 ₃

Step 1 : Preparing the following solution or dispersion:

Silver nitrate solution: 0.03mol AgN0 ₃ in 300ml glycerol

PVP solution: 0.05mol PVP (K85) in 500ml 1 ,2-propylene glycol

AgCl dispersion: 0.00 2mol AgCl in 300ml 1 ,2-propylene glycol

Step 2: Heating the PVP solution to 170°C and then adding the above AgCl dispersion into the PVP solution;

Step 3: After that, the mixture was heated to 170°C and the silver nitrate solution was subsequently dropwisely added at an addition rate of 2ml/min;

Step 4: After addition of the silver nitrate solution, the whole mixture was heated to 170°C for 20 minutes under vigorous stirring to ensure that the reactions is partially complete.

Step 5: The silver nanowires product mixture was poured into 2500 mL of water. Centrifugalization was used to remove unnecessary solvent and PVP. It was determined that this product mixture contained less than 10% weight percent (10% wgt %) silver nanowires as compared with a weight percent of all other silver nanostructures in the product mixture.

Table 1 lists the average length, average diameter, aspect ratio of bulk samples and the silver nanowires obtained according to the Examples 1-5 and Comparative Examples 1 and 2.

Example 3 21 75 280 >60%

Example 4 26 55 472 >80%

Example 5 23 45 511 >90%

Comparative example

<1.5 >150 10 <5%

1 (nanoparticles)

Comparative example

2 <1.5 >100 10 <5%

(nanoparticles)

Comparative Example 5 (Neither halide nor acid compound is added)

Step 1 : Prepared the following polyol solutions:

A: 0.06mol/L silver nitrate dissolved in the propylene glycol;

B: 0.2 mol/L PDADMAC dissolved in the ethylene glycol;

Step 2: Mixed 1000 volume silver nitrate solution and 1000 volume PDADMAC solution, and then stirred to obtain a homogeneous solution.

Step 3: Heated the above solution by microwave to 160°C and then maintained the 160°C temperature in oven for 1 hour;

Step 4: No silver nanowires were obtained after the above step; only silver

nanoparticles were obtained.

Comparative Example 6 (Neither halide nor acid compound is added)

Step 1 : Prepared the following polyol solutions:

A: 0.04mol/L silver nitrate dissolved in the propylene glycol;

B: 0.1 mol/L PDADMAC dissolved in the ethylene glycol;

Step 2: Obtained 1000 volume PDADMAC solution, and heated the above solutions by oil bath to 140°C.

Step 3: Added the 1000 volume silver nitrate solution dropwisely to the PDADMAC solution and then maintained the 140°C temperature in the oil bath for 2 hours;

Step 4: No silver nanowires were obtained after the above step; only silver nanoparticles were obtained from the detection using SEM.

Comparative Example 7 (Neither halide nor acid compound is added)

Step 1 : Prepared the following polyol solutions:

A: 0.05mol/L silver nitrate dissolved in the glycerol;

B: 0.1 mol/L PDADMAC dissolved in the ethylene glycol;

Step 2: Obtained 1000 volume glycerol and then heated it by oil bath to 130°C.

Step 3: Simultaneously, added 1000 volume silver nitrate solution and 1000 volume

PDADMAC solutions dropwisely within 15 minutes and then maintained the 130°C

temperature in the oil bath for 3 hours;

Step 4: No silver nanowires were obtained after the above step; only silver nanoparticles were obtained from the detection using SEM.