Methods for synthesizing silver nanoplates and noble metal coated silver nanoplates and their use in transparent films for control of light hue
Desirable methods for larger scale silver nanoplate synthesis are described along with methods for applying a noble metal coating onto the silver nanoplates to form coated silver nanoplates with a desirable absorption spectrum. The silver nanoplates are suitable for use in coatings for altering the hue of a transparent film. The hue adjustment can be particularly desirable for transparent conductive films.
1. A method for synthesizing silver nanoplates, the method comprising:
gradually adding a second quantity of hydrogen peroxide to an aqueous solution formed by blending silver ions, a polycarboxylate anion, a polyfunctional hydroxide compound, a first quantity of hydrogen peroxide and a reducing agent under mixing conditions, wherein the aqueous solution has a silver ion concentration from about 0.00025 M to about 0.01M, the aqueous solution not having a polymer capping agent distinct from polycarboxylate anions, wherein a molar ratio of the total hydrogen peroxide to reducing agent is from about 10 to about 120, and wherein the silver nanoplates have an electromagnetic absorption maximum in the visible portion of the electromagnetic absorption spectrum from about 500 nm to about 750 nm.
2. The method of claim 1 wherein the polycarboxylate anion is citrate, succinate, citramalate, malonate, tartrate, isocitrate, cis-aconate, tricarballylate or a combination thereof.
3. The method of claim 1 wherein the polyfunctional hydroxide compound is represented by the formula R 1 C(OH)R 2 R 3 where R 1 is a moiety with a hydroxyl group, ester groups, ether groups, aldehyde groups, carboxylic acid group, ketone groups, heterocyclic groups, amino groups, amide groups or a plurality thereof, and R 2 and R 3 are independently H or an alkyl moiety optionally with a hydroxyl group, ester group, ether group, aldehyde group, carboxylic acid group, ketone group, heterocyclic group, amino group, amide group or a plurality thereof, in which the R 1 , R 2 and R 3 moieties have a carbon atom bonded to the C(OH) group with the indicated functional group, if present, adjacent or spaced by an ethylene —CH 2 — moiety from the —C(OH)— moiety.
4. The method of claim 1 wherein the polyfunctional hydroxide compound is glycerol, ethyl lactate, diacetone alcohol, propylene glycol or a mixture thereof.
5. The method of claim 1 wherein the molar ratio of peroxide to reducing agent is at least about 70.
6. The method of claim 5 wherein the reducing agent comprises borohydride.
7. The method of claim 1 wherein the reducing agent is injected into the reaction mixture and the reaction is continued to complete the synthesis.
8. The method of claim 1 wherein the volume of reaction solution is at least about 500 milliliters.
9. The method of claim 1 wherein initial concentrations of the aqueous solution are from about 0.0003M to about 0.005M polycarboxylate anion, from about 0.0002M to about 0.0025M polyfunctional hydroxide compound, from about 0.00005M to about 0.002M reducing agent.
10. The method of claim 9 wherein the hydrogen peroxide concentration in the aqueous solution is from about 0.05M to about 1 M.
11. The method of claim 1 wherein initial concentrations of the aqueous solution are from about 0.0006M to about 0.0035M polycarboxylate anion, from about 0.00035M to about 0.002M polyfunctional hydroxide compound, from about 0.0001M to about 0.001M reducing agent.
12. The method of claim 1 wherein the molar ratio of the first quantity of hydrogen peroxide to the second quantity of hydrogen peroxide is greater than about 0.5 and wherein the first portion of the hydrogen peroxide is blended second to last to form the aqueous solution with the reducing agent being blended last.
13. The method of claim 1 wherein the molar ratio of the first quantity of hydrogen peroxide to the second quantity of hydrogen peroxide is from 1 to 10 and wherein the first portion of the hydrogen peroxide is blended second to last to form the aqueous solution with the reducing agent being blended last.
14. The method of claim 1 wherein the second quantity of hydrogen peroxide is added over a period of time from about 2 minutes to about 1.5 hours.
15. The method of claim 1 wherein the polycarboxylate anion comprises citrate, succinate, citramalate or a mixture thereof and wherein the polyfunctional hydroxide comprises glycerol (CH 2 (OH)CH(OH)C(OH)H 2 ), ethyl lactate (CH 3 CH 2 OC(O)CH(OH)CH 3 ), diacetone alcohol (CH 3 C(O)CH 2 C(OH)(CH 3 ) 2 ), ethylene glycol monomethyl ether (CH 3 OCH 2 CH 2 OH), propylene glycol monomethyl ether (CH 3 OCH(CH 3 )CH 2 OH), ethylene glycol, propylene glycol, diethylene glycol, or polyethylene glycol.
16. The method of claim 1 wherein the first quantity of hydrogen peroxide is blended into the aqueous solution next to last, and the reducing agent is blended last prior to addition of the second quantity of hydrogen peroxide and after the addition of the second quantity of hydrogen peroxide, the reaction is continued for a time from about 8 minutes to about 3 hours.
17. The method of claim 1 wherein the synthesized silver nanoplates are free of a polymer coating or an inorganic coating.
18. The method of claim 1 wherein the synthesized silver nanoplates have an equivalent circular diameter from about 25 nm to about 90 nm.