Nano Gold, Silver and Copper: PPG Industries Ohio Patents Metal Nanostructured Colorants for High Redox Glass Compositions

PPG Industries Ohio, Inc. (Cleveland, OH) claimed U.S. Patent 7,659,221 for  nano iron, gold, silver and copper colorants for high redox glass compositions.  The colorant composition is comprised of: total iron (Fe₂O₃) 0 to 1.1 weight percent; and from 0.0001 to 0.15 weight percent of at least one of the following: copper (Cu) nanostructures,  gold (Au) nanostructures, or silver (Ag) nanostructures, wherein the weight percents are based on the total weight of the glass composition. The nano colorants can be used to make glass compositions with various colors, say inventors Mehran Arbab, Larry Shelestak and  Songwei Lu

Glass substrates are used for various applications including automotive applications, architectural applications, aircraft applications, etc. Depending on the application, the glass substrate will need to exhibit certain performance properties such as visible light transmittance, infrared absorbance, etc. and aesthetic properties such as color and brightness.

The precursors for the various nanostructures are as follows. For Au nanostructures, gold-containing materials are suitable precursors. Non-limiting examples of suitable gold-containing materials are hydrogen tetrachloreaurate (III) trihydrate (HAuCl₄.3H₂O), gold (III) chloride, gold (III) oxide, sodium aurothiomalate hydrate, and gold (III) hydroxide, as well as mixtures and combinations.

For Ag nanostructures, silver-containing materials are suitable precursors. Non-limiting examples of suitable silver-containing materials are silver nitrate (AgNO₃), silver chloride, silver oxide, silver acetate, silver perchlorate, and silver acetylacetonate, as well as mixtures and combinations.

For Cu nanostructures, copper-containing materials are suitable precursors. Non-limiting examples of suitable copper-containing materials include copper-containing sulfates, copper-containing nitrates and copper-containing oxides such cuprous oxide (Cu₂O) and cupric oxide (CuO), as well as mixtures and combinations.

The nanostructures are formed during the melting step as a result of the high (0.35 or greater) redox ratio of the glass composition. Specifically, the solubility of the metal-containing precursor material in the glass composition is directly related the redox ratio. The higher the redox ratio of the glass composition, the less soluble the metal-containing precursor colorant material is in the glass composition resulting in a higher concentration of metal nanostructures in the glass composition.