To synthesize nanogold, sodium citrate solution is added to a gold chloride solution and the mixture is heated up causing the two compounds to dissociate. Upon cooling the mixture, gold atoms, sodium chloride and negatively charged citrate ions are produced. Since the gold atoms are not charged, they tend to clump or cluster together, negatively charged citrates surround the gold particles, “caging” them in and dividing the gold atoms into smaller groups. The amount of citrate in the solution determines the size of the gold clusters. More citrate results in smaller clusters of gold, less citrate in larger clusters.

Commercial nano gold solution contains nano sized pure gold having a size of 5-20 nm and the solution is based on pure water, with solution content in ppm levels.

NanoGold Inks

Nanogold conductive inks have nanocrystals with small particle size less than 10 nm with low processing temperature (less than 200°C), which is largely desired for printing electronic devices on plastics or papers. Nanogold ink contains 10%-12% Au, available in a variety of surface chemistry for different solvent dispersions and applications with low resistivity and low process temperature.