ABSORPTION-SPECTRA AND REACTIONS OF COLLOIDAL BIMETALLIC NANOPARTICLES CONTAINING MERCURY

Silver and mercury ions are reduced in a common solution by sodium bor ohydride in the presence of poly(ethyleneimine). Colloidal alloy parti cles are formed, whose plasmon absorption band is blue-shifted with in creasing mercury-to-silver ratio. The reduction mechanism is rather co mplex: large mercury ''drops'' are first formed, although silver ions are reduced simultaneously. This effect is explained by an interaction of the two metal redox systems, as silver clusters are reoxidized by mercury ions. The final particles are formed in a reaction of the merc ury drops with reduced silver clusters, yielding amalgam particles sma ller than the mercury drops. These processes are followed by spectroph otometric and light-scattering measurements. The alloy colloids are st able up to a mercury to silver molar ratio of 2. Upon exposure to air, part of the mercury in the alloy particles is oxidized.