CHEMISORPTION OF PHOSPHINE ON COLLOIDAL SILVER IN AQUEOUS-SOLUTION

The plasmon absorption band of 6-nm silver particles in aqueous soluti on is blue-shifted and strongly broadened upon the adsorption of phosp hine, PH3. The effects are more pronounced in alkaline than acidic sol ution. In alkaline solution, the adsorption is completely irreversible . Upon aging of the silver solutions containing PH3, hydrogen and phos phate are generated in the mole ratio 4:1. A mechanism is proposed for the catalytic action of the silver particles in the reaction of phosp hine with water, in which donation of electron density from absorbed p hosphine into the silver particles is an important step. Conductivity measurements indicate that phosphine in alkaline solution is adsorbed as PH2-. It is shown in coadsorption experiments that phosphine is mor e strongly adsorbed than I- and that SH- and phosphine are about equal ly strongly adsorbed.