Nucleation and growth of Au and Au-Pd nanoparticles at the beginning of electrochemical deposition

Gold and gold-palladium nanodeposits were obtained by pulse electrolysis in dimethylformamide with 4 x 10(-3) M HAuCl4 and in dimethyl sulfoxide solution with a mixture of 4 x 10(-3) M HAuCl4 and 4 x 10(-3) M PdCl2, respectively. Isolated gold nanoparticles of about 15 nm in diameter were found by SEM observation after 6 ms of electrochemical deposition. Three pulse and pause periods with duration of 6 ms and 300 ms respectively led to an increase in the particle size approximately two times. In case of gold-palladium deposition, no particles were detected after 10 electrochemical cycles while after 50 cycles 10-35 nm nanoparticles were found. Detailed SEM analysis of electrode surface suggested that at the beginning of electrochemical deposition the growth of gold/nucleation of gold-palladium NPs is a preference for mono-Au/bimetallic Au-Pd system.