The expansion/contraction of gold microparticles during voltammetrically induced amalgamation leads to mechanical instability

The mech. stability of gold microparticles during anodic stripping voltammetric (ASV) detection over a large range of mercury concns. was studied. Mercury was detected at gold microparticles chem. deposited onto glassy carbon microspheres using ASV. Oxidn. was obsd. at 0.5 and 0.8 V vs. SCE Which peak was obsd. was dependent on the concn. of mercury and the deposition potential. The formation of the amalgam was of interest. As mercury was deposited for longer time intervals, SEM anal. showed the microparticles increasing in size from 0.76 ± 0.03 µm (initial) to 1.51 ± 0.14 µm (Hg2+ deposited for 1980 s at 0.35 V) in diam. To ascertain if multiple expansion and contraction cycles damaged the gold microparticles, cyclic voltammetry was used to monitor the amt. of gold on the electrode as mercury was deposited and stripped repeatedly. The area under the cathodic gold peak decreased with repetitive scans. SEM anal. revealed that the mech. stress of repetitive deposition and stripping cycles of mercury caused the gold microparticles to fracture, appearing as irregular cuboid crystals rather than as the orderly polycrystallite formations seen initially. Energy dispersive x-ray (EDX) anal. indicated that the compn. of the microparticles changed over repetitive deposition and stripping cycles from gold to an Au-Hg amalgam, which may not be in elec. contact with the carbon support. [on SciFinder(R)]