Quartz Crystal Microbalance Study of Q-State PbS Particle Formation in Lead Arachidate Langmuir-BIodgett Films

The formation of Q-state PbS particle in lead arachidate (PbAr) Langmuir-Blodgett films has been monitored using the quartz crystal microbalance (QCM) measurement. The study showed that the mass uptake of PbAr films with different thicknesses on exposure to hydrogen sulfide was consistent with that expected for the quantitative conversion of Pb²⁺ in the films to PbS and the corresponding conversion of PbAr to arachidic acid. Mass uptake measurement on PbAr films extensively exposed to H₂S gas showed the arachidic acid molecules left after Q-state particle formation could be quantitatively converted to PbAr by immersing the film in a stirred aqueous solution containing lead ions. Subsequent reexposure of the film to H₂S increases the mole fraction of PbS in the film.