Mixed-ligand nanoparticles of chlorobenzenemethanethiol and n-octanethiol as chemical sensors

A series of mixed-ligand gold nanoparticles were synthesized, characterized and used to form transducer films to investigate and enhance vapor-sensing properties. Chlorobenzenemethanethiol (CBMT) nanoparticle, prepared using a two-phase method, was used for place-exchange reactions with a varying amount of n-octanethiol (OT) to produce a series of mixed-ligand gold nanoparticles (Au_CBMT-OT-1, Au_CBMT-OT-2, and Au_CBMT-OT-3). The nanoclusters were characterized by 1H NMR spectroscopy, thermal gravimetric analysis (TGA), and transmission electron microscopy (TEM). Thin film transducers of the monolayer-protected nanoparticles were formed through a dip-coating procedure on glass substrates mounted with interdigitated gold electrodes. SEM analysis indicated that mostly the surfaces of the sensors films were smooth. Nanoparticle sensors experienced repeated cycles of analyte vapors and blank air gas as the analyte concentrations were varied. Mostly the nanoparticle sensors produced rapid and reversible responses toward the vapors of 1-propanol, acetone and cyclohexane. Linear relationship between maximum resistance changes and vapor concentrations were observed. Above all the variations in compositions of the ligand molecules (CBMT and OT) resulted in differences in signal amplitudes.