Thiol-Functionalized Palladium Nanoparticles Networks: Synthesis,Characterization, and Room Temperature (Toxic) Vapor Detection

The preparation of three different functionalized palladium nanoparticles (PdNPs) systems for room temperature BTX (benzene, toluene, p-xylene) sensing detection and their morphostructural characterization is described. PdNPs are prepared through a two-phase water/toluene wet chemical reduction method in the presence of bifunctional organic thiols as stabilizing agents suitable for the formation of covalently linked PdNPs networks: p-terphenyl-4,4″-dithiol (PdNPs-TR), biphenyl-4,4′-dithiol (PdNPs-BP), or with 9,9-didodecyl-2,7-bis(acetylthio)fluorene (PdNPs-FL). Comparing the hydrodynamic diameter values, TR and BP ligands help to obtain networks consisting of spherical NPs of about 2 nm, in which each bifunctional ligand act as a bridge between PdNPs. In contrast, PdNPs-FL show a population centered at <2R_H> = 45 ± 5 nm. To perform preliminary gas sensing measurements, PdNPs networks are cast deposited on interdigitated electrodes to study their resistive response toward volatile organic compounds (VOCs) such as benzene (0–5%), toluene (0–1.7%), and p-xylene (0–0.4%) (BTX) and common interfering gases (H₂S, NH₃, SO₂, and relative humidity, RH). PdNPs-FL show enhanced response to BTX with an appreciable response also toward H₂S and RH. PdNPs-TR exhibit a better ability to discriminate benzene gas with a negligible response after H₂S exposure. Moreover, all the PdNPs systems show little to no response to NH₃ and SO₂ gases, offering an interesting perspective in practical sensing applications.