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

The preparation of three different functionalized PdNPs systems for room temperature BTX sensing detection and their morphostructural characterization is described. PdNPs are prepared through 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 allow 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 <2RH> = 45 ± 5 nm. To perform preliminary gas sensing measurements, PdNPs networks are cast deposited on interdigitated electrodes to study their resistive response towards 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 better ability to discriminate benzene gas with 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.