Copolysiloxane solvent detector using Langmuir-Blodgett surface potential method

Abstract

A quick detection for volatile organic compounds (VOCs), especially in the indoor environment is a must as the build-up level of VOCs is multiple times greater than outdoor environment. By using a surface potential probe, we have analyzed the interaction between copolysiloxane Langmuir-Blodgett (LB) thin films with several commercially used VOCs solvent, specifically chloroform (CHCl₃), isopropyl alcohol (IPA) and dichloromethane (DCM). These copolysiloxane LB thin films, namely P_50:50 and P_25:75 had been deposited onto aluminium-coated substrates. Subsequently, the surface potential (ΔV) of copolysiloxane LB thin films were monitored during exposure to each solvent. Interaction of these thin films with each solvent produced non-identical changes in ΔV values. In addition, ∆V_max value and halftime response for half ∆V_max value (t₅₀) were determined. Later, a figure of merit, ƒ was calculated to determine the optimum sensing material per solvent. The most promising candidates particularly as IPA solvent vapour sensors is P_50:50 copolysiloxanes LB thin film that presented ΔV_max (106 mV), smallest halftime response for half ∆V_max value achieved, t₅₀ (65 s), and considerable ƒ (1.631 mV/s), as compared to others.