A Novel Conductometric Micro-sensor for Methanol Detection Based on Chitosan/Zinc Sulfide-Nanoparticles Composite Obtained by Green Synthesis

Methanol (MeOH) is largely used in industry but it is poisonous when ingested. A new microconductometric transducer is proposed for the detection of methanol vapor. The sensitive part of this methanol microsensor is prepared by the encapsulation of zinc sulfide (ZnS) nanoparticles (NPs) in chitosan. ZnS NPs were prepared through an aqueous colloidal route, Artemisia Herba Alba (AHA) plant extract being used as a capping agent. ZnS AHA NPs presents an average nanocrystal size of 3.93 nm with a cubic zinc blende structure. The ZnS AHA NPs were well dispersed in an electrodeposited chitosan film on interdigitated electrodes, for conductometric measurements. The ethanol, methanol and acetone gas-sensing responses of the films were measured at room temperature. The sensors’ response time (tRec) for methanol is from 11 to 25 s from lower to higher concentrations. The limit of detection for methanol is 1400 ppm in the gas phase. The methanol sensor presents 3.8 times lower sensitivity for ethanol and 30 times lower sensitivity for acetone. The shelf life of the methanol sensor is one month.