Development of Silicon-Based Micro-Sensor for Selective Methanol Discrimination and Detection over Interfering VOC

Abstract

Volatile organic compounds (VOCs) must be identified and measured for a range of applications, including breath analysis-based disease diagnosis, air quality monitoring, food quality monitoring, and air pollution assessment, among others. The monitoring of VOCs in various application areas can help to maintain good health and safety. Chemical sensor arrays have the capabilities to offer the essential VOC identification and measurement. Gas micro-sensors built from nanostructures of chitosan doped nickel phthalocyanine as the basis sensing material have several advantages, including tunable characteristics, room temperature sensing, and the potential to be amenable to a wide range of applications. Using the Chronoamperometric electropolymerization process, a thin-film hybrid of chitosan/NiPc was electrochemically deposited across the fingers of interdigitated gold electrodes. Scanning electron microscopy is used to characterize the surface of the pure chitosan and the chitosan doped with NiPc (SEM). Acetone, ethanol, and methanol gas-sensing properties of the films prepared at optimum conditions were studied at atmospheric temperature using lock-in amplifier differential measurements at an optimized frequency of 10 kHz. The methanol sensor has the highest sensitivity of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$12.3\mu \text{Scm}-1(\mathrm{v}/\mathrm{v})$</tex> and 700 ppmv as the limit of detection. In a situation where, methanol poisoning is not detected in time, it can cause blindness, organ failure, and even death. There is currently no methanol detector available for early breath analysis diagnosis or screening of contaminated beverages. Chemical sensors, on the whole, are unable to distinguish methanol from the significantly greater ethanol background. We describe a non-invasive, low-cost, and portable sensor for highly selective methanol sensing in this paper. The innovative conductometric chitosan doped NiPc sensor can be used to separate methanol from interferants such as ethanol, acetone, or hydrogen in a separation column before actual detection in gas chromatography.