Nanoparticle-coated chemiresistors with CMOS baseline tracking and cancellation

Chemiresistors (CR) with thiolate-monolayer-protected gold nanoparticle (MPN) interfacial layers can provide sensitive detection of volatile organic compounds (VOCs). However, baseline resistances are high (~M-ohm) relative to the typical responses (~ohms), and baseline drifts can be large. These factors represent impediments to the implementation of CRs and CR arrays in microanalytical systems for multi-VOC monitoring. This paper presents a new baseline cancellation and tracking system for MPN-coated CRs. This system separates the sensor response and baseline in the analog domain. Concentrations down to hundreds of ppm were measured. The circuitry of the system demonstrated a sensor input range of over 45.8 dB. Most importantly, it accurately tracked and removed baseline drifts on the order of 2 mV/min and measured multiple sensors whose baselines differed by 27 MOmega.