(Invited) Suspended Graphene-Based Sensor for Real-Time and Highly Sensitive Monitoring of VOCs

Abstract

Volatile organic compounds (VOCs) are emitted from solids or liquids with high vapor pressure and are often combustible and toxic, so on site real-time monitoring is vital. Currently photoionization detectors (PIDs) are used for VOC monitoring. PID devices are bulky and expensive to make and operated at high voltage to operate. As such there is a need for more portable and less expensive methods for detecting VOCs. We developed a novel gas sensor for (VOCs) detection. This technology utilizes suspended graphene membranes to provide real-time, ultrasensitive VOC detection. A freestanding graphene film suspended over an array of cavities or trench can offers increased surface area (twice over) and gives a direct method of sensing when VOCs adsorbed at the surface of graphene. Our sensor requires low voltages to operate, immediate response, high sensitivity and a larger theoretical range of detection than photoionization detectors sensors and it is a non-specific as PIDs. In this work, we shall present a 3 mm X 3 mm square chip, fabricated using conventional photolithography, containing an array of two terminal devices. Each individual device consists of a monolayer graphene sheet suspended over multiple cavities and clamped by two metal contacts. Suspended graphene, as opposed to substrate-based graphene, significantly reduces the surface charge hindrances and allows for ultrasensitive detection of gas molecules. The fabricated graphene chip has been successfully tested for toluene vapors. Currently, testing is underway to functionalize graphene for selective detection of different gases.