A room temperature volatile organic compound sensor with enhanced performance, fast response and recovery based on N-doped graphene quantum dots and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) nanocomposite

A highly efficient and facile sensing system made of N-doped graphene quantum dots (N-GQDs)/poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) was fabricated by drop coating on interdigitated Au electrodes with high uniformity over a large area of silicon substrate, and was used to sense the vapors of volatile organic compounds (VOCs) for detection at room temperature. An innovative method was developed for the synthesis of N-GQDs through hydrothermal processing of citric acid. The N-GQDs obtained have a N to C atomic ratio of 0.058 and a diameter of 2-7 nm. The nanocomposite sensing system exhibits highly sensitive, selective, rapid, and reversible responses for the detection of 1-1000 ppm VOCs. The N-GQDs/PEDOT-PSS nanocomposite gas sensor has an enhanced methanol sensing property of 13 times the value for pristine PEDOT-PSS in a low concentration of 50 ppm methanol. Moreover, the gas sensor based on the nanocomposite has a fast response (ca. 12 s) and recovery (ca. 32 s) behavior, excellent room temperature selectivity and stability. The methanol-sensing mechanisms of the N-GQDs/PEDOT-PSS nanocomposite gas sensor, based on direct charge transfer and a swelling process, are highlighted.