Graphene-Wrapped ZnO Nanocomposite with Enhanced Room-Temperature Photo-Activated Toluene Sensing Properties

Abstract

Graphene-wrapped ZnO nanocomposites were fabricated by a simple solvothermal technology with a one-pot route. The structure and morphology of these as-fabricated samples were systematically characterized. The adding of graphene enhanced the content of the oxygen vacancy defect of the sample. All gas-sensing performances of sensors based on as-prepared samples were thoroughly studied. Sensors displayed an ultrahigh response and exceptional selectivity at room temperature under blue light irradiation. This excellent and enhanced toluene gas-sensing property was principally attributed to the synergistic impacts of the oxygen vacancy defect and the wrapped graphene in the composite sensor. The photo-activated graphene-wrapped ZnO sensor illustrated potential application in the practical detection of low concentrations of toluene under explosive environments.

Keywords: ZnO; gas sensing; graphene; photo-activated; room temperature; solvothermal technology; toluene.

Figure 1

The schematic illustration of the fabrication process of gas-sensing materials (a), the detailed electrode configuration and gas sensor structure (b), and the procedure for photo-activated gas sensor testing and typical test curve (c).

Figure 2

XRD spectra (a) of G-ZnO and pure ZnO, SEM image (b) and HRTEM image (d) of G-ZnO, SEM image (c) of pure ZnO.

Figure 3

Raman (a), EPR (b), and XPS (c,d) spectra of G-ZnO and pure ZnO. The inserts in (c,d) are quantitative calculation results of O 1s based on fitting peaks.

Figure 4

Dynamic response curves of G-ZnO at 20, 40, 60, 80, and 100 ppm toluene (a), dynamic response curves of pure ZnO at 20, 40, 60, 80, and 100 ppm toluene (b), and response values of G-ZnO and pure ZnO at 20, 40, 60, 80, and 100 ppm toluene, respectively (c).

Figure 5

Sensing response of G-ZnO to 100 ppm toluene at different RH levels (a) and sensing response of G-ZnO to 100 ppm of different VOCs (b).