Graphene-Modified ZnO Nanostructures for Low-Temperature NO₂ Sensing

Abstract

This paper develops a novel ultrasonic spray-assisted solvothermal (USS) method to synthesize wrapped ZnO/reduced graphene oxide (rGO) nanocomposites with a Schottky junction for gas-sensing applications. The as-obtained ZnO/rGO- x samples with different graphene oxide (GO) contents ( x = 0–1.5 wt %) are characterized by various techniques, and their gas-sensing properties for NO 2 and other VOC gases are also evaluated. The results show that the USS-derived ZnO/rGO samples exhibit high NO 2 -sensing property at low operating temperatures (e.g., 70–130 °C) because of their high specific surface area and porous structures when compared with the ZnO/rGO sample obtained by the traditional precipitation method. The content of rGO shows an obvious effect on their NO 2 -sensing properties, and the ZnO/rGO-0.5 sample has a high response of 62 operating at 130 °C, three times that of pure ZnO. The detection limit of the ZnO/rGO-0.5 sensor to NO 2 is as low as 10 ppb under the present test condition. In addition, the ZnO/rGO-0.5 sensor shows a highly selective response to NO 2 gas when compared with organic vapors and other inflammable or toxic gases. The theoretical and experimental analyses indicate that the enhancement in NO 2 -sensing performance of the ZnO/rGO sensor is attributed to the formation of wrapped ZnO/rGO Schottky junctions.

Elaboration of Fe3O4/ZnO nanocomposite with highly performance photocatalytic activity for degradation methylene blue under visible light irradiation

“…In addition, the zinc peak at 121 eV corresponds to Zn 2p3/2 which it was bound to ZnO in Figure 3-b [65]. XPS of oxygen 1s in Figure 3-c at 530.4 eV related to lattice oxygen (OL) [66] in the Fe3O4/ZnO nanocomposite.…”

Low-temperature operating ZnO-based NO2 sensors: a review

“…An example of a composite material based on ZnO and rGO that responses to trace NO 2 at low temperature was published by Qu's group. 122 The wrapped ZnO/ rGO nanocomposites were developed using a novel ultrasonic spray-assisted solvothermal (USS) method. Subsequently, various mass ratios of ZnO/rGO have been investigated.…”

The Influence of Deposition Time on the Structural, Morphological, Optical and Electrical Properties of ZnO-rGO Nanocomposite Thin Films Grown in a Single Step by USP

“…Where ZnO acts like a narrow barrier in an insulating rGO matrix, when the concentration of ZnO is high (there is no rGO), the charge transport is dominated by a hopping conduction mechanism. On the contrary, if the concentration of ZnO decreases, an insulating gap (a small potential barrier) appears between semiconducting ZnO nanoparticles on the rGO surface and the conduction mechanism is now governed by the electrons tunneling across these little barriers separating large conducting regions of ZnO [47,48]. As a consequence, the conductivity of the ZnO-rGO thin films increases when compared to pure ZnO thin films.…”