Combinatorial Structures of Graphene Oxide and SnO2 for Sensing various VOCs

Graphene (GR) and reduced graphene oxide (r-GO) are outstanding candidates for gas-sensing elements due to extremely high surface-to-volume ratio and excellent electrical properties [1]. Their unique and attractive properties can lead to novel sensors with minimum power consumption, room temperature sensing, and sensitivity. But limitations of slow reaction speed and recovery rate of the GR based sensors were observed [2]. The addition of metal oxide to make combinatorial structures with GR is being exploited as a potential way to overcome such limits

The nanostructured metal oxides such as zinc oxide (ZnO) and tin oxide (SnO₂) have been demonstrated as gas sensing materials with excellent semiconducting properties [3]. However, gas sensing of the metal oxide typically requires elevated temperatures, which causes energy consumption, and limits wide range of applications. Combination of GR/r-GO and metal oxide, especially SnO₂, may present potential benefits by reducing energy consumption and enhancing response rate. Several approaches were attempted to make this combinatorial structure for gas sensing, but the approaches were mostly to utilize good electrical properties of r-GO. Few studies were conducted in applying non-treated graphene oxide (GO) for gas sensing. Since multilayer of GO has been demonstrated as good semiconducting materials [4], systematic approach to combine non-treated GO and metal oxide with changing the ratio as well as their combinatorial structures on gas sensing behaviors are investigated in this study.

Combinatorial structures of GO and SnO₂ were fabricated via electrophoretic deposition (EPD). The hierarchical oxide nanostructure of GO and SnO₂ was analyzed by SEM and XRD as shown in Fig. 1. Mixture ratio was adjusted by adding different amount of SnO₂ nanoparticles, and its effect on gas sensing behaviors was investigated. Fig. 2 shows the gas sensing behaviors of the GO/SnO₂ composite films with 100 ppm of formaldehyde gas (HCHO). Gas sensing performance with non-treated GO and GO/SnO₂mixture were demonstrated at room temperature. The strategies to construct combinatorial structure and their sensing behaviors in conjunction with sensing mechanisms are discussed in detail.

This research was partially supported by a grant from a Strategic Research Project (2013-0132) funded by the Korea Institute of Construction Technology, and Auburn University IGP.

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[4] Wang, C., Yin, L., Zhang, L., Xiang, D., & Gao, R. 10(3), 2088-2106. (2010).