Volatile organic compounds (VOCs) that easily evaporate at room temperature have caused detrimental to respiratory, allergic, and/or immune effects in humans. Increased awareness of toxicity on these VOC gases has led many studies to focus on direct measurement of these harmful VOCs with high sensitivity at lower operating temperature. Gas sensors based on surface chemical reaction of semiconducting metal oxides are readily available commercially. To improve gas sensing performance with lowered operating temperature and high sensitivity, adequate catalysts are commonly used. However, there is still limit to lower sensing temperature of metal oxides to room temperature.  It has been reported that graphene oxide (GO), a graphene sheet linked to oxygen functional groups,  has potential to realize room temperature operation. Additional advantage of the GO includes large scale and low cost production for commercial application.

In this study, GO thin films were deposited by drop coating and thermally reduced under Ar to eliminate the functional groups from GO films. The electrical properties of GO transformed from an insulator to semiconductor support GO to easily be activated for sensing gases. To enhance selective gas sensing at room temperature, many types of noble metals such as Pt and Au can be considered as an activators or sensitizers. We investigated GO with silver catalyst with relatively low cost. The formation of Ag island clusters driven by deposition conditions and their VOC gas sensing was characterized to find optimal condition of catalysts. The morphologies of silver catalyst decoated GO film were analyzed with SEM, TEM, and XRD, and the quantity of the silver catalyst was measured by EDS. Gas sensing response to VOCs was measured at room temperature to extract characteristic feature. In order to determine selective detection of specific VOC gas, 2 types and 5 types of mixed gases such as formaldehyde, benzene, styrene, toluene, and xylene were used. Detailed discussion on and the mechanism of silver catalytic effect on GO will be given.

Acknowledgement

This research was partially supported by the Korea Institute of Energy Technology Evaluation and Planning (20158520000210) grant funded by the Korea Government Ministry of Trade, Industry and Energy, 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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