Enhanced Gas Sensor Based on Nitrogen-Vacancy Graphene Nanoribbons

Enhanced gas sensor based on nitrogen-vacancy graphene nanoribbons

Xiao-Lin Wei, Yuan-Ping Chen, Wen-Liang Liu and Jian-Xin Zhong

Laboratory for Quantum Engineering and Micro-Nano Energy Technology, Department of Physics, Xiangtan University, Xiangtan, Hunan 411105, China

Abstract:

The new 1D carbon-based nanoribbons are considered as more ideal gas sensors.1-3Recent some studies also indicate that grapheme nanoribons(GNRs) can present significant conductance changes as absorbing several kinds of gas molecules.1 However,the interaction of many kinds gas molecules with the pristine GNRs is not very strong. 1To remedy this situation,a strategy is to functionalize them by substitutional doping. Inthat aspect, nitrogen as a substitutional dopant has beeninvestigated.4-8 Besides single atom doping, some special doping defects, such as pyridinelikesubstructures, can be also formed in GNRs.8There are two kinds of pyridinelikesubstructures, namely, three-nitrogen vacancy(3NV) (nitrogen atoms are substitutedfor three carbon atoms neighboring the vacancy) and four-nitrogen divacancy (4ND). The former study has indicated that the pyridinelikesubstructures can improve the sensitivity of CNT-based gas sensor,9 which is because of the interaction between the gas molecule and the nitrogen vacancy present in thenanotube.Then, whether the nitrogen vacancies in GNRs can improve the sensitivity to the gas molecules? In another word, are the nitrogen-vacancy GNRs better gas sensors than the pristine GNRs? To the best of our knowledge,there is no study on this question.

By using the density-functional theory in combinationwith the nonequilibrium Green’s function method,we study transport properties of nitrogen-vacancy (3NV and 4ND) zigzag GNRs (ZGNRs) absorbing two kinds of gas molecules, NH3 and CO. It is found that the nitrogen-vacancy ZGNRs are more sensitive to the absorbing molecules than the pristine ZGNRs. The gas molecule absorbed on the three-nitrogen vacancy leads to sharp resonant peaks on conductance, while that absorbed on the four-nitrogen vacancy leads to anti-resonant dips. Different gas molecule corresponds to different energy conductance peaks (or dips), thus each kind of gas molecules can be detectedout by itsown unique resonant profile. Our results indicate that the nitrogen vacancy in ZGNRs can enhance the sensitivity to gas molecules, i.e., nitrogen-vacancy ZGNRs can serve as better gas sensors than the pristine ZGNRs.

Key words: nitrogen vacancy, graphene nanoribbons, gas sensor

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