A Review on Graphene-Based Gas/Vapor Sensors with Unique Properties and Potential Applications

Nano-Micro Lett. (2016) 8(2):95–119 DOI 10.1007/s40820-015-0073-1 REVIEW A Review on Graphene-Based Gas/Vapor Sensors with Unique Properties and Potential Applications Tao Wang1 . Da Huang1 . Zhi Yang1,2 . Shusheng Xu1 . Guili He1 . Xiaolin Li1 . Nantao Hu1 . Guilin Yin2 . Dannong He2 . Liying Zhang1 Received: 17 July 2015 / Accepted: 31 August 2015 / Published online: 26 November 2015 Ó The Author(s) 2015. This article is published with open access at Springerlink.com Abstract Graphene-based gas/vapor sensors have attracted much attention in recent years due to their variety of structures, unique sensing performances, room-temperature working conditions, and tremendous application prospects, etc. Herein, we summarize recent advantages in graphene preparation, sensor construction, and sensing properties of various graphene-based gas/vapor sensors, such as NH3, NO2, H2, CO, SO2, H2S, as well as vapor of volatile organic compounds. The detection mechanisms pertaining to various gases are also discussed. In conclusion part, some existing problems which may hinder the sensor applications are presented. Several possible methods to solve these problems are proposed, for example, conceived solutions, hybrid nanostructures, multiple sensor arrays, and new recognition algorithm. Keywords Graphene  Gas/Vapor sensor  Chemiresistor  Detection mechanism 1 Introduction The past several decades have witnessed a tremendous development of chemical sensors in many fields [1–4]. Gases detecting and harmful vapors with early warning feature are playing increasingly important roles in many fields, including environmental protection, industrial manufacture, medical diagnosis, and national defense. Meanwhile, sensing materials are of intense significance in promoting the combination properties of gas/vapor sensors, such as sensitivity, selectivity, and stability. Thus, various materials [5–13], covering from inorganic semiconductors, & Zhi Yang & Liying Zhang 1 2 Key Laboratory for Thin Film and Microfabrication of Ministry of Education, Department of Micro/Nano Electronics, School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240, People’s Republic of China National Engineering Research Center for Nanotechnology, Shanghai 200241, People’s Republic of China metal oxides, and solid electrolytes, to conducting polymers, have been exploited to assemble sensing devices with small sizes, low power consumption, high sensitivity, and long reliability. Among them, nanomaterials, such as carbon nanotubes (CNTs), metal-oxide nanoparticles, and graphenes, are widely used in gas sensing for their excellent responsive characteristics, mature preparation technology, and low cost of mass production, since the traditional silicon-based semiconducting metal-oxide technologies will have reached their limits [14]. Figure 1 shows a module of MQ-9, a SnO2-based gas sensor for CO detection, which can be easily obtained in the market. As one of the most fascinating materials, graphene has aroused scientists’ great enthusiasms in its synthesis, modification, and applications in many fields since 2004 [15], due to its remarkable overall properties, for instance, single-atom-thick two-dimensional conjugated structures, room-temperature stability, ballistic transport, and large available specific surface areas [16–39]. Graphene can be served as an ideal platform to carry other components for specific roles, because of its special structure. High conductivity and ballistic transport ensure that graphene exhibits very little signal disturbance when it works as a chemical sensor [40], which do not require auxiliary 123 96 Nano-Micro Lett. (2016) 8(2):95–119 32 mm Indicator lamp for power supply Sensitivity adjuster Anode (5V) Cathode (5V) Digital signal out Analog signal out 15 mm 20 mm 27 mm Indicator lamp for digital signal Fig. 1 SnO2-based gas sensor for CO detection, product model: MQ-9 electric heating devices due to its excellent chemical stability at ambient temperature [16, 27]. All of these features for graphene are beneficial for its sensing properties, making it an ideal candidate for gas/vapor detecting. Therefore, great efforts have been put into the research of graphene-based gas/vapor sensors, leading to a giant leap in the development of graphene-based gas-sensing devices [24, 41–57]. We can clearly see that the number of published papers on graphene-based gas sensors has sharply increased over the period from 2007, as shown in Fig. 2. The first experiment focusing on the detection of gas molecules based on graphene was carried out in 2007. Schedin et al. reported that micrometer-size sensors made from graphene were capable of detecting single gas molecules attached to or detached from graphene’s surface, as depicted in Fig. 3 [24]. Their discovery indicated that graphene had a great potential for detecting and sensing. In principle, a sensor is a device, purpose of which is to sense (i.e., to detect) some characteristics of its environs. It detects events or changes in quantities and provides a corresponding output, generally as an electrical or optical signal. According to different forms of reaction with external atmospheres, gas/vapor sensors can be classified into chemiresistor, silicon-based field-effect transistor (FET), capacitance sensor (CS), surface work function (SWF) change transistor, surface acoustic wave (SAW) change transistor, optical fiber sensor (OFS), and so on 123 600 550 500 450 400 350 300 250 200 150 100 50 0 2007 2008 2009 2010 2011 2012 2013 2014 Fig. 2 Histogram detailing the number of graphene-based gas/vapor sensors publications per year for the period from 2007 to 2014 (data obtained from ISI Web of Knowledge, January 28, 2015) [58]. Among them, chemiresistor is the most widely used in the construction of gas/vapor sensors and also the most popular product for practical applications, because of its long-history research, simple structure, convenience to implement, room-temperature operation, and relatively low cost [59, 60]. Actually, we usually apply voltage on both electrodes of the device, and detect the current fluctuating over time when gas composition changes. Figure 4 Nano-Micro Lett. (2016) 8(2):95–119 97 (b) 1e 20 1e Desorption 10 0 0 200 400 t(s) 600 600 Number of steps 30 (c) 600 Adsorption Number of steps Changes in ρxy (Ω) (a) 40 400 200 0 −4 −2 0 δR (Ω) 2 4 Desorption events +1e Adsorption events −1e 400 200 0 −4 −2 0 δR (Ω) 2 4 Fig. 3 Single-molecule detection. a Examples of changes in Hall resistivity observed near the neutrality point (|n| \ 1011 cm-2) during adsorption of strongly diluted NO2 (blue curve) and its desorption in vacuum at 50 °C (red curve). The green curve is a reference—the same device thoroughly annealed and then exposed to pure He. The curves are for a three-layered device in B = 10 T. The grid lines correspond to changes (...truncated)