Permanent water swelling effect in low temperature thermally reduced graphene oxide (original) (raw)
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Effect of Water Vapor on Electrical Properties of Individual Reduced Graphene Oxide Sheets
The Journal of Physical Chemistry C, 2008
The electrical conductivity and gas-sensing characteristics of individual sheets of partially reduced graphene oxide are studied, and the results display a strong dependence on the chosen reduction method. Three reduction procedures are considered here: thermal, chemical, and a combined chemical/thermal approach. Samples treated by chemical/thermal reduction display the highest conductivity whereas thermally reduced samples display the fastest gas-sensing response times. The chemo-resistive response to water vapor adsorption is well fit by a linear driving force model. The conductivity upon exposure to water vapor and measured as a function of the gated electric field displays significant hysteresis. These results illustrate how the chemical structure of graphene oxide may be tailored to optimize specific properties for applications such as field effect devices and gas sensors.
In situ real time monitoring of hygroscopic properties of graphene oxide and reduced graphene oxide
Adsorption, 2019
Graphene oxide (GO) and reduced graphene oxide (RGO) has gained much attention in the field of gas sensing. However to realize its full potential in this regard, it is important to understand the influence of moisture on GO and RGO. Therefore, in situ and real time monitoring of adsorption and desorption of water molecules on GO and RGO coatings were investigated using quartz crystal microbalance (QCM). Water adsorption were studied under constant relative humidity (RH) levels over a period of time. For both GO and RGO the results show that the adsorption is followed by an equilibrium state. It is shown that for GO the initial rate of water adsorption, the amount of water at the equilibrium and the time to reach the equlibrium vary with RH, where as for RGO no such variations were observed. These observations indicate that at low RH adsorption is primarily throught surface and the edges where as at high RHs water penetrate into the intersitial layers of GO. Thus the latter becoming the rate limiting step for water adsorption at high RH. The results also elucidate on the contribution of surface oxygen functional groups towards the water adsorption rate and the amount adsorbed. The above results provde important information that can be used during GO-based sensor design and calibration.
Resistive chemical sensors were developed having as sensitive film graphene oxide (GO) spin-coated on glass. Sensor electrical behaviour to room temperature relative humidity was evaluated. High sensitivity characterizes GO sensor. However, it lacks repeatability and long term stability. To this end, we developed spin-coated GO sensors with different active layer thickness, which were subjected to subsequent thermal annealing steps. It was found that the resulting reduced GO (rGO) sensors demonstrate excellent stability compromising, though, the sensitivity which mainly depends on the number of annealing steps and film thickness. Finally, we propose a rapid, transparent, low-power consumption rGO sensor, enabling its use in relevant applications.
The effect of ambient humidity on the electrical properties of graphene oxide films
2012
We investigate the effect of water adsorption on the electrical properties of graphene oxide (GO) films using the direct current (DC) measurement and alternating current (AC) complex impedance spectroscopy. GO suspension synthesized by a modified Hummer's method is deposited on Au interdigitated electrodes. The strong electrical interaction of water molecules with GO films was observed through electrical characterizations. The DC measurement results show that the electrical properties of GO films are humidity-and applied voltage amplitudedependent. The AC complex impedance spectroscopy method is used to analyze the mechanism of electrical interaction between water molecules and GO films in detail. At low humidity, GO films exhibit poor conductivity and can be seen as an insulator. However, at high humidity, the conductivity of GO films increases due to the enhancement of ion conduction. Our systematic research on this effect provides the fundamental supports for the development of graphene devices originating from solution-processed graphene oxide.
A route to detect H2 in ambient conditions using a sensor based on reduced graphene oxide
Sensors and Actuators A-physical, 2020
Change in resistance of rGO/AZO and AZO sensor under an accumulated exposition at 40 sccm of H2 (g) over time. Highlights Positioning of GO flakes across electrodes using a positive dielectrophoretic force. A rGO work function in the range of 4.7-4.9 eV At 40 sccm, the sensitivity of the rGO sensor is of ~100 % at 1 V Relative humidity is a critical factor for the performance of rGO Abstract Graphene Oxide (GO) is considered an ideal candidate for the fabrication of hydrogen gas (H2 (g)) sensors due to its excellent capabilities for direct wiring, thanks to the presence of functional groups, which provide an opportunity to modify its chemical functionalities. In this study, we have fabricated a H2 (g) sensor based J o u r n a l P r e-p r o o f on the precise positioning of GO flakes across sputtered aluminium-doped ZnO (AZO) electrodes on a glass substrate using a positive dielectrophoretic force (DEP). GO flakes assembly was performed between AZO electrodes gap of 4 m and optimized by controlling the DEP parameters. A chemical reduction using a solution of 10 mM sodium borohydride was used to enhance the conductivity of the GO flakes up to two orders of magnitude. The arrangement of the GO flakes, the efficiency of the reduction process, the morphology and the surface potential of these was analyzed by Atomic Force and Kelvin Probe Microscopies. A reduced Graphene Oxide (rGO) work function in the range of 4.7-4.9 eV was obtained. Moreover, the H2 (g) response of rGO/AZO sensor was studied by two types of tests. First test consists of a single 10 min exposure of pure H2 (g), collecting the IV directly data in order to obtain the sensitivity of the rGO to be of ~100 % at 1 V. Second test consists of a batch of different time exposures to analyze the stress performance and the saturation level of the sensor. Finally, the impact of the ambient conditions on our sensor sensitivity was studied.
Highly sensitive and portable gas sensing system based on reduced graphene oxide
Tsinghua Science and Technology, 2016
Graphene has been widely used in gas-sensing applications due to its large specific surface area and strong adsorption ability. Among different forms of graphene used as gas-sensing materials, reduced graphene oxide is one of the most convenient and economical materials to integrate with Si-based electronics, which is very important to graphene-based gas sensors. In addition, the stacking structure of graphene oxide flakes facilitates absorption and detection of gas molecules. Based on reduced graphene oxide, a highly sensitive and portable gas-sensing system was demonstrated here. Solution-based graphene oxide was cast on a chip like a TF memory card and then reduced thermally. A signal acquisition system was designed to monitor resistance variation as a sign of gas concentration. This miniature graphene-based gas sensor array demonstrates a new path for the use of graphene in gas-detection technologies. And the creation of a sensitive and portable graphene gas sensor also shows great potential in fields such as medicine and environmental science.
Graphene Oxide as a Practical Solution to High Sensitivity Gas Sensing
The Journal of Physical Chemistry C, 2013
Graphene and its related materials have attracted much interest in sensing applications because of their optimized ratio between active surface and bulk volume. In particular, several forms of oxidized graphene have been studied to optimize the sensing efficiency, sometimes moving away from practical solutions to boost performance. In this paper, we propose a practical, high-sensitivity, and easy to fabricate gas sensor based on high quality graphene oxide (GO), and we give the rationale to the high performance of the device. The device is fabricated by drop-casting water-dispersed single-layer GO flakes on standard 30 μm spaced interdigitated Pt electrodes. The exceptional size of the GO flakes (27 μm mean size and ∼500 μm maximum size) allows single GO flake to bridge adjacent electrodes. A typical p-type response is observed by testing the device in both reducing and oxidizing environments. The specific response to NO 2 is studied by varying the operating temperature and the gas concentration. Sensing activity is demonstrated to be mainly mediated by the oxygen functional groups. A 20 ppb detection limit is measured. Besides illustrating a simple and efficient approach to gas sensing, this work is an example of the versatility of graphene oxide, accomplishing tasks that are complementary to graphene.
Ultrahigh humidity sensitivity of graphene oxide
Scientific reports, 2013
Humidity sensors have been extensively used in various fields, and numerous problems are encountered when using humidity sensors, including low sensitivity, long response and recovery times, and narrow humidity detection ranges. Using graphene oxide (G-O) films as humidity sensing materials, we fabricate here a microscale capacitive humidity sensor. Compared with conventional capacitive humidity sensors, the G-O based humidity sensor has a sensitivity of up to 37800% which is more than 10 times higher than that of the best one among conventional sensors at 15%-95% relative humidity. Moreover, our humidity sensor shows a fast response time (less than 1/4 of that of the conventional one) and recovery time (less than 1/2 of that of the conventional one). Therefore, G-O appears to be an ideal material for constructing humidity sensors with ultrahigh sensitivity for widespread applications.
Efficient reducing method of graphene oxide for gas sensor applications
2011
This research reports efficient reducing method of graphene oxide for gas sensor application. Graphene has been known to response gas such as nitrogen oxide (NO 2 ) or ammonia (NH 3 ) and change resistivity corresponding to the gas concentration. Here we carried out reduction of graphene oxide by hydriodic acid (HI) method [1], NH 2 NH 2 [2] and thermal annealing [3] under H 2 atmosphere and compared gas sensing behavior of each reduced graphene oxide. We found that the reduced graphene oxide by HI method responded to nitrogen oxide gas strongly (sensitivity 5%) compared to that by NH 2 NH 2 (sensitivity 2%) or thermal annealing under H 2 (sensitivity 0.15%).