Guang Zhong Xie

The Investigation of a New NO2 OTFT Sensor Based on Heterojunction F16CuPc/CuPc Thin Films

The bottom contact heterojunction organic thin film transistors (OTFTs) based on n-type hexadecafluorophthalocyaninatocopper (F16CuPc) and p-type copper phthalocyanine (CuPc) bilayer were developed by the vacuum evaporation, which were applied to detect nitrogen dioxide (NO2). The sensors with different thickness (5nm, 10nm, 15nm and 20nm) of CuPc were prepared to investigate the influence of CuPc film thickness on the properties of devices. The results showed that four parameters including the source-drain current (IDS), grid current (IGS), threshold voltage (VT) and carrier mobility (μ) changed in a few seconds when the sensors were exposed to the atmosphere of NO2. Further more, IDS and IGS presented extremely similar variation trend. So the grid current would be taken as a new parameter to reveal the response characteristic of OTFT gas sensor. By comparison, the device with 15nm CuPc thin film exhibited the optimum electronic and gas sensing properties.

A PVP-Based Quartz Crystal Microbalance Sensor for H2S Detection

Hydrogen sulfide is a typical toxic, inflammable gas. The detection of H2S is crucial in the areas of oil, natural gas and so on. However, studies on H2S gas sensors at room temperature were seldom reported. In this study, Quartz crystal microbalance (QCM) sensors have been utilized, and PVP film were prepared on the QCM by airbrush method with different airbrush volume for H2S detection. The results showed that the PVP film with airbrush volume 0.2ml exhibited a better sensing response to H2S gas. Besides, sensitive characteristics parameters, i.e. selectivity, stability, linearity and sensitivity of prepared sensors were studied for comparison. The relative sensing mechanism associated with SEM pictures was studied as well.

Fabrication and Formaldehyde-Sensing Property of Quartz Crystal Microbalance (QCM) Coated with PVP-MWCNTs Composites

In this paper, the quartz crystal microbalance (QCM) sensors coated with polyvinyl pyrrolidone (PVP)-multiwalled carbon nanotubes (MCWNTs) nanocomposite thin films were developed by the spray process, which were used for the detection of low concentration formaldehyde at room temperature. The surface morphology and structure of films was analyzed by scanning electron microscope (SEM), UV-Vis absorption spectrometry, respectively, and the formaldehyde-sensing properties of sensors were investigated. The results showed that the prepared QCM gas sensor exhibited the linear characteristic, fast response, good reproducibility to low concentration formaldehyde within 6 ppm, and the poisoning of films was observed when the formaldehyde concentration exceeded 6ppm. Moreover, the sensitivity of the sensor could achieve up to 1Hz/ppm and had the good stability of response values.

Resistive Gas Sensors Based on MWCNTs-PVP Composite Films

In this paper, multiple-walled carbon nanotubes (MWCNTs) monolayer film and MWCNTs-polyvinylpyrrolidone (PVP) composite films were fabricated on interdigitated electrodes (IDEs) by airbrush technology, respectively. Response performance of all the sensors to various concentrations of vapors including methanol, ethanol, acetone, tetrahydrofuran, water and 1,2-dichloroethane were investigated. The results showed that a larger sensing response was obtained for the composite films compared with the MWCNTs monolayer film. Moreover, the MWCNTs-PVP composite films had a good selectivity for 1,2-dichloroethane vapor.

Comparison of Hydrogen Sulfide Sensing Properties between Multiple-Walled Carbon Nanotubes (MWNTs) and MWNTs-HAuCl4 Materials

The rapid and precise detection of hydrogen sulfide (H2S) has great significance due to its high toxicity. In this work, the response properties of multiple-walled carbon nanotubes (MWNTs) and MWNTs-HAuCl4 to H2S at room temperature were compared. Scanning electron microscopy (SEM) technique was used to characterize MWNTs and MWNTs-HAuCl4 films. It was found that sensors with MWNTs-HAuCl4 exhibited much higher response value. On the other hand, sensors with MWNTs were observed to have faster response time and better recovery properties.

Formaldehyde Detection Based on P3HT/InSnO Composite Thin Film Transistor

Formaldehyde, a colorless and pungent-smelling gas, had been confirmed be a huge threat to people health. The detection of formaldehyde was necessary and important at room temperature. Sprayed P3HT/InSnO composite film based on organic thin film transistors (OTFT) was fabricated to detect formaldehyde at room temperature in this paper. The results showed that P3HT/ InSnO-OTFT showed better response and recovery to HCHO compared with P3HT-OTFT at room temperature.

Preparation of Ethanol-Sensing Gas Sensor Based on PECH/Multi-Wall Carbon Nanotubes Sensitive Films

Abstract: In this paper, Polyepichlorohyron(PECH)/multi-wall carbon nanotubes(MWCNTs) composite films and PECH/multi-wall carbon nanotubes twolayer film were deposited on interdigitated electrodes by airbrush technology to detect ethanol vapor of various concentrations at room temperature. Thickness and structure of the film were taken into account, so films of different thicknesses and with different structures were prepared respectively. The responses of the sensors to ethanol showed that composite film had a higher response thantwolayer film, and the thick composite film performed better than its counterpart when they were exposed to ethanol vapor.

The Formaldehyde OTFT Sensor Based on the Airbrushed P3HT/ZnO Composite Thin Film

The pure conducting polymer P3HT film is less sensitive to the formaldehyde (HCHO), and the pure ZnO film needs a high temperature to militate the HCHO, as a result, the P3HT/ZnO composite was fabricated on the organic thin film transistor (OTFT) by spraying to detect the HCHO at room temperature, the electrical properties and sensing properties of all the prepared OTFT devices were measured by Keithley 4200-SCS source measurement unit. What is more, the effect of different P3HT/ZnO composite masses on the response of sensors were tested, all the sensors showed a remarkable response to HCHO, and the optimized composite mass of 1.0ml was obtained. Since most detecting methods for the HCHO vapor require an high temperature, the experiments and results in this paper showed the important significance for the field of HCHO detecting.

Preparation and Investigation of Toluene-Sensing Properties of Polymer/Inorganic Composite and Multi-Layer Films

In this paper, poly 4-vinylphenol (P4VP)/multi-wall carbon nanotubes (MWNTs) composite film, P4VP/ carbon black (CB) composite film and P4VP/MWNTs multi-layer sensitive films prepared using airbrush technology were deposited on interdigitated electrodes to detect tolunene vapor at room temperature. The surface of the composite film was observed under a scanning electron microscope (SEM). It was found that the resistance of the sensor increased after the exposure to toluene vapor and the increased magnitude of the changes had a good linearity with concentrations of toluene. Meanwhile, the P4VP/MWNTs composite film sensor also has a higher sensitivity than P4VP/CB composite film sensor. P4VP/MWNTs three-layer film sensor was fabricated as well. It was estimated that the response time and recovery time of P4VP/MWNTs three-layer films sensor were about 15 s and 20 s, respectively. The sensor responses of S=0.12% at 10mg/m3 toluene vapor for P4VP/MWNTs three-layer films. The results showed that the multi-layer films sensor exhibited a lower detection limit and better sensing properties compared with the sensors based composite film.

The Humidity Sensitive Behavior of Poly(Ethyleneimine)/Multiwall Carbon Nanotube Composite Films

In this paper, a novel humidity sensor based on polymer-carbon nanotube composites was prepared and characterized. Two different methods were adopted to fabricate the humidity-sensing film for these sensors. The surface of the films was observed by a scanning electron microscope (SEM). The sensing material made up of poly(ethyleneimine) and multiwall carbon nanotube was sprayed on the interdigitated microelectrode pairs(IDTs). The resistance between the two electrodes was measured at different relative humidity levels at 19°C. The data shows that the resistance increases with the rise of the relative humidity over the range of 5-90% RH and that, the resistance increases almost linearly in the range of 5-71% RH. The response of the sensors to NO2 and NH3 were also examined, and the results reveal that the sensor is not sensitive to both of them.