In this paper,bottom contact organic thin-film transistor(OTFT)gas sensors were prepared.Silicon dioxide(SiO2)and titanium/aurum(Ti/Au)were used as the insulating layer and the electrode for the device,respectively.The multi-walled carbon nanotubes(MWCNTs)/α-sexithiophene(α-6T)bilayer films were used as the active layer,andα-6T single layer sensitive film was also prepared for comparison purpose.The electrical and trace NO2-sening properties of these two OTFT gas sensors were tested and analyzed.The results showed that,the OTFT device based on MWCNTs/α-6T bilayer had obviously better electrical properties,better stabilities and higher NO2-sening response values than the device withα-6T single layer,in which both the carrier mobility(μ)and on/off current ratio enhanced two order of magnitude.The improved performance of bilayer OTFT can be explained that MWCNTs acted as highly conducting bridges connecting the crystalline terraces in theα-6T film.Threshold voltage(VT),carrier mobility,on/off current ratio and grid current which showed extremely similar variation trend as source-drain current,were optional parameters to reveal the gas-sensing characteristic of OTFT gas sensors.Morphology analysis showed that the special feature of MWCNTs had certain influence on the gas-sensing properties.
TAI HuiLingZHANG BoDUAN ChengLiXIE GuangZhongJIANG YaDong
Formaldehyde(HCHO),a colorless and pungent-smelling gas,is confirmed be a huge threat to human health.The detection of formaldehyde is necessary and important.The Poly(3-hexythiophene)(P3HT)/ZnO organic-inorganic composite thin film was fabricated and used as the sensitive layer of organic thin film transistors(OTFT) by spray-deposited method to detect HCHO at room temperature.The process parameters such as P3HT/ZnO weight ratios and airbrushed masses were optimized.The results showed that P3HT/ZnO OTFT exhibited good sensing response to HCHO.Airbrushed mass of 1ml was the optimal mass,and the 1:1 and 1:5 weight ratios of P3HT/ZnO exhibited better sensing properties compared with others.OTFT gas sensors based on P3HT/ZnO composite film provides a novel promising approach to the detection of HCHO.
LI XianJIANG YaDongTAI HuiLingXIE GuangZhongDAN WenChao
A carbon monoxide gas sensor based on single-walled carbon nanotube （SWCNT） has been developed for detection of carbon monoxide （CO） at room temperature. Copper chloride （CuC1） was mixed with SWNT by mechanical blending. The thin film was deposited on interdigitated electrodes by using airbrush technology. This paper described the fabrication of the sensor for detecting carbon monoxide with concentrations from 20 ppm to 100 ppm. The performance of CO gas sensor was measured by using relevant apparatus to obtain the continuous sensor electric resistance change on exposure to CO and air atmosphere at room temperature, respectively. The results exhibited that the senor presented a larger sensitivity and a good recoverability. The experimental results suggested the potential use of CuC1 doped SWCNT for CO detecting.
The bilayer poly(ethylene oxide)/multiple-walled carbon nanotubes(PEO/MWCNTs) and three-layer PEO/MWCNTs/PEO composite thin films were fabricated with the spraying process on the interdigitated transducers(IDTs) as gas sensors for toluene-sensing application.Compared with the bilayer thin film sensor,the sensor with three-layer thin films exhibited higher response values and better recovery property.The microstructures of sensing films were characterized by scanning electron microscopy(SEM) to indicate that the better sensing response of three-layer thin films might be ascribed to the sufficient adsorption of toluene molecules on the surfaces of upper and bottom PEO films.The selectivity of the three-layer film sensor was further investigated by comparing responses upon exposure to different interference vapors with the response to toluene exposure,and much higher response was observed in the case of toluene.Good repeatability of the three-layer film sensor was also observed.
TAI HuiLingLIAO JianDAN WenChaoDUAN ChengLiLI Xian
A strong hydrogen-bond acidic(HBA)polymer linear fluoroalcoholic polysiloxane(PLF),synthesized by one-step hydrosilylation,was introduced for 2,4-dinitrotoluene(2,4-DNT)detection using surface acoustic wave(SAW)devices.FT-IR spectra and1H NMR spectra characterizations confirmed its molecular structure.Then,PLF was dissolved in chloroform,and spray coated onto a434 MHz SAW device.And subsequently,the sensitivity and selectivity of the fabricated sensor were studied based on a SAW test platform.To 2,4-DNT of 1 ppm and 100 ppb(for DNT,1 ppm=8.1 mg/m3;1 ppb=8.1 lg/m3),the responses of the sensor rose 7.7 and 1.5 kHz,respectively.Furthermore,compared with some common interference vapors at 10 mg/m3,the response of the sensor to 2,4-DNT at1 ppm was 5 times stronger.The sensitive property was attributed to the hydrogen bond interaction between the hexafluoroisopropanol(HFIP)group in PLF and the basic lone electron pairs of nitro-groups in 2,4-DNT.Comparison between the PLF sensor and hydroxyl group functionalized polymer(carbowax and MOBCD)-coated sensors was investigated,and the results showed that the PLF sensor exhibited better sensitivity.In a word,the PLF sensor exhibited fast response,negligible baseline drifts and excellent reversibility,indicating good candidates of HFIP group functionalized HBA polymers for practical nitroaromatic explosives detection.
Yang WangXiaosong DuYin LongHuiling TaiYadong Jiang
