Xingfa Ma

Development of QCM Trimethylamine Sensor Based on Water Soluble Polyaniline

A rapid, sensitive, low-cost device to detect trimethylamine was presented in this paper. The preparation of water soluble polyaniline was firstly studied. Then the polyaniline was characterized via Fourier transform infrared spectroscopy (FTIR), UV-visible spectroscopy and scanning electron microscopy (SEM). Based on the water soluble polyaniline film, a quartz crystal microbalance (QCM) sensor for trimethylamine detection was fabricated and its characteristics were examined. The sensor consisted of one quartz crystal oscillator coated with the polyaniline film for sensing and the other one for reference. Pretreated with trimethylamine, the QCM sensor had an excellent linear sensitivity to trimethylamine. Easily recovered by N2 purgation, the response of the sensor exhibited a good repeatability. Responses of the sensor to trimethylamine, ethanol and ethyl acetate were compared, and the results showed that the response was related to the polarity of the analyte vapor. Experimental result also showed that the sensitivity of the sensor was relatively stable within one month. The simple and feasible method to prepare and coat the polyaniline sensing film makes it promising for mass production.

Preparation of water soluble poly(aniline) and its gas-sensitivity

Water soluble poly(aniline) was prepared using the chemical oxide method by adding a small amount of poly(sodium-p-styrenesulfonate). Poly(aniline) composite film on interdigital electrodes of carbon was formed via the spin-coating approach. After pretreatment of exposure in an alkalescence atmosphere and desorption with high-purity N2, the film showed an excellent sensitivity to trimethylamine of 5.14 × 10−7 mol mL−1. Moreover, this film also had a good selectivity to analogous gases and a fast response while exhibiting a good reproducibility. It was easily recovered by high-purity N2.

Unusual electrical response of a poly(aniline) composite film on exposure to a basic atmosphere and its application to sensors

An unusual electrical response of a poly(aniline) composite film on exposure to a basic atmosphere is reported in this paper. Based on this feature, it was possible to develop a novel kind of gas-sensor exhibiting high sensitivity, rapid response, good repeatability which can be easily recovered by purging with highly pure N2. In order to study the gas-response mechanism of this unusual electrical response, comparative tests were carried out on the gas-sensing properties of N-type and P-type silicon with porosity under similar conditions. The electric field-induced surface photovoltage spectrum (FISPS) on the poly(aniline) composite film before and after pretreatment was also examined. The experimental results indicated that the transition from P-type to N-type of a poly(aniline) composite film may exist as a result of a doping effect.

Preparation, modification, morphology tailor and application of conjugated conductive polymer in chemical sensors

Polyaniline nanotube was prepared with aid of lactic acid assembly. A chemical prototype sensor was constructed based on nanotube-structured polyaniline and two typical structured chemical sensors, one is an interdigital electrodes on flexible polymer substrate, the other is a highly sensitive quartz resonators. The gas-sensing behavior of the two typical sensors to some organic vapors operating at room temperature was investigated. Results showed rapid response, and good reversibility of these two typical sensors. The response time is 10-20 s, the reversible time is about 100 s. This study provides a simple approach for preparation of materials needed for a chemical sensor to selected organic volatiles with rapid response or organic flexible nanoelectronic devices.

Photoconductivity Study of Modified Single-Wall Carbon Nanotube/ Oxotitanium Phthalocyanine

Single-wall Carbon nanotubes (SWNTs) bonded with dodecylamine groups were obtained by chemical modification. The modified SWNTs showed improved solubility in organic solvents. Both its chemical and aggregated structure was characterized by means of FTIR and TEM. The photoconductivity of oxotitanium phthalocyanine (TiOPc) doped with the modified SWNTs was investigated by xerographic photoinduced discharge method. The results showed that the photosensitivity of the double-layered photoreceptor composed of the SWNTs/TiOPc composite as charge generation material was higher than that of pristine TiOPc, and the sensitivity increased with the content of modified SWNTs in the composites. It is the photoinduced charge transfer between TiOPc and SWNTs that contributes to the improved photosensitivity of the modified SWNTs/TiOPc composites.