We have prepared nanocomposites of polymers and platelet CMK-5-like carbon and have demonstrated their superior performance for gravimetric gas detection. The zirconium-containing platelet SBA-15 was used as hard template to prepare CMK-5-like carbon, which was then applied as a lightweight and high-surface-area scaffold for the growth of polymers by radical polymerization. Mesoporous nanocomposites composed of four different polymers were used as sensing materials for surface acoustic wave devices to detect ppm-level ammonia gas. The sensors showed much better sensitivity and reversibility than those coated with dense polymer films, and the sensor array could still generate a characteristic pattern for the analyte with a concentration of 16 ppm. The results show that the nanocomposite sensing materials are promising for highly sensitive gravimetric-type electronic nose applications.
A surface acoustic wave (SAW) sensor array was developed for sensing amino gas. Poly-N-vinylpyrrolidone (PNVP) composite film as a sensitive interface material was deposited onto a 128° YX-LiNbO 3 substrate by the spin coating technique. Moreover, we have developed an improved portable electronic noise based on a 2x2 non-continuously working oscillators equipped with coated SAW sensor array. This gas sensor array system consists of SAW sensors, polymers with different polarity of function groups, signal readout electronics with quick connector, miniature sensing chamber made by acrylic, and aluminum plates. The adsorption of amino gas by the sensitive coating material modulates the phase velocity of the acoustic wave due to the mass loading and acoustoelectric effect. Thus, the targeted amino gas can be evaluated by recording the frequency shift of the SAW device. The fast response time (49 s) and recovery time (64 s), and larger frequency response of 800 Hz were observed from the fabricated SAW sensor under 150 ppm concentration of amino gas. The detection response and large frequency shift have been improved under current generation of SAW sensing array system.
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