Pd/Ni nanowire film coated SAW hydrogen sensor with fast response

Abstract

A Pd/Ni nanowires (NWs) film-coated surface acoustic wave (SAW) device is proposed for sensing hydrogen with fast response. The gas adsorption in Pd/Ni NW film modulates the conductivity, and perturbs the SAW velocity, and the corresponding changes in phase can be collected as the sensing signal. 200 MHz SAW device with delay line pattern is prepared by using the lithographic technique on Y35oX quartz substrate. The larger specific surface of Pd/Ni NW contributes well to improvement of the response time. By using anode-aluminum-oxide (AAO) template-confined electrodeposition, the Pd/Ni NWs have been prepared, then dissolved in ethanol and finally deposited on the surface of the SAW device by drop coating method to build the SAW hydrogen sensor. The developed SAW sensor is integrated in a phase discriminating circuit, and experimentally characterized. Fast response less than 2 s, high sensitivity of 1.65 mV/% (0.3–3.5 v/v % in nitrogen gas), and low detection limit of 7 ppm have been achieved at room temperature (25 ℃). Further, the developed sensors show excellent selectivity and stability. Also, the film thickness - and humidity - dependent sensing performance was studied.