Room temperature gas sensor based on metallic nanowires

Novel and cost effective methods of fabricating nanosturctures is very important in the current state of art of nanotechnology. Arrays of palladium nanowires have been electrodeposited from aqueous plating solution of Pd onto the step edges of highly oriented pyrolytic graphite (HOPG). The structural characterization of the nanowires was performed using atomic force microscope (AFM) and scanning electron microscope (SEM). The deposition of the continuous wires was achieved by optimizing the deposition parameters. The AFM studies revealed that the nanowires were granular in nature and the diameter of the grain was approximately 250 nm in order to form continuous nanowires. SEM images proved that the deposited wires on the substrate formed parallel arrays. The wires were transferred onto non-conducting polymer surfaces in order to study the electrical and the gas sensing properties. Silver contact pads across the nanowires were patterned by thermal evaporation using shadow masking. The electrodes silver contact pads were connected to the macroelectrodes for measuring the electrical characteristics and the sensing properties of the nanowires. The structural changes of the Pd nanowires in the presence of H2 were carefully monitored using scanning electron microscopy. The sensor response to hydrogen was fast and resembled a switch with two-order magnitude change in the conductance. A sensor mechanism is proposed based on the SEM studies and the sensor response.