Inducing analytical orthogonality in tungsten oxide-based microsensors using materials structure and dynamic temperature control

The influence of material Structure and dimension on the chemical sensing performance was investigated as a function of sensor operating temperature. Polycrystalline tungsten oxides (WO3) were prepared both as nanowires of different diameters (d approximate to 100 nm, 175 non; l = 4-5 mu m) using a template-directed electrodeposition process, and as a continuous film through thermal decomposition of peroxytungstate solution. The WO3 materials were integrated with microscale conductometric platforms featuring millisecond dynamic temperature control up to 500,C. The nanowires and film were assessed for efficacy as transducers in gas-phase chemical sensors using these platforms, both in a fixed-temperature operating mode and in a dynamic pulsed-temperature operating mode. Statistical analysis of the tungsten oxide chemiresistor responses to analytes at varied operating temperatures revealed that orthogonal information can be obtained from stoichiometrically similar materials; the differences were exaggerated by probing the sensor responses with different dynamic temperature programs. We conclude that nanowire sensors yield non-redundant analytical information with respect to their complementary film-based sensor. These results demonstrate that as sensors move to nanoscale Structures, unique interactions will differentiate the materials and the devices' performance from their microscale counterparts. Published by Elsevier B.V.