In this brief review, we summarize the recent research activities involved in the development of amperometric-type immunosensors based on screen-printed electrodes (SPEs). We focus on the underlying principle involved in these types of sensors, their fabrication and electrode surface modification. We also discuss the various factors involved in the designing of such immunosensors and how they affect their performances. Finally we provide an insight into the drawbacks associated with these SPEs.

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Metal oxide semiconductors (MOS) are well known as reducing gas sensors. However, their selectivity and operating temperature have major limitations. Most of them show cross sensitivity and the operating temperatures are also relatively higher than the value reported here. To resolve these problems, here, we report the use of palladium−silver (70−30%) activated ZnO thin films as a highly selective methane sensor at low operating temperature (∼100 °C). Porous ZnO thin films were deposited on fluorinedoped tin oxide (FTO)-coated glass substrates by galvanic technique. X-ray diffraction showed polycrystalline nature of the films, whereas the morphological analyses (field emission scanning electron microscopy) showed flake like growth of the grains mainly on xy plane with high surface roughness (107 nm). Pd−Ag (70−30%) alloy was deposited on such ZnO films by ebeam evaporation technique with three different patterns, namely, random dots, ultrathin (∼1 nm) layer and thin (∼5 nm) layer as the activation layer. ZnO films with Pd−Ag dotted pattern were found show high selectivity towards methane (with respect to H 2 S and CO) and sensitivity (∼80%) at a comparatively low operating temperature of about 100°C. This type of sensor was found to have higher methane selectivity in comparison to other commercially available reducing gas sensor.

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We report an electrochemically fabricated silicon oxide nanoporous structure for ultrasensitive detection of AfB1 in food by shift in peak frequency corresponding to maximum sensitivity. It has been observed that the impedance sensitivity changes from 19% to 40% (which is only twice) where as the peak frequency shifts from 500 Hz to 50 kHz, for a change in concentration from 1 fg/ml to 1 pg/ml. This has been attributed to the combined effect of the significant pore narrowing with increasing AfB1 concentration and the opposing nature of impedance change within the nanopores and the conducting substrate immediately below the nanoporous layer.

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