Doped ZnO Nanorod Array for Ultra Low NO2 Sensing
S = Rair/Rgas , where, Rgas is the resistance of the film in presence of testing analyte and Rair is the resistance of the film in air. The gas detection occurs because of the reaction on the ZnO surface in presence of the NO2 molecule which causes a reduction in electron concentration and hence fluctuation in electrical resistance. This can be explained by the following equation:
NO2 + e- = NO+ + O-ads
Here we report synthesis of TiO2 coated ZnO, Mg, Co, and Ag doped as well as undoped thin ZnO nanorod array directly on Au interdigitated electrodes using a low cost, environmentally friendly and large area application two-step chemical bath deposition (CBD) technique [1, 2] for selective detection of ultralow (0.1 ppm) NO2 in humid air at 280 °C. The structure and morphology of the ZnO films prepared by CBD has been probed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The as-prepared doped and undoped ZnO sensors were tested for the detection of NO2 (0.1-5 ppm in simulated breath) in the temperature range of 50-280 ˚C as shown in the figure 1. Characteristics such as sensitivity, selectivity, limit of detection, reproducibility, and stability will be reported. Role of dopants in enhancing the selectivity will be explained. The selectivity for the interfering analytes such as humidity, CO2, NO2, H2 and ammonia will also be investigated. Finally the sensing mechanism will be discussed in detail.
 V. Manthina, T. Patel, A.G. Agrios, Number Density and Diameter Control of Chemical Bath Deposition of ZnO Nanorods on FTO by Forced Hydrolysis of Seed Crystals, Journal of the American Ceramic Society, 97 (2014) 1028-1034.
 V. Manthina, J.P. Correa Baena, G. Liu, A.G. Agrios, ZnO–TiO2 Nanocomposite Films for High Light Harvesting Efficiency and Fast Electron Transport in Dye-Sensitized Solar Cells, The Journal of Physical Chemistry C, 116 (2012) 23864-23870.