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There is considerable interest in nanostructured materials with interdigitated electrodes (IDEs) platforms to detect and monitor the level of various ions in numerous applications. Herein, we report the design and fabrication of IDEs based pH sensor by using hydrothermal growth of ZnO nanorods (NRs). A four-step deposition of ZnO seed layer followed by a hydrothermal treatment lead to the heavily ordered ZnO NRs patterns on the screen printed IDEs. The structural, chemical compositional and electrical properties of the NRs were investigated and examined by using field emission scanning electron microscopy (FeSEM), atomic force microscopy (AFM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) technique and Keithley 4200 semiconductor characterization system respectively. The sensor capacitance and pH were found to be inversely proportional at a working frequency of 1 kHz. The sensor displayed sensitivity of 1.06 nF/pH in the range of pH 4−10.

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This review article elaborates the pH and nutrients detection sensitive materials and methods along with their principle of operations, merits, demerits, and application area. The sensitive materials used in the sensors react with the analytes and shows variation in electrical, physical, chemical, biological and optical parameters. The glass probe method, optical light spectroscopy, ion-selective electrodes, ion-selective field effective transistors, electrochemical interdigitated conductimetric method and microcantilever methods are the predominant techniques to detect the pH and nutrients in various medium. Most of the researchers have discussed the fabrication of pH and nutrients sensors individually in various applications, but very few numbers of sensitive materials and techniques discussed to detect the pH and nutrients in the soil. There is a strong relationship between pH and nutrients in the soil based on a number of important physical and chemical properties of the soil. We are strongly recommending that soil pH and nutrients measuring sensors can develop through the combinational approach of pH and nutrients with the help of nanostructured materials, seems to be more effective for agriculture applications.

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The effects of film thickness, electrode size and substrate thickness on the impedance parameters of alternating frequency dielectric measurements of insulating thin films deposited on conductive substrates were studied through parametric finite-element simulations. The quasi-static forms of Maxwell's electromagnetic equations in a time harmonic mode were solved using COMSOL Multiphysics® for several types of 2D models (linear and axisymmetric). The full 2D model deals with a configuration in which the impedance is measured between two surface electrodes on top of a film deposited on a conductive substrate. For the simplified 2D models, the conductive substrate is ignored and the two electrodes are placed on the top and bottom of the film. By comparing the full model and the simplified models, approximations and generalizations are deduced. For highly insulating films, such as the case of insulating SiO2 films on a conducting Si substrate, even the simplified models predict accurate capacitance values at all frequencies. However, the edge effects on the capacitance are found to be significant when the film thickness increases and/or the top electrode contact size decreases. The thickness of the substrate affects predominantly the resistive components of the dielectric response while having no significant effect on the capacitive components. Changing the electrode contact size or the film thickness determines the specific values of the measured resistance or capacitance while the material time constant remains the same, and thus this affects the frequency dependence that is able to be detected. This work highlights the importance of keeping in mind the film thickness and electrode contact size for the correct interpretation of the measured dielectric properties of micro/nanoscale structures that are often investigated using nanoscale capacitance measurements.