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A capacitive approach is employed to find moisture of the soil at various depths (4.5−20 cm). The sensor probe having dimensions 22 × 4 × 0.5 cm 3 , embedded with a series of five microsensors (scalable according to the need), is developed using a graphene oxide (GO) sensor array. The measurement electrodes were designed in an interdigitated manner having eight pairs of comblike-shaped fingers with 100 nm thickness and 90 μm spacing. It has been observed that, for black soil, all of the microsensors displayed response in the range of 500−550% when the soil water content is varied from 3.2 to 55.5%. The graphene oxide-based array probe sensor (GO-APS) shows fast response and recovery time of 140 and 20 s, respectively, for 10% soil moisture samples. The soil moisture profile has been monitored up to a scale of 20 cm depth using the fabricated design. In-depth soil moisture profiling shows a maximum deviation of ±2.4% compared with a standard oven-drying method. The lump formation effect in soil mass showed a maximum deviation of ±4% for the GO-APS array. This robust and low-cost GO-APS with high sensitivity is promising for technological advances in agricultural application.

Recently, perovskite oxides have shown a lot of promise as active materials for photovoltaic (PV) and photoelectrochemical (PEC) devices. In this article, a series of oxides Ba2Bi1+xNb1−xO6 (0 ≤ x ≤ 0.8) is evaluated for PV/PEC applications via a combined theoretical and experimental study. Ab‐initio calculation reveals that the stoichiometric compound (Ba2BiNbO6) spontaneously induces the formation of BiNb antisites, leading to off‐stoichiometric structure. The electronic structure of off‐stoichiometric compounds confirms mixed valence character of Bi, introducing intermediate bands in the band structure. UV–vis diffuse reflectance spectroscopy (DRS) predicts the bandgap in the visible range (1.5–1.9 eV). Simulation reveals excellent absorption properties, indicating the possibility of high photoconversion efficiency. Lack of sharp peaks in the DRS, however, raises concern about the level of nonradiative recombination. Point defect simulation suggests the possibility of few deep level donors BiBa, NbBi, VO, in high concentrations (≈1018–1019 cm−3), which can act as nonradiative recombination centers. Ultraviolet photoelectron spectroscopy confirms majority carriers to be n‐type. Self‐consistent simulation of the Fermi level (EF) suggests an overall cancellation of donors and acceptors, leading to EF pinning at the mid‐gap region explaining the observed high bulk resistivity. This indicates the requirement of extrinsic doping to achieve desired properties for applications.

A simple pH sensor has been developed employing a 3D porous graphene framework blended with quinizarin. The performance of the fabricated sensor was tested via square wave voltammetry technique by applying different buffer solutions and real samples. The peak potential of the designed electrode varies with the change in pH of solutions due to 2e−/2H+ transfer process of pH-dependent quinone/hydroquinone redox couple. For varying pH (1-13), the designed sensor has a sensitivity of 65.6 ± 0.4 mV/pH at 25°C. Soil pH sensing was performed for different types of soil samples prepared using 1M KCl and 0.01M CaCl2 solutions with a potential shift of 63.5 ± 0.9 mV/pH and 57.9 ± 0.3 mV/pH, respectively. The 3D graphene-quinizarin pH sensing probe demonstrates negligible hysteresis (± 0.3 pH) and long-term stability (six months and more). In comparison to the commercial pH meter, the fabricated sensor shows a relative inaccuracy of less than 5%. Moreover, a single electrode could be used to detect the pH of multiple environments by mild rinsing with deionized water and is reusable for more than 500 cycles without significant potential drift. These low-cost and reusable electrodes with linear Nernstian response are promising candidates for for diverse pH-sensing applications.

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