Fabrication of hierarchically mesoporous NiO nanostructures and their role in heterogeneous photocatalysis and sensing activity

The exposure of high surface area with NiO mesoporous material and assembling hetero-structures by incorporating TiO₂ nanoparticles represent a valuable way for producing high-performance photocatalysts and sensitive electrochemical sensor. Acid base free modified sol–gel route was used to synthesize highly porous and photoactive NiO, NiO/TiO₂ and NiO/TiO₂/Dextran catalysts. Powder X-ray diffraction analysis, UV–Vis spectroscopy, Energy dispersive X-ray (EDX) spectroscopy, Scanning electron microscopy, Transmission electron microscopy, Atomic force microscopy, Thermo-gravimetric analysis and Brunauer-Emmitt- Teller (BET) adsorption isotherm techniques were used to characterize the materials. The as-synthesized mesoporous NiO/TiO₂/Dextran is crystalline, pure and highly porous with the surface area of 225 m²g^− 1. The mesoporous NiO/TiO₂/Dextran exhibited significant photochemical degradation capability for Malachite Green Oxalate (MG-Oxalate) dye. It was found that MG-Oxalate dye of 20 ppm concentration has been completely degraded and decolorized with the optimum NiO/TiO₂/Dextran catalyst dose of 0.8 g/L in 60 min at pH 8.0. The reaction kinetics revealed that the photocatalytic degradation of MG-Oxalate dye follows pseudo-first-order reaction kinetics with the rate constant, k of 0.049 min^− 1 and can be recycled up to 10 cycles. An electrochemical sensor was developed based on NiO/TiO₂/Dextran modified Glassy carbon electrode (GCE) for sensitive and selective sensing of dye. The differential pulse voltammetry response of NiO/TiO₂/Dextran/GCE for MG-Oxalate shows linear dependence in the concentration range of 1–25 ppm with a limit of detection 0.0056 µM and Sensitivity 0.16 µA mM^− 1 cm^− 2.