In this paper, we present a novel, one-step synthesis of SnO 2 nanoparticle–CeO 2 nanorod sensing material using a surfactant-mediated hydrothermal method. The bifunctional utility of the synthesized sensing material toward room-temperature sensing of CO gas and low-concentration optosensing of arsenic has been thoroughly investigated. The CeO 2 –SnO 2 nanohybrid was characterized using sophisticated analytical techniques such as transmission electron microscopy, X-ray diffraction analysis, energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy, and so forth. The CeO 2 –SnO 2 nanohybrid-based sensor exhibited a strong response toward CO gas at room temperature. Under a low concentration (3 ppm) of CO gas, the CeO 2 –SnO 2 sensing material showed an excellent response time of 21.1 s for 90% of the response was achieved with a higher recovery time of 59.6 s. The nanohybrid sensor showed excellent low-concentration (1 ppm) sensing behavior which is ∼6.7 times higher than that of the pristine SnO 2 sensors. The synergistically enhanced sensing properties of CeO 2 –SnO 2 nanohybrid-based sensors were discussed from the viewpoint of the CeO 2 –SnO 2 n–n heterojunction and the effect of oxygen vacancies. Furthermore, the SnO 2 –CeO 2 nanoheterojunction showed luminescence centers and prolonged electron–hole recombination, thereby resulting in quenching of luminescence in the presence of arsenate ions. The photoluminescence of CeO 2 –SnO 2 is sensitive to the arsenate ion concentration in water and can be used for sensing arsenate with a limit of detection of 4.5 ppb in a wide linear range of 0 to 100 ppb.

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A ternary nanohybrid CuO/Mn3O4/CeO2 was developed in the present work using a co-precipitation-assisted hydrothermal method. The designed photocatalyst's structural, morphology, elemental composition, electronic states of elements, and optical properties were studied using corresponding analytical techniques. Results from PXRD, TEM/HRTEM, XPS, EDAX, and PL showed that the desired nanostructure had formed. Using Tauc's energy band gap plot, it was determined that the nanostructures band gap was ~ 2.44 eV, which showed the band margins of the various moieties, CeO2, Mn3O4, and CuO, had modified. Thus, improved redox conditions led to a substantial decrease in the recombination rate of electron–hole pairs, which was further explained by a PL study in that charge separation plays a key role. Under exposure to visible light irradiation for 60 min, it was revealed that the photocatalyst achieved 98.98% of photodegradation efficiency for malachite green (MG) dye. The process of photodegradation proceeded according to a pseudo-first-order reaction kinetic model with an excellent rate of reaction of 0.07295 min−1 with R2 = 0.99144. The impacts of different reaction variables, inorganic salts, and water matrices were investigated. This research seeks to create a ternary nanohybrid photocatalyst with high photostability, visible spectrum activity, and reusability up to four cycles.

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