Over the past decade, perovskite-based nanomaterials have gained notoriety within the scientific community and have been used for a variety of viable applications. The unique structural properties of these materials, namely good direct bandgap, low density of defects, large absorption coefficient, high sensitivity, long charge carrier lifetime, good selectivity, acceptable stability at room temperature, and good diffusion length have prompted researchers to explore their potential applications in photovoltaics, light-emitting devices, transistors, sensors, and other areas. Perovskite-based devices have shown very excellent sensing performances to numerous chemical and biological compounds in both solid and liquid mediums. When used in sensing devices, Perovskite nanomaterials are for the most part able to detect O₂, NO₂, CO₂, H₂O, and other smaller molecules. This review article looks at the use of lead-free halide perovskite materials for humidity sensing. A complete description of the underlying mechanisms and charge transport characteristics that are necessary for a thorough comprehension of the sensing performance will be provided. An overview of considerations and potential recommendations for the creation of new lead-free perovskite nanostructure-based sensors is presented.

The detection of toxic gases has long been a priority in industrial manufacturing, environmental monitoring, medical diagnosis, and national defense. The importance of gas sensing is not only of high benefit to such industries but also to the daily lives of people. Graphene-based gas sensors have elicited a lot of interest recently, due to the excellent physical properties of graphene and its derivatives, such as graphene oxide (GO) and reduced graphene oxide (rGO). Graphene oxide and rGO have been shown to offer large surface areas that extend their active sites for adsorbing gas molecules, thereby improving the sensitivity of the sensor. There are several literature reports on the promising functionalization of GO and rGO surfaces with metal oxide, for enhanced performance with regard to selectivity and sensitivity in gas sensing. These synthetic and functionalization methods provide the ideal combination/s required for enhanced gas sensors. In this review, the functionalization of graphene, synthesis of heterostructured nanohybrids, and the assessment of their collaborative performance towards gas-sensing applications are discussed.

A functionalized polyoxometalate/graphitic carbon nitride (PMo₁₂/g-C₃N₄) composite has been constructed to promote direct electron and ion exchange based on a facile, rapid wetness incipient method. The PMo₁₂ displayed a natural affinity towards the carbon support which facilitated enhanced reversible redox processes with surface-controlled electron diffusion. The g-C₃N₄-functionalized PMo₁₂ composite promoted effective oxidation and reduction of the Keggin molecule addenda atoms with reduced overpotential without the mediation of a polymeric linker to promote their exposure and interaction. The g-C₃N₄ offered increased surface area for anchoring PMo₁₂, structural stability at increased temperatures, and repeated cycling as well as control of the density and position of PMo₁₂ as probed by scanning electron microscopy and nuclear magnetic resonance spectroscopy, respectively. These results demonstrate that PMo₁₂ clusters are sensitive to their local environment, including the interaction with the support, which stimulated enhanced current mobility.

Zinc cobaltite (ZnCo₂O₄) is a ternary metal oxide found in spinel with promising properties for various applications. Optimizing its catalytic activity requires an understanding of its electrochemical behavior. The electrochemical properties of ZnCo₂O₄ have significantly improved due to recent developments in nanostructuring, doping, surface modification, hybridization, structural engineering, and electrochemical activation. These improvements have inspired and motivated researchers by presenting the latest developments in the field. The spinel structure, coupled with the redox properties of cobalt ions, semiconducting characteristics, and electrocatalytic potential, positions ZnCo₂O₄ as a versatile material for several electrochemical energy storage and conversion systems. This review explores these advancements; the notable properties of ZnCo₂O₄; and its applications in sensors, batteries, photovoltaics, and supercapacitors.

Meeting our current energy demands requires a reliable and efficient renewable energy source that will bring balance between power generation and energy consumption. Organic photovoltaic cells (OPVs), perovskite solar cells and dye-sensitized solar cells (DSSCs) are among the next-generation technologies that are progressing as potential sustainable renewable energy sources. Since the discoveries of highly conductive organic charge-transfer compounds in the 1950s, organic semiconductors have captured attention. Organic photovoltaic solar cells possess key characteristics ideal for emerging next-generation technologies such as being nontoxic, abundant, an inexpensive nanomaterial with ease of production, including production under ambient conditions. In this review article, we discuss recent methods developed towards improving the stability and average efficiency of nanostructured materials in OPVs aimed at sustainable agriculture and improve land-use efficiency. A comprehensive overview on developing cost-effective and user-friendly organic solar cells to contribute towards improved environmental stability is provided. We also summarize recent advances in the synthetic methods used to produce nanostructured active absorber layers of OPVs with improved efficiencies to supply the energy required towards ending poverty and protecting the planet.