Ultra-fast Microwave Synthesis of ZnO Nanowires and their Dynamic Response Toward Hydrogen Gas

Ultra-fast and large-quantity (grams) synthesis of one-dimensional ZnO nanowires has been carried out by a novel microwave-assisted method. High purity Zinc (Zn) metal was used as source material and placed on microwave absorber. The evaporation/oxidation process occurs under exposure to microwave in less than 100 s. Field effect scanning electron microscopy analysis reveals the formation of high aspect-ratio and high density ZnO nanowires with diameter ranging from 70 to 80 nm. Comprehensive structural analysis showed that these ZnO nanowires are single crystal in nature with excellent crystal quality. The gas sensor made of these ZnO nanowires exhibited excellent sensitivity, fast response, and good reproducibility. Furthermore, the method can be extended for the synthesis of other oxide nanowires that will be the building block of future nanoscale devices

Sonoelectrochemistry: ultrasound-assisted organic electrosynthesis

The application of ultrasound with electrochemistry in organic chemistry (known as organic sonoelectrochemistry) accelerates the activation process of chemical reactions. This hybrid technology enhances electrical efficiency and modifies and increases the product yield. Moreover, it facilitates the mass transfer phenomena and the processes of cleaning, degassing, and activation of the electrode surfaces; maintains higher current densities for efficient chemical transformations; and also works efficiently for mixing of reactants in multiphase systems. The ultrasound technology has a prominent effect in heterogeneous reaction systems especially during the solid (electrode)–liquid (electrolytic mixture) interfacial cavitation process. The ultrasound technology gains attention due to its fundamental and positive effect in organic chemistry to make possible the challenging electrosynthetic processes. Herein, we report the sonoelectrosynthetic methods that will help researchers to understand and apply this methodology for scale-up of processes in organic synthesis and also in more modern innovative continuous-flow organic electrochemistry. Therefore, this study will provide valuable insight into the effects caused by ultrasound-assisted electrosynthesis and how this technology revolutionizes organic synthesis. It is believed that the hybrid sonoelectrochemical synthesis serves as a solution to the limitations of the commercialization of synthetic processes and offers a new, modern aspect in organic synthesis in a clean, hassle-free, and sustainable approach

Sonochemical-Assisted In Situ Electrochemical Synthesis of Ag/α-Fe₂O₃/TiO₂ Nanoarrays to Harness Energy from Photoelectrochemical Water Splitting

Numerous protocols in heterostructure engineering hold promise for effectively improving the optical properties of nanomaterials for energy-harvesting applications. In this work, we successfully fabricated Ag/α-Fe₂O₃/TiO₂ heterostructures via electrochemical anodization assisted by pulse sonication. The morphological features of the silver (Ag) deposited on α-Fe₂O₃/TiO₂ showed a layered distribution of the α-Fe₂O₃ nanoparticles (NPs) over the TiO₂ nanotube arrays (NTAs), whereas Ag existed in a pseudocubical form. X-ray diffraction (XRD) patterns and X-ray photoelectron spectrometer (XPS) analysis validated the formation of α-Fe₂O₃ and anatase TiO₂ crystalline phases and Ag/α-Fe₂O₃/TiO₂ heterostructure. The diffuse reflectance spectroscopy (DRS) UV–vis spectroscopy results displayed a gradual decrease in the band gap with enhanced absorption in the visible region of the spectrum due to optically active heterostructure formation in the order Ag/α-Fe₂O₃/TiO₂ (470 nm) > α-Fe₂O₃/TiO₂ (424 nm) > TiO₂ (386 nm). The DRS absorption spectrum of Ag/α-Fe₂O₃/TiO₂ also exhibits a characteristic plasmon shoulder of Ag at ∼420 nm. The photocurrent density of Ag/α-Fe₂O₃/TiO₂ (2.59 mA/cm²) is almost 2.5- and 5-fold higher than that of α-Fe₂O₃/TiO₂ (1.05 mA/cm²) and pristine TiO₂ (0.54 mA/cm²), respectively, which can be related with the plasmonic behavior of Ag and lower band gap of α-Fe₂O₃. The results of electron impedance spectroscopy (EIS) analysis also showed facile charge transfer in the same order observed using UV–vis spectroscopy. These results demonstrate the effectiveness of the in situ electrochemical protocol to fabricate tunable heterostructures for efficient solar-driven water splitting

Interfacial photoelectrochemical catalysis: solar-induced green synthesis of organic molecules

Many oxidation and reduction reactions in conventional organic synthesis rely on harsh conditions, toxic or corrosive substances, and environmentally damaging chemicals. In addition, competing reactions may take place, some of which produce hazardous waste products and, therefore, reaction selectivity suffers. To overcome such synthetic drawbacks, an enormous effort is being devoted to find alternative processes that operate much more efficiently, requiring milder conditions to contribute to a greener economy and provide urgently needed new pathways with enhanced selectivity. Fortunately, there is a strategy that has attracted global interest from multiple disciplines that involves the use of sunlight to perform artificial photosynthesis, in which a photoelectrochemical cell splits water into hydrogen fuel, reduces CO2 into “solar” fuels, and more recently, convert organic chemicals into higher value products. Recently, photoanode and photocathode materials have emerged as useful tools to perform organic oxidations and reductions for the synthesis of important molecules, other than just hydrogen or oxygen. Whereas many studies have focused on the degradation of unwanted and dangerous chemicals, solar‐induced organic transformations have attracted much less attention. This Minireview summarizes some of latest research efforts in using photoelectrochemical cells to facilitate organic oxidation and reduction reactions to avoid valuable substances while avoiding toxic reagents and expensive precious metal catalysts. Future developments that will enable such technologies to broaden their scope are also considered