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The scarcity of fuels, high pollution levels, climate change, and other major environmental issues are critical challenges that modern societies are facing, mostly originating from fossil fuels-based economies. These challenges can be addressed by developing green, eco-friendly, inexpensive energy sources and energy storage devices. Electrochemical energy storage materials possess high capacitance and superior power density. To engineer highly efficient next-generation electrochemical energy storage devices, the mechanisms of electrochemical reactions and redox behavior must be probed in operational environments. They can be studied by investigating atomic and electronic structures using in situ x-ray absorption spectroscopy (XAS) analysis. Such a technique has attracted substantial research and development interest in the field of energy science for over a decade. The mechanisms of charge/discharge, carrier transport, and ion intercalation/deintercalation can be elucidated. Supercapacitors generally store energy by two specific mechanisms—pseudocapacitance and electrochemical double-layer capacitance. In situ XAS is a powerful tool for probing and understanding these mechanisms. In this Review, both soft and hard x rays are used for the in situ XAS analysis of various representative electrochemical energy storage systems. This Review also showcases some of the highly efficient energy and power density candidates. Furthermore, the importance of synchrotron-based x-ray spectroscopy characterization techniques is enlightened. The impact of the electronic structure, local atomic structure, and electronically active elements/sites of the typical electrochemical energy storage candidates in operational conditions is elucidated. Regarding electrochemical energy storage mechanisms in their respective working environments, the unknown valence states and reversible/irreversible nature of elements, local hybridization, delocalized d-electrons spin states, participation of coordination shells, disorder, and faradaic/non-faradaic behavior are thoroughly discussed. Finally, the future direction of in situ XAS analysis combined with spatial chemical mapping from operando scanning transmission x-ray microscopy and other emerging characterization techniques is presented and discussed. [ABSTRACT FROM AUTHOR]

The Ag-ZnO nanocomposite thin films of varying Ag contents were synthesized successfully using simultaneous RF- and DC-magnetron sputterings on quartz substrates. The as-prepared nanocomposites were then annealed in a mixture of hydrogen plus argon environment (95%Ar+5%H2) at a temperature of 300 °C. The pristine and annealed films were then subjected to synchrotron XRD to study for any possible structural modifications induced in the films. The crystalline behavior of the hexagonal wurtzite structure of ZnO, in the pristine and annealed samples of Ag-ZnO nanocomposites, was evident in samples prepared at low Ag content, but with increasing Ag content, the crystalline behavior of the hexagonal wurtzite structure was suppressed. FESEM utilized to study the formation of nanoparticles in the films revealed the non-uniform distribution and agglomeration of nanoparticles increases as the Ag content increases. A broad surface plasmon region in the range of 380–450 nm was observed for different compositions with remarkable blue and red shifts using UV-visible spectroscopy. These high-quality Ag-ZnO nanocomposite thin films with tunable optical properties were then used as surface-enhanced Raman spectroscopy (SERS) substrates for the detection of rhodamine B (RhB) at low concentrations of 10−6 M. The detection of RhB in trace amounts is important in the current scenario as wastewater discharge is a serious threat to our ecosystem. [ABSTRACT FROM AUTHOR]

The exploration of zinc oxide (ZnO) has seen rapid growth due to its wide bandgap, high thermal conductivity, and high electron mobility within its nanostructures, making it highly valuable for applications in electronic and optical devices. This study involves the deposition of ZnO nanostructures onto a quartz substrate using the thermal evaporation deposition technique. The research delves into the influence of various annealing environments on morphology and electronic/atomic structures. X-ray Diffraction (XRD) analysis reveals the development of the ZnO phase with a preferred orientation when annealed in a mixture of hydrogen and argon gases. It was observed that the films do not transform into complete ZnO for the as-prepared and for lower temperatures (< 400 °C). Annealing at lower temperatures or room temperature retains the metallic Zn. When subjected to higher annealing temperatures in the presence of oxygen and ambient conditions, formation of ZnO hexagonal wurtzite structures was evident. A wide variation in the morphology was observed for films annealed in different annealing environments, from petal-like structures to rods. Both the band edge and defect emissions using photoluminescence were observed to vary with varying annealing conditions. In-situ XANES uncovers the reduction of Zn and metallic nature noticed in the as-prepared sample and argon annealing at 400 °C. A higher charge transfer by Zn with a prominent delocalization of Zn 4p state was observed in oxygen annealing environment at 400 °C with an enhanced coordination of Zn–O and Zn–Zn. These distinct photoluminescence emissions from the films were correlated to the electronic structure and local atomic structure. Further, this investigation provides a path to develop next-generation optoelectronic devices. [ABSTRACT FROM AUTHOR]

Al-doped LiMn2O4 nanostructures are prepared by a single-step solution combustion method. The phase and vibrational mode of the prepared nanostructures are confirmed by XRD and Raman analyses. The SEM showed nanorod and nanosphere morphologies of the prepared samples. The nanostructures have a high specific surface area of 29.75 m2g−1 and a high specific capacitance of 361 Fg−1, in addition to better cyclic stability and high rate capability of oleic acid-based Al-doped LiMn2O4 electrodes. The nanostructures have a better performance in a stable electrolyte solution, a desirable electrolyte for supercapacitor applications under ambient conditions. [ABSTRACT FROM AUTHOR]

Young stage neem leaf (Azadirachta indica) was collected at Thiruvallur district in Tamil Nadu, South India. Multi-elemental analysis of neem leaf was carried out using non-destructive techniques (NDT) of proton-induced X-ray emission (PIXE, 2.5 MeV) which is one of the well-known surface chemical sophisticated analytical methods of ion beam analyses (IBA). From the emitted X-ray output of the target specimen specimen fingerprint multi-elements such as, aluminium (Al), silicon (Si), phosphorus (P), sulphur (S), chloride (Cl), potassium (K), calcium (Ca), titanium (Ti), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn) and strontium (Sr) are found to be present in the leaf in different ppm levels. Among the elements, silicon (Si, 42034 + 1198.0 ppm) and potassium (K, 28985 + 747.8 ppm) showed the highest concentration. Minor elements (Mn, Sr, Fe, Zn, Cu and Ti) are observed in the neem plant. The variation in elemental concentration in the leaf may be due to soil, water, etc. However, there are no toxic elements observed like arsenic and lead in the leaf. Further, though the presence of different medicinal values in the target specimen chemical multi-elements observed in ppm level. However, there are more chemical analysis to be required for the functionalization of active biomedical applications for these kinds of medicinal species. [ABSTRACT FROM AUTHOR]

A Correction to this paper has been published: https://doi.org/10.1007/s12011-020-02522-z [ABSTRACT FROM AUTHOR]