The influence of M site substitution on the properties of MCr₂O₄ nanoceramics is examined in this research. This study is an attempt to correlate the structural, morphological and optical properties of M site-modified chromites. The MCr₂O₄ nanoceramics-CuCr₂O₄, CoCr₂O₄ and NiCr₂O₄ were synthesized by a wet-chemical sol–gel auto-combustion method, and were annealed for 4 hours at 900℃. X-ray diffraction investigation revealed that the XRD pattern of CuCr₂O₄ matched with ICSD reference no. 00-034-0424, which confirmed the formation of a tetragonal structure, and the XRD pattern of CoCr₂O₄ and NiCr₂O₄ matched with JCPDS card no. 04-0763 and 89-6615, respectively, which confirmed the single-phase cubic crystal structure with space group Fd-3m. The crystallite sizes calculuated from the Scherrer equation were found to be 9.86nm, 6.73nm and 10.73nm for CuCr₂O₄, CoCr₂O₄ and NiCr₂O_4, respectively. Other parameters, including crystal structure, micro strain, lattice constant, unit cell volume, X-ray density, packing factor, and stacking fault of the calcined powder samples, were determined from data acquired from the X-ray diffractometer. Energy dispersive X-ray spectroscopy (EDX) was employed to confirm the appropriate chromite elements in their expected stoichiometric proportions were free of other impurities. Identification of the functional groups of the samples was performed using Fourier Transform Infrared Spectroscopy (FTIR). The absorption bands characteristic of the tetrahedral and octahedral coordination compounds of the spinel structure were found between 450 and 750cm^-1 for all 3 samples in the spectrum. From the UV-absorption spectra, using Tauc’s plot, the energy bandgap values for CuCr₂O₄, CoCr₂O₄ and NiCr₂O₄ were measured to be 1.66 eV, 1.82 eV and 2.01 eV, respectively. The dielectric properties of the chromites were studied using an LCR meter. Frequency-dependent dielectric properties, including Dielectric constant and Tangent loss, were calculated. These findings suggest the feasibility of the synthesized chromites for optical devices and other optoelectronic applications.

Micro-electro-magnetic Vibration Energy Harvesters: Analysis and Comparative Assessment

Abstract

The development of micro-electromagnetic vibration energy harvesters (MEMVEHs) plays a crucial role in advancing self-powered nanophotonic, nanoelectronic, and nanosensor systems. As energy autonomy becomes critical for miniaturized devices, MEMVEHs offer a sustainable power source for low-power nanodevices operating in wireless sensor networks, wearable electronics, and biomedical implants. This study provides a comparative assessment of MEMVEH technologies and evaluates their integration potential within next-generation nanoscale systems, enabling enhanced performance, longevity, and energy efficiency of emerging nanotechnologies.
Electromagnetic vibration energy harvesters (EMEHs) based on microelectromechanical systems (MEMS) technology are promising solutions for powering small-scale, autonomous electronic devices. In this study, two electromagnetic vibration energy harvesters based on microelectromechanical (MEMS) technology are presented. Two models with distinct vibration structures were designed and fabricated . A permanent magnet is connected to a silicon vibration structure (resonator) and a tiny wire-wound coil as part of the energy harvester. The coil has a total volume of roughly 0.8 cm3. Two energy harvesters with various resonators are tested and compared.
Model A's maximum load voltage is 163 mV, whereas Model B's is 208 mV. A maximum load power of 59.52 μW was produced by Model A at 347 Hz across a 405 Ω load. At 311.4 Hz, Model B produced a maximum load power of 149.13 μW while accelerating by 0.4 g. Model B features a larger working bandwidth and a higher output voltage than Model A. Model B performs better than Model A in comparable experimental settings. Simple study revealed that Model B's electromagnetic energy harvesting produced superior outcomes. Additionally, it indicates that a non-linear spring may be able to raise the output voltage and widen the frequency bandwidth.

Keywords

Electromagnetic, Energy, Harvester, MEMS, Model, Load, Resonators, Voltage, Frequency, Bandwidth.

The development of efficient, durable, cost-effective, and scalable electrocatalysts for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is essential for advancing water-splitting technologies in sustainable energy systems. In this work, we report the synthesis of a Sn-doped NiFe layered double hydroxide (LDH)/carbon nanotube (CNT) composite as a bifunctional electrocatalyst, with particular emphasis on its OER activity. The Sn-NiFe LDH was synthesized via a simple co-precipitation method, followed by its integration with CNTs using a wet impregnation approach.

Comprehensive characterizations were performed using X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM). Electrochemical properties were investigated in 1 M KOH using linear sweep voltammetry (LSV), cyclic voltammetry (CV), electrochemical active surface area (ECSA), electrochemical impedance spectroscopy (EIS), and Tafel slope analysis.

The optimized Sn-NiFe-4 LDH/CNTs electrocatalyst exhibited outstanding OER performance, achieving a low overpotential of 203 mV at 10 mA cm^-2 and a Tafel slope of 13 mV dec^-1. For HER, the material showed an overpotential of 488 mV at the same current density, with a Tafel slope of 104.07 mV dec^-1. These results highlight the potential of Sn-doped NiFe LDH/CNT composites as effective, durable, and scalable bifunctional electrocatalysts, paving the way for cost-efficient and scalable hydrogen production through overall water splitting.

Efficient and robust electrocatalysts for the hydrogen evolution reaction (HER) are essential to support the transition to clean and sustainable energy systems. Transition metal chalcogenides, particularly those with tunable compositions, have shown great promise due to their intrinsic catalytic activity and cost-effectiveness. In this study, a quaternary NiWSSe electrocatalyst was developed by integrating nickel (Ni), tungsten (W), sulfur (S), and selenium (Se) to enhance HER performance through synergistic electronic effects and optimized active sites. The catalysts were synthesized via a hydrothermal method followed by thermal annealing under a reducing atmosphere. Structural and compositional analyses were performed using XRD, SEM, EDS, and XPS techniques. Electrochemical performance was evaluated in 0.5 M H₂SO₄ using linear sweep voltammetry (LSV), Tafel slope analysis, and electrochemical impedance spectroscopy (EIS). Among the various compositions tested, Ni_0.25W_0.75SSe exhibited the highest catalytic activity, achieving a low overpotential of 137 mV at a current density of 10 mA cm^-2 and a Tafel slope of 43.07 mV dec^-1. The Ni_0.25W_0.75SSe catalyst exhibits a low charge transfer resistance (R_ct) of 40 Ω, as revealed by EIS measurements, indicating enhanced electrical conductivity and faster HER kinetics. The enhanced performance is attributed to W-induced electronic modulation and Se-associated defect sites, which collectively promote efficient charge transport and increase the availability of catalytically active edge sites. Overall, Ni_0.25W_0.75SSe demonstrates excellent HER activity and stability, making it a promising material for scalable hydrogen production applications.

The production of titanium dioxide generates substantial quantities of wastes and by-products, especially spent acids. Conventional treatment methods require large amounts of alkalis, leading to the formation of secondary wastes such as red gypsum. This study aims to valorize titanium dioxide spent acids from India through the synthesis of value-added products, specifically nano-sized iron phosphate for energy-related applications. The process involves a comprehensive evaluation of the physical and chemical properties of the spent acids, the selective removal of impurities, the oxidation of Fe (II) to Fe (III), and the precipitation of iron as FePO₄ using an appropriate phosphoric source. Advanced characterization techniques, including XRF, XRD, SEM, TEM, and ICP-MS, were employed. TEM analysis confirmed that the synthesized iron phosphate exhibits a nanoscale particle size (below 200nm), while SEM revealed uniform particle morphology. ICP-MS results showed low levels of impurities in the final product, demonstrating its suitability for high-performance applications.
The TEM images collectively reveal the successful synthesis of nanoscale, plate-like or flake-like particles, with uniform shape, good dispersion, and thin morphology across multiple magnifications.
Morphology shows plate-like, flake-like, or nanosheet structures with polygonal shapes and varied orientations. Sharp and angular edges typically suggest a crystalline nature, while variations in contrast imply stacking or thickness differences.

The production and consumption of non-renewable energy are causes of environmental degradation. To control these effects, a higher percentage of renewable energy should be used in activities instead of non-renewable energy sources. One alternative to solve this problem is to modify the efficiency of generators, converters and storage devices through the use of nanomaterials. Synthesis of these materials in their traditional form requires a large investment of resources and generally a slow yield. However, with methods such as DFT, we can gain access to their physical properties in an accelerated manner. On the other hand, using machine learning (ML), minimal computational resources are needed to make predictions. In this work, ML was used to predict ABO3-type perovskites of the groups Pm-3m, Pnma, P4/mmm, R-3c, I4/mcm, Pbnm, P2-I/c, C2/m, P4mm, Amm2/R3c and Imma, obtaining a total of 1287 compounds. We used as descriptors the formation energy, the energy gap, the polarity (1 if they were not centrosymmetric and 0 if they were), the magnetization and the energy above the contour. Our proposed function for evaluating and prioritizing piezoelectric materials is as follows:

F=P(α·stability +β·norm_band_gap+γ·norm_formation_energy+δ·norm_magnetization

We evaluated four ML models: random forest, XGBoost, gradient boosting and a multilayer perceptron. The best model achieved an R2 value of 0.994 and an RMSE of 0.006; in this case, the best model was XGBoost. According to this model, the three best candidates for piezoelectrics are LaTiO₃, LiNbO₃ and BaTiO₃. With DFT, we calculated the piezoelectric tensor of this material, dij, and the polarization change Pi under deformation, ei.

Secnidazole, a second-generation nitroimidazole, is widely utilized for its high efficacy in treating infections such as bacterial vaginosis, amoebiasis, and giardiasis, especially in the treatment of genital infections in females. Herein, a smartphone-based sensing platform with a UV lamp has been developed, in combination with a microfluidic-based paper device, to enable a visual, quick, instrument-free, sensitive, and quantitative analysis in real-time conditions. Through a fluorescence "turn-off" response, the platform demonstrated the feasibility of visual quantitative drug detection. In addition to having a high sensitivity for the label-free and on-site detection of secnidazole, our suggested smartphone-assisted N-CDs@WS₂ composite demonstrated a prominent anti-interference capability to ensure accurate point-of-care identification of secnidazole based on the fluorescent output, successfully removing the effects of environmental fluctuations. The N-CDs@WS₂-based fluorescent sensor has a limit of detection (LOD) of 0.117 µM and 117 nM for secnidazole, while its limit of quantification (LOQ) is 0.3573 µM and 357 nM. The fact that such a portable sensor has effectively achieved real-time monitoring of secnidazole in real blood serum samples with encouraging outcomes opens up a promising path to accurate on-site determination. The detection efficiency of the suggested fluorescent sensor was confirmed through an LC-MS analysis and the UPLC method, which is recommended by the US Environmental Protection Agency. As indicated by the recoveries from the UPLC and LC-MS analyses and the fluorescence of N-CDs@WS2, the current sensor is capable of quantitatively analyzing secnidazole in real samples.

The present work demonstrates a green route to synthesizing unique-structural-property ZnO nanostructures with enhanced photocatalytic efficiency, utilizing 80 ml of aqueous leaf extract from Azadirachta indica and Moringa oleifera. The crystalline nature of the synthesised ZnO NPs -80-A and M was examined using X-ray diffraction (XRD), where the peak positions at Bragg angles (2θ) of 31.8°, 34.42°, 36.57°, 56.42°, 62.56°, and 66.40° corresponded to Miller indices of (100),(002), (101), (110), (103), and (200), respectively, confirming the hexagonal wurtzite structure; however, the Fourier transform spectroscopy (FT-IR) analysis confirmed the functional groups' purity, and the presence of broad absorption bands appearing at 3340-3400 cm⁻¹ indicated the O-H stretching vibrations of absorbed H₂O molecules, while another strong peak around 476 cm⁻¹ indicated the stretching mode of crystalline ZnO. To examine the photocatalytic activity, 0.1 g/L of ZnO NPs-A and ZnO-NPs-M was immersed in 100 mL of 10 ppm brilliant cresyl blue and Malachite green dye solution, stirred for 25 minutes, and kept in the dark to establish adsorption–desorption equilibrium, followed by open irradiation under sunlight. During irradiation, a 3 ml suspension was taken out at intervals of 20 minutes; the absorbance was measured, which decreased with time. Moreover, the ZnO NPs-A displayed good photocatalytic activity after 160 min of sunlight exposure. The degradation of the dyes followed pseudo-first-order kinetics.

Graphene is renowned for its exceptional electrical and mechanical properties; however, its lack of an intrinsic bandgap leads to a limited on/off current ratio, restricting its role as a direct replacement for silicon in logic devices. Nevertheless, its integration with silicon-based platforms offers new opportunities in broadband nanophotonic and optoelectronic applications. This hybrid strategy has the potential to improve the performance of key components such as photodetectors, modulators, and polarizing elements.

In this context, graphene oxide (GO) emerges as a promising material due to its high transparency in the visible range, making it suitable for use as a transparent electrode and optical coating. Here, we investigate the role of dip-coated GO thin films in enhancing the electro-optical response of n-type crystalline silicon. GO layers were deposited via immersion onto Si/SiO₂ substrates, and the resulting heterostructures were characterized through Raman spectroscopy and cyclic voltammetry.

Raman analysis revealed the slight broadening (~0.7 cm⁻¹) of the silicon TO phonon mode at 514 cm⁻¹, indicating the presence of local interfacial strain. Cyclic voltammetry measurements demonstrated a marked increase in the photocurrent compared to uncoated silicon, suggesting improved interfacial charge transfer and the formation of a GO-induced p-type inversion layer. These results highlight the potential of GO as a functional interlayer in the development of advanced silicon-based nano-optoelectronic and photoelectrochemical devices.

This work introduces a self-shielded optical nanoantenna probe designed for sub-diffraction confinement and multifunctional nanophotonics applications. Our approach utilizes a simplified wet chemical etching process to create a wedge-shaped aperture in a a photosensitive single‑mode optical fiber, yielding a robust, compact, and cost-effective platform for advanced optical manipulation and quantum sensing applications. The wedge geometry controls the formation of a high-intensity annular region with a well-defined low-intensity center, desirable for optical trapping, biosensing, high-resolution imaging, and the potential excitation of quantum emitters, such as nitrogen vacancy (NV) centers in diamonds. Furthermore, placing a microsphere in the nanoantenna’s vicinity can enable the generation of a classical photonics nanojet alongside the non-diffracting bottle beam, thereby offering additional functionality and control for a range of multimodal applications. Our results show that this wedge-tipped nanoantenna maintains strong field confinement, with a spot size and depth of field comparable to those of previously reported microsphere-assisted nanojets, while retaining greater robustness, reproducibility, and ease of fabrication. The ability to generate both non-diffracting bottle beams and enhanced nanojets using a single platform paves the way for developing integrated nanophotonics, optical tweezers, high-resolution imaging, biosensing technologies, and platforms for investigating light–matter interactions with nitrogen vacancy (NV) color centers in diamonds and other materials.