NanoNEXT

Effect of Mg Doping Level on the Physical Properties of CuO Nanoparticles and Fabrication of p-MDC/n-Si Junction Diodes for Optoelectronic Applications

Rajapandi P — 2026-09-24

Magnesium doping offers a route to modify the structural and optical properties of copper oxide (CuO) nanoparticles for optoelectronic devices. This study investigates the influence of Mg concentration on CuO nanoparticles and evaluates a p-type Mg-doped CuO/n-type silicon (p-MDC/n-Si) heterojunction photodiode. Undoped and Mg-doped CuO nanoparticles containing 1, 3, 6, and 9 wt% Mg were synthesized by coprecipitation. Their structural, morphological, elemental, vibrational, and optical properties were characterized using X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy, and photoluminescence measurements. X-ray diffraction confirmed a monoclinic CuO phase, with the smallest average crystallite size of 27 nm obtained at 3 wt% Mg. Electron microscopy revealed aggregated grains with varying morphologies, while elemental analysis detected Cu, O, and Mg. Optical measurements indicated Mg-dependent changes in absorption and estimated band gaps ranging from 1.3 to 2.5 eV. Infrared spectra exhibited Cu–O vibrations at 474 and 606 cm⁻¹, and photoluminescence peaks occurred at 364, 383, and 414 nm. Nanoparticles containing 9 wt% Mg were selected for diode fabrication. Current–voltage measurements demonstrated light-dependent electrical behavior, with the ideality factor decreasing from 6.8 in darkness to 3.9 under illumination. The diode exhibited 1085% photosensitivity and a reported specific detectivity of 2.1 × 10⁹ Jones. These findings indicate the potential of Mg-doped CuO/silicon heterojunctions for photodetection, subject to further device validation and systematic measurements of stability and response speed.

Green Nanoparticle Synthesis using Xerophytic Medicinal Plants: Linking Stress-Adapted Phytochemistry with Nanoparticle Formation and Surface Properties

Harsh Bhardwaj — 2026-09-18

Green nanoparticle synthesis using plant extracts avoids the toxic reagents and high energy demands of chemical reduction methods, but most published work treats plant identity as interchangeable and rarely identifies which phytochemicals actually drive metal-ion reduction. Xerophytic and semi-arid medicinal flora carry measurably elevated concentrations of redox-active phenolics and flavonoids relative to unstressed vegetation, yet Indian arid and semi-arid species specifically have received little of the same nanoparticle synthesis attention already given to comparable flora in Sudan and southern Africa. This review draws together the phytochemical rationale for using such flora as synthesis precursors, the mechanism connecting specific compounds to metal-ion reduction and surface capping, and a species-level survey of eleven plants across nineteen separately reported nanoparticle systems. Particle size varied by more than an order of magnitude with no consistent relationship to plant genus or precursor metal. Antimicrobial activity was confirmed in seventeen of the nineteen systems, and the phytochemical capping layer itself contributed measurable antimicrobial activity independent of the metal core. Reaction conditions, including temperature, pH, and extract-to-metal ratio, shaped particle outcomes as much as plant chemistry did. Reproducibility, compound-level mechanistic resolution, and long-term safety evidence remain unresolved. Three species originally scoped for this review, Capparis decidua, Balanites aegyptiaca, and Tecomella undulata, lacked adequate species-specific literature. No related species were substituted in their place.

High-Entropy Oxides for Energy Storage and Electrocatalysis: Defect Chemistry, Entropy Stabilization, and Structure–Performance Design Rules

Pradeep I — 2026-08-08

High-entropy oxides (HEOs) are an important class of compositionally complex oxide materials for energy storage and electrocatalysis. Their significance does not arise solely from the presence of five or more cations; multication disorder also influences phase stability, defect chemistry, oxygen-vacancy formation, local lattice strain, redox activity, and surface reconstruction. Since the first experimental demonstration of entropy-stabilized rocksalt (MgCoNiCuZn)O, the field has expanded to include rocksalt, spinel, perovskite, fluorite, pyrochlore, layered, and mixed-anion oxide frameworks. These structures are now being explored for solid electrolytes, supercapacitors, oxygen evolution, oxygen reduction, hydrogen evolution, lithium-ion and sodium-ion batteries, and bifunctional water-splitting systems. This review examines the thermodynamic basis of HEO formation, the role of crystal structure in compositional design, the impact of synthesis techniques on phase purity and defect populations, and the mechanistic links between local disorder and electrochemical function. Particular attention is given to oxygen vacancies, mixed-valence cations, short-range ordering, operando surface reconstruction, and descriptor-based catalyst design. The review also assesses how density functional theory, CALPHAD, machine learning, active learning, and inverse design are accelerating HEO development. One key conclusion is that future progress will depend more on designing the right type of disorder for a specific function than on simply adding more components. Standardized terminology, reproducible synthesis protocols, improved local and operando characterization, morphology-matched benchmarking, open datasets, and device-level validation are all required for the field to advance reliably.