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Abstract: The electronic, elastic constants and optical properties of rutile TiO2 have been investigated using first principle pseudopotential method within generalized gradient approximation (GGA) proposed by Perdew–Burke–Ernzerhof (PBE). The calculated volume, bulk modulus and pressure derivative of bulk modulus are in good agreement with previous experimental and computational results. An underestimated band gap (1.970eV) along with the higher density of states and expanded energy bands around the fermi level is obtained. Calculated elastic constants satisfying the Born stability criteria suggest that rutile TiO2 is mechanically stable under higher hydrostatic pressure. The acoustic wave speeds in [100], [010], [001], [110] and [45° to [100] and [001]] directions are predicted using the investigated elastic constants. The dielectric constant is identified with respect to electronic band structure and is utilized to derive the other optical properties like refractive index, energy loss function, reflectivity and absorption. The effect of hydrostatic pressure (0–70GPa) is described for listed properties. Our investigated results are in good accord with the existing theoretical and experimental results. [Copyright &y& Elsevier]

Abstract: Untreated and pre-treated with aqueous NH3, GaN nanowires have been synthesized by nickel assisted CVD method at 1050°C. The effect of pre-treating has been studied on the morphology, electrical and optical properties of the as-grown NWs. The resistivities of untreated and pre-treated NWs are calculated to be 40.5Ω-cm and 2.85Ω-cm respectively, which demonstrate that the conductivity of the pre-treated NWs has been enhanced significantly. The carrier concentrations (Nd) are calculated to be 8.54×1017 cm−3 and 3.65×1018 cm−3 whereas electron mobilities (μ) are 25cm2/Vs and 86cm2/Vs for untreated and pre-treated NWs respectively. Due to dramatic increase in the carrier concentrations and mobilities, these pre-treated GaN NWs are potentially applicable in low voltage and nano-scale electronics devices fabrications. Room temperature photoluminescence (PL) measurements of pre-treated NWs show a strong near-band-edge emission at 370nm (3.35eV) without blue and yellow emission indicating good optical quality of the NWs which have also potential application in optoelectronics and LEDs. [Copyright &y& Elsevier]

Abstract: We report here the simultaneous growth of ZnSe cactus-like structures with nanorods emerging from their surface and selenium microflowers using Zn and Se powders as precursors. ZnSe cactuses were obtained by solid state chemical reaction whereas selenium microflowers were obtained by thermal evaporation and condensation process. ZnSe cactuses consist of spheres with diameter range 2–3μm having nanorods with diameter in the range 60–90nm on the exterior surface. The mixture of zinc and selenium powders with few drops of aqueous ammonia loaded in semicircular long alumina boat was heated inside horizontal tube furnace at 500°C for 180min under ammonia atmosphere. The structural, compositional and morphological characterizations have been performed by means of Scanning Electron Microscope (SEM), the Energy Dispersive Spectroscopy (EDS) and X-ray diffraction (XRD). Room temperature photoluminescence (PL) measurement of as-synthesized products show two intensive peaks centered at 404nm and 427nm (2.85eV), which are attributed to the band edge emission of ZnSe. These two strong emission bands are blue shifted; this blue shift is because of quantum size confinement effect of nanostructures. A very weak peak centered at 464nm (2.67eV) is also observed in our sample which is exactly equivalent to the peak associated with the bulk ZnSe, and is attributed to near band edge emission (NBE) for the ZnSe nanostructures. [Copyright &y& Elsevier]

Abstract: Metallic zinc layered polyhedral microparticles have been fabricated by thermal evaporation and condensation technique using zinc as precursor at 750°C for 120min and NH3 as a carrier gas. The zinc polyhedral microparticles with oblate spherical shape are observed to be 2–9μm in diameter along major axes and 1–7μm in thickness along minor axes. The structural, compositional and morphological characterizations were performed by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). A vapour–solid (VS) mechanism based growth model has been proposed for the formation of Zn microparticles. Room temperature photoluminescence (PL) emission spectrum of the product exhibited a strong emission band at 369nm attributed to the radiative recombination of electrons in the s, p conduction band near Fermi surface and the holes in the d bands generated by the optical excitation. [Copyright &y& Elsevier]

Two-dimensional (2D) materials have been considered as promising applicants, to address the existing energy crisis, for solar energy conversion and photocatalytic water splitting. Here as efficient photocatalysts for water splitting under a wide spectrum from near-infrared, visible to ultraviolet radiation, chromium pristine and Janus monolayers are proposed. A comprehensive investigation of electronic and optical properties of CrS 2 , CrSe 2 and CrTe 2 pristine dichalcogenide, CrSSe, CrSTe and CrSeTe Janus monolayers under biaxial strain and electric field using ab-initio method are presented. Binding energy, phonon spectrum and elastic constants illustrate their high dynamic and mechanical stability. The hybrid functional (HSE06) is employed to accurately assess the electronic properties of all monolayers. Band alignment investigation using empirical and DFT methods have revealed that CrSe 2 and all Janus monolayers are potential candidates for photocatalytic overall splitting of water. All dichalcogenides and Janus structures have high optical absorption coefficients (~1.0–1.4 × 10 5 cm − 1 ) which lies from infrared to UV region. Furthermore, it is also observed that due to increase in applied strain, the bandgaps almost decrease linearly. Conversely, there is no significant influence of external electrical field on pristine and Janus dichalcogenides except CrSTe and CrSeTe monolayers. While, strong absorption intensity is slightly increased and move towards high energy in ultraviolet region. Present work not just only highlights the photocatalytic efficiency of pristine CrA 2 (A=S, Se, Te) and Janus CrAB (A/B= S, Se, and Te, A ≠ B) monolayers but also offers an approach to tune the electronic and optical properties by strain and external electrical field engineering. [Display omitted] • All Chromium dichalcogenides monolayers show high dynamic & mechanical stability. • Janus monolayers are potential candidates for overall water splitting. • The effect of biaxial strain and external electric field has been investigated. • All monolayers have high optical absorption coefficients (~1.0–1.4 × 10 5 cm − 1 ). • Present work offers an approach to tune the optoelectronic properties by strain and electric field. [ABSTRACT FROM AUTHOR]

Abstract: Zinc nitride (Zn3N2) hollow structures with 10–25μm size have been prepared by solvo-solid approach using aqueous ammonia treated Zn precursor at reaction temperature of 600°C for reaction time of 240min under ammonia gas flow. The structural, compositional and morphological characterizations of the as-obtained product were performed by XRD, EDS and SEM. Room temperature photoluminescence (PL) spectrum of zinc nitride hollow structures (ZNHSs) exhibited UV emission band at 384nm and a defect related yellow emission band at 605nm. The first ever studies on hydrogen absorption characteristics of ZNHSs performed at 373K showed an absorption capacity of 1.29wt.%. Growth mechanism proposed for the formation of ZNHSs is also discussed briefly. [Copyright &y& Elsevier]

• LMO with specific facets and different morphologies are controlled synthesized. • LMO-MST delivers superior rate capability up to 124.2 mAh g−1 at 10 C. • LMO-MST demonstrates 84.3 % capacity retention after 1000 cycles at 10 C. • LMO-MST cathodes still maintains optimal cycling stability at 55 and -5°C. • The superior performance results from sphere-bridged-tube structure and {111} facets. Recently, spinel-type LiMn 2 O 4 (LMO) cathode has attracted great attention to mitigate manganese dissolution especially at elevated temperature. In this work, LMO with surface specific facets and different morphologies are successfully controlled synthesized via a facile solvothermal-lithiation method. It suggests that microspheres, micro-tubes and hybrid sphere-interconnected-tube microstructures with different surface lattice orientation using urea, oxalic acid and mixture of urea and oxalic acid as precipitants at solvothermal stage, respectively. Specifically, LMO microspheres (LMO-MS) display (111) facets and the micro-tubular LMO materials (LMO-MT) exhibit the high index lattice (311). It is more interesting is that hybrid sphere-interconnected-tube microstructures (LMO-MST) are clearly observed the densest (111) facets at the micro-spherical surface and a new (111) plane appearance on the surface of microtubes. LMO-MST demonstrates excellent cycling performance (84.3 % capacity retention after 1000 cycles at 10 C) and superior rate capability up to 10 C (124.2 mAh g−1 at 10 C). The electrochemical performances of LMO-MST cathodes are also investigated at elevated (55°C) and lower (-5°C) temperatures, under which LMO-MST still maintains optimal cycling stability. The superior electrochemical performance of LMO-MST cathodes can be attributed to the unique sphere-bridged-tube seamless outer structure and the preferentially exposed stable facets on the crystal surface. Hybrid micro-nanostructured LMO sphere-bridged-tube with {111} facets demonstrates superior rate capability and cycling performance both under 55 and -5°C. Image, graphical abstract [ABSTRACT FROM AUTHOR]

To achieve efficient and cost-effective electrochemical water splitting, highly active and affordable nanostructured catalysts are the key requirement. The current study presents the investigations of the efficacy of metal (Mn, Fe and Ni)-doped Co(OH) 2 nanofibers towards oxygen evolution via water splitting. Notably, Ni-doped Co(OH) 2 demonstrates superior OER performance in KOH electrolyte, surpassing standard IrO 2 with a modest potential of 1.62 V at 10 mA cm -2 . The remarkable activity is attributed to the nanofiber structure, facilitating faster conduction and offering readily available active sites. Ni-doped Co(OH) 2 nanofibers displayed enduring stability even after 1000 cycles. This work underscores the importance of transition-metal based catalysts as effective electrocatalysts, providing the groundwork for the development of cutting-edge catalysts. Additionally, the electrochemical sensing capability towards ascorbic acid is evaluated, with Ni-doped Co(OH) 2 showing the most promising response, characterized by the lowest LOD and LOQ values. These findings highlight the potential of Ni-doped Co(OH) 2 nanofibers for upcoming diagnostic detection devices., Competing Interests: There are no conflict of interests to declare., (This journal is © The Royal Society of Chemistry.)

The extensive applications of MXenes, a novel type of layered materials known for their favorable characteristics, have sparked significant interest. This research focuses on investigating the influence of surface functionalization on the behavior of Mn 2 NT x (T x =O 2 , F 2 ) MXenes monolayers using the "Density functional theory (DFT) based full-potential linearized augmented-plane-wave (FP-LAPW)" method. We elucidate the differences in the physical properties of Mn 2 NT x through the influence of F and O surface functional groups. We found that O-termination results in half-metallic behavior, whereas the F-termination evolves metallic characteristics within these MXene systems. Similarly, surface termination has effectively influenced their optical absorption efficiency. For instance, Mn 2 NO 2 and Mn 2 NF 2 effectively absorb UV light ~50.15×10 4  cm -1 and 37.71×10 4  cm -1 , respectively. Additionally, they demonstrated prominent refraction and reflection characteristics, which are comprehensively discussed in the present work. Our predictions offer valuable perspectives into the optical and electronic characteristics of Mn 2 NT x -based MXenes, presenting the promising potential for implementing them in diverse optoelectronic devices., (© 2024 Wiley-VCH GmbH.)

Improvements of visible light activity, slow recombination rate, stability, and efficiency are major challenges facing photocatalyst technologies today. Utilizing heterostructures of g-C 3 N 4 (bandgap ∼2.7eV) with Nb 2 O 5 (bandgap ∼3.4eV) as an alternative materials for the first time, we tried to overcome such challenges in this work. Heterostructures of Nb 2 O 5 /g-C 3 N 4 have been synthesized via hydrothermal technique. And then a time-resolved laser flash photolysis of those heterostructures has been analyzed, focusing on seeking how to improve photocatalytic efficiency for molecular hydrogen (H 2 ) evolution. The transient absorption spectra and the lifetime of charge carriers at different wavelengths have been observed for Nb 2 O 5 /g-C 3 N 4 , where g-C 3 N 4 was used for a control. The role of hole scavenger (methanol) has also been investigated for the purpose of boosting charge trapping and H 2 evolution. The long lifetime of Nb 2 O 5 /g-C 3 N 4 heterostructures (6.54165 μs) compared to g-C 3 N 4 (3.1651897 μs) has successfully supported the increased H 2 evolution of 75 mmol/h.g. An enhancement in the rate of H 2 evolution (160 mmol/h.g) in the presence of methanol has been confirmed. This study not only deepens our understanding of the role of scavenger, but also enables a rigorous quantification of the recombination rate crucial for photocatalytic applications in relation with efficient H 2 production., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Authors. Published by Elsevier Ltd.)

We have developed a facile, scale up, and efficient method for the preparation of graphitic-C3N4 nanofibers (GCNNFs) as electrodes for supercapacitors and photocatalysts. The as-synthesized GCNNFs have 1D structure with higher concentration of nitrogen that is favorable for higher conductivity and electrochemical performance. Secondly, the high surface area of GCNNF provides a large electrode-electrolyte contact area, sufficient light harvesting and mass transfer, as well as increased redox potential. Thus, the GCNNF supercapacitor electrode shows high capacitance of 263.75 F g(-1) and excellent cyclic stability in 0.1 M Na2SO4 aqueous electrolyte with the capacitance retention of 93.6% after 2000 cycles at 1 A g(-1) current density. GCNNFs exhibit high capacitance of 208 F g(-1) even at 10 A g(-1), with the appreciable capacitance retention of 89.5%, which proves its better rate capability. Moreover, the GCNNF shows enhanced photocatalytic activity in the photodegradation of RhB in comparison to the bulk graphitic-C3N4 (GCN). The degradation rate constant of GCNNF photocatalyst is almost 4 times higher than GCN. The enhanced photocatalytic activity of GCNNF is mainly due to the higher surface area, appropriate bandgap, and fewer defects in GCNNF as compared to GCN. As an economical precursor (melamine) and harmless, facile, and template-free synthesis method with excellent performance both in supercapacitors and in photodegradation, GCNNF is a strong candidate for energy storage and environment protection applications.