Impact of temperature-induced oxygen vacancies in polyhedron MnFe2O4 nanoparticles: As excellent electrochemical sensor,supercapacitor and active photocatalyst

Here, we investigate the effect of temperature on solution combustion synthesized MnFe₂O₄ nanoparticles (NPs) as supercapacitor electrode material that would affect the structural, optical, electrochemical, magnetic and sensing properties. The variation in temperature influences the structure and morphology of synthesized NPs which in turn produces defect states in NPs. Powder X-ray diffraction studies confirms the presence of cubic spinel structure with increase in crystallinity and crystallite size with increase in temperature. Scanning electron microscopy analysis indicates the morphology change in NPs from spherical to network like interlinking to the formation of polyhedron structure at higher temperature. Photoluminescence, energy dispersive X-ray analysis, X-ray photoelectron scpectroscopy and UV-visible diffused reflectance spectroscopy studies emphasize the increase in surface oxygen vacancies concentration with narrowing of band gap from 2.9 to 2.5 eV. Electrochemical studies designate the excellent performance and desirable cyclic stability of synthesized NPs. In particular, the specific capacitance of synthesized NP increases with increase in temperature, reaching highest specific capacitance from CV was 297.7 F/g for 0.1 M HCl and 158.85 F/g for 0.1 M NaNO₃ electrolytes for NP synthesized at 500 °C. The synthesized NPs show excellent stability with high capacity retention in both the electrolytes. The graphite modified electrode can also sense Paracetamol and d-Glucose at a very low concentration of 1–5 mM. Meanwhile, it acts as a very good photocatalyst to decolourize Methylene Blue and Alizarin Red S dye under Sunlight illumination due to the increase in concentration of surface oxygen vacancies with narrow band gap. Finally, the synthesized MnFe₂O₄ NP can be used as a potential supercapacitor electrode with excellent stability and recyclability, to sense the analyte even at very low concentration and also act as a photocatalyst with high recyclability with the help of magnetic nature towards environmental cleaning.     

Mycosynthesis of zinc oxide nanoparticles using Pleurotus floridanus and optimization of process parameters

Zinc nanoparticles are ideal candidates for biomedical applications due to their exceptional properties and biocompatible nature. The conventional methods are unsuitable for biomedical applications owing to the use of toxic chemicals during synthesis. In this context, the synthesis of biocompatible nanoparticles using plants and microorganisms are gaining more attention. In the present study, the mycosysnthesis of zinc oxide nanoparticles were carried out using P. floridanus culture filtrate employing four different methods. The spectral analysis of the samples revealed that the method described by Malek et al. is an efficient method for the synthesis of zinc nanoparticles using mushroom culture extract. The zinc nanoparticles exhibited absorption maxima at 360 nm. The optimum pH and substrate concentration were identified to be 10 and 300 mM respectively. TEM analysis of the synthesized nanoparticles revealed that they have a spherical shape and the SAED analysis confirmed the crystalline nature of the nanoparticles with an average size of 7 nm. The stoichiometric mass percentages of zinc and oxygen were determined using EDAX and found to be 80.34% and 19.66%, respectively which corresponds to the mass percentage for pure zinc oxide nanoparticles. The XRD analysis confirmed that the synthesized nanoparticles had a hexagonal wurtzite structure.     

Synthesis of CuO samples by co-precipitation and green mediated combustion routes: Comparison of their structural,optical properties,photocatalytic, antibacterial,haemolytic and cytotoxic activities

The goal of this research is to prepare novel, inexpensive, environment friendly and efficient crystalline CuO samples by green mediated combustion and co-precipitation routes towards environmental remediation and biomedical applications. The influence of preparation routes and Aloe barbadensis miller (Aloe vera) gel on the morphology, size, crystallinity, band gap, defects, photocatalytic, antibacterial, haemolytic and anticancer behaviour of CuO samples were explored. The PXRD, XPS, SEM, TEM, HRTEM and FT-IR were performed to confirm the formation of CuO samples. FTIR studies showed all possible bands of Aloe barbadensis miller gel. FTIR displaying the occurrence of new peaks and peak shifts in the CuO synthesized by green mediated combustion route compared to co-precipitation route is an evidence of the effective interactions between CuO and Aloe vera gel. The PL and UV–Vis-DRS techniques measured the optical sensitivity and tuning of band gap of the CuO samples. The crystallinity and surface properties dependent photocatalytic activities for decolourization of MB and RhB under both UV and Sunlight irradiation were investigated. The results indicated that green mediated synthesized CuO sample displayed high photocatalytic activity compared with co-precipitation route synthesized CuO sample, which mainly resulted from the low crystallinity and crystallite size (6 nm), narrow band gap (1.73 eV) and lower recombination of charge carriers. These synthesized CuO samples also demonstrate excellent antibacterial activity against the bacteria Gram-positive (S. aureus) and Gram-negative (E. coli). The present study probes into the cytotoxicity of CuO samples employing root cells of Allium cepa. In addition, we report the haemolytic activity on goat and human blood along with the implementation of green synthesized CuO sample using an Aloe barbadensis miller extract for the evaluation of anticancer activity in human cervical cancer (HeLa) cells with IC50 value of 310.1 μg/ml. Our studies focus on developing biosynthesized nanomaterials for environmental remediation and biomedical applications.     

Controlled synthesis of (CuO-Cu2O)Cu/ZnO multi oxide nanocomposites by facile combustion route: A potential photocatalytic,antimicrobial and anticancer activity

Photocatalytic activity of (CuO-Cu₂O)Cu/ZnO hetero-junction nanocomposites along with their luminescent, biological applications in the progress of anticancer and antibacterial agents is investigated. The Cu and Zn bi-components modified (CuO-Cu₂O)Cu/ZnO nanocomposites were synthesized via facile combustion route in the presence of controlled fuel to oxidizer ratio and were characterized by X-Ray Diffraction (XRD) patterns, Transmission electron microscopy (TEM), High resolution Transmission electron microscopy (HRTEM), Scanning Electron Microscopy (SEM), X-ray photoelectron Spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), photoluminescence (PL) and energy dispersive X-ray (EDX) analysis. The PL and UV–Visible diffused reflectance spectral (UV–Vis-DRS) techniques were used to measure the optical sensitivity and tuning of band gap in the samples. The excellent photocatalytic degradation of Methylene Blue and industrial waste water under Sunlight irradiation depends on the mass ratios of Cu/Zn. The findings show that the addition of a certain proportion of CuO, Cu₂O, ZnO, and Cu can promote efficiency in Sunlight harvesting and separation of charge carriers. Process parameters namely catalyst quantity, dye concentration and a proposal for the mechanism of degradation pathway, experiments for trapping and enhancer are investigated. The study of photoluminescence, CIE and CCT calculations suggests that the present nanocomposite may find applications as phosphor material in warm white LEDs. The second segment of this study deals with the investigation of antibacterial performance of composites upon Gram-negative and Gram-positive bacteria. The results indicate that nanocomposites can be used in antibacterial control systems and as an important growth inhibitor in various microorganisms. The cytotoxic effect of the (CuO-Cu₂O)Cu/ZnO (CCCZ11) nanocomposite was determined by colorimetric and flow cytometric cell cycle analysis. Our experimental results show that the nanocomposite can induce apoptosis and suppress the proliferation of HeLa cells. The applications of nanocomposites based on Cu, an abundant and inexpensive metal has created much interest in various multifunctional applications.     

Challenges in Biomaterial-Based Drug Delivery Approach for the Treatment of Neurodegenerative Diseases: Opportunities for Extracellular Vesicles

Biomaterials have been the subject of numerous studies to pursue potential therapeutic interventions for a wide variety of disorders and diseases. The physical and chemical properties of various materials have been explored to develop natural, synthetic, or semi-synthetic materials with distinct advantages for use as drug delivery systems for the central nervous system (CNS) and non-CNS diseases. In this review, an overview of popular biomaterials as drug delivery systems for neurogenerative diseases is provided, balancing the potential and challenges associated with the CNS drug delivery. As an effective drug delivery system, desired properties of biomaterials are discussed, addressing the persistent challenges such as targeted drug delivery, stimuli responsiveness, and controlled drug release in vivo. Finally, we discuss the prospects and limitations of incorporating extracellular vesicles (EVs) as a drug delivery system and their use for biocompatible, stable, and targeted delivery with limited immunogenicity, as well as their ability to be delivered via a non-invasive approach for the treatment of neurodegenerative diseases.     

Synthesis of Nanocrystalline CaWO4 as Low-Temperature Co-fired Ceramic Material: Processing, Structural and Physical Properties

Nanocrystalline scheelite CaWO₄, a promising material for low-temperature co-fired ceramic (LTCC) applications, has been successfully synthesized through a single-step autoignition combustion route. Structural analysis of the sample was performed by powder x-ray diffraction (XRD), Fourier-transform infrared spectroscopy, and Raman spectroscopy. The XRD analysis revealed that the as-prepared sample was single phase with scheelite tetragonal structure. The basic optical properties and optical constants of the CaWO₄ nanopowder were studied using ultraviolet (UV)-visible absorption spectroscopy, which showed that the material was a wide-bandgap semiconductor with bandgap of 4.7 eV at room temperature. The sample showed poor transmittance in the ultraviolet region but maximum transmission in the visible/near-infrared regions. The photoluminescence spectra recorded at different temperatures showed intense emission in the green region. The particle size estimated from transmission electron microscopy was 23 nm. The feasibility of CaWO₄ for LTCC applications was studied from its sintering behavior. The sample was sintered at a relatively low temperature of 810°C to high density, without using any sintering aid. The surface morphology of the sintered sample was analyzed by scanning electron microscopy. The dielectric constant and loss factor of the sample measured at 5 MHz were found to be 10.50 and 1.56 × 10^?3 at room temperature. The temperature coefficient of the dielectric constant was ?88.71 ppm/°C. The experimental results obtained in this work demonstrate the potential of nano-CaWO₄ as a low-temperature co-fired ceramic as well as an excellent luminescent material.     

Sunlight-Assisted Photocatalytic Oxidation of Methane over Uranyl-Anchored MCM-41

Uranyl ions anchored within the mesopores of MCM-41 silicate host matrix served as highly efficient heterogeneous catalysts for sunlight-assisted room-temperature photooxidation of methane in the presence of air to selectively form carbon dioxide. The extent of conversion depended upon the methane content; lower the concentration, faster was the completion of reaction. It was also confirmed that no thermocatalytic reaction occurred below 200 °C in the absence of radiation, other test conditions remaining the same. These results are of relevance from the point of view of abatement of VOCs in the environment.     

Structural and optical characterization of BaSnO3 nanopowder synthesized through a novel combustion technique

Nanocrystalline Barium stannate (BaSnO₃) was synthesized through auto-ignited combustion technique. The X-ray diffraction studies of BaSnO₃ nanoparticles reveals that the nanopowder is single phase, crystalline, and has a cubic perovskite structure with a lattice constant a = 4.115 Å. The average particle size calculated from full width half maximum (FWHM) using Scherer formula is ∼25 nm. The phase purity of the powder was further examined using Fourier transform infrared spectroscopy, Raman spectroscopy and transmission electron microscopic techniques. XRD pattern of BaSnO₃ was refined for atomic coordinates, lattice parameters and occupancies using Rietveld analysis. Vibrational analysis of sample shows that there is a phase transition from distorted cubic to ideal cubic structure during heat treatment. The thermal stability of BaSnO₃ nanopowder has been confirmed using thermo gravimetric analysis (TGA) and differential thermal analysis (DTA). The particle size of the as-prepared powder from transmission electron microscopy was found to be in the range 20-30 nm. The absorption spectra and photoluminescence spectra of the sample were also studied. The band gap determined was 2.887 eV and found to be a semiconductor.     

First-principles density-functional calculations on HCr3O8: An exercise to better understand the ACr3O8(A = alkali metal) family

Accurate ab initio density-functional calculations are performed to understand structural stability, electronic structure, and magnetic properties of the ACr₃O₈(A = H, Li, Na, K, Rb, Cs) series. The ground-state structures for the compounds with A = Li−Rb take the same KCr₃O₈-type atomic arrangement (space group C2/m), whereas CsCr₃O₈adopts a modified atomic architecture (prototype; space group Pnma), in agreement with available experimental findings. The hypothetical compound HCr₃O₈is found to stabilize in an LiV₃O₈-type structure (space group P2₁/m), with an unexpectedly large equilibrium volume. The electronic structures of the ACr₃O₈compounds are analyzed using density-of-states, charge-density, and electron-localization-function plots, and all are found to exhibit semiconducting (insulating at 0 K) properties with very narrow band gaps. The Cr atoms occur in two different valence states and all compounds (except NaCr₃O₈) are found to exhibit antiferromagnetic ordering of magnetic moments at 0 K.