Theory-guided unraveling of the mechanism underlying Cu1.0/Mn1.0-ZnO with dual reaction centers for enhanced peroxymonosulfate activation

Developing efficient catalytic systems for water contamination removal is a topic of great interest. However, the use of heterogeneous catalysts faces challenges due to insufficient active sites and electron cycling. In this study, results from first-principles calculations demonstrate that dual reaction centers (DRCs) are produced around the Cu and Mn sites in Cu1.0/Mn1.0-ZnO due to the electronegativity difference. Experimental results reveal the material with DRCs greatly enhances electron transfer efficiency and significantly impacts the oxidation and reduction of peroxymonosulfate (PMS). In addition, the self-consistent potential correction (SCPC) method was introduced to correct the energy and charge of charged periodic systems simulating a catalytic process, resulting in more precise catalytic results. Specifically, the material exhibits a preference for adsorbing negatively charged PMS anions at electron-deficient Mn sites, facilitating PMS oxidation for the generation of 1O2, and PMS reduction around the electron-rich Cu for the formation of •OH and SO4•-. The major reactive oxygen species is 1O2, showcasing effective performance in various degradation systems. Overall, our work provides novel insights into the persulfate-based heterogeneous catalytic oxidation process, paving the way for the development of high-performance catalytic systems for water purification.

Unveiling the effect of strain engineering on the electrochemical properties of hydrothermally grown nanostructured indium doped ZnSeO3 for photoanode applications

The crucial role of In as a dopant on the structural, optical, and thermogravimetric characteristics of the zinc selenite (ZnSeO3) nanopowders has been investigated in detail using X-Ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Energy Dispersive Spectroscopy (EDS), Raman spectroscopy, diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, and Thermogravimetric Analysis (TGA). The structural analysis indicates that all patterns are assigned to the ZnSeO3 orthorhombic structure. Also, XRD analysis shows that In3+ ions may have replaced Zn2+ ions, which causes lattice expansion. Both the Debye-Scherrer method, and the Williamson-Hall method have also been applied to study the influence of strain on the calculation of the crystallite size. The crystallite size was observed to increase with an increase in dopant concentration. The FE-SEM corroborated that the prepared samples are orthorhombic, with the EDS and mapping confirming the presence of In as a dopant. Raman spectroscopy results corroborated the XRD results indicating an expansion in the crystal structure of ZnSeO3 with the introduction of dopants. Based on DRS data, the introduction of In decreases the energy band gap of the synthesized ZnSeO3 nanopowder samples from 3.305 to 3.276. PL spectra confirm the presence of indium with the green emission band attributed to dopants dominating the emission. The TGA investigation shows an improvement in the mass loss with the introduction of dopants. EIS results indicated an improvement in the conductivity as the charge transfer resistance decreased from 525.04 to 21.95 kΩ for the undoped ZnSeO3 and 0.75% In-ZnSeO3 thin films showing improvement in charge mobility.

Encapsulation of ZnO and Ho:ZnO Nanoparticles in the Core of Wrinkled Mesoporous Silica

Wrinkled mesoporous silica (WMS) has a flower- or dendritic-like morphology, tunable pore size, and highly ordered and accessible three-dimensional (3D) pore structures. In this research, a method to encapsulate semiconductor nanoparticles in the core of the wrinkled mesoporous silica during synthesis is described. Highly uniform zinc oxide and holmium-doped zinc oxide nanoparticles have been synthesized by a sonochemical method. Zinc oxide and holmium-doped zinc oxide nanoparticles have been encapsulated in wrinkled mesoporous silica during synthesis. The ZnO@WMS and Ho:ZnO@WMS particles have been characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV-vis spectroscopy, fluorescence, dynamic light scattering (DLS), confocal microscopy, and X-ray diffraction (XRD).

Engineered Zn-based nano-pesticides as an opportunity for treatment of phytopathogens in agriculture

People's desire for food has never slowed, despite the deterioration of the global agricultural environment and the threat to food security. People rely on agrochemicals to ensure normal crop growth and to relieve the existing demand pressure. Phytopathogens have acquired resistance to traditional pesticides as a result of pesticdes' abuse. Compared with traditional formulations, nano-pesticides have superior antimicrobial performance and are environmentally friendly. Zn-based nanoparticles (NPs) have shown their potential as strong antipathogen activity. However, their full potential has not been demonstrated yet. Here, we analyzed the prerequisites for the use of Zn-based NPs as nano-pesticides in agriculture including both intrinsic properties of the materials and environmental conditions. We also summarized the mechanisms of Zn-based NPs against phytopathogens including direct and indirect strategies to alleviate plant disease stress. Finally, the current challenges and future directions are highlighted to advance our understanding of this field and guide future studies.

Sm3+ driven enhancement in photocatalytic degradation of hazardous dyes and photoluminescence properties of hexagonal-ZnO nanocolumns

Samarium doped ZnO (Sm-ZnO) nanocolumns were grown by wet chemical method and the doping effect of Sm3+ on visible light photocatalytic (PC) and photoluminescence (PL) properties of ZnO was investigated. Methylene blue (MB) and methyl orange (MO) were considered for the degradation study as a step initiated towards the remediation of industrial wastewater. Subsequent characterization studies by x-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) enumerate that the hexagonal-wurtzite structured Sm-ZnO is highly crystalline in nature and possesses hexagonal column like nano-architectures. Although, a charge imbalance exists between the ions, the substitutional effects of Sm3+ at Zn2+ sites have been observed from the XRD spectra and discussed by suitable mechanisms. FTIR measurement gives the information on the evolution of peaks related to metal-oxygen bond in Sm-ZnO which may be linked with Sm ions. PC measurement shows that the degradation efficiency of 95% can be achieved by Sm-ZnO photocatalysts in degrading MB and 91% for MO. Sm doping induces high charge separation efficiency and generation of OH ions in ZnO leading to such improvisation in degradation efficiency. The prepared Sm-ZnO nanocatalysts possess high degree of photostability and reusability even after fourth cycle of photodegradation. PL spectra show the suppression of the sharp and intense excitonic emission band of ZnO in Sm-ZnO due to low rated direct recombination of carriers. Incorporation of Sm3+ ends up with intrinsic defect mediated enhancement in the visible emissions especially in the blue, yellow and red region of light spectrum.

Evidence of oxygen defects mediated enhanced photocatalytic and antibacterial performance of ZnO nanorods

Defect engineered one-dimensional (1D) ZnO nanostructures have found great interest in diverse fields, including water detoxification and environmental remediation. In this article, we report a facile, low-temperature hydrothermal synthesis of defect enriched ZnO nanorods at different pH conditions. The dimension of all the synthesized ZnO nanostructures was restricted to 1D with changes only in their aspect ratios, unlike previous reports where change in morphology accompanies the effect of pH. With an increment in the pH value of the reaction mixture, oxygen defect concentration was controlled and confirmed using XPS and Raman spectroscopy. Considerable increase in optical light absorption and reduction in the bandgap, as inferred from the UV-vis study, corroborating the pH-dependent enrichment of defect states in 1D ZnO. Superior photosensitivity of oxygen defect rich ZnO nanorods was utilized to study their sunlight-induced photocatalytic and bactericidal activity towards its application in wastewater treatment. Within 4 h and 30 min of sunlight exposure (900 W/cm²), a 100% bacterial population (S.aureus, 10⁶ cells/m) killing and complete degradation of methylene blue dye (10μM) were achieved. Enhanced reactive oxidative species (ROS) formation due to the presence of additional oxygen defect states is ascribed to be the prime factor facilitating improved degradation efficiency. Additionally, during the optimization study, ZnO nanorods were found to be active against bacterial cells even in the absence of light opening avenues in antimicrobial food packaging and protective surface coatings.

Lattice defect-formulated ferromagnetism and UV photo-response in pure and Nd, Sm substituted ZnO thin films

The induction of charge and spin in diluted magnetic semiconductor ZnO is explored for spintronic devices and its wide direct band gap (3.37 eV) and large exciton binding energy (60 meV) exhibit potential in UV photodetectors. We reported the ferromagnetic and optical properties of pure ZnO, Zn_0.97Nd_0.03O and Zn_0.97Sm_0.03O thin films. These thin films were synthesized by a metallo-organic decomposition method and annealed at 500 °C for 7 h. Rietveld refinement of the XRD data results in a wurtzite ZnO structure with Nd, Sm doping. The dopants and nanoparticle size are responsible for wurtzite structural deformation, inducing lattice strain effect, which may influence the band gap energy and high-T_C ferromagnetism of ZnO. The average size of ZnO nanoparticles with Nd, Sm doping is 10 nm, confirmed with atomic force microscopy. The Raman spectra confirm the wurtzite structure of ZnO with crystalline quality and lattice defect formation with dopant Nd, Sm ions. A near-band-edge emission due to band gap energy is evaluated with photoluminescence spectra, which also involved multiple visible emissions due to oxygen vacancies. The oxygen vacancies-mediated magnetic interactions impart room temperature ferromagnetism in pure ZnO which is enhanced with Nd, Sm doping. The electron paramagnetic resonance spectra revealed the effects of defects and unpaired electrons responsible for observed room temperature ferromagnetism. The zero field cooling and field cooling magnetic measurements include antiferromagnetic interactions without any spin-glass formation. The observed ferromagnetism also correlates with first principle calculations reported for Nd, Sm-doped ZnO and suggests long-range ferromagnetic ordering attributed to defect carriers. The Nd, Sm doping into ZnO thin films significantly enhances absorption in the UV region and suggests its usability for UV detectors. Under UV irradiation (λ = 325 nm), the value of photocurrent in Nd, Sm:ZnO thin films is highly enhanced for possible use in UV sensors.

Influence of defect structure on colour tunability and magneto optical behaviour of WO3 nanoforms

The present study reports the impact of thermal annealing on the structural, optical and magnetic properties of WO₃ nanostructures, synthesized using an acid precipitation method by, employing various spectroscopic and magnetic measurements. The X-ray diffraction and Raman measurements confirmed the orthorhombic structure of as dried WO₃·H₂O and monoclinic structure of WO₃ nanopowders annealed at or above 500 °C. The morphological characterization shows the formation of different microstructures like nanosheets, nanoplatelets and nanocuboids in the micro-scale with the variation of annealing temperatures. The optical band gap has been calculated using the Kubelka–Munk function. The room temperature photoluminescence (PL) spectra recorded at different excitation wavelengths show intense near ultraviolet (NUV) emission which might be due to the presence of localized states associated with oxygen vacancies, and the surface states in the conduction band. The emissions in visible region correspond to the structural defects such as oxygen vacancies present within the band gap and band to band transitions. The spectral chromaticity colour coordinates indicate that the light emitted from the prepared samples shows shift from violet to red region with the change of excitation wavelength. Magnetic measurements show decrease in room temperature ferromagnetism (FM) with annealing temperature. The X-ray absorption spectroscopy (XAS) measurements at O K-edge show the significant change in the W–O hybridizations. The decrease in PL intensity and ferromagnetic ordering with increase in annealing temperatures are directly correlated with the filling up of oxygen vacancies in the samples. The oxygen vacancies based F-Center exchange model is discussed to understand the origin of FM in WO₃ nanostructures.

Colour tunability in WO₃ nanoparticles with variation in excitation wavelength. Typical hysteresis loops of the annealed samples at 300 K.

Unraveling the effect of Gd doping on the structural, optical, and magnetic properties of ZnO based diluted magnetic semiconductor nanorods

The structural, magnetic, and optical properties of the pristine and Gd-doped ZnO nanorods (NRs), prepared by facile thermal decomposition, have been studied using a combination of experimental and density functional theory (DFT) with Hubbard U correction approaches. The XRD patterns demonstrate the single-phase wurtzite structure of the pristine and doped ZnO. The rod-like shape of the nanoparticles has been examined by FESEM and TEM techniques. Elemental compositions of the pure and doped samples were identified by EDX measurement. Due to the Burstein–Moss shift, the optical band gaps of the doped samples have been widened compared to pristine ZnO. The PL spectra show the presence of complex defects. Room temperature magnetic properties have been measured using VSM and revealed the coexistence of paramagnetic and weak ferromagnetic ordering in Gd³⁺ doped ZnO-NRs. The magnetic moment was increased upon addition of more Gd ions into the ZnO host lattice. The DFT+U calculations confirm that the presence of vacancy-complexes has a significant effect on the structural, electronic, and magnetic properties of a pristine ZnO system.

Gd doped ZnO nanorods.

Solution-processed ZnO/Si based heterostructures with enhanced photocatalytic performance

Well-incorporated ZnO/SiNW arrays with reliable photocatalytic activity were prepared by an all-solution processed method.

Understanding the origin of ferromagnetism in Er-doped ZnO system

The present study reports the structural, optical and magnetic properties of ZnO with doping of Er ions at dilute concentrations (0 ≤ x ≤ 0.05).

Enhancement of optical and mechanical properties of Si nanopillars by ALD TiO2 coating

The mechanical and optical properties of Si and TiO₂–Si nanopillars (NPl) were investigated.