ZnO Phase Research Articles

“Enhancing wastewater treatment: DFT and experimental insights into ZnO-implanted TiO2 Z-scheme photocatalyst mediated via Smilax aspera"

This comprehensive study aimed to optimize the performance of photogenerated carriers in catalytic and optoelectronic systems by effectively separating electron-hole pairs. Green-synthesized TiO₂ nanoparticles (average size ∼21 nm) and zinc acetate (99.5 % purity), augmented with eco-friendly integration of the plant Smilax aspera, resulted in a tailored hollow direct Z-scheme photocatalyst, ZnO–TiO₂, with adjustable ZnO loading ranging from 0.5 wt% to 5 wt%. Characterization techniques such as X-ray Diffraction, Fourier Transform Infrared Spectroscopy, Ultraviolet–Visible Spectroscopy, Transmission Electron Microscopy, Thermogravimetric Analysis and Energy-Dispersive X-ray Spectroscopy provided detailed insights into the atomic and electronic properties of the material. The analysis revealed the coexistence of anatase TiO₂ and wurtzite ZnO phases, each exhibiting distinct electronic band structures within the composite. Density functional theory calculated band gap values of 2.02 eV for TiO₂ and 2.89 eV for ZnO–TiO₂ corroborated the experimental results, offering a deeper understanding of electronic transitions within the heterojunction. The ZnO–TiO₂ composite showed significant photocatalytic efficacy in degrading Methylene Blue (98 % in 15 min) and Rose Bengal (79.69 % in 40 min) under UV light. It also exhibited antifungal potential against Aspergillus niger and Candida albicans, with inhibition zones of 28.0 ± 0.12 mm and 30.23 ± 0.68 mm, respectively. This research provides valuable insights into the eco-friendly, multifunctional applications of the ZnO–TiO₂ Z-scheme photocatalyst. This research thus provides valuable insights into the multifaceted applications of this synergistic, eco-friendly heterojunction photocatalyst in environmental remediation and its role as an effective antifungal agent.

Blue-green emitting ZnS0.75O0.25:Ce3+,x%Tb3+ phosphor with tunable fluorescence lifetime

A series of ZnS0.75O0.25:0.1%Ce3+,x%Tb3+ phosphors were prepared by high temperature solid state reaction method. These phosphors exhibited two mixed phases consisting of hexagonal phase ZnS and hexagonal phase ZnO with the average particle size of 13.83 μm and emitted blue-green light. The luminescence mechanism consisted of Zn vacancy defects, the 5d1 → 2F5/2 radiative transitions of Ce3+, the 5D4 → 7F5 and 5D4 → 7F6 radiative transition of Tb3+ induced by the energy transfer of Ce3+ → Tb3+. An equation for the variation of the fluorescence lifetime of ZnS0.75O0.25:0.1%Ce3+,x%Tb3+ phosphors with concentration of Tb3+ fraction was obtained by exponential fitting. The short fluorescence lifetime could be tuned within the range of 113 μs to 550 μs with the increase of Tb3+ concentration, and the color was tunable from blue to blue-green, which is of important application in the field of high-energy particle detection.

Effect of TiO2 on Acidity and Dispersion of H3PW12O40 in Bifunctional Cu-ZnO(Al)-H3PW12O40/TiO2 Catalysts for Direct Dimethyl Ether Synthesis

The performance of bifunctional hybrid catalysts based on phosphotungstic acid (H3PW12O40, HPW) supported on TiO2 combined with a Cu-ZnO(Al) catalyst in the direct synthesis of dimethyl ether (DME) from syngas has been investigated. In this work, different types of TiO2 were used as a support to study the effect of changes in the structure of the TiO2 support on the acidity and dispersion of HPW. Various TiO2 supports with different structural and surface characteristics have been studied and the results indicate that: (i) the crystallinity and crystallite size of the primary particles of the HPW units depend on the TiO2 support; (ii) the pore size distribution of the TiO2 support affects the surface segregation of the heteropolyacids; and (iii) changes in the supported HPW acid catalysts do not significantly alter the crystal structure of the CuO and ZnO phases after contact with CZA in bifunctional catalysts. The activity results indicate that the variation in the intrinsic activity of the Cu-ZnOx centers in the bifunctional catalysts for direct DME synthesis is minimal due to the limited alteration of the crystal structure of the centers.

Structural, optical, and gas sensing characteristics of synthesized environmentally friendly ZnO-ZnAl2O4 nanocomposites

In this study, we synthesized ZnO-ZnAl2O4 composites from orange peel extract by using an environmentally friendly approach. ZnO-ZnAl2O4 composites with different Al content, namely 30, 40, 50, 60, and 70 at%, were successfully synthesized, and they were characterized in detail using advanced techniques to study their structures, phases, morphologies, and electrical and optical properties. Gas sensing measurements for H2S gas showed that the sensor with 70 at% Al had the best response at 350 °C along with long-term stability. We attribute this high response to the high specific surface area (48.8 m2·g−1), the formation of ZnO-ZnO homojunctions and ZnO-ZnAl2O4 heterojunctions, and the high intrinsic sensing properties of the ZnO phase. This study is expected to contribute to the development of green approaches for the synthesis of environmentally friendly gas sensing materials.

First‐Principles Calculation of Elastic Properties in LixZn1−xO:Nd3+ Mechanoluminescence Material

AbstractIn this study, the elastic properties of the newly discovered mechanoluminescence (ML) material LixZn1−xO:Nd3+ are investigated by first‐principles calculations. The elastic properties such as Young's modulus, bulk modulus, and shear modulus are calculated from the elastic tensor. As a result of investigating the phase stability of LixZn1−xO:Nd3+, it indicates that the wurtzite ZnO phase is stable in the Li additive range of 0 ≤ x ≤ 0.44, and an excess addition caused a structural transition to the h‐BN structure. Besides, elastic properties, such as Young's modulus, bulk modulus, and shear modulus of LixZn1−xO:Nd3+ are decreased with increasing Li concentration in the examined range of 0 ≤ x ≤ 0.44. Furthermore, it reveals from bonding analysis between cation and anion that the bonding strength of Li─O bonding for the covalent bonding is weaker than that of Zn─O bonding. The elastic softening derives from atomic interaction in the covalent bonding. Therefore, it concludes that elastic softening is promoted by the increase in Li─O bonding with weak covalent bonding as the Li concentration increases.

Greenly synthesized zinc oxide nanoparticles: An efficient, cost-effective catalyst for dehydrogenation of formic acid and with improved antioxidant and phyto-toxic properties

Formic acid (FA) dehydrogenation is of particular industrial interest as a source of alternative fuels such as H2. However, the development of economical, highly efficient, and selective catalysts for this reaction is a challenging task. Most highly selective catalysts for the conversion of formic acid (FA)/sodium formate (SF) system into hydrogen are based on precious noble metals. Rendering their large-scale utilization more cumbersome and expensive. Therefore, it is of utmost importance to explore a facile and cost-effective strategy for the fabrication of a simple structured solid nano-catalyst with outstanding performance and selectivity for H2 generation without CO evolution from the FA/SF system. In the current study, a phenolic-enriched extract of wild olive leaves was employed for the synthesis of ZnO nanoparticles (ZnO@WOLE-NPs). TEM analysis revealed that the size of ZnO@WOLE nanoparticles was about33 nm. Zeta potential evaluation (38.39 ± 1.32 mV) demonstrated the significant stability of the nanoparticles. XRD analysis provided insights into the formation of hexagonal wurtzite phase ZnO nanoparticles. The reaction conditions were optimized. These resulting ZnO@WOLE-NPs showed extraordinarily high catalytic performance and about 80 % selectivity for H2 generation from the FA/SF system at 50 °C. A turn over frequency and activation energy values for dehydrogenation of FA were noted as 1519 h−1 and 32.1 kJ mol−1, respectively. The kinetics and thermodynamics of FA dehydrogenation were also determined. Furthermore, ZnO@WOLE-NPs exhibited potent antioxidant activity against hydroxyl, DPPH, superoxide, and peroxide radicals. Moreover, the synthesized nanoparticles demonstrated the highest seed germination of Okra seed at a concentration of 1.25 µg mL−1. Whereas, the highest shoot length and root length were observed at the concentration of 1 µg mL−1.

Synergetic effect of optimized β-Zn(OH)2/ZnO heterostructure towards electrochemical dopamine detection

In this study, we have synthesized β-Zn(OH)2/ZnO heterostructures via a simple one-pot hydrothermal method followed by calcination at different temperatures under air for electrochemical dopamine (DA) detection. We found that the synergetic effect between optimized β-Zn(OH)2 and ZnO phases in β-Zn(OH)2/ZnO heterostructures boosts electrocatalytic activity. Moreover, β-Zn(OH)2/ZnO heterostructures calcined at 300 °C (i.e.,β-Zn(OH)2/ZnO300) showed enhanced electrochemical activity towards DA oxidation due to its larger electrochemical active surface area and higher adsorption capacity compared to other β-Zn(OH)2/ZnO heterostructures and ZnO. Additionally, β-Zn(OH)2/ZnO300 heterostructures demonstrated remarkable DA selectivity in the presence of over eight biomolecules, achieving rapid detection response in less than 10 seconds with a low detection limit of 0.17 nM and 1.0 nM within a linear range of (1.75–263 nM) and (263–1300 nM), respectively. Moreover, β-Zn(OH)2/ZnO300 heterostructures showed remarkable reproducibility (98.8 %), high stability (98.1 %), and real-time DA detection in human urine samples with a recovery rate ranging from 95.9 % to 103.2 %. Therefore, β-Zn(OH)2/ZnO heterostructures, especially those optimized under 300 °C, possess great potential for electrochemical applications, particularly in DA detection.

Antifungal Activity of ZnO Nanoparticles Synthesized from Eichhornia crassipes Extract for Construction Applications.

Fungal growth on construction materials in tropical climates can degrade aesthetics and manifestations on modern and historical sick buildings, affecting the health of their inhabitants. This study synthesized ZnO nanoparticles with enhanced antifungal properties using a precipitation method. Different concentrations (25%, 50%, and 100%) of Eichhornia crassipes aqueous extract were used with Zn(NO3)2·6H2O as the precursor to evaluate their spectroscopic, morphological, textural, and antifungal properties. X-ray diffraction confirmed the hexagonal wurtzite phase of ZnO with crystallite sizes up to 20 nm. Fourier-transform infrared spectroscopy identified absorption bands at 426, 503, and 567 cm-1 for ZnO-100, ZnO-50, and ZnO-25, respectively. Nitrogen physisorption indicated a type II isotherm with macropores and a fractal dimension coefficient near 2 across all concentrations. Polydispersity index analysis showed that ZnO-50 had a higher PDI, indicating a broader size distribution, while ZnO-25 and ZnO-100 exhibited lower PDI values, reflecting uniform and monodisperse particle sizes. FESEM observations revealed semi-spherical ZnO morphologies prone to agglomeration, particularly in ZnO-25. Antifungal tests highlighted ZnO-25 as the most effective, especially against Phoma sp. with an MFC/MIC ratio of 78 µg/mL. Poisoned plate assays demonstrated over 50% inhibition at 312 µg/mL for all tested fungi, outperforming commercial antifungals. The results indicate that ZnO NPs synthesized using E. crassipes extract effectively inhibit fungal growth on construction materials. This procedure offers a practical approach to improving the durability of building aesthetics and may contribute to reducing the health risks associated with exposure to fungal compounds.

In-vitro biocompatibility, antibacterial activity, and corrosion resistance of HA-TiO2/ZnO coating fabricated by plasma electrolytic oxidation on Ti6Al4V

The hydroxyapatite/Zinc Oxide (HA-TiO2/ZnO) coatings were grown on the Ti6Al4V substrate by plasma electrolyte oxidation from the CaP-based electrolyte containing 1, 3, and 6 g/L ZnO nanoparticles. XRD results confirmed the presence of ZnO, HA, and rutile phases in all coatings. According to SEM observations, coatings presented the porous morphology as a result of micro-arc discharges during the PEO process, whereas some of the pores in the composite coatings were filled by ZnO proportional to its content. After 7 days of immersion in SBF solution, accumulations of bone-like clusters were visible on the surface, demonstrating a promising bio-mineralization ability for all coatings, although the higher amount of 6 g/L ZnO had partially an inhibitory effect on the apatite nucleation. In-vitro studies demonstrated a time and concentration-dependent impact of ZnO on the viability of MG-63 osteoblast-like cells so that the concentration of 3 and 6 g/L caused the death of some cells after 7 days. The antibacterial tests also showcased that the presence of ZnO decreased the activity of gram-negative bacteria (E. coli) and gram-positive bacteria (S. aureus), while the higher concentration of ZnO particles led to more antibacterial activity of the coating. Finally, evaluating the corrosion behavior of PEO coatings through a potentiodynamic polarization test in Ringer's solution manifested a better protection against corrosion by increasing the ZnO content in the coating, mainly owing to the blocking of the pores by the ZnO particles, and as a result, the greater difficulty of electrolyte to reach the titanium substrate.

Enhanced photocatalytic activity in AgCu-decorated ZnO nanoparticles under UV and sunlight

This study investigates the structural, morphological, and photocatalytic properties of monometallic (Ag and Cu) and bimetallic (AgCu) nanoparticles (NPs) incorporated into ZnO NPs and their photocatalytic performance. X-ray diffraction and Rietveld refinement were employed to analyze the structural characteristics, revealing the formation of a hexagonal wurtzite structure of ZnO and cubic phases of Ag and Cu within the metal-decorated NPs. Scanning electron microscopy provided visual evidence of the spherical morphology, with an average particle size of 50 nm. Energy-dispersive X-ray spectroscopy confirmed the successful deposition of Ag, Cu, and AgCu NPs onto the ZnO surface. The photocatalytic efficiency of the NPs was evaluated by the degradation of methylene blue dye under UV light at a wavelength of 254 nm under sunlight irradiation. Under UV light, the bimetallic AgCu/ZnO system exhibited exceptional performance, achieving a degradation rate of about 95% with 10% AgCu/ZnO. Conversely, under sunlight illumination, the monometallic Cu/ZnO and Ag/ZnO NPs exhibited outstanding photocatalytic properties, with degradation rates of about 99 and 98%, respectively. These findings underscore the influence of the light source on photocatalytic performance as well as the significance of the plasmonic effects and charge-transfer mechanisms.

Optimizing luminescent properties of ZnO: Er3+ through temperature and dopant variation: XRD and emission spectroscopy studies

This study focuses on optimizing the synthesis conditions for the luminescent properties of ZnO:Er3[Formula: see text], a key step toward improving its applicability in optoelectronics. X-ray diffraction (XRD) patterns at [Formula: see text]C with Er3[Formula: see text] dopant concentrations (1, 3 and 5[Formula: see text]wt.%) show the preservation of the crystalline phase of ZnO, indicating that the dopants did not affect the structural integrity. Luminescence properties were observed in ZnO with 1[Formula: see text]wt.% erbium doping at 900–[Formula: see text]C, with the sample at [Formula: see text]C exhibiting the highest emission peak at 533[Formula: see text]nm. The optimal conditions for significant luminescence were identified at [Formula: see text]C, with 5[Formula: see text]wt.% Er3[Formula: see text] showing the most pronounced effect. The practical implications of the achievement of optimal luminescence in ZnO:Er3[Formula: see text] are profound for optoelectronics. These conditions are critical for efficient light-emitting devices, particularly in applications such as light-emitting diodes (LEDs) and lasers, where emission characteristics have a direct impact on performance. In addition, the enhanced luminescence holds great promise for sensors, especially in biomedical and environmental monitoring, as well as in quantum technologies. It contributes to the advancement of quantum sensors and quantum computing applications. This research provides a basis for tailoring the properties of ZnO:Er3[Formula: see text] for specific applications by identifying optimal luminescence conditions at different dopant concentrations. While the identification of optimal conditions has been successful, further research is essential to unravel the underlying mechanisms at the atomic and molecular levels. Overcoming these challenges and exploring additional applications will be critical to realizing the practical impact of these findings in various technological fields, as the study paves the way for advances in optoelectronics, sensing, and quantum information processing.

Tailoring of dielectric, ferroelectric, and optical properties of Bi0.99Nd0.1Fe2O3/ZnO nanocomposite at room temperature

We observe the fine-tuning of electrical and optical properties in a composite nanoparticle system consisting of varying weight fractions of semiconducting ZnO grains (x) embedded into Nd-doped multiferroic Bi0.99Nd0.1Fe2O3 matrix and annealed at 500 °C. X-ray diffraction (XRD) is used to validate the phase which further reveals the existence of cubic ZnO phases and rhombohedral BFO with some impurity phases. With the aid of SEM and EDX, the morphological and elemental composition of grains are found to be affected by ZnO nanoparticles. To understand the nature of dielectric response impedance analysis is performed which reveals the presence of large resistance offered by a composite maximum of 46.8 KΩ at x = 10 %. The enhancement in dielectric constant and dielectric loss is observed at higher concentrations for (x = 5 %). The Ferroelectric investigation shows that the maximum polarization achieved at low frequency for x = 10 % is 22.13 μc/cm2. The optical band gap in the composite sample exhibits significant dependence on ZnO concentrations, thus indicating potential application in optoelectronic devices.

Impact of blocking layers based on TiO2 and ZnO prepared via direct current reactive magnetron sputtering on DSSC solar cells

The optimization of dye-sensitized solar cells (DSSCs) technology towards suppressing charge recombination between the contact and the electron transport layer is a key factor in achieving high conversion efficiency and the successful commercialization of this type of product. An important aspect of the DSSC structure is the front blocking layer (BL): optimizing this component may increase the efficiency of photoelectron transfer from the dye to the semiconductor by reduction charge recombination at the TiO2/electrolyte and FTO/electrolyte interfaces. In this paper, a series of blocking layer variants, based on TiO2 and ZnO:TiO2, were obtained using the reactive magnetron sputtering method. Material composition, structure and layer thickness were referred to each process parameters. Complete DSSCs with structure FTO/BL/m-TiO2@N719/ EL-HSE/Pt/FTO were obtained on such bases. In the final results, verification of opto-electrical parameters of these cells were tested and used for the conclusions on the optimal blocking layer composition. As the conclusion, application of blocking layer consists of neat TiO2 resulted in improvement of device efficiency. It should be noted that for TiO2:ZnO/CuxO and TiO2/CuxO cells, higher efficiencies were also achieved when pure TiO2 was used as window layer. Additionally it was proven that the admixture of ZnO phase inspires Voc and FF growth, but is overall unfavorable compared to pristine TiO2 blocking layer and the reference cell, according to the final cell efficiency.

Atomic contributions to ZnO mechanical properties at negative and positive pressures

The energy-volume curve of a crystalline solid is critically examined in terms of the mechanical contributions of its constituent atoms. In addition to the usual analysis in the positive compression regime, our computational approach covers the tensile behavior in the negative pressure region up to the spinodal stability limit. Using the rich polymorphism of ZnO as a test-bed example, we propose two atomic decomposition schemes that are able to recover the bulk moduli and the critical strengths of four ZnO phases providing an intriguing interpretation of the chemical bonding network as a parallel circuit of mechanical resistors. Our scheme also allows the identification of the role played by the cation and anion in the densification of the high-pressure polymorphs and up to the material rupture points. This approach may help in the quest for tailored materials with outstanding mechanical performance.

WO3/ZnWO4 microcomposites with potential application in photocatalysis

The paper presents the results of a comprehensive study of the structural, optical and strength features, changes in the morphology of grains of (1-x)WO3 – xZnO ceramics depending on the concentration of the initial components when they vary. Using the X-ray diffraction method, it was found that mechanochemical grinding of samples of (1-x)WO3 – xZnO ceramics, regardless of the concentration of the components, does not lead to the initiation of phase transformation processes associated with the formation of the monoclinic ZnWO4 phase, the formation of which is observed during thermal annealing of samples at a temperature of 1000 °C. Based on data obtained using scanning electron microscopy and X-ray diffraction methods, the dynamics of phase transformations in ceramics of the type WO3/ZnWO4 → ZnWO4 → ZnO/ZnWO4 was established. It was found that with a given ratio of WO3: ZnO components equal to 0.7 : 0.3, under selected conditions of mechanochemical grinding and an annealing temperature of 1000 °C, highly ordered single-phase ZnWO4 ceramics with a wolframite structure can be obtained. Analysis of the optical characteristics and changes in the band gap depending on the ratio of the components showed a direct dependence of changes in the band gap on the phase composition of the ceramics. An assessment of the strength characteristics made it possible to establish that the formation of two-phase WO3/ZnWO4 ceramics leads to strengthening of the surface layer, while for two-phase ZnO/ZnWO4 ceramics a decrease in hardness is observed, the decrease of which directly correlates with changes in the content of the ZnO phase in the composition of the ceramics.

Mechanism Analysis and Experimental Research on Leaching Zn from Zinc Oxide Dust with an Ultrasound-Enhanced NH3-NH4Cl-H2O System

Zinc oxide dust (ZOD) is an industrial solid waste produced in the production process of wet smelting Zn, with large output and great pollution to the environment. The recycling of metallurgical solid waste such as zinc oxide dust is very important to achieve the sustainable development of the circular economy. An experimental study of zinc (Zn) leaching from zinc oxide dust using an ultrasound-enhanced ammonia–ammonium chloride system was performed. The effects of ultrasonic power, leaching time, total ammonia concentration, and other factors on the leaching rate of zinc from zinc oxide dust were investigated. The results revealed that the leaching rate of Zn reached up to 80.70% under the condition of ultrasound power of 1000 W, reaction time of 15 min, total ammonia concentration of 6 mol/L, [NH3]:[NH4+] of 1:1, L/S of 5:1, temperature of 45 °C, and stirring speed of 100 r/min. The conventional leaching was conducted under similar conditions, except that the time was controlled to 40 min and the zinc leaching rate was 71.15%. The leaching rate of Zn in the ultrasound condition was improved by 9.55% compared with that in the conventional leaching process. XRD, laser particle size, and SEM-EDS analyses were conducted to study the leaching residues of ZOD. The analysis results showed that in the ultrasound condition, the largest leaching rate of soluble ZnO phases was achieved after 15 min of leaching. Under the ammoniacal system, it was difficult to leach ZnFe2O4, Zn2SiO4, and ZnS phases, which partly accounted for the low zinc leaching rate. Additionally, through ultrasound-enhanced treatment, the ZnO particles encapsulated in ZOD particles were broken into smaller sizes and exposed to the leaching solution. Thus, the leaching rate of Zn was improved. The experimental results show that ultrasound can tremendously improve the effect of Zn extraction from ZOD, shorten reaction time, and help reduce energy consumption and environmental pollution, making it a promising application in the treatment of secondary Zn resources.

Amine functionalized graphene oxide decorated with ZnO-WO3 nanocomposites for remediation of organic dye from wastewater

Photocatalytic degradation is as an efficient technique to eradicate toxic chemical pollutants from contaminated water sources. However, the selectivity and photocatalytic activity are the challenging targets to explore the new photocatalysts. Therefore, our research goal is to develop a suitable photocatalyst to satisfy the recent photocatalytic degradation demand. In this work, amine functionalized graphene oxide (NH2-GO) supported heterojunction ternary novel nanocomposites (NH2-GO/ZnO-WO3) were prepared via simple solvothermal method. Structural and morphological investigations of the prepared composites are systematically observed by Field Emission Scanning Electron Spectroscopy (FE-SEM), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), and Ultraviolet–Visible (UV–vis) Spectroscopy. FT-IR analysis confirmed the effective functionalization of amine on graphene oxide. The XRD results indicated that the prepared nanocomposites were free from any impurities and the binary composite (NH2-GO/ZnO) showed hexagonal wurtzite structure, whereas the ternary composite (NH2-GO/ZnO-WO3) exhibited mix crystal structure of monoclinic and hexagonal phase of WO3 and ZnO, respectively. The synthesized ternary photocatalyst (NH2-GO/ZnO-WO3) demonstrated superior photocatalytic efficiency towards various organic dyes such as cationic dye methylene blue (MB, 85.89%) and anionic dye methyl orange (MO, 60.98%) compared to binary photocatalyst (NH2-GO/ZnO) that showed only 52.28% of MB and 25.8% of MO dye degradation under UV light irradiation. The enhanced photocatalytic performance was mainly due to the low recombination rate of photogenerated electron-hole pair, narrow band gap, and large surface area of ternary composite. The presence of lone pair electrons in amino group provides a negative-charged surface composite resulting good interaction with cationic dye is the key to upgrade the photocatalytic performance. The ternary nanocomposite NH2-GO/ZnO-WO3 has the capacity to be a competent and acceptable photocatalyst for the photodegradation of organic dyes used in industries.

Influence of sintering temperature on structural and optical properties of pure and Cl-doped ZnO nanoparticles

In this study, we conducted a detailed analysis of the sintering process of both pristine and 25 mg/g Cl-doped ZnO nanoparticles at varying temperatures to determine the optimum sintering temperature. Our findings revealed an optimal sintering temperature of 600 °C, resulting in higher phase purity (only hexagonal ZnO phase), smaller particle sizes of about 88–92 nm, and higher emission intensity for both pristine and Cl-doped ZnO nanoparticles. The band gap reduces from 3.63 eV to 3.20 for pristine and 3.63 eV to 3.10 for Cl-doped ZnO nanoparticles by increasing the sintering temperature from 200 °C to 1000 °C. The introduction of Cl in the ZnO lattice introduced a new defect level, having a broadband excitation band peaking at 374 nm. The luminescence of ZnO peaked at approximately 503 nm, which can be attributed to the transition from oxygen vacancies in the ZnO lattice. Notably, the emission intensity of the Cl-doped samples sintered at 600 °C was found to be 6.5 times higher than that of the pristine ones. Moreover, we found that the luminosity of ZnO:Cl nanoparticles was around 68% that of ZnS:Ag nanoparticles, which are typically used for radon detection and have similar efficiency to standard Lucas cells. Our preliminary findings suggest that Cl-doped ZnO nanoparticles sintered at 600 °C for 5 h could effectively develop radiation detectors, particularly for radon monitoring and related applications.

Immobilization of Bi2MoO6/ZnO heterojunctions on glass substrate: Design of drug and dye mixture degradation by solar-driven photocatalysis

In this study, the Bi2MoO6/ZnO heterostructures were quickly and easily obtained using the sonochemical method and impregnated on a glass plate using epoxy resin. The influence of increasing the percentage of ZnO (1:1, 2:1, 4:1 and 8:1% by weight) in relation to Bi2MoO6 on the formation of the heterostructure was investigated. The XRD results of the heterostructures indicated the presence of ZnO phases with a hexagonal structure and Bi2MoO6 with an orthorhombic structure. According to FESEM and HRTEM analyses, the morphology of ZnO is controlled with the addition of Bi2MoO6. The photocatalytic activity of the heterostructures was evaluated using a mixture (MIX) of methylene blue dye and diclofenac potassium, obtaining photocatalytic efficiency of 99.7 % and 90 % in 100 min under solar irradiation, with the ZN8B1 heterostructure, respectively. Aiming to increase the reuse of the material, the ZN8B1 heterostructure was impregnated into a glass plate, obtaining an efficiency of on average 65.2 % for 10 reuse cycles, showing that the impregnate can be applied to effluent treatment. The evaluation of the effect of photocatalyst dosage, contaminant concentration and pH effect was carried out with the MIX solution in order to simulate real conditions. Furthermore, a possible photocatalytic mechanism was proposed based on inhibition tests, verifying that the •O2– and •OH radicals were the dominant active species, which followed the Z-scheme mechanism.

ZnxFe3-xO4–ZnO heterojunction interfaced with poly(L-DOPA) electron transfer mediator layer for enhanced visible light photocatalytic activity

Z-scheme heterojunctions comprising ZnxFe3-xO4@poly(L-DOPA)@ZnO (ZF@PD@ZnO) were synthesized using solvothermal and precipitation techniques. The study aimed to investigate the impact of the poly(L-DOPA) electron transfer mediator on the photocatalytic performance of ZnxFe3-xO4@ZnO (ZF@ZnO) nanocomposites under visible light irradiation. X-ray diffraction (XRD) and HRTEM analysis confirmed the formation of heterostructures, identifying the crystalline phases of both ZnO and zinc ferrite. BFTEM images revealed a polyhedral shape for all samples, with a tendency toward mild agglomeration. The partial inversion of the zinc ferrite cubic spinel structure was evidenced by FT-IR, XPS, and VSM analyses. Zinc ferrite was found to be ferromagnetic, with cation distributions between tetrahedral (A) and octahedral (B) positions as [Zn0.62+Fe0.43+]A[Fe0.42+Fe1.63+]BO4. The samples exhibited notable photocatalytic activity against Rhodamine B, serving as a model contaminant. Furthermore, the stability and reusability of the samples were examined. Additionally, the study elucidated the photocatalytic mechanism produced by the ternary Z-scheme ZF@PD@ZnO, involving spin-polarized charge carriers. Energy band alignment was evaluated by combining ultraviolet photoelectron spectroscopy (UPS) with UV-Vis spectroscopy. The interplay between band alignment and reactive oxygen species (ROS) generation was discussed in correlation with EPR results. Enhanced ROS generation under visible light illumination, observed in the ZF@PD@ZnO nanocomposite, is mainly due to the addition of the conductive poly(L-DOPA) layer, acting as an electron transfer mediator in the Z-scheme heterojunction, ensuring enhanced charge separation.