ZnO Rods Research Articles

Investigation of ZnO@CdS nanocomposite with amplified photocatalytic H2 production under visible light irradiation

Researchers are trying to develop an efficient solar-powered catalytic water splitting system to solve the energy dilemma and generate green hydrogen. In this study, ZnO@CdS nano-heterostructures were synthesized using sol-gel and co-precipitation techniques. The pristine ZnO, CdS, and their heterostructures were characterized through various characterization tools such as XRD, SAED, XPS, FTIR, EDX, SEM, FE-TEM, UV–vis, Mott-Schottky, GCG, EIS, and PL, to know the crystal structure, chemical state, elemental composition, morphology, band gap, scheme mechanism, hydrogen production and charge transfer resistance characteristics of the samples, respectively. The SEM, FE-TEM, confirm that CdS NPs are well decorated on hexagonal ZnO rods. The efficient H2 production of 587.86 μmolg−1 h−1 were measured for the optimized sample which is 3.91 times greater than pure ZnO rods and 3.22 times than CdS NPs. Strong photo-cyclic stability test was carried out for 20 h in four cycles while, PL spectroscopy confirms the suppressed charge recombination. All of the above characterization prove that (ZC-20) optimized sample, has a potential to be used as an efficient and stable photocatalyst for H2 production via photocatalytic water splitting.

Hydrothermally synthesized ZnO/WS2 composite with impressive photocatalytic, antibacterial, and electrochemical performances

In this study, we prepared a multifunctional ZnO/WS2 composite by a hydrothermal process, in which ZnO rods are wrapped with WS2 sheets, and investigated its photocatalytic, antibacterial, and electrochemical properties. It was observed that the loading of WS2 sheets into ZnO rods significantly enhanced the catalytic activity of the resultant composite in terms of photocatalytic degradation of methylene blue (MB) and destruction of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria. Additionally, the ZnO/WS2 composite was implied as a substantial electrode material for supercapacitors. In a three-electrode system, the composite electrode exhibited good electrochemical performance with a specific capacitance of 180F/g at the current density of 0.5 A/g in a 2 M KOH electrolyte, which is 81 % enhancement than that of ZnO rods. Further, cyclic stability of ∼75 % was recorded after 5000 runs. The enhanced optical, photocatalytic, antibacterial, and electrochemical properties are ascribed to the combined effect of ZnO and WS2 in the composite system.

Design of novel FeSe2/ZnO composites and their application in photodegradation of methylene blue

Water pollution has become one of the major global issues, posing serious threat to both humans and aquatic life. The elimination of organic industrial pollutants from wastewater is currently a major area of research. Herein, we report for the first time a novel FeSe2/ZnO composite system for highly efficient removal of organic dyes under visible light. FeSe2/ZnO composites with varying mass ratios of FeSe2 were successfully prepared through simple and low-cost chemical method. The physiochemical properties of the prepared FeSe2/ZnO composites were carefully evaluated and compared with those of pure ZnO rods and FeSe2 flowers. UV–vis spectroscopy confirmed that the coupling of FeSe2 with ZnO caused a significant improvement in the optical absorption of ZnO. The bandgap energies of FeSe2/ZnO composites showed a red shift with increasing the ratio of FeSe2 flowers. The prepared samples were evaluated for their photocatalytic response against the removal of methylene blue dye. Compared to the pure FeSe2 and ZnO, the composites displayed impressive photocatalytic performance. Among the prepared samples, composite with an optimum ratio of 75 wt% FeSe2 revealed outstanding photocatalytic efficiency, making it a promising candidate for the removal of organic pollutants.

Facile synthesis of NiSe2-ZnO nanocomposites for enhanced photocatalysis and wastewater remediation.

In this study, NiSe2 nanocubes, ZnO rods, and their composites were prepared by simple chemical methods to investigate their photocatalytic response and antibacterial activity. The optimal concentration of NiSe2 nanocubes was explored for enhanced photocatalytic performance by varying its percentage in the NiSe2-ZnO composites. The findings suggested that the optical response of ZnO was significantly improved and shifted towards visible region by incorporating NiSe2 as a co-catalyst. The photocatalytic properties of NiSe2, ZnO, and NiSe2-ZnO composites were assessed under visible light by using methylene blue (MB) as a model pollutant. The results showed that the optimized composite containing 75% NiSe2 with ZnO exhibited outstanding photocatalytic efficiency of 97%. The degradation of MB dye by NiSe2, ZnO, and their composites followed the pseudo-first-order reaction kinetics (Langmuir-Hinshelwood model). Furthermore, the prepared NiSe2-ZnO composite displayed exceptional reusability and stability over a number of cycles, demonstrating its practical applicability. This research presents unique findings, showcasing the comparative antibacterial performance of NiSe2, ZnO, and NiSe2-ZnO nanocomposites against Bacillus cereus (B. cereus). Of all the prepared photocatalysts, the 75% NiSe2-ZnO nanocomposite revealed the best performance, exhibiting an inhibition zone of 28 mm.

Enhanced piezo-catalysis in ZnO rods with built-in nanopores

Enhanced piezo-catalysis in ZnO rods with built-in nanopores

Analysis of nonlinear multi-field coupling responses of piezoelectric semiconductor rods via machine learning

ABSTRACT Piezoelectric semiconductors (PSs) have widespread applications in semiconductor devices due to the coexistence of piezoelectricity and semiconducting properties. It is very important to conduct a theoretical analysis of PS structures. However, the present of nonlinearity in the partial differential equations (PDEs) that describe those multi-field coupling mechanical behaviors of PSs poses a significant mathematical challenge when studying these PS structures. In this paper, we present a novel approach based on machine learning for solving multi-field coupling problems in PS structures. A physics-informed neural networks (PINNs) is constructed for predicting the multi-field coupling behaviors of PS rods with extensional deformation. By utilizing the proposed PINNs, we evaluate the multi-field coupling responses of a ZnO rod under static and dynamic axial forces. Numerical results demonstrate that the proposed PINNs exhibit high accuracy in solving both static and dynamic problems associated with PS structures. It provides an effective approach to predicting the nonlinear multi-field coupling phenomena in PS structures.

Preparation, Characterization, Photochromic Properties, and Mechanism of PMoA/ZnO/PVP Composite Film.

A novel photochromic heteropolyacid-based composite film consisting of phosphomolybdic acid (PMoA), ZnO, and polyvinylpyrrolidone (PVP) was fabricated by a sol-gel process. The microstructure and photochromic properties of the PMoA/ZnO/PVP were characterized via Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible spectroscopy (UV-Vis). The FTIR spectra showed that the basic structures of ZnO and PVP, and the Keggin structure of PMoA in the PMoA/ZnO/PVP composite film, had not been destroyed during the preparation. The TEM images demonstrated that ZnO presented a rod-like structure, while PMoA was spherical, and many PMoA balls adhered to the surface of the ZnO rods. The XPS spectra of Mo 3d indicated that the valency of Mo atoms in the PMoA/ZnO/PVP was changed by visible light exposure. After visible light irradiation, the PMoA/ZnO/PVP varied from slight yellow to blue, while undergoing an opposite color change upon heating. The discoloration mechanism of the PMoA/ZnO/PVP was consistent with the photoelectron transfer mechanism.

Enhancing photoelectrochemical performance through surface engineering of CdSe and Al-doped CdSe nanoparticles on ZnO/FTO photoanodes

This study presents a comprehensive investigation into the enhanced performance of photoelectrochemical (PEC) cells through the decoration of CdSe and Al-doped CdSe nanoparticles on ZnO rods. The capacitance-voltage study reveals that Al doping increases the donor concentration and improves minority carrier diffusion time while reducing dispersion at grain boundaries. Spectral response analysis demonstrates that CdSe/ZnO/FTO and Al: CdSe/ZnO/FTO photoanodes exhibit maximum short-circuit currents at a wavelength of 675 nm, corresponding to a bandgap of 1.84 eV. Al doping shifts the spectral response to longer wavelengths, indicating an estimated bandgap of 1.72 eV. Furthermore, the effect of surface free energy and polarity on the developed photoanode materials is investigated. CdSe and Al-doped CdSe nano particles on ZnO/FTO surfaces exhibit reduced water contact angles, indicating improved wettability. The surface free energy decreases with Al doping, potentially influencing electrolyte absorption and the interaction between photoanodes and electrolytes. The presence of polar hydroxyl (-OH) groups and Al+++ ions on the Al: CdSe nano particles contributes to their impact on surface free energy. These findings provide valuable insights for optimizing PEC cell performance by manipulating doping concentrations and surface characteristics.

Influence of Synthesis Conditions on the Properties of Zinc Oxide Obtained in the Presence of Nonionic Structure-Forming Compounds.

This work investigated the influence of synthesis conditions, including the use of nonionic structure-forming compounds (surfactants) with different molecular weights (400-12,600 g/mol) and various hydrophilic/hydrophobic characteristics, as well as the use of a glass substrate and hydrothermal exposure on the texture and structural properties of ZnO samples. By X-ray analysis, it was determined that the synthesis intermediate in all cases is the compound Zn5(OH)8(NO3)2∙2H2O. It was shown that thermolysis of this compound at 600 °C, regardless of the physicochemical properties of the surfactants, leads to the formation of ZnO with a wurtzite structure and spherical or oval particles. The particle size increased slightly as the molecular weight and viscosity of the surfactants grew, from 30 nm using Pluronic F-127 (MM = 12,600) to 80 nm using Pluronic L-31 (MM = 1100), PE-block-PEG (MM = 500) and PEG (MM = 400). Holding the pre-washed synthetic intermediates (Zn5(OH)8(NO3)2∙2H2O) under hydrothermal conditions resulted in the formation of hexagonal ZnO rod crystal structures of various sizes. It was shown that the largest ZnO particles (10-15 μm) were observed in a sample obtained during hydrothermal exposure using Pluronic P-123 (MM = 5800). Atomic adsorption spectroscopy performed comparative quantitative analysis of residual Zn2+ ions in the supernatant of ZnO samples with different particle sizes and shapes. It was shown that the residual amount of Zn2+ ions was higher in the case of examining ZnO samples which have spherical particles of 30-80 nm. For example, in the supernatant of a ZnO sample that had a particle size of 30 nm, the quantitative content of Zn2+ ions was 10.22 mg/L.

Au- or Ag-Decorated ZnO-Rod/rGO Nanocomposite with Enhanced Room-Temperature NO2-Sensing Performance.

To improve the gas sensitivity of reduced oxide graphene (rGO)-based NO2 room-temperature sensors, different contents (0-3 wt%) of rGO, ZnO rods, and noble metal nanoparticles (Au or Ag NPs) were synthesized to construct ternary hybrids that combine the advantages of each component. The prepared ZnO rods had a diameter of around 200 nm and a length of about 2 μm. Au or Ag NPs with diameters of 20-30 nm were loaded on the ZnO-rod/rGO hybrid. It was found that rGO simply connects the monodispersed ZnO rods and does not change the morphology of ZnO rods. In addition, the rod-like ZnO prevents rGO stacking and makes nanocomposite-based ZnO/rGO achieve a porous structure, which facilitates the diffusion of gas molecules. The sensors' gas-sensing properties for NO2 were evaluated. The results reveal that Ag@ZnO rods-2% rGO and Au@ZnO rods-2% rGO perform better in low concentrations of NO2 gas, with greater response and shorter recovery time at the ambient temperature. The response and recovery times with 15 ppm NO2 were 132 s, 139 s and 108 s, 120 s, and the sensitivity values were 2.26 and 2.87, respectively. The synergistic impact of ZnO and Au (Ag) doping was proposed to explain the improved gas sensing. The p-n junction formed on the ZnO and rGO interface and the catalytic effects of Au (Ag) NPs are the main reasons for the enhanced sensitivity of Au (Ag)@ZnO rods-2% rGO.

Biochar-ZnO/polyaniline composite in energy storage application: Synthesis, characterization and electrochemical analysis

Carbon materials displaying electrical double layer capacitance are widely used in the electrochemical energy storage devices. To enhance the electrochemical performance, compositing carbon with transition metal oxides and conducting polymers have been very much appreciated. A novel and effective approach to prepare a high energy density and high specific capacitance composite electrode material from a biomass is presented in the work. Pyrolysis of biomass at 500 °C in the nitrogen atmosphere yielded a biochar (BC) with well-developed porosity, surface functionality and suitable morphological characteristics. Anchoring ZnO nanoparticles on BC and subsequently coating it with a conducting polymeric material, polyaniline (PANI) obtained the hierarchical BC-ZnO/PANI composite. Both BC-ZnO and BC-ZnO/PANI composites have been characterized by FTIR, UV–Visible, XRD, SEM and TEM studies. The characteristic signals at 2θ values 18.5°, 28.4°, 24.0° and 31.4° in XRD correspond to wurtzite structure of ZnO nanoparticles. ZnO rod like structural morphology was confirmed by SEM analysis. The maximum specific capacitance was found to be 110.0 F/g for BC-ZnO and 198.0 F/g for BC-ZnO/PANI. The ternary composite displayed low solution resistance and charge transfer resistance as evident from the Nyquist plots. The results proved that PANI coating is a promising methodology in the fabrication of electrode materials for energy storage applications.

Melamine-Assisted Thermal Activation Method for Vacancy-Rich ZnO: Calcination Effects on Microstructure and Photocatalytic Properties.

Defect engineering is considered an effective method to adjust the photocatalytic properties of materials. In this work, we synthesized the vacancy-rich ZnO rods with (100) planes via the melamine-assisted thermal activation method. A high concentration of oxygen vacancies was successfully introduced into non-polar oriented ZnO rods by calcination. The effect of oxygen vacancy on the photocatalytic properties of non-polar-oriented ZnO rods was investigated. Raman and XPS spectra revealed the formation of oxygen vacancies in the ZnO. The results showed that the growth habit and defects in ZnO can be controlled by changing the ratio of ZnO to melamine. The higher ratio of ZnO to melamine led to more amounts of (100) planes and oxygen vacancies in ZnO, and it reached the highest when the ratio was 1.2:1. When the ratio was 1.2:1, ZnO exhibited a high methyl orange degradation rate (95.8%). The differences in oxygen vacancy concentration and non-polar planes were responsible for the improvement in photocatalytic performance. ZnO exhibited good stability and regeneration capacity. After recycling four times, the degradation rate was still at 92%. Using the same method, vacancy-rich α-Fe2O3 was obtained. This work could offer a new and simple strategy for designing a photocatalyst with oxygen vacancies.

Heterostructured Interface Enables Uniform Zinc Deposition for High-Performance Zinc-Ion Batteries.

Zinc metal has considerable potential as a high-energy anode material for aqueous batteries due to its high theoretical capacity and environmental friendliness. However, dendrite growth and parasitic reactions at the electrode/electrolyte interface remain two serious problems for the Zn metal anode. Here, the heterostructured interface of ZnO rod array and CuZn5 layer is fabricated on the Zn substrate (ZnCu@Zn) to address these two issues. The zincophilic CuZn5 layer with abundant nucleation sites ensures the initial uniform Zn nucleation process during cycling. Meanwhile, the ZnO rod array grown on the surface of the CuZn5 layer can guide the subsequent homogeneous Zn deposition via spatial confinement and electrostatic attraction effects, leading to the dendrite-free Zn electrodeposition process. Consequently, the derived ZnCu@Zn anode exhibits an ultra-long lifespan of up to 2500h with symmetric cells at the current density and capacity of 0.5mAcm-2 /0.5mAhcm-2 . Besides, a remarkable cyclability (75% retention for 2500 cycles at 2Ag-1 ) is achieved in the ZnCu@Zn||MnO2 full cell with a capacity of 139.7mAhg-1 . This heterostructured interface with specific functional layers provides a feasible strategy for the design of high-performance metal anodes.

Changes to Material Phase and Morphology Due to High-Level Molybdenum Doping of ZnO Nanorods: Influence on Luminescence and Defects.

The influence of Mo on the electronic states and crystalline structure, as well as morphology, phase composition, luminescence, and defects in ZnO rods grown as free-standing nanoparticles, was studied using a variety of experimental techniques. Mo has almost no influence on the luminescence of the grown ZnO particles, whereas shallow donors are strongly affected in ZnO rods. Annealing in air causes exciton and defect-related bands to drop upon Mo doping level. The increase of the Mo doping level from 20 to 30% leads to the creation of dominating molybdates. This leads to a concomitant drop in the number of formed ZnO nanorods.

Room-temperature methane sensors based on ZnO with different exposed facets: A combined experimental and first-principle study

Methane is a flammable and explosive gas, which is difficult to detect at room temperature. In this work, the photo-activation route was explored to realize the monitoring of methane at room temperature, and the strategy of surface morphology engineering was used to boost excellent methane gas-sensing performance. Three types of ZnO structures: rods, plates, and spheres with exposed (001) and (100) crystal facets in different ratios, were obtained using solvothermal methods. Such characteristics of samples were confirmed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N2 adsorption-desorption analyzer. The gas-sensing performances of sensors based on as-prepared materials were tested under UV light and in the dark. The results indicate that sensors exhibit excellent gas-sensing performances toward methane under UV light at room temperature. ZnO spheres showed a much better response of 20.577 toward 5000 ppm methane and a faster response time of 6 s compared to ZnO plates and rods. The enhanced gas sensing properties were ascribed to high-energy exposed facets and unique hollow structures. In addition, density functional theory (DFT) was investigated to support the effect of crystal facets

Investigation of the influence for ZnSe phase in Ag2ZnSnSe4 and ZnO/Ag2ZnSnSe4 photoanodes on their photoelectrochemical activities in salt water solution

In this study, quaternary Ag2ZnSnSe4 (AZTSe) photoanodes with low and high ratios of ZnSe phase are made to understand the influence on the charge-transfer mechanisms, reaction kinetics and photoelectrochemical activities in electrolyte. Photoelectrochemical activities of 7.5 and 5.25 mA/cm2 at the given voltage of 1 V (vs. Ag/AgCl) are obtained using the AZTSe sample containing low ratio (atomic percentage of around 21% in sample) and high ratio (atomic percentage of around 37% in sample) of ZnSe phase, respectively. From the electrochemical measurements and X-ray absorption spectra of samples, the ZnSe phase can attract the light-driven electrons from the sample with low ratio of ZnSe phase (atomic percentage of 21% in sample). However, for the sample containing high ratio of ZnSe phase (atomic percentage of 37% in sample), the ZnSe acts as the recombination center and results in poor photoelectrochemical activity. With the modification of ZnO rods on sample, its long-term photoelectrochemical activity is improved due to high charge transportation kinetic and photo-driven holes accumulation on ZnO rods rather than on AZTSe sample. Our study reports a significant observation on the influence of ZnSe phase for photoelectrochemical salt-water splitting.

Laser induced hydrothermal growth of ZnO rods for UV detector application

Laser induced hydrothermal growth of ZnO rods for UV detector application

Post-Consumer Polyurethane Foams Hydrophobization Through Surface Modifications for Oil Spill Sorption

To increase oil sorption, polyurethane foams were modified with MoS2, ZnO grafting and/or hexadecanoic acid coating. The foams were characterized by Scanning Electron Microscopy + Energy Dispersive X-ray Spectroscopy and Contact Angle techniques. Three sorption tests were performed. In tests with 100% water, the ZnO-PC modification showed a reduction of 35.7% in the seawater sorption when compared to Un-PC. In tests with 100% oil, there was a 29-fold increase in sorption (more than 2803%) of S46 lubricant oil when Un-PC performance was compared with ZnO-PC. In tests on the multicomponent systems, the lowest seawater sorption was 0.01 ± 0.00 g.g-1 (HA-PC), 0.08 ± 0.01 g.g-1 (Un-PC), and 1.39 ± 0.02 g.g-1 (Un-PC) for 20W40 engine oil, S46 lubricating oil, and diesel, respectively. The highest oil sorption in the systems was 41.34 ± 1.02 g.g-1 (HA-PC), 32.81 ± 0.31 g.g-1 (MoS2-PC), and 14.78 ± 0.27 g.g-1 (ZnO-PC) for diesel, S46 lubricating oil, and 20W40 engine oil, respectively. The reuse tests indicated that even after 10 cycles, the ZnO-PC foam kept its sorption capacity unchanged. Post-consumer foams proved to be effective in the sorption of different oils spilled into seawater, especially those grafted with ZnO rods or impregnated with MoS2.

Hydrophilic ionic liquid assisted hydrothermal synthesis of ZnO nanostructures with controllable morphology.

Nanostructured ZnO with controllable morphology was prepared by a hydrothermal method in the presence of three different hydrophilic ionic liquids (ILs), 1-ethyl-3-methylimidazolium methylsulfate, ([C2mim]CH3SO4), 1-butyl-3-methylimidazolium methylsulfate, ([C4mim]CH3SO4) and 1-ethyl-3-methylimidazolium ethylsulfate, ([C2mim]C2H5SO4) as soft templates. The formation of ZnO nanoparticles (NPs) with and without IL was verified using FT-IR and UV-visible spectroscopy. X-ray diffraction (XRD) and selected area electron diffraction (SAED) patterns indicated the formation of pure crystalline ZnO with a hexagonal wurtzite phase. Field emission scanning electron microscopic (FESEM) and high-resolution transmission electron microscopic (HRTEM) images confirmed the formation of rod-shaped ZnO nanostructures without using IL, whereas the morphology varied widely following addition of ILs. With increasing concentrations of [C2mim]CH3SO4, the rod-shaped ZnO nanostructures transformed into flower-shaped nanostructures whereas with rising concentrations of [C4mim]CH3SO4 and [C2mim]C2H5SO4 the morphology changed into petal- and flake-like nanostructures, respectively. The selective adsorption effect of the ILs could protect certain facets during the formation of ZnO rods and promote the growth in directions other than [0001] to yield petal- or flake-like architectures. The morphology of ZnO nanostructures was, therefore, tunable by the controlled addition of hydrophilic ILs of different structures. The size of the nanostructures was widely distributed and the Z-average diameter, evaluated from dynamic light scattering measurements, increased as the concentration of the IL increased and passed through a maximum before decreasing again. The optical band gap energy of the ZnO nanostructures decreased when IL was added during the synthesis which is consistent with the morphology of the ZnO nanostructures. Thus, the hydrophilic ILs serve as self-directing agents and soft templates for the synthesis of ZnO nanostructures and the morphology and optical properties of ZnO nanostructures are tunable by changing the structure of the ILs as well as systematic variation of the concentration of ILs during synthesis.

Preparation of Oriented ZnO Rod Arrays Using Hexagonal Plate-Like Particles as a Seed Layer

ZnO rod film is a promising material for electrodes and sensors due to its large surface area and high electrical conductivity. One of the drawbacks of conventional ZnO rod film is the random orientation of rods. In this study, an oriented ZnO seed layer composed of hexagonal plate-like ZnO particles was prepared by dip-coating. An oriented ZnO rod film was then synthesized by growing this seed layer using a hydrothermal synthesis method. We optimized the concentration of the precursor and the hydrothermal treatment time to synthesize homogeneous ZnO rod arrays. The uniformity of the rod arrays was improved by applying a strong magnetic field (12 T) during hydrothermal treatment.