Morphology Of Zinc Oxide Research Articles

ZnO nanostructures grown from spent batteries: Ambient catalytic aspects and novel mechanistic insights

The present work includes a facile and economic microwave assisted hydrothermal synthesis of Zinc Oxide (ZnO), Diethylene Triamine Pentaacetic Acid (DTPA) stabilized Zinc Oxide (ZD) and DTPA stabilized Silver doped Zinc Oxide (ZAD) nanostructures using Zn from spent alkaline batteries. The synthesised nanostructures were well characterised using electronic, vibrational and X-Ray spectroscopic techniques as well as thermal and microscopic techniques revealing the successful stabilisation of DTPA in ZD and doping of Ag in ZAD. The Fourier Transform Infrared Spectroscopy (FTIR) spectra showed peaks characteristic to the presence of ZnO in the fingerprint region and those to the presence of DTPA. The X-Ray Diffraction Spectroscopy (XRD) pattern of ZnO, ZD and ZAD indicated the hexagonal wurtzite structure of ZnO and face centred cubic metallic Ag in ZAD. The Transmission Electron Microscopy (TEM) images revealed rod shaped morphology for ZnO and spherical morphologies for ZD and ZAD. The nanostructures proved to be efficient catalysts to achieve 100 % degradation of Malachite Green, Crystal Violet and Reactive Blue-21 and their binary mixtures under ambient conditions in presence of Hydrogen peroxide (H2O2). ZAD exhibited relatively rapid degradation with rate constants 0.754 min−1, 0.187 min−1 and 0.0150 min−1 for MG, CV, and RB-21 respectively as well as 99 % reduction in Chemical Oxygen Demand (COD) value of the dye solutions. Scavenging studies and Electron Paramagnetic Resonance (EPR) studies using different spin trapping agents revealed the involvement of singlet oxygen species, hydroxyl radicals (OH.) and superoxide radicals (O2.-) in the degradation process. This work aligns with Sustainable Development Goals 6, 12 and 13.

The figure of merit improvement of (Sn, Co)–ZnO sprayed thin films for optoelectronic applications

Nanocrystalline zinc oxide (ZnO) has garnered significant attention from researchers and industries due to its superior properties as an optoelectronic material, particularly in solar cells as a transparent electrode. Doping, especially with tin (Sn) and co-doping with tin and cobalt (Co), can refine its optoelectronic properties. In this manuscript, we report on the optoelectronic properties of undoped ZnO thin films, as well as those doped with Sn and/or Co, elaborated using a simple chemical pneumatic spray pyrolysis method on glass substrates. A 1 % Sn doping concentration was used, with Co doping concentrations of 0 %, 0.5 %, and 1 %. The effects of Sn and/or Co doping concentration on the structure, morphology, optical, and electrical properties of nanocrystalline ZnO were studied using X-ray diffractometer (XRD), Raman spectroscopy, Field emission scanning electron microscopy (FESEM), UV–Vis–NIR spectroscopy and Hall effect measurements. All the films studied exhibit wurtzite ZnO structures with a predominant (002) orientation and no secondary phase, as confirmed by X-ray diffraction (XRD) analysis. The Raman spectroscopy also reveals the presence of a wurtzite structure in all the films. The FESEM images reveal the kind and concentration of the dopants significantly influenced the surface morphology of the films. The elemental analysis with energy dispersive X-ray analysis (EDS) analysis successfully detected the doping of Sn and Co. The analysis of UV–Vis spectroscopy provide that the optical band gap for the undoped ZnO film is 3.25 eV. This band gap increases upon doping and co-doping, reaching a peak value of 3.30 eV for the Sn:Co (1 %:0.5 %) co-doped ZnO film. The ZnO film shows an improvement in the electrical resistivity upon doping and co-doping with low resistivity value of 1.95 × 10−2 Ω cm for the film (1%Sn, 0.5 % Co)–ZnO. The highest figure of merit (FOM) achieved is 1.41 × 10−4 Ω−1 for a ZnO thin film co-doped with (1 % Sn, 0.5 % Co). The existence of (1 % Sn, 0.5 % Co) film with improved optical gap, low electrical resistivity and high FOM supports its use in transparent conductive oxide applications.

Investigation of the effects of coating numbers of thin films and metal contact type on physical properties of undoped ZnO, Fe-doped ZnO, and Fe–B co-doped ZnO thin films

This study was designed for three purposes. The first objective was to examine the effects of iron (Fe) and boron (B) elements on the physical properties (structural, electrical, optical, and optoelectronic) of zinc oxide (ZnO) material. For this reason, pristine ZnO, 6% Fe-doped ZnO (Zn0.94Fe0.06O), and 6% Fe-4% B co-doped ZnO (Zn0.90Fe0.06B0.04O) thin films with different thicknesses (4, 6, 8, and 10 layers of coatings for each sample type) were produced using sol–gel dip coating and spraying method on glass and silicon (Si) substrates. In the second stage, we examined the effects of film thickness on optical, electrical, and optoelectronic properties for these three sample types. In the final stage, the MIS (metal/interlayer/semiconductor) structures were created using the three groups of samples produced as interlayers. Gold (Au) was initially applied as the metal contacts in these MIS structures. We investigated optoelectronic and electrical properties such as ideality factor, barrier height, and series resistance for all samples with Au contacts. Afterward, aluminum (Al) contacts were coated on the sample that yielded the best results with Au contacts, and the same properties were re-examined, thereby determining the effects of the contact material, especially on optoelectronic properties. All samples were produced as pure and wurtzite ZnO polycrystalline with preferred orientation along the (002) plane. Although Hall measurement results indicated that all sample groups were n-type semiconductors, the carrier density decreased from − 7.5 × 1013 for pristine ZnO to − 8.7 × 1011 with Fe–B co-doping. The irregular nanodots-shaped surface morphology of ZnO transformed into a homogeneous and smooth one by incorporating boron into the structure. In all sample groups except the 6% Fe-doped ZnO thin films, the band gaps of the thin films decreased as the film thickness increased. For pure ZnO and Fe-B co-doped ZnO sample groups, the band gap energy decreased from 3.245 to 3.215 eV, and from 3.540 to 3.180 eV, respectively, depending on the thicknesses of films. On the other hand, the band gap energy of only Fe–doped ZnO samples increased from 3.34 eV to 3.46 eV. It was observed that as the thicknesses of films increased, the ideality factor of Au/ZnO/p-Si, Au/Zn0.94Fe0.06O/p-Si, and Au/Zn0.90Fe0.06B0.04O/p-Si diodes increased, and the barrier heights of them decreased in the three sample groups. However, when we look at the average value of the electrical properties including all layers, we can say that the best results were obtained for the Fe–B co-doped sample group. Specifically, Fe–B co-doped ZnO sample with 6 layers of coating exhibited an ideality factor of 3.25, a barrier height of approximately 0.51 eV, and a serial resistance of 8.42 kΩ. The best performance as solar cell and photodiode was again obtained for this sample. While the solar cell efficiency of this sample (6 layers of coated Zn0.90Fe0.06B0.04O) was 0.04% with Au contacts, it increased to 0.08% with Al contacts.In summary, it was observed that the electrical, optical, structural, and optoelectronic (as solar cell and photodiode) properties of ZnO material were improved very well made with Al contact and 6 layers of coated Fe and B co-doping. Therefore, Zn0.90Fe0.06B0.04O sample may be promising material for optoelectronic devices.

Investigation of structural, optical, electrical, thermoelectric and optoelectronic properties of undoped ZnO, Sb-doped ZnO and Sb–B co-doped ZnO thin films

Pure ZnO (Zinc oxide), 1 % Sb (antimony) doped ZnO (Zn0.99Sb0.01O), and 1 % Sb–1% B (boron) co-doped ZnO (Zn0.98Sb0.01B0.01O) solutions were prepared using the sol-gel method. These solutions were deposited as thin films on glass and Si (silicon) substrates via dip coating and spraying methods. In this study, doping ZnO with low amounts of Sb and B provided the conversion of the n-type semiconductor ZnO into a p-type semiconductor. The produced thin films were pure and had wurtzite ZnO polycrystalline structure. The nanodot morphology of ZnO turned into a mixture of nanodot and nanorod structures with only Sb doping. Moreover, the band gap energy of ZnO decreased from 3.26 eV to 3.24 eV with Sb doping and to 3.23 eV with Sb and B co-doping, accompanied by a decrease in optical transmittance depending on film thickness. All samples exhibited diode characteristics. According to the created Au/ZnO–Zn0.99Sb0.01O – Zn0.98Sb0.01B0.01O/Si diodes, it was understood that the ideality factor, barrier height, and serial resistance of ZnO material decreased with doping. Especially, the ideality factor, barrier height, and serial resistance of the ZnO sample decreased from 4.95, 6.80 eV, and 1.42 × 105Ω to 4.35, 6.25 eV, and 2.60 × 103Ω, respectively, with Sb and B co-doping. The photovoltaic performance of 1 % Sb-doped thin film increased 100 times compared to pure ZnO, reaching the efficiency from 0.006 to 0.600. However, the most suitable material for use as a photodiode was found to be the 1 % Sb–1% B co-doped sample. While the leakage current of this sample is around −8.0 × 10−5 A at −3 V under 100 mW/cm2 light, it is 9.5 × 10−8 A at −3 V in the dark. Furthermore, the 1 % Sb-doped thin film exhibited the best performance as a thermoelectric material at 600 K, achieving a figure of merit (ZT) of 0.00052. Overall, co-doping with Sb and B enhanced the optical, electrical, and structural (more homogeneous and less surface roughness) properties of ZnO, while improving its optoelectronic functionality such as photodiode. On the other hand, thermoelectric and solar cell properties of ZnO were enhanced with only 1 % Sb doping. A hybrid energy system containing thermoelectric and solar cells was produced cheaply and simply for wide application areas with this study. Moreover, with such a low doping amount, p-type material production was achieved, and important physical properties of the ZnO material were improved.

Layered double hydroxide (LDH)-derived zinc oxide (ZnO) nanorod on exfoliated graphene oxide (GO) nanosheet for photocatalytic dye degradation and hexavalent chromium reduction

A new low-temperature facile chemical decomposition of layered double hydroxide (LDH) has been developed for the large-scale controlled synthesis of zinc oxide (ZnO) nanorod on exfoliated graphene oxide (GO) nanosheet. ZnAl-LDH/GO composite precursor was prepared via in situ growth of the LDH on the exfoliated GO nanosheets. Thermo-chemical decomposition of ZnAl-LDH/GO composite at 80 °C produced highly dispersed ZnO nanorods on GO nanosheets. Although, neat ZnAl-LDH produces ZnO nanoparticle aggregates in the absence of GO. The morphology and properties of ZnO nanorods/GO nanocomposite was studied by X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), UV–vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The band gap engineering of the nanocomposite was evaluated by varying GO content. The ZnO/GO nanocomposites materials exhibited excellent photo-catalytic activity towards the degradation of methylene blue (MB) and Cr(VI) reduction under the irradiation of direct sunlight at ambient condition. GO plays a crucial role in the directional growth of nanorods and enhances the photocatalytic activity of ZnO nanorods via the synergistic hole formation and electron transfer effect for the potential remediation of waste water.

Effect of surfactants (cetyl trimethyl ammonium-bromide, ethyl di-tetra amine and polyacrylamide) on the synthesis of zinc oxide for photocatalytic application

In this work, we report the effect of cetyl trimethyl ammonium bromide (CTAB), ethyl di-tetra amine (EDTA) and polyacrylamide as surfactants on synthesis of zinc oxide for photocatalytic application. The ZnO nanoparticles were synthesized with and without the surfactants and characterized using powder X-ray diffraction (PXRD), and Fourier transform infrared spectroscopy (FTIR). In addition to this, the morphology of zinc oxide prepared in the absence and presence of these surfactants investigated through scanning electron microscopy (SEM). As confirmed from XRD and FTIR characterization results, the use of different surfactants did not affect the composition of ZnO nanomaterials. The photocatalytic activities were investigated by the degradation of methylene blue (MB) dye under sunlight irradiation. To optimize the effects of operational parameters, the study was carried out as a function of dye concentration, catalyst dose, and pH on the degradation efficiency of the photocatalysts. The optimum values of catalyst dose, dye concentration and pH of solution were found to be 0.09 g, 5 mg/L and 10, respectively. The ZnO nanomaterials prepared with CTAB surfactant showed highest degradation efficiency of 98% indicating potential application for practical decontamination of wastewater from toxic organic pollutants. KEY WORDS: Surfactants, Zinc oxide nanoparticles, Photocatalysis, Methylene blue Bull. Chem. Soc. Ethiop. 2024, 38(4), 923-935. DOI: https://dx.doi.org/10.4314/bcse.v38i4.9

Cd doped ZnO nano-rectangles and their correlation with properties

Nowadays, the size, shapes and morphologies of zinc oxide (ZnO) can be controlled in a fascinating way by improved synthesis methods and controlled nucleation and growth processes driven by varying the experimental conditions. Nanoscience holds a particular fascination with ZnO because of its properties, which vary based on shape and how they evolve across a wide range of applications. We report here the room temperature synthesis of rectangular shaped cadmium (Cd) doped ZnO nanostructures by a wet chemical route employing surface modifications with the surfactants polyvinyl pyrrolidone, polyvinyl alcohol and biotin. A simple and general mechanism for the formation of the Cd doped ZnO nano-rectangles is discussed. The crystallographic, morphological and optical properties of the prepared nanostructures are also studied in connection with the role of surfactants and dopant, and correlated with their shape.

Effect of Size and Morphology of Different ZnO Nanostructures on the Performance of Dye-Sensitized Solar Cells

In this study, the influence of zinc oxide (ZnO) nanostructures with various morphologies on the performance of dye-sensitized solar cells (DSSCs) was investigated. Photo-electrodes were fabricated incorporating ZnO transport layers of distinct nanoscale morphologies—namely nanoparticles, microballs, spiky microballs, belts, and triangles—and their respective current–voltage characteristics were evaluated. It was observed that the DSSCs employing the triangular ZnO nanostructures, with a side length of approximately 30 nm, achieved the highest power conversion efficiency of 2.62%. This was closely followed by the DSSCs using spherical nanoparticles with an average diameter of approximately 20 nm, yielding an efficiency of 2.54%. In contrast, the efficiencies of DSSCs with microball and spiky microball ZnO nanostructures were significantly lower, measuring 0.31 and 1.79%, respectively. The reduction in efficiency for the microball-based DSSCs is attributed to the formation of micro-cracks within the thin film during the fabrication process. All DSSC configurations maintained a uniform active area of 4 mm². Remarkably, the highest fill factor of 59.88% was recorded for DSSCs utilizing the triangular ZnO morphology, with the spherical nanoparticles attaining a marginally lower fill factor of 59.38%. This investigation corroborates the hypothesis that reduced particle size in the transport layer correlates with enhanced DSSC performance, which is further amplified when the nanoparticles possess pointed geometries that induce strong electric fields due to elevated charge concentrations.

Controlling surface morphology of Ag-doped ZnO as a buffer layer by dispersion engineering in planar perovskite solar cells

In recent years, the power conversion efficiency (PCE (%)) of perovskite solar cells (PSCs) has improved to over 26%. To enhance the photovoltaic properties of PSCs, several materials for the electron transport layer (ETL) have been investigated. Zinc oxide (ZnO) is a significant ETL due to its high electron mobility and optical transparency in PSCs. As a result of various deposition methods, ZnO ETL can be processed at low temperatures. On the other hand, based on several studies, metal-doped ZnO can facilitate electron transfer, thereby improving the performance of un-doped ZnO ETL-based PSCs. Here, to improve the PCE (%) and long-term stability of un-doped ZnO ETL-PSCs, silver (Ag)-doped ZnO 1wt% as a buffer layer is examined. In this paper, with the addition of an organic solvent (ethanol) to the dispersion of Ag-doped ZnO 1 wt% nanoparticles (NPs) in deionized (DI) water, the morphology of the buffer layer (Ag-doped ZnO 1 wt%) can be controlled. This approach focuses on reducing the wettability of the ZnO/Ag-doped ZnO 1 wt% bilayer ETLs and enhancing the stability of un-doped ZnO ETL-PSCs. According to the results, the ZnO/H2O-ethanol mixtures-Ag-doped ZnO 1 wt% bilayer ETL leads to the formation of high-quality perovskite with low defects, reducing the recombination rate, and long-term stability of un-doped ZnO ETL-PSCs in ambient conditions.

Ultraviolet Photodegradation of Ciprofloxacin Using Zinc Oxide and Iron-Doped Zinc Oxide (Fe-ZnO) Nanoparticles (NPs): Kinetic and Isotherm Measurements

This article describes the auto-combustion sol-gel synthesis of zinc oxide (ZnO), 0.1% iron-doped zinc oxide (0.1% Fe-ZnO), and 0.2% iron-doped zinc xide (0.2% Fe-ZnO) NPs with the goal of determining their suitability as a photocatalyst for the degradation of a hazardous antibiotic drug (ciprofloxacin). The functional group, surface morphology, and crystallinity of ZnO, 0.1% Fe-ZnO, and 0.2% Fe-ZnO NPs were studied using Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), and x-ray diffraction analysis (XRD). Various parameters, such as solution pH, catalyst dosage, light exposure period, and initial drug concentration, were optimized for quantitative degradation. The photocatalytic degradation of ciprofloxacin using ZnO, 0.1% Fe-ZnO, and 0.2% Fe-ZnO follows pseudo-first-order kinetics. The proposed method has been applied to commercial formulations such as Ciprofloxacinro, Ciprofloxacinro XR, and Ciprofloxacinro ProQuin XR with satisfactory results.

Efficient synthesis of 3D ZnO nanostructures on ITO surfaces for enhanced photoelectrochemical water splitting

New photoactive materials with uniform and well-defined morphologies were developed for efficient and sustainable photoelectrochemical (PEC) water splitting and hydrogen production. The investigation is focused on hydrothermal deposition of zinc oxide (ZnO) onto indium tin oxide (ITO) conductive surfaces and optimization of hydrothermal temperature for growing uniform sized 3D ZnO morphologies. Fine-tuning of hydrothermal temperature enhanced the scalability, efficiency, and performance of ZnO-decorated ITO electrodes used in PEC water splitting. Under UV light irradiation and using eco-friendly low-cost hydrothermal process in the presence of stable ZnO offered uniform 3D ZnO, which exhibited a high photocurrent of 0.6 mA/cm2 having stability up to 5 h under light-on and light-off conditions. The impact of hydrothermal temperature on the morphological properties of the deposited ZnO and its subsequent performance in PEC water splitting was investigated. The work contributes to advancement of scalable and efficient fabrication technique for developing energy converting photoactive materials.

Investigation on the electrocatalytic oxidation of alcohol using zinc oxide thin films deposited by pulsed electrodeposition on an indium tin oxide surface

To perform electro-catalytic oxidation of alcohols in an alkaline media, zinc oxide (ZnO) thin films were effectively deposited on indium tin oxide (ITO) substrates using the pulsed electrodeposition (PE) method in a zinc nitrate aqueous solution. Analyses of microstructural, photoelectrochemical, and optical characteristics of ZnO thin films were performed as a function of pulsed electrodeposition parameters. XRD analysis was applied to determine structural properties, and SEM and AFM analysis were used to investigate morphological characteristics. X-ray diffraction analyses revealed that the produced films were polycrystalline and had a (002) preferentially oriented, hexagonal wurtzite structure. The morphology of ZnO has improved in the direction of nanorod films, as evidenced by scanning electron microscopy (SEM) and atomic force microscopy (AFM) images. UV transmittance data was used using Tauc's relationship to determine the film's bandgap to be 3.26 eV. The photocurrent response shows that ZnO films have high values, at 305.17 A/cm2, and good optical characteristics. The electrocatalytic oxidation of methanol was finally evaluated on the films. After being optimized in the pulsed electrodeposition mode, ZnO thin film characteristics and methanol electrocatalytic oxidation both saw substantial improvements.

Exploring zinc oxide morphologies for aqueous solar cells by a photoelectrochemical, computational, and multivariate approach.

Dye-sensitized solar cells assembled with aqueous electrolytes are emerging as a sustainable photovoltaic technology suitable for safe indoor and portable electronics use. While the scientific community is exploring unconventional materials for preparing electrodes and electrolytes, this work presents the first study on zinc oxide as a semiconductor material to fabricate photoanodes for aqueous solar cells. Different morphologies (i.e., nanoparticles, multipods, and desert roses) are synthesized, characterized, and tested in laboratory-scale prototypes. This exploratory work, also integrated by a computational study and a multivariate investigation on the factors that influence electrode sensitization, confirms the possibility of using zinc oxide in the field of aqueous photovoltaics and opens the way to new morphologies and processes of functionalization or surface activation to boost the overall cell efficiency.

High Speed Shearing: A novel approach for high-quality ZnO nanoparticle synthesis and photocatalytic activity control

Zinc oxide (ZnO) nanoparticles show the great promise in photocatalysis due to their exceptional characteristics. However, achieving precise control over ZnO nanoparticle size, morphology, and agglomeration remains a challenge. We applied the high-speed shearing (HSS) method for synthesizing ZnO with enhanced properties. HSS employs a high-speed rotor to generate intense shear forces, enabling efficient particle size reduction, improved homogeneity, and enlarged surface area. HSS method could provide crushing effect and powerful mixing effect to synthesize smaller ZnO nanoparticles with less agglomeration. ZnO nanoparticles are optimized from 9.69 nm to 7.09 nm for single particle and from 955 nm to 26.5 nm for secondary particle size. Ultraviolet diffuse reflectance spectroscopy has been used to further analyze the in-situ formation reaction. Besides, we investigate the photocatalytic efficiency of ZnO towards methylene blue. ZnO nanoparticles made using HSS have more active sites, improving the photocatalytic degradation from 38.6% to 70.8%.

Electrochemical detection of kynurenic acid in the presence of tryptophan with the carbon paste electrode modified with the flower-like nanostructures of zinc oxide doped with terbium.

With the help of a hydrothermal approach in this study, we could provide flower-like nanostructures (NSs) of zinc oxide (ZnO) doped with Tb (FL-NS Tb3+/ZnO). Then, FL-NS Tb3+/ZnO morphology was investigated by energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and map analysis. The results revealed higher activity centers and porosity of this nanocomposite, which were followed by acceptable electrochemical function. Hence, it can be utilized for fabricating an electrochemical sensor with an appropriate response for the simultaneous determination of kynurenic acid (KYN) and tryptophan (TRP). However, as compared with the modified carbon paste electrode (FL-NS Tb3+/ZnO/CPE), the bare carbon paste electrode (BCPE) exhibited a weak response toward KYN and TRP but the modified electrode was followed by a high current response for KYN and TRP at a potential 0.35 and 0.809V. Therefore, cyclic voltammetry (CV) was applied in optimal experimental conditions to study the electrochemical behaviors of KYN and TRP over the surface of the proposed modified electrode. Moreover, we used differential pulse voltammetry (DPV) for quantitative measurements. It was found that this new modified electrode linearly ranged from 0.001 to 700.0μM, with detection limits of 0.34nM and 0.22nM for KYN and TRP, respectively. In addition, KYN and TRP in real samples can be analyzed by this sensor, with a recovery of 97.75%-103.6% for the spiked KYN and TRP in real samples.

Surface coated ZnO powder as flame retardant for wood: A short communication

In the present study, the ability of a coating of zinc oxide (ZnO) powder to improve the fire-safety of wood exposed to radiative heat flux was examined, focusing on the ignition time of the wood. To test ZnO's efficiency on the wood substrate, two different amounts of ZnO (0.5 and 1 g ZnO per dm2) were applied to the wood surface and exposed to radiative heat from a cone calorimeter wherein a pristine piece of wood with no ZnO treatment was taken as control. The experiments were conducted at three different irradiation levels i.e., 20, 35, and 50 kWm−2. The results showed that applying ZnO on the surface of the wood significantly increased the ignition time (TTI). For the three different heat fluxes, using 0.5 g ZnO per dm2 coating on the wood surface increased the TTI by 26–33 %. Furthermore, the application of 1 g of ZnO per dm2 generated a TTI increment of 37–40 %. All three irradiation levels showed similar trends in TTI. The micrographs taken before and after combustion showed no significant disparity in the morphology of ZnO. The agglomerated ZnO particles on the wood surface remained intact after combustion. This study demonstrates a facile method of using ZnO to delay the ignition of wood. This could potentially impart fire-safety to wooden structures/façades in wildland-urban interfaces and elsewhere by reducing flame spread.

Influence of zinc oxide morphology on its photocatalytic properties

The rapid development of industry, in addition to the positive impact, has led to environmental problems. The release of polluting waste containing substances such as dyes, pesticides, heavy metals and pharmaceutical waste leads to contamination of water reservoirs, that has a negative impact on humans and aquatic organisms. In this regard, the development of an inexpensive, effective, environmentally friendly method of waste water treatment from organic pollutants is an urgent research priority. Zinc oxide (ZnO) is one of the most active semiconductor photocatalysts. In this paper, the influence of the morphology of nanostructured zinc oxide synthesized by effective methods on photocatalytic properties with respect to the rhodamine-B dye (RhB)was investigated, and the influence of the length-to-thickness ratio (aspect ratio AR) of ZnO samples on its structural and optical properties was studied. The results of the study showed that an increase in the annealing temperature of zinc acetate in the atmosphere leads to an increase in the size of zinc oxide crystallites, while an increase in the concentration of alkali in the growth solution (synthesis of ZnO by chemical deposition from 0.4 M to 0.7 M) makes it possible to synthesize thinner extended 2D plates. It is shown that an increase in the AR value of the synthesized samples makes it possible to increase their photocatalytic activity.

Impact of carbon nanotubes concentrations on the performance of carbon nanotubes/zinc oxide nanocomposite for photoelectrochemical water splitting

Under the influence of visible light, the photoelectrochemical (PEC) method of water splitting offers a green method for producing sustainable hydrogen. In this work, several volume ratios of carbon nanotubes (CNTs) were incorporated in the zinc oxide (ZnO) matrix to prepare ZnO/CNTs nanocomposites on a glass substrate as photoelectrodes for hydrogen production. These electrodes were synthesized via the spray pyrolysis technique and chemical vapor deposition. Various approaches were used to analyze the chemical composition, crystal structure, morphology, and optical properties of pure ZnO and ZnO/CNTs nanocomposites. The structural properties showed that crystallite size is decreased from 44.2 nm to 36.8 nm, and the optical shows that the energy bandgap (Eg) enhanced from 3.07 to 2.87 eV for pure ZnO and the optimum sample of ZnO/7 mL CNTs nanocomposite, respectively. The maximum photocurrent density (Jph) was found for the 7 mL CNTs among the produced ZnO/X CNTs nanostructures. The value of Jph for ZnO/7 mL CNTs (200.7 µA/cm2) is around 33 times greater compared with pure ZnO (6.96 µA/cm2). At 490 nm, the incident photon-to-current efficiency (IPCE) of ZnO/7 mL CNTs is roughly 9.85 %. The ZnO/CNTs photoelectrode showed a hydrogen evolution rate of 4.34 mmole/h.cm2. The improved photoelectrode additionally exhibits strong chemical stability and a lengthy lifetime under visible light without photo-corrosion. Finally, the electrochemical impedance spectroscopy and the PEC water-splitting mechanism for ZnO/CNTs were discussed. This study presents a simple method that enables the fabrication of inexpensive and efficient ZnO/CNTs photoelectrode for renewable energy applications.

Free-standing nanowire printed surfaces with high variability in substrate selection for boiling heat transfer enhancement

Nanowires (NWs) constitute a promising solution to the overheating of high-heat-load surfaces in multiphase heat transfer. Typical nanostructure fabrication methods such as complex photolithography and metal-assisted chemical etching (MACE) that utilize patterned templates are limited by high manufacturing costs and type of substrate materials. These limitations significantly hinder the industrial applicability of NW structures in high heat flux units. In this study, we first examine the effect of the morphology of Zinc oxide (ZnO) NW printed substrates, fabricated via microcontact printing (µCP) and solution based growing, on the heat transfer characteristics in pool boiling. Unlike advanced photolithography, µCP offers greater variability and convenience in terms of the substrate selection and large area creation for NW fabrication. Compared with the silicon substrate, the underlying mechanisms for enhancing both the critical heat flux and heat transfer coefficient of ZnO NW substrates are explored by analyzing the surface morphology, bubble, and wicking characteristics of the test surfaces, in order to determine the applicability of boiling heat transfer using ZnO NWs in industrial fields.

Effect of Zinc Nitrate Concentration on the Morphology of ZnO Nanostructures Grown by Hydrothermal Method

Herein, the influence of the precursor concentration on the morphology of zinc oxide (ZnO) nanostructures prepared via hydrothermal process using zinc nitrate salt with varied concentrations (from 0.01 to 0.15 m) is investigated. Scanning electron microscopy (SEM), UV–vis transmittance, photoluminescence, and X‐ray diffraction are used to characterize the synthetized nanostructures. It is revealed in the obtained results that the salt concentration is a key parameter that controls the ZnO nanostructure. It is concluded that a low salt concentration (0.01 and 0.05 m) leads to the formation of ZnO nanorods while increasing the salt concentration (from 0.1 to 0.15 m) leads to the formation of nanosheets mixed with nanorods‐ and nanosheets‐like morphology. The ZnO nanostructures growth mechanism is discussed.