Morphology Of Zinc Oxide Nanostructures Research Articles

Effect of Au nanoparticles on mitigating the negative impacts of humidity on ZnO gas sensors to detect triethylamine at room temperature

The impact of humidity on the efficiency of gas sensors has become highlighted in the realm of gas detection. Due to the complex relationship between humidity and gas sensor performance, the development of gas sensors has recently focused on minimizing humidity-related interference. This research aims to address humidity-related challenges in zinc oxide (ZnO) gas sensors designed to detect triethylamine. The ZnO nanostructures (NSs) were synthesized using thermal decomposition methods at varying temperatures (380 °C, 480 °C, and 580 °C) and annealing times (3 h, 7 h, 12 h, and 21 h). X-ray diffraction (XRD) confirmed the formation of a wurtzite hexagonal close-packed structure in ZnO NSs. Scanning electron microscopy (SEM) images provided insights into the morphologies of ZnO NSs at different annealing temperatures, while energy dispersive spectroscopy (EDS) demonstrated the elemental distribution. Subsequently, gold (Au) nanoparticles were uniformly sputtered onto ZnO sensors with thickness variations (0.1 nm, 0.6 nm, 1 nm, 5 nm, and 10 nm). XPS was employed to analyse the elemental composition and oxygen vacancies of the synthesized sensing materials. The effectiveness of 0.6 nm-thick Au nanoparticles in mitigating humidity effects was observed in ZnO sensors synthesized at 380 °C. The results indicated that ZnO sensors coated with 0.6 nm-thick Au nanoparticles exhibited highly stable responses to ethanol and triethylamine at different humidity levels from 50 % to 90 %. Notably, these sensors demonstrated promising selectivity towards triethylamine (with a response of 17.57) compared to various gas targets at room temperature. The sensor exhibited rapid response and recovery times of 9.8 s and 4.4 s, respectively, toward triethylamine with excellent stability in variable humid environments. The sensor maintained a consistent response over 24 days, demonstrating good stability at high humidity.

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.

Morphological features and photoluminescence of ZnO and ZnO decorated S,N-doped few-layered graphene (ZnO–S, N-FLGs)

Zinc oxide (ZnO) nanoparticles and ZnO decorated S, N doped few-layered graphene (1 wt%, 2 wt%, and 3 wt %) were synthesized using a simple chemical method followed by calcination. The chemical composition, morphology, lattice vibrations, and distinct structural features of the ZnO and ZnO–S,N-FLGs composites have been characterized by X-ray diffraction (XRD) and μ-Raman spectroscopy. X-ray diffraction (XRD) patterns conform that the pristine ZnO nanostructures and ZnO–S,N-FLGs composites were formed. Electron microscopic techniques (FESEM & TEM) were employed to observe the morphologies. Field emission electron microscope (FESEM) images showed that different morphologies of ZnO nanostructures were decorated on S,N-FLGs sheets. Transmission electron microscope (TEM) images exposed that ZnO different morphologies were uniformly distributed on S,N-FLGs sheets. However, the TEM images showed that nanocomposites' morphology changed significantly with increased S,N-FLGs concentration. The results showed that ZnO with different morphologies was well dispersed on the S,N doped FLGs, which serve as ZnO nanoparticle growing supports and the morphology controller. The Raman shift of the 2D peak shows the interaction between ZnO and S,N-FLGs. It was found that control of the incorporated functional groups of the S,N-FLGs with the assistance of calcination temperature during the synthesis. The morphology of ZnO, such as hexagonal, nanorods, and nanospheres (1 wt%, 2 wt%, and 3 wt% S,N-FLGs). The bandgap of all the synthesized materials was calculated by UV–vis spectroscopy (UV–vis). The photoluminescence (PL) spectra were measured at room temperature (RT). The intensity of peaks of ZnO–S, N-FLGs composites decreased compared to ZnO in PL spectra because of oxygen vacancies and defects. The intense UV emission indicates interesting optical properties were reported in detail.

Physical characterization and antibacterial activity of zinc oxide nanostructures synthesized via facile hydrothermal method

Infections caused by multi drug-resistant pathogens are emerging as a major threat to public health. New antibiotics with improved antimicrobial characteristics are being developed to combat the ever increasing treatment-resistant infections in the existing healthcare settings. Metal oxide nanoparticles are a promising class of antimicrobial alternatives owing to their ability to kill microbes by mechanism such as surface-charge based attraction, destabilization of microbial cell functions and initiation of killing of microbes by production of reactive oxygen species (ROS). Amongst the metal oxides, zinc oxide (ZnO) is one of the promising material for biomedical applications due to the added benefits such as non-toxicity, biocompatibility, chemical stability and biodegradability. Micro and nano-sized ZnO exhibiting diverse morphologies show significant antibacterial activity against a wide spectrum of pathogenic bacteria. The morphology of ZnO nanoparticles play an important role in its antibacterial activity and it can be controlled by the choice of synthesizing method and controlling of reaction parameters such as concentration of precursors, choice of additives, pH and temperature conditions and time of reaction period. The present work is an attempt to investigate the influence of reaction time and addition method of the precipitator on the morphology of ZnO nanoparticles synthesized by hydrothermal method. The structure of ZnO nanoparticles synthesized using different reaction parameters were characterized by X-Ray Diffractometer (XRD) and Fourier Transform Infrared Spectrometer (FTIR). The morphology of ZnO nanostructures were analyzed using Field Emission Scanning Electron Microscope (FESEM) and the elemental composition analysis was carried out by Energy Dispersive X-ray (EDAX) Analyzer. Further, investigation of antibacterial activity of synthesized ZnO against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria was carried out by disk diffusion method. The results confirmed the influence of surface morphology on bactericidal efficiency of ZnO nanostructures.

Precursor Dependent Tailoring of Morphology and Crystallite Size of Biogenic ZnO Nanostructures with Enhanced Antimicrobial Activity- a Novel Green Chemistry Approach

During recent years, there has been a growing pursuit in researching and developing new therapeutic antimicrobial agents from several sources to combat microbial resistance. Therefore, a greater attention has been paid in screening of antimicrobial activity and evaluating methods. The objective of the present study was to synthesize, characterize, and explore nanosized biogenic zinc oxide (ZnO) NPs and evaluate its performance for the antimicrobial activity. Biogenic zinc oxide nanoparticles (ZnO NPs) were fabricated with the two different zinc salts (zinc acetate and zinc nitrate) from aqueous Achyranthes aspera leaf extract and characterized using modern methods and tools, such as X-ray diffraction, Fourier transform infrared spectroscopy, and UV-vis spectroscopy, which indicated the formation of very pure ZnO NPs. The scanning electron microscopic analysis (SEM) explored the formation of flower-like morphology in the sample of zinc acetate precursor and spherical morphology in the sample of zinc nitrate precursor. Further, the elemental composition of both samples was analyzed by energy dispersive spectroscopy (EDS). The antibacterial of ZnO NPs was evaluated by disk diffusion method on Gram-negative pathogen Escherichia coli and Gram-positive pathogen Staphylococcus aureus. ZnO nanoparticles exhibited a higher zone of inhibition (29 mm) because of having a larger specific surface area. Minimum inhibitory concentration (MIC) values of biogenic ZnO NPs were observed in the range of 40–60 μg/mL against selected oral pathogens. Overall, the green synthesized ZnO NPs demonstrated the astounding potential for the antimicrobial activity as an alternative clean-green therapeutic solution.

Effects of Experimental Configuration on the Morphology of Two-Dimensional ZnO Nanostructures Synthesized by Thermal Chemical-Vapor Deposition

Using two experimental configurations, self-assembled zinc oxide (ZnO) nanostructures including nanoplates, nanosaws, and nanobelts were synthesized by thermal chemical-vapor deposition (CVD), and their morphological properties were investigated. ZnO nanostructures grown on Au-coated Si substrates in a parallel setup revealed highly defined ZnO nanoplates and branched nanowires. ZnO nanostructures grown in a perpendicular setup using Si substrates with and without the Au catalyst exhibited vertically oriented ZnO nanosaws and randomly aligned nanobelts, respectively. In the thermal CVD method, experiment conditions such as oxygen-flow rate, growth temperature, and catalyst, and experimental configurations (i.e., parallel and perpendicular setups) were important parameters to control the morphologies of two-dimensional ZnO nanostructures showing platelike, sawlike, and beltlike shapes.

Effect of annealing temperature on phase and morphology of zinc oxide nanostructures with dielectric studies

In the present work we synthesized the pure phase Zinc Oxide nanostructures via co-precipitation method. The phase and size of synthesized nanostructures were examined via X-ray diffraction (XRD). The crystalline size, inter planner spacing and volume of the ZnO sample calcined at 300 °C is 30 nm, 2.6498 Å and 61.737 Å3. The morphological studied were carried via scanning electron microscope (SEM). IR studies were carried out via using FTIR spectrometer and the IR peaks near about 530 cm−1 are corresponding to stretching of the Zn–O bonds. The current-voltage characteristics and resistivity of zinc oxide nanostructures were carried out via kaithely source meter. The impedance spectroscopy of synthesized samples were carried out via potentiostat at applied voltage 100 mV in the frequency range 10 Hz to 5 MHz at room temperature. The grain boundary resistance is about 27 MΩ (at 300 K) for ZnO calcined at 300 °C.

Influence of concentration on the geometry of ZnO nanostructures prepared by chemical bath deposition

Zinc Oxide (ZnO) nanostructures such as nanorods (NRs), nanowalls (NWs) and nanoflakes (NFs) were successfully grown on a glass substrate via chemical bath deposition (CBD) method by varying solutions concentration (0.01 M, 0.05 M, 0.10 M, 0.15 M, 0.20 M and 0.25 M). Effect of CBD concentration on the growth and morphology of ZnO nanostructures are dignified. The structural and optical properties of ZnO NRs, NWs, and NFs were investigated by Field Emission Scanning Electron Microscope (FESEM), energy-dispersive X-ray (EDX), X-Ray Diffraction (XRD), and UV-Visible (UV-Vis) analyses. Results reveal that as the CBD concentration increases, FESEM images showed differ top-down morphology of ZnO nanostructures from NRs, NWs to NFs. Likewise, the alignment of ZnO cross-section evolved from randomly oriented to vertically oriented. As revealed by EDX, the stoichiometric ratio of Zn:O were mostly towards 1:1. From XRD analyses, the preferred structure was wurtzite hexagonal with c-axis orientation along (002) plane. The UV-Vis analysis exposed the optical band gap energy closes to the standard energy gap value of ZnO at 3.37 eV. Thus, this work introduces a variable geometry of ZnO nanostructures (NRs, NWs, and NFs) grown on glass with high structural and optical quality as standard ZnO. The fabricated materials are potential candidates for investigating random lasing in ZnO from different structural geometry.

Effect of organic ligand on ZnO nanostructures and to investigate the photocatalytic activity under visible light illumination

Controlled morphology of zinc oxide (ZnO) was synthesized by simple hydrothermal method. Morphology and size of ZnO nanostructures was controlled by using pyridine as a passivating agent. Pyridine played a crucial role in modifying the morphological size of ZnO nanostructures. The structural analysis confirms the formation of hexagonal phase of ZnO with good crystalline nature. The elemental and composition analysis confirm the presence of ZnO and the existence of pyridine in the composition. The morphological analysis was performed by field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM) and high-resolution transmission electron microscope (HR-TEM). The degradation property of organic pollutant was studied under visible light irradiation. Maximum degradation efficiency was observed for 0.6 mL of pyridine sample which disappeared completely after 18 min of irradiation. Furthermore, the degradation property of ZnO was studied by different value of pH, concentration of dye and photocatalyst dosage. The optimum values of solution pH, dye concentration, and photocatalyst dosage was 11, 10 ppm, and 75 mg/L, respectively.

Effects of persistence time and Au catalyst on the morphology and optical properties of ZnO micro/nanostructures

Zinc oxide (ZnO) micro and nanostructures were synthesised on a quartz substrate by the carbothermal evaporation method. The thin layers of gold were used as a catalyst and syntheses were carried out at different persistence time. Characterisation of the layer was conducted in order to study the effect of persistence time on morphology and crystal structure and optical properties of the fabricated ZnO nanostructures. The samples were characterised by scanning electron microscopy, X-ray diffraction (XRD) and UV–vis spectrophotometry which were performed to investigate the optical properties of the fabricated ZnO layer. The XRD spectrum clearly shows that the structure is in a hexagonal wurtzite phase. Optical properties of ZnO micro and nanostructures were evaluated from transmittance data using the method proposed by Swanepoel (in the regions λ = 200–900 nm). The study’s results indicate that increasing the persistence time as well as decreasing the size of ZnO nanostructures enhances the optical bandgap to about 3.‏46 eV. To the best of this work's knowledge, this is the first report on the study of the correlation of optical properties obtained by Swanepoel method and morphology of ZnO nanostructures.

High performance room temperature gas sensor based on novel morphology of zinc oxide nanostructures

Abstract Zinc oxide uniform nanostructures with novel morphologies were synthesized through simple and fast ammonia based controlled precipitation method in aqueous media and in the absence of any additive. Selected batches of the synthesized solids were characterized by SEM, XRD, FTIR and TG/DTA. FTIR analysis revealed that the morphology of nanostructures had little effect on their IR spectral profile of the synthesized material. The as-prepared, calcined and commercial ZnO nanostructures (ZnO-AP, ZnO-Cal and ZnO-Com) were then employed as gas sensors for the detection of ammonia, acetone and ethanol. ZnO-AP and ZnO-Cal based sensors showed superior and reproducible performance towards 1×10−6 ammonia with gas response of 63.79% and 66.87% and response/recovery time of 13 and 3 s, respectively, at room temperature (29 °C). This was attributed to the unique morphology and remarkable uniformity in shape and size of the synthesized nanostructures. In contrast, the ZnO-Com based sensor did not respond to ammonia concentration less than 200×10−6. In addition, ZnO-Cal showed high selectivity to ammonia as compared to acetone and ethanol at room temperature. Moreover, the lowest detection limit was 1×10−6, which demonstrates excellent ammonia sensing characteristics of the synthesized ZnO.

Enhanced optical and electrical properties of antimony doped ZnO nanostructures based MSM UV photodetector fabricated on a flexible substrate

Undoped Zinc oxide (ZnO) and Antimony doped Zinc Oxide (Sb: ZnO) nanostructures (nanocones and nanoflakes) with different doping concentrations of Sb (3 at%, 6 at% and 9 at%), were grown on flexible (ITO/PET) substrate using a simple hydrothermal method. The seed layer of ZnO was prepared using sol-gel method, which was then used as the base to grow Sb: ZnO nanostructures by hydrothermal method. Structural, optical and electrical characteristics of undoped and Sb: ZnO nanostructures were studied for three different doping concentrations of Sb. The structural and morphological studies of the prepared samples were carried out using XRD and FESEM. EDAX was used for elemental analysis. The XRD spectrum reveals ZnO wurtzite structures. The FESEM results clearly indicate that there was no change in morphology of ZnO nanostructures with the substitution of Sb in ZnO lattices. The optical studies were performed on all samples using UV–Vis spectroscopy. It was observed that the transmission and the bandgap energy reduced with an increase in doping concentration. IV curves were plotted using an impedance analyzer. The samples were studied under dark conditions and under UV light of 365 nm. A monotonic increase in electrical conductivity was observed with increase in doping concentration, asserting the fact that addition of Sb to ZnO increases the conductivity of the samples, making Sb: ZnO a good candidate for photodetection. The responsivity and efficiency of the device under UV illumination of 365 nm were found to be 2.62 A/W and 893.35% respectively, with the highest values being observed for 9 at% of Sb doping.

Tuning the Morphology of ZnO Nanostructures with the Ultrasonic Spray Pyrolysis Process

Nanostructured zinc oxide (ZnO) particles were synthesized by the one step Ultrasonic Spray Pyrolysis (USP) process from nitrate salt solution (Zn(NO3)2·6H2O). Various influential parameters, from Zn(NO3)2·6H2O concentrations (0.01875–0.0375 M) in the initial solution, carrier gas (N2) flow rates (0.5–0.75 L/min) to reaction temperature (400–800 °C), were tested to investigate their role on the final ZnO particles’ morphology. For this purpose, Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (HRTEM) and (Selected Area Electron Diffraction) SAED techniques were used to gain insight into how the ZnO morphology is dependent on the USP process. It was revealed that, by certain parameter selection, different ZnO morphology could be achieved, from spherical to sphere-like structures assembled by interwoven nanoplate and nanoplate ZnO particles. Further, a more detailed crystallographic investigation was performed by XRD and Williamson-Hall (W-H) analysis on the ZnO with unique and non-typical planar morphology that was not reported before by USP synthesis. Moreover, for the first time, a flexible USP formation model was proposed, ending up in various ZnO morphologies rather than only ideal spheres, which is highly promising to target a wide application area.

Effect of the morphology of solution‐grown ZnO nanostructures on gas‐sensing properties

AbstractDespite the great potential of zinc oxide (ZnO) nanostructures as a sensing material for high‐performance gas sensors, the correlation between the morphology of ZnO nanostructure and its gas‐sensing performance has not been systematically investigated yet. In this work, ZnO nanostructures with controlled morphologies were synthesized by low‐temperature solution route and chemical bath deposition method. Thin film gas sensors were fabricated from the nanostructures and the sensor performance such as the response, recovery time, and stability was examined for several gases. It is demonstrated that the gas‐sensing performance of a ZnO nanostructure sensor is strongly influenced by its morphology. One dimensional ZnO nanocones are highly promising for practical application to gas sensors, due to their large surface area per unit mass and unique conical structure.

Hydrogen sensors based on gold nanoclusters assembled onto ZnO nanostructures at low operating temperature

In this work, the hydrogen (H2) sensor performance of gold nanoclusters (Au NCs) assembled onto zinc oxide (ZnO) nanostructures films were investigated and compared to ZnO nanostructures films. ZnO nanostructures were prepared by thermal oxidation of zinc films on glass substrate at different oxidation temperatures. Au NCs were assembled onto obtained ZnO nanostructures via photoreduction of HAuCl4 solution. The morphology of ZnO nanostructures were comprised of short rods branched into their ZnO bases. The diameters of cylindrical ZnO nanostructures increased approximately 50 to 90 nm upon increasing the oxidation temperatures. The morphology of Au NCs assembled onto ZnO nanostructures exhibited growth to encapsulate individual ZnO nanostructures as cluster−like with dimensions less than 100–150 nm. The amount of Au NCs assembly was proportion to crystallinity and materials’ stoichiometry of ZnO nanostructures. H2 sensor performance of the films were investigated at different operating temperature in the range of 150–450 °C. It was found that optimum operating temperatures of Au NCs assembled ZnO nanostructures films were 200 °C in all cases less than that 350 °C of pure ZnO nanostructures. Au NCs assembled ZnO nanostructures films had still high H2 sensor response at operating temperature of 150 °C. Furthermore, the sensor response of Au NCs assembled ZnO nanostructures seems to have higher than those ZnO nanostructures and their sensor response was directly proportion to amount of Au NCs. Accordingly, the enhancement of sensor response can be explained in terms of the reaction rate constant (kOxy) by considering the catalytic effect of Au. These results can be further explored for H2 safety sensor in fuel cell due to the demand of high H2 response at the low operating temperature.

Catalyst-free growth and tailoring morphology of zinc oxide nanostructures by plasma-enhanced deposition at low temperature

ZnO nanostructures were grown under different deposition conditions from Zn films pre-deposited onto Si substrates in O2-Ar plasma, ignited in an advanced custom-designed plasma-enhanced horizontal tube furnace deposition system. The morphology and structure of the synthesized ZnO nanostructures were systematically and extensively investigated by scanning and transmission electron microscopy, Raman spectroscopy, and atomic force microscopy. It is shown that the morphology of ZnO nanostructures changes from the hybrid ZnO/nanoparticle and nanorod system to the mixture of ZnO nanosheets and nanorods when the growth temperature increases, and the density of ZnO nanorods increases with the increase of oxygen flow rate. The formation of ZnO nanostructures was explained in terms of motion of Zn atoms on the Zn nanoparticle surfaces, and to the local melting of Zn nanoparticles or nanosheets. Moreover, the photoluminescence properties of ZnO nanostructures were studied, and it was revealed that the photoluminescence spectrum features two strong ultraviolet bands at about 378 and 399Â nm and a series of weak blue bands within a range of 440--484Â nm, related to the emissions of free excitons, near-band edge, and defects of ZnO nanostructures. The obtained results enrich our knowledge on the synthesis of ZnO-based nanostructures and contribute to the development of ZnO-based optoelectronic devices.

Effect of Hydroxide Concentration and Adding Ascorbic Acid on Morphology Shape of Zinc Oxide Nanostructure Prepared by Simple Chemical Precipitation Method

A chemical precipitation method was used to prepare zinc oxide (ZnO) nanostructure in the present of zinc nitrate and ammonium hydroxide as zinc precursor and hydroxide precursor respectively. The effect of the hydroxide concentration and the effect of adding ascorbic acid as modifier into the mixture solution on the morphology property of zinc oxide was studied. The morphology and the structural of ZnO nanostructures were investigated by field-emission scanning electron microscope (FE-SEM) and X-ray diffractometer (XRD) techniques, respectively. The results showed that the basicity solution and adding stabilizer are important parameters on the morphology and structural properties of ZnO nanostructure. At a low hydroxide concentration, ZnO exhibited flower-like structure with short petal. With a further increase to higher concentration, ZnO crystal have more crystal directional growth. When the ascorbic acid was added, the morphology changed to particle-like structure. ZnO nanostructure with different shape might be used for specific applications such as gas sensor etc.

Hydrothermal derived nanostructure rare earth (Er, Yb)-doped ZnO: structural, optical and electrical properties

The structural, optical and electrical properties of undoped and rare-earth (Er, Yb) doped zinc oxide (ZnO) nanopowder samples synthesized by hydrothermal method were investigated. The obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy. The optical properties of undoped and rare-earth (Er, Yb) doped ZnO were carried out with UV–visible diffuse reflectance spectroscopy techniques. XRD results reveal that Yb and Er doped ZnO nanopowders have single phase hexagonal (Wurtzite) structure without any impurities. SEM analysis indicate that dopants with different radii affected the surface morphology of ZnO nanostructures. The optical band gap of all samples were calculated from UV–Vis diffuse reflectance spectroscopy data. We have obtained band gap values of undoped, Er and Yb doped ZnO as 3.24, 3.23, 3.22 eV, respectively. Electrical characterization of the samples were made in the 280–350 K temperature range using Van der Pauw method based on Hall effect measurement. The carrier concentrations decreased for both Er and Yb doping while the Hall mobility and electrical resistivity increased with Yb, Er doping compared to undoped ZnO nanopowder at room temperature. The temperature dependent resistivity measurements of Er doped ZnO showed a metal–semiconductor transition at about 295 K, while Yb doped ZnO showed characteristic semiconductor behavior.

The effect of Cu doping on the mechanical and optical properties of zinc oxide nanowires synthesized by hydrothermal route

Zinc oxide (ZnO) is a wide-bandgap semiconductor material with applications in a variety of fields such as electronics, optoelectronic and solar cells. However, much of these applications demand a reproducible, reliable and controllable synthesis method that takes special care of their functional properties. In this work ZnO and Cu-doped ZnO nanowires are obtained by an optimized hydrothermal method, following the promising results which ZnO nanostructures have shown in the past few years. The morphology of as-prepared and copper-doped ZnO nanostructures is investigated by means of scanning electron microscopy and high resolution transmission electron microscopy. X-ray diffraction is used to study the impact of doping on the crystalline structure of the wires. Furthermore, the mechanical properties (nanoindentation) and the functional properties (absorption and photoluminescence measurements) of ZnO nanostructures are examined in order to assess their applicability in photovoltaics, piezoelectric and hybrids nanodevices. This work shows a strong correlation between growing conditions, morphology, doping and mechanical as well as optical properties of ZnO nanowires.

The growth of AZO nanostructures with high doping concentration using vertical reaction layer synthesizing method and their applications

This study developed a hybrid nanostructure comprising zinc oxide (ZnO) nanorods and aluminium doped ZnO (AZO) nanowalls using a chemical bath deposition method for use in near-ultraviolet (NUV) photosensors. We report on a means of tuning the morphology of ZnO nanostructure using Al thin film as a doping source. An increase in the thickness of the Al thin film causes the evolution of the morphology from nanorods to nanowalls. X-ray photoelectron spectroscopy (XPS) data indicate an increase in the concentration of Al doping from 0 to 9.59wt.%. Transmission electron microscopy indicates that the ZnO nanorods are single-crystal formations whereas the AZO nanowalls are composed of numerous single-crystal grains. UV–vis absorption spectra revealed a new area of absorption resulting from the AZO nanostructure. The resulting photosensor was tested using a 405nm light-emitting diode (LED) at a voltage bias of 1V across the device, wherein a photocurrent-to-dark-current ratio of 99.5 was observed. Our results demonstrate that the low-temperature fabrication of near-UV photosensors using a novel structure comprising nanorods and nanowalls is a feasible and effective approach.