Growth Of Zinc Oxide Nanostructures Research Articles

Flow-induced fabrication of ZnO nanostructures in pillar-arrayed microchannels.

The emergence of microfluidic devices integrated with nanostructures enables highly efficient, flexible and controllable biosensing, among which zinc oxide (ZnO) nanostructure-based fluorescence detection has been demonstrated to be a promising methodology due to its high electrical point and unique fluorescence enhancement properties. The optimization of microfluidic synthesis of ZnO nanostructures for biosensing on chip has been in demand due to its low cost and high efficiency, but still the flow-induced growth of ZnO nanostructures is not extensively studied. Here, we report a simple and versatile strategy that could manipulate the local flow field by creating periodically arranged micropillars within a straight microchannel. We have explored the effects of perfusion speed and flow direction of seed solution, localized flow variation of growth solution and growth time on the morphology of nanostructures. This provided a comprehensive understanding which governs nanostructure fabrication controlled by flow. The results demonstrated that localized flow in microfluidic devices was essential for the initiation and growth of zinc oxide crystals, enabling precise control over their properties and morphology. Furthermore, a model protein was used to demonstrate the intrinsic fluorescence enhancement of ZnO nanostructures as an example to reveal the morphology-related enhancement properties.

Investigation of ambient regulated enhanced photo-responsive properties of GO-ZnO and transition metal doped GO-ZnO nanocomposite: Improved photocurrent and swift response

In this work, UV photodetector was fabricated by synthesising zinc oxide (ZnO) on fluorine doped tin oxide (FTO) thin film via a one-pot synthesis method. The incorporation of GO into the ZnO growth solution resulted in an increase of UV photocurrent of the ZnO UV detector by up to 300%, while cooper doping of the GO-ZnO nanocomposite enhanced the response time by 22%. The photo-responsive property is enhanced by including graphene oxide (GO) (0.1%–10%) in the ZnO growth solution. The increased growth of nano-flake like ZnO nanostructure is confirmed from FE-SEM images. 0.5% GO-ZnO nanocomposite devices have shown a photocurrent of 610.4 μA. The FTO-0.5% GO-ZnO device also had a responsivity of 4.92 AW-1, an EQE of 1696.48%, and a specific detectivity of 7.3 × 1011 Jones. The devices were tested under varied working temperatures and relative humidity levels to ensure their utility and effectiveness. The FTO/GO-ZnO:Cu device showed a response and recovery times of 62.47 s and 174.22 s, respectively, 22% faster than the other reported devices.

In Situ Growth and UV Photocatalytic Effect of ZnO Nanostructures on a Zn Plate Immersed in Methylene Blue

Nanostructures of zinc oxide (ZnO) are considered promising photocatalysts for the degradation of organic pollutants in water. This work discusses an in situ growth and UV photocatalytic effect of ZnO nanostructures on a Zn plate immersed in methylene blue (MB) at room temperature. First, the Zn surfaces were pretreated via sandblasting to introduce a micro-scale roughness. Then, the Zn plates were immersed in MB and exposed to UV light, to observe ZnO nanostructure growth and photocatalytic degradation of MB. Scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and UV-Vis diffuse reflectance spectroscopy were used to characterize the Zn surfaces. We observed the growth of stoichiometric and crystalline ZnO with a nano-leaf morphology and an estimated bandgap of 3.08 eV. The photocatalytic degradation of MB was also observed in the presence of the ZnO nanostructures and UV light. The average percentage degradation was 76% in 4 h, and the degradation rate constant was 0.3535 h−1. The experimental results suggest that room temperature growth of ZnO nanostructures (on Zn surfaces) in organic dye solutions is possible. Furthermore, the nanostructured surface can be used simultaneously for the photocatalytic degradation of the organic dye.

Direct One-Step Seedless Hydrothermal Growth of ZnO Nanostructures on Zinc: Primary Study for Photocatalytic Roof Development for Rainwater Purification

To shift towards the greener city, photocatalytic urban infrastructures have emerged as a promising solution for pollution remediation. To reach this goal, the large bandgap semiconductors, such as nontoxic Zinc Oxide (ZnO), already proved their excellent photocatalytic performances. However, integrating and developing cost-effective and greener photocatalytic surfaces with an easily scaled-up synthesis method and without energy and chemical product overconsumption is still challenging. Therefore, this work proposes to develop a depolluting Zinc (Zn) roof covered by ZnO nanostructures (NSs) using a one-step seedless hydrothermal growth method in 2 h. The feasibility of this synthesis was firstly studied on small areas of Zn (1.25 cm2) before being scaled up to medium-sized areas (25 cm2). The efficiency of this functionalization route for ZnO NSs grown without seed layer was attributed to the presence of Zn2+ sites and the native oxide film on the Zn surface. Their photocatalytic efficiency was demonstrated by removing in less than 3 h the Methylene Blue (MB) and Acid Red 14 (AR14) in both DI water and rainwater under UV-light. Promising results were also recorded under solar light. Therefore, the photocatalytic Zn roof functionalized by ZnO NSs is a promising route for rainwater purification by photocatalysis.

Single-step hydrothermal synthesis of nitrogen-doped ZnO nanostructures and an insight into its electrochemical properties

Zinc oxide (ZnO) nanostructures have been extensively used as electrochemical sensing material for the development of biosensors and bioimplantable devices. It is important to evaluate their electrochemical performance while developing materials with rapid response time and higher sensitivity. Herein, we present a novel one-step low-temperature hydrothermal technique for simultaneous nitrogen doping and growth of ZnO (N-ZnO) nanostructures. Nitrogen addition is expected to enhance the electron mobility and hence the electrical conductivity of ZnO. The nanostructures were characterized by X-ray diffraction, UV–Vis spectroscopy and field emission scanning electron microscopy. The electrochemical properties were studied by electrochemical impedance spectroscopy and cyclic voltammetry using an N-ZnO/Ag/Glass symmetric two-electrode system. The nitrogen addition to ZnO lattice is suggested by XRD peak shift, changing lattice parameters and dislocation density as compared to pristine ZnO. A substantial increase in the electrochemical response and conductivity can be attributed to nitrogen incorporation into ZnO lattice.

Growth of zinc oxide nanostructures by mass transfer through a micro-sized vacuum zone in a temperature gradient field

This paper presents the results of studies on the controlled production of ZnO nanostructures with specified physical properties. It has been shown experimentally that by using the mass transfer of a substance through a micro-sized vacuum zone in a temperature gradient field, it is possible to grow quasi-one-dimensional ZnO nanostructures stochastically or orderly located on a substrate. The density of deposition of quasi-one-dimensional ZnO nanostructures is determined depending on the substrate material. It was found that the resulting ZnO nanostructures have good crystal perfection and stoichiometric compositions, and also have pronounced piezoelectric properties.

Electrochemical growth and characterisation of ZnO nanostructures for dye‐sensitised solar cells

This Letter presents the electrodeposition of zinc oxide (ZnO) nanostructures by varying the negative potential and investigation of structural, optical, and morphological characteristics. UV–vis spectroscopy investigation showed the redshift of the absorption peak with the increased negative potential. Using Tauc relation, the optical bandgap values estimated to be 3.09, 2.97, 2.93, 2.91, 2.90, and 2.84 eV corresponding to the samples prepared at potential −0.5, −0.7, −0.9, −1.1, −1.3 and −1.5 V. Fluorescence spectra exhibited the UV emission band at wavelength 392 nm along with a peak at 650 nm corresponds to the second-order nature of ZnO. Fourier-transform infrared spectroscopy analysis confirmed the various vibration modes at 403, 493, and 702 cm−1 originated by the ZnO nanostructures. X-ray diffraction pattern revealed the hexagonal wurtzite phase of ZnO. Scanning electron microscopy investigation evidenced the distinct morphology of ZnO with the increased negative potential; however, the dense and perpendicularly oriented ZnO nanorods are prepared at highest negative potential as compared to rice grain-like ZnO structure prepared at least negative potential. Furthermore, the prepared nanostructures are used as dye-sensitised solar cells (DSSCs) photoanodes, while the DSSC-Z6 showed the increased cell efficiency up to 1.2%, due to the aligned growth of the ZnO nanorods.

One Dimensional ZnO Nanostructures: Growth and Chemical Sensing Performances.

Recently, one-dimensional (1D) nanostructures have attracted the scientific community attention as sensitive materials for conductometric chemical sensors. However, finding facile and low-cost techniques for their production, controlling the morphology and the aspect ratio of these nanostructures is still challenging. In this study, we report the vapor-liquid-solid (VLS) synthesis of one dimensional (1D) zinc oxide (ZnO) nanorods (NRs) and nanowires (NWs) by using different metal catalysts and their impact on the performances of conductometric chemical sensors. In VLS mechanism, catalysts are of great interest due to their role in the nucleation and the crystallization of 1D nanostructures. Here, Au, Pt, Ag and Cu nanoparticles (NPs) were used to grow 1D ZnO. Depending on catalyst nature, different morphology, geometry, size and nanowires/nanorods abundance were established. The mechanism leading to the VLS growth of 1D ZnO nanostructures and the transition from nanorods to nanowires have been interpreted. The formation of ZnO crystals exhibiting a hexagonal crystal structure was confirmed by X-ray diffraction (XRD) and ZnO composition was identified using transmission electron microscopy (TEM) mapping. The chemical sensing characteristics showed that 1D ZnO has good and fast response, good stability and selectivity. ZnO (Au) showed the best performances towards hydrogen (H2). At the optimal working temperature of 350 °C, the measured response towards 500 ppm of H2 was 300 for ZnO NWs and 50 for ZnO NRs. Moreover, a good selectivity to hydrogen was demonstrated over CO, acetone and ethanol.

Palladium Role in Growth of ZnO Nanostructure with Plasmonics Layering by Seed Mediated Hydrothermal Method

The electrical and optical properties of nanomaterials depend on their structural form. As an effort to develop an advanced nanomaterial, zinc oxide (ZnO) is interesting to synthesis for many applications such as active material for solar cells and biosensors. This paper provides the role of palladium and plasmonic materials in growing ZnO nanostructure, with a focus on its structural analysis. Nanomaterial ZnO was grown by seed-mediated hydrothermal method with layering by plasmonic materials, i.e. gold (Au) and platinum (Ag). X-ray diffraction analysis shows the presence of three dominant peak angles, i.e 34.43o, 36.32o, and 47.49o corresponding to crystal orientation of (002), (101) and (102), respectively. Palladium (Pd) treatment plus layering by plasmonic materials give a higher size of the nanostructure, but their electric band gaps are decreasing slightly. These findings also supported by high absorbance in UV-vis spectra. Gold layering on the nanomaterial gives a more significant role than platinum which indicated by higher size in diameter and higher absorption of UV-Vis spectra. The average size of pristine ZnO, ZnO:Pd, ZnO:Pd:Ag, and ZnO:Pd:Ag are 44.13, 45.99, 45.28, and 44.81 nm, respectively.

Synthesis of Zinc Oxide Nanostructure by Chemical Bath Deposition (CBD) Method: Influence of Growth Time towards Nanostructure Characteristics

Growth of zinc oxide (ZnO) nanostructure on seeded indium tin oxide (ITO) via chemical bath deposition were presented in this study. Growth time is believed to have vital role in order to control the physical (morphology), optical and structural characteristics of ZnO nanostructures. Several growth time of ZnO nanostructure were varied (1 H – 3.5 H) as the purpose to investigate its effect towards the growth of ZnO nanostructures, as well as their characteristics. In this study, the influence of growth time was determined using field emission scanning electron microscope (FESEM), ultra-violet visible spectrometer (UV-Vis) and x-ray diffraction (XRD). Based on the results obtained, morphological, optical and structural characteristics of ZnO nanostructure thin films grown at various growth time present different characteristics and properties. According to the results obtained, it is proved that growth time is a vital parameter to control the ZnO nanostructure growing process. ZnO nanostructure morphological changes significantly with the changes of the growing time process. As well as optical properties, the changes of absorbance and transmittance value influence the optical energy band gap of ZnO nanostructure in this study, which is the average value is 3.31 -3.40 eV. The structural characteristic of the ZnO nanostructure also affected significantly with the difference of growth time, where the crystallinity is improved with the longer growth time.

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.

Tailoring morphological characteristics of zinc oxide using a one-step hydrothermal method for photoelectrochemical water splitting application

In the present paper describe the zinc oxide (ZnO) with various morphologies have been synthesized using the one-step hydrothermal method, in which the growth of ZnO nanostructures are significantly tailored by adjusting the pH level between 9 and 12 using 0.1 M Sodium hydroxide (NaOH). Significant results reveal the morphological properties of ZnO nanostructures varied with different pH values with the formation of ZnO nanostructures have different morphological such as a baton, star, flower, and rod-like structures. The present results show the rod-like structure of ZnO nanostructures exhibits the highest photocurrent density of 746.61 μAcm−2 (at 1.23 V vs RHE) under simulated solar AM 1.5G illumination in Potassium hydroxide (KOH) medium, also the other morphologies. The dependent of the photoelectrochemical (PEC) water splitting properties on the different morphological of ZnO nanostructures are studied. Achieving the morphological evolution mechanism has become one of the method to obtain the production of the hydrogen growth regime used for solar energy conversion and their applied storage potentials. The application of the ZnO nanostructures for PEC water splitting was proposed with the adoption of screen-printed carbon electrodes (SPCEs). These are to quantify the best degree of the highest photocurrent density with one-step tailoring with an ideal modeling system to enhance PEC water splitting performances. Thus, the screen-printed carbon electrodes (SPEs) has been used as an alternative method for fabrication and photoelectrodes testings.

Designing zinc oxide nanostructures (nanoworms, nanoflowers, nanowalls, and nanorods) by pulsed laser ablation technique for gas‐sensing application

AbstractIn this study, pulsed laser ablation technique, also known as pulsed laser deposition (PLD), is used to design and grow zinc oxide (ZnO) nanostructures (nanoworms, nanowalls, and nanorods) by template/seeding approach for gas‐sensing applications. Conventionally, ZnO nanostructures used for gas‐sensing have been usually prepared via chemical route, where the 3D/2D nanostructures are chemically synthesized and subsequently plated on an appropriate substrate. However, using pulsed laser ablation technique, the ZnO nanostructures are structurally designed and grown directly on a substrate using a two‐step temperature‐pressure seeding approach. This approach has been optimized to design various ZnO nanostructures by understanding the effect of substrate temperature in the 300‐750°C range under O2 gas pressure from 10‐mTorr to 10 Torr. Using a thin ZnO seed layer as template that is deposited first at substrate temperature of ~300°C at background oxygen pressure of 10 mTorr on Si(100), ZnO nanostructures, such as nanoworms, nanowalls, and nanorods (with secondary flower‐like growth) were grown at substrate temperatures and oxygen background pressures of (550°C and 2 Torr), (550°C and 0.5 Torr), and (650°C and 2 Torr), respectively. The morphology and the optical properties of ZnO nanostructures were examined by Scanning Electron Microscope (SEM‐EDX), X‐ray Diffraction (XRD), and photoluminescence (PL). The PLD‐grown ZnO nanostructures are single‐crystals and are highly oriented in the c‐axis. The vapor‐solid (VS) model is proposed to be responsible for the growth of ZnO nanostructures by PLD process. Furthermore, the ZnO nanowall structure is a very promising nanostructure due to its very high surface‐to‐volume ratio. Although ZnO nanowalls have been grown by other methods for sensor application, to this date, only a very few ZnO nanowalls have been grown by PLD for this purpose. In this regard, ZnO nanowall structures are deposited by PLD on an Al2O3 test sensor and assessed for their responses to CO and ethanol gases at 50 ppm, where good responses were observed at 350 and 400°C, respectively. The PLD‐grown ZnO nanostructures are very excellent materials for potential applications such as in dye‐sensitized solar cells, perovskite solar cells and biological and gas sensors.

Fabrication of an efficient Electrode/Organic Interface for Flexible Sensors

Abstract For obtaining a superior device performance it is necessary to have an efficient electrode/organic material interface. The use of Zinc Oxide as an efficient nano material has various advantages and its compatibility with aluminium makes a desirable combination result in an effective carrier balance which leads to enhanced device performance in terms of efficiency. The paper discusses the method of fabrication of the electrode nanomaterial interface by an inexpensive chemical synthesis sol-gel growth of Zinc Oxide nanostructures for a flexible sensor. Among the wideband Gap semiconductors, Zinc oxide has a large band gap of 3.37 eV and has a large excitation binding energy of 60meV. The method is inexpensive and can be adopted for large scale. Zinc oxide is inexpensive, chemically stable and non-toxic hence it is a popular choice for fabrication of devices. Aluminium is also readily available, conductive and inexpensive choice for an electrode. The structural, morphological and the electrical properties of the thin films are investigated using and Scanning Electron Microscopy (SEM). Controllable electrical conductivities and good film properties of the sintered Aluminium patterns with Zinc Oxide growth form the basis of flexible sensors.

Hydrothermal Growth of Zinc Oxide (ZnO) Nanorods (NRs), Structural, and Chemical Composition Studies for pH Measurement Sensor Applications

Nanostructured Zinc Oxide (ZnO) have a significant interest in electrochemical sensor applications. This paper presents the design and fabrication of ZnO nanorods (NRs) based electrochemical capacitive sensor for pH measurement applications. Two-step programmed spin coating deposition of ZnO seed layer followed by the hydrothermal growth of ZnO nanostructures having NRs morphology lead to the fabrication and calibration of the capacitive sensor. The structural and chemical composition of the ZnO thin film layers is examined with field emission scanning electron microscopy (FeSEM) with energy dispersive spectrometer (EDS) and X-Ray diffraction (XRD) studies. The synthesized NRs exhibit crystallinity properties and average crystallite size of the ZnO NRs is 54.18 nm. The ZnO NRs developed on Aluminum substrate was used as a capacitive sensor and it has a potential application in pH measurement in a micro solutions media.

Circumferential growth of zinc oxide nanostructure anchored over carbon fabric and its photocatalytic performance towards p-nitrophenol

In present study, zinc oxide (ZnO) nanostructure anchored on carbon fabric (CF) was prepared using a combinational techniques of RF magnetron sputtering and hydrothermal method. The sputter seeded CF aided for the circumferential growth of ZnO nanostructure and its structural and optical characterization evidencing the c-axis orientation with the band gap of, 3.21 eV. ZnO nanostructure anchored CF was subjected towards UV light photocatalytic activity of p-nitrophenol for 150 min and remarkably higher activity of 98% was observed with better retrieval and recyclability upto 5 cycles. Because of these conspicuous features, it can serve as an expedient hybrid platform for photocatalytic application, better than the benchmark acid treated ZnO/CF.

Influence of the precursor and annealing temperature on the hydrothermal growth of ZnO nanostructures

Wet synthesis of zinc oxide (ZnO) has been reported as an effective and low cost process for large production thin films. The purpose of this project is to investigate the effect of different precursor, different concentration and annealing temperature on the growth of ZnO nanostructures. The ZnO nanostructures is synthesised via a hydrothermal process on a glass substrate and characterized using Field Emission Scanning Electron Microscopy (FESEM). The morphological changes of the nanostructures are systematically investigated as a function of precursors and concentration as well as annealing temperature. The process use two different types of precursor which are Zinc acetate dihydrate and Zinc nitrate hexahydrate.

Non-mutually exclusive dual role of hexamethylenetetramine on the growth of ZnO nanostructures and their sensing footprints

Zinc oxide (ZnO) nanostructures were grown on glass substrates using hydrothermal technique followed by a sputter deposited ZnO seed layer. The influence of hexamethylenetetramine (HMTA) concentrations on the growth of ZnO nanostructures and their room temperature sensing performance were investigated. Further, the non-mutually exclusive dual role of HMTA on the growth of ZnO nanostructures were evaluated by morphological studies. Various morphologies such as nanoprisms, nanoparticles decorated nanoprisms and nanodisks were observed concerning various molar concentrations of zinc acetate and HMTA. Protonation of HMTA acted as a capping agent, which offered a unique impact on the anisotropic growth of ZnO along the c-axis direction. Nanoparticles decorated nanoprisms showed good selectivity towards acetaldehyde vapor amidst ethanol, ammonia, and acetone, which was well supported by bond dissociation energy. The presence of increased number of junction types, densities, and networked structure showed a prospect towards better sensing performance.

In Situ Observation of the Growth of ZnO Nanostructures Using Liquid Cell Electron Microscopy

Understanding the growth mechanisms and associated kinetics is a fundamental issue toward the specific function-oriented controlled synthesis of nanostructures. In this work, the growth of zinc oxide nanostructures with different sizes and morphologies are directly observed by in situ liquid-cell transmission electron microscopy (TEM). Real-time observation and quantitative analysis reveal that the concentration ratios of the precursors are responsible for the different growth kinetics, resulting in different morphology and size of the synthesized ZnO nanostructures.

Electrochemical synthesis of one-dimensional ZnO nanostructures on ZnO seed layer for DSSC applications

Abstract Electrochemical deposition of vertically aligned zinc oxide (ZnO) nanorods were prepared on ZnO seeded fluorine doped tin oxide (FTO) substrate in the solutions consisting of different concentrations of hexamethylenetetramine (HMTA). The electrochemical, structural, morphological, vibrational and optical properties were characterized by cyclic voltammetry (CV), X-ray diffraction (XRD), scanning electron microscope (SEM), Raman spectroscopy and photoluminescence (PL) spectroscopy, respectively. CV curves confirm that metallic zinc phase is not deposited as the HMTA concentration is about 9 mM in a deposition solution. XRD patterns of the as-prepared films show that the increasing HMTA concentrations from 0 mM to 9 mM not only increase the formation of zinc hydrate chloride (Zn 5 (OH) 8 Cl 2 ·H 2 O) but also decrease and finally disappear the metallic Zn deposition. After the as-prepared films annealed at 450 ° C, the crystalline phases of Zn and Zn 5 (OH) 8 Cl 2 ·H 2 O are completely converted to ZnO hexagonal wurtzite phase with high intense growth (002) plane orientation. SEM images support that the vertical growth of ZnO nanostructures (nanorods and petals) with a few flowers is found to be in the cordillera structure as the films are deposited in the solutions consisting of 3 mM, 6 mM and 9 mM HMTA respectively. Raman and PL spectra confirm that the ZnO film deposited in the solution consisting of 9 mM HMTA has a higher crystalline nature with lesser atomic defects and is also higher c-axis growth than that of other films deposited in the solutions consisting of 0 mM, 3 mM and 6 mM, respectively. UV–vis absorbance spectra corroborate that the ZnO film deposited in the solution consisting of 9 mM HMTA shows a high dye absorbance as compared with other films. The efficiency of DSSCs based on ZnO photoanodes deposited in the solutions consisting of 0 mM and 9 mM HMTA was 1.79 and 3.75%, respectively. Electrochemical impedance spectra revealed that DSSC based on ZnO photoanode deposited in the solution consisting of 9 mM HMTA has a higher charge recombination resistance (Rrec) than that of another DSSC.