Length Of ZnO Nanorods Research Articles

Morphology-Dependent Chemiresistive-Potentiometric Gas Sensing Properties of ZnO Nanorods for CH4 and CO

In this study, one-dimensional ZnO nanorods sensing electrodes were grown in situ on the surface of the Ce0.8Gd0.2O1.9 electrolyte to fabricate chemiresistive-potentiometric (C-P) bivariate sensors for the detection and identification of CH4 and CO. Four C-P sensors were developed by adjusting the hydrothermal growth time of the nanorods. The effect of hydrothermal duration on the morphology of nanorods was examined. The C-P response to CH4 and CO initially increased and then decreased with increasing hydrothermal duration. Similar variations in the response to the gas mixtures of CH4 and CO with the hydrothermal duration were observed. The highest C and P response values for CH4, CO, and their mixtures were obtained at a hydrothermal duration of 1.5 h. The enhanced C-P sensing performance was discussed in terms of the defect density, the number of contact junctions, and the length of ZnO nanorods. Accurate differentiation of five different gases (CH4, CO, and three gas mixtures) with an identification accuracy of 100% was achieved by the array assembled with the ZnO-1.0 and the ZnO-1.5 sensors. Our findings demonstrate the morphology-dependent C-P sensing behaviors of ZnO nanorods and provide a facile and cost-effective method for the detection and identification of CH4 and CO.

Synergism induced sensitive SERS sensing to detect 2,6-Di-t-butyl-p-hydroxytoluene (BHT) with silver nanotriangles sensitized ZnO nanorod arrays for food security applications

By the over exploitation of synthetic phenolic antioxidants [2,6-Di-t-butyl-p-hydroxytoluene (BHT)] alarm the society with greater health risk urge for careful monitoring and assessment. To accomplish the objective, surface enhanced Raman scattering (SERS) is explored as prominent technique for direct detection of food additives with the development of semiconductor/metallic junction (1D ZnO nanorods/ silver nanotriangles) sensor on stainless steel substrate. Stainless steel substrate offers cost-effective, highly thermal resistant, improves Raman signal strength and suppresses background signal fluorescence. The influence of growth parameters with respect to length of the nanorods (ZNR) are optimized. Silver nanotriangles (AgT) are sensitized upon the surface of ZnO nanorods (ZNR/AgT). The hybrid nanostructures structural, morphology and optical property are discussed in detail. Highly sensitive sensor was identified with ZnO nanorod length 0.49 µm attained at growth interval of 3 h (Z3/AgT). The underlying mechanisms responsible for ultra-sensitivity is highlighted with the point of synergism. With synergistic mechanism, ∼5.2-fold increment in sensitivity is attained. The fabricated Z3/AgT sensor portrays high stability, vastly reusable, extreme uniformity (RSD values -8.3%) as well ultrasensitive in sensing the food additive BHT at very low concentration (0.1 ng/mL). The developed sensor is highly suitable for onsite monitoring of foodstuffs to conserve the food safety.

The Effect of Oxygen and Air Flow on the Characteristic of Zinc Oxide ZnO Nanorods

In this study, ZnO nanorods are synthesized by the means of chemical bath deposition (CBD). Further objectives, to study the effect of new parameters (oxygen and air flow) on ZnO nanorods on morphology and length of alignment of the nanorods. It was observed that 0.100M for both zinc nitrate hexahydrate and hexamethylenetetramine give a best result. Here, we added an oxygen gas pressure as others idea in chemical bath deposition method and a p-type silicon substrate to investigate the length of ZnO nanorods through their cross-section. It was found that the biggest grain sizes obtain from sample 14, which is 58.87nm produces a high crystal quality, among others. Sample 14 also has a long nanorods (1.434μm-1.451μm) compared to other samples. The hexagonal structure was observed by Field Emission Scanning Electron Microscope, FESEM and well aligned, compact and perpendicular ZnO nanorods grew on the surface of glass substrate. XRD data shows that it has a larger grain size with low lattice strain. The cross-sectional view of the samples demonstrates long nanorods with a range 2.763μm-2.844μm. Finally, the growth of ultra-long ZnO nanorods by using a modified chemical bath setup was successfully observed and recorded.Keywords: ZnO nanorods, CBD, Growth duration, FESEM images, pressure flow.

SYNTHESIS OF Ag-DOPED ZnO NANOMATERIALS FOR DYE SENSITIZED SOLAR CELLS AND INVESTIGATION OF THE OPTIMUM Ag DOPING RATE

Silver (Ag) doped ZnO (SZO) nanomaterials were synthesized by hydrothermal method and characterized. ZnO nanostructures were doped with 0.0%, 0.5%, 1%, 1.5mol% Ag. These obtained SZO nanomaterials were analyzed using X-ray diffraction measurement (XRD), Scanning Electron Microscopy (SEM), and Energy Dissipative X-ray spectroscopy (EDX). The structural analysis confirmed the formation of synthesized SZO samples having a hexagonal ZnO wurtzite phase. The morphology of SZO samples changed partially and the ZnO nanorod length increased somewhat as the Ag doping ratio increased. Despite this increase, it was seen that the average crystal sizes first increased and then decreased. The crystallite sizes calculated from XRD data for 0.0, 0.5, 1.0 and 1.5mol% SZO were obtained as 41, 42, 38 and 37 nm, respectively. Ag doping concentration has increased the absorbance of SZO nanomaterials increased and the transmission decreased was observed. The band gap of the 0.0%, 0.5%, 1.0% and 1.5mol% SZO nanomaterials were measured 3.19, 3.18, 3.16 and 3.19 eV, respectively. Then dye sensitized solar cells (DSSCs) were fabricated using these SZO nanomaterials, Z907dye, N719 dye and examined their photovoltaic performances. The calculated efficiencies of DSSCs fabricated using Z907 dye for 0.0%, 0.5%, 1.0% and 1.5mol% SZO were 0.005, 0.51, 0.46 and 0.22%, respectively. Then the calculated efficiencies of DSSCs fabricated using N719 dye for 0.0%, 0.5%, 1.0% and 1.5mol% SZO were 0.06, 0.17, 0.07 and 0.06%, respectively. In both works, DSSCs with ZnO film doped with 0.5mol% SZO showed the best photovoltaic performance. Consequently, these results indicated that the synthesized SZO nanomaterial for DSSCs of the optimum ratio of Ag doping is 0.5mol% clearly.

Efficiency improvement of perovskite solar cells by charge transport balancing using length tunable ZnO nanorods and optimized perovskite morphology

Well-aligned ZnO nanorods with tunable length are successfully deposited using a low-temperature chemical bath deposition method, and subsequently used in constructing solar cells with the structure of FTO/ZnO nanorods/MAPbI 3-x Cl x /P3HT/Au. The charge transport is balanced by tuning the length of nanorods and improving the morphology of the perovskite layer. Uniformity and charge transport within the film is improved by doping the perovskite structure with Cl − ions. The photovoltaic characteristics of the cells are improved as the length of nanorods increases from 300 nm to 460 nm, and deteriorate as it increases further. Using nanorods with the length of 460 nm, power conversion efficiency of 12.85% and J sc over 22 mA/cm 2 are obtained. This efficiency is in the range of the best efficiencies reported so far using P3HT as the hole transporting layer (HTL) and ZnO as the electron transporting layer (ETL). For the first time, PSCs based on ZnO nanorods are fabricated, in which copper iodide is deposited as the inorganic HTL through vapor iodination of Cu film. A promising efficiency of 8.09% is achived which is in the range of the highest efficiencies reported for n-i-p PSCs with CuI as the HTL. • Charge transport was balanced by tuning the length of ZnO nanorods and improving their morphology. • P3HT was used as an effective, relatively inexpensive, hydrophobic hole transport layer. • The Morphology was improved by using Cl ions doping and solvent engineering. • Open circuit voltage and fill factor of the cells were found to both depend on the length of ZnO nanorods (layer thickness). • For the first time, using CuI as the hole transport layer, all-inorganic PSC based on ZnO nanorods was fabricated.

P–N junction-based ZnO wearable textile nanogenerator for biomechanical energy harvesting

Abstract Wearable nanogenerators have attracted intensive interest owing to their ability to convert the energy from body movement and the surrounding environment to electronic signals, which can power portable/wearable electronic devices for sensing, motion tracking or monitoring to improve the quality of human life. Herein, a p-n junction ZnO textile nanogenerator is successfully fabricated on conductive textiles utilising PEDOT:PSS/CuSCN-coated ZnO nanorods, combining the advantage of ZnO piezoelectricity and textile flexibility. It is found that by increasing the length of ZnO nanorods, the nanogenerators exhibit increasing output voltage and power density. The device with optimized ZnO nanorods length produces increasing output voltage from 0.2 V to 1.81 V as the shaking frequency increases from 19 Hz to 26 Hz, which can activate an LCD screen display. In addition, the device is able to generate increasing negative voltage from 1.64 V to 5.08 V by an increasing impacting force. Other mechanical forces such as flicking, gentle finger bending and tapping can also be harvested by the fabricated device. These results are of particular importance in designing future flexible self-powered devices and wearable electronics.

The enhanced performance of piezoelectric nanogenerator by increasing zinc precursor concentration during the growth of ZnO nanorods on stainless steel foil

This study aims to investigate the structural and morphology of ZnO nanorods in the variation of precursor ratio on stainless steel substrate and its piezoelectric nanogenerator performance. ZnO nanorods are grown on a stainless steel substrate that has been coated with ZnO as a seed layer by a modified hydrothermal method in the variation of molar ration between Zinc nitrate tetrahydrate (ZNT) and hexamethylenetetramine (HMT). X-ray diffraction (XRD) and scanning electron microscope (SEM) were performed for structural properties and morphology characterization. The performance of the piezoelectric nanogenerator was carried out by measuring voltage and current in applying an external force to the device. The ZnO-nanorods has a hexagonal wurtzite structure. The average length of ZnO-nanorods increased and the average diameter decreased by increasing ZNT/HMT ratio. The current and voltage of the piezoelectric nanogenerator increased with increasing by increasing the zinc nitrate ratio. These results indicate that the ZNT and HMT precursor ratio is playing an important role in the growth of ZnO nanorods that implicates the performance of the piezoelectric nanogenerator with stainless steel substrate.

Improving performance of perovskite solar cells based on ZnO nanorods via rod-length control and sulfidation treatment

The structure and properties of electron transport layers play an important role in determining device performance of perovskite solar cells (PSCs). PSCs based on one-dimensional ZnO nanorods still suffer from serious efficiency losses. In this work, length of ZnO nanorods was firstly optimized by exploring steady photoluminescence quenching of perovskite films deposited on ZnO nanorods of various lengths and their photovoltaic performance. PSCs fabricated on ZnO nanorods of ~400 nm yield the best power conversion efficiency of ~10% due to their relatively balanced charge carrier transfer and transport properties. On this basis, sulfidation treatment was applied on these ZnO nanorods to further improve device performance. It is found that the sulfidation treatment of ZnO nanorods may play a role in at least three aspects: (I) passivating defects on the surface of ZnO nanorods; (II) facilitating charge carrier transfer and transport by forming ZnO/ZnS type II heterojunctions; (III) alleviating perovskite dissociation to some extent. Due to these benefits, the power conversion efficiency of perovskite solar cells based on ZnO nanorods was improved to 11.72%, along with less hysteresis. This work not only demonstrates the importance of rod-length and sulfidation treatment on device performance of perovskite solar cells based on ZnO nanorods but also provides a feasible method to improve their power conversion efficiency.

The dependence of the optical properties of ZnO nanorod arrays on their growth time

As a multifunctional optoelectronic material, ZnO nanorod array has attracted wide attention. In this work, transparent and highly c-axis oriented ZnO nanorod arrays were grown by a simple chemical solution method using zinc acetate and urea as raw materials. Compared with widely used zinc nitrate and hexamethyltetramine, zinc acetate and urea are safer and cheaper. The relationship between crystallization quality, surface defects, optical properties and growth time of ZnO nanorods was investigated. The results show that with the rise of growth time, the length of ZnO nanorods gradually increases, and the crystalline quality gradually improves. The transmittance in the visible range is gradually enhanced, and the absorption edge near 375 nm becomes steeper. The photoluminescence spectra show that as the growth time increases, the intrinsic emission of the ZnO nanorods, i.e., the ultraviolet emission, is gradually enhanced, and the visible emissions related to the defects are gradually weakened. X-ray photoelectron spectroscopy (XPS) analysis show that the oxygen-related defects on the surface of ZnO nanorods gradually decrease with the increase of growth time, which is consistent with the results of the photoluminescence spectra.

Dependence of the Spontaneous Luminescence Intensity in ZnO Nanorods on their Length

The influence of the length of ZnO nanorods (500 nm in diameter) on the mode structure and spontaneous luminescence in the ultraviolet spectral region is studied by optical luminescence microscopy. It is shown that individual nanorods with a metal mirror on one face exhibit only two or three laser modes in the case of short nanocavity lengths (8–30 μm). Different values of the optical losses of the longitudinal and transverse waveguide modes are established for a ZnO nanorod lying on a glassy substrate. The quadratic dependence of the spontaneous luminescence intensity on the rod length can be attributed to improvement of the optical quality factor Q of bound longitudinal modes of light within longer rods (the Purcell effect).

Charge transport on vertically aligned ZnO nanorods with different aspect ratios

Zinc Oxide is a semiconductor widely used in sensitized solar cells as an electron transport layer. Among the different nanostructures obtainable for this material, the vertically-aligned ZnO nanorods are of great interest for the design of photoanodes; mainly due to the directionality of charge transport. Vertically-aligned ZnO nanorods of different aspect ratios were prepared via hydrothermal synthesis. UV–Vis absorption was used to determine the dependence of the optical band gap energy on the nanorod diameter according to the Burstein-Moss shift theory due to the presence of surface states. Information about the electronic properties of the different nanorods was obtained by spectroelectrochemical measurements used to monitor the absorbance decrease and Egap shift at different potentials. Time of flight photocurrent transients indicated a dependence on charge transport time with ZnO nanorod length. All evidences point to a large distribution of trap states located in the semiconductor band gap.

One step synthesis of vertically grown Mn-doped ZnO nanorods for photocatalytic application

Pure and Mn-doped ZnO nanorods thin films on glass substrates were successfully synthesized by a one-step hydrothermal route. It was confirmed from XRD data that pure and Mn-doped ZnO samples show hexagonal (wurtzite) structures and the particle size was found to be in the range 27–31 nm. From XRD data it was clearly found that vertical growth along (002) plane after Mn-doping into ZnO lattice. Functional groups and chemical species were detected using FT-IR spectra. Diameter and length of ZnO nanorods were determined by TEM which is in the range 350 nm, 1–4 μm respectively. UV–Vis results exhibit red shift with increasing Mn concentration in ZnO lattice. The 5% Mn-doped ZnO sample exhibits higher fluorescence intensity in visible region with surface defects. The electrical resistance of pure and Mn-doped ZnO nanorods was demonstrated by I–V characteristics. It was explicitly outlined from Raman spectra E 2 high mode was shifted towards the higher wavenumber from 439 to 440 cm−1 owing to Mn doping in ZnO lattice. The average surface area, pore volume, and pore diameter were measured by using the BET isotherm. The photocatalytic activity of pure and Mn-doped ZnO was evaluated by the degradation of methylene blue (MB) under UV–Vis light irradiation which indicates that 5% Mn-doped ZnO nanorods have better photocatalytic activity than other samples.

Preparation of (002)-oriented ZnO for CO gas sensor

In this work, (002) oriented ZnO thin film for carbon monoxide (CO) gas sensing application has been synthesized on the glass substrate using diethanolamine (DEA) as a chelating agent by two-step process. First, the seed layers were formed at a glass substrate using dip coating method, and second, ZnO nanostructure was grown using Chemical Bath Deposition (CBD) at low temperature. The structural and orientation of ZnO films were confirmed using x-ray Diffraction (XRD) while their morphologies and size were analyzed using Scanning Electron Microscopy (SEM). Diffraction pattern showed that the resulting film has wurtzite structure and an extremely sharp (002) peak was found, indicated that the ZnO nanostructure was growth along (002) orientation. The SEM image showed that the (002) oriented ZnO has hexagonal shape nanorods which vertically aligned. It was found that the diameter and length of ZnO nanorods were 71–96 nm and 666 nm, respectively. The gas sensing performance was investigated at various temperatures (160 °C, 200 °C, 250 °C, and 300 °C) and CO gas concentrations (10, 30, 50, 70 and 90 ppm). The results showed that the highest response, 53.25% was obtained at 200 °C toward 90 ppm CO gas. The response and CO gas concentration have a good linearity relationship which indicated that the (002) oriented ZnO has high potential for high sensitive CO gas sensor.

Зависимость интенсивности спонтанной люминесценции наностержней ZnO от их длины

AbstractThe influence of the length of ZnO nanorods (500 nm in diameter) on the mode structure and spontaneous luminescence in the ultraviolet spectral region is studied by optical luminescence microscopy. It is shown that individual nanorods with a metal mirror on one face exhibit only two or three laser modes in the case of short nanocavity lengths (8–30 μm). Different values of the optical losses of the longitudinal and transverse waveguide modes are established for a ZnO nanorod lying on a glassy substrate. The quadratic dependence of the spontaneous luminescence intensity on the rod length can be attributed to improvement of the optical quality factor Q of bound longitudinal modes of light within longer rods (the Purcell effect).

Influence of growth temperature and duration on different properties of ultra-long ZnO nanorods grown by modified chemical bath deposition method

In this work, ultra-long ZnO nanorods (NRs) were grown on ZnO buffered Si substrates by using direct heat substrate-modified chemical bath deposition (DHS-MCBD) method. Initially, the growth temperature was varied in the range 140 °C to 250 °C while keeping the time fixed at 4h. In the second stage, the growth temperature was kept fixed at 220 °C and the time was changed from 4h to 8 h. The morphological, structural and optical properties of ZnO NRs at different growth temperatures were investigated by using field emission scanning electron microscope (FESEM), x-ray diffraction (XRD) and photoluminescence (PL) spectroscopy techniques. The surface morphology results revealed the formation of hexagonal-shaped, ultra-long and vertically-aligned ZnO NRs. The average length of the NRs was increased from 5.7 μm to 24.5 μm by increasing the growth temperature from 140 °C to 250 °C. The XRD results specified the formation of c-axis oriented diffraction peak corresponding to hexagonal ZnO NRs in all the samples. The intensity of this peak was increased by increasing the growth temperature up to 220 °C, however, on further increasing the temperature to 250 °C, the c-axis peak intensity was decreased. The PL analysis indicated higher UV to deep level emission intensity ratio (IUV/IDLE) of the NRs grown at 220 °C as compared to the others. Similarly, by changing the growth time from 4h to 8h, the length of ZnO NRs was also increased. The results obtained were correlated and the chemical reactions for ZnO NRs growth were discussed in this paper.

ZnO-based inverted hybrid solar cells: Technical adjustment for performance optimization step by step

In this work, we reported on the effect of adjusted technical conditions on device morphology including inorganic semiconductor ZnO and the obtained active layers. Specifically, by different concentrations of sol–gel precursors and various hydrothermal time, density and length of ZnO nanorods were controlled; then the stacking of polymer chains was regulated with the thermal treatment temperature; and hole transporting property of PEDOT:PSS was adjusted with different spin-coating layers. Through a series of technical control, the cell devices performance was improved to 1.44% under 100 mW cm−2 step by step. The intrinsic mechanisms about charge separation, transport, and recombination kinetics were systematically discussed by various optical and electrochemical techniques.

Separating light absorption layer from channel in ZnO vertical nanorod arrays based photodetectors for high-performance image sensors

Photoconductor arrays with both high responsivity and large ON/OFF ratios are of great importance for the application of image sensors. Herein, a ZnO vertical nanorod array based photoconductor with a light absorption layer separated from the device channel has been designed, in which the photo-generated carriers along the axial ZnO nanorods drive to the external electrodes through nanorod-nanorod junctions in the dense layer at the bottom. This design allows us to enhance the photocurrent with unchanged dark current by increasing the ratio between the ZnO nanorod length and the thickness of the dense layer to achieve both high responsivity and large ON/OFF ratios. As a result, the as-fabricated devices possess a high responsivity of 1.3 × 105 A/W, a high ON/OFF ratio of 790, a high detectivity of 1.3 × 1013 Jones, and a low detectable light intensity of 1 μW/cm2. More importantly, the developed approach enables the integration of ZnO vertical nanorod array based photodetectors as image sensors with uniform device-to-device performance.

Electrochemical determination of uric acid in the presence of ascorbic acid by hybrid of ZnO nanorods and graphene nanosheets

ZnO nanorods and graphene foam were synthesized via hydrothermal synthesis and chemical vapor deposition, respectively. Hybrid of ZnO nanorods and graphene nanosheets was prepared by ultrasonic treatment. The hybrid was sprayed onto the ITO glass. The hybrid was characterized by scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. The electrochemical properties of the hybrid were measured by cyclic voltammetry and differential pulse voltammetry. The results show that the diameter and length of ZnO nanorods are ~ 50 nm and 5 μm, respectively. Graphene nanosheets with high quality are made up of few layers and the sheet size is ~ 2 μm. The sensitivity of the hybrid for detection of uric acid is 0.3 μM μA−1 cm−2 in the range of 5~80 μM. The electrode can accurately detect uric acid in the presence of ascorbic acid. Meanwhile, the electrode also shows good repeatability and stability.

The Influence of ZnO Nanorod Length and Counter Electrode Material on the Photovoltaic Properties of CdS/CdSe Quantum Dots Cosensitized ZnO Nanorods Solar Cells

In this work, a highly efficient quantum dot-sensitized solar cell (QDSSC) was fabricated using CdS/CdSe cosensitized ZnO nanorod arrays (NRs) as photoelectrode, and the CuS prepared by a microwave-assisted hydrothermal method as counter electrode (CE). For the assembled solar cells, the vertically aligned one-dimensional ZnO NRs offer a large surface area for deposition of quantum dots and serve as direct pathways for fast electron transport. The CuS nanoplate CEs provide high surface area for more active catalytic sites and easy accessibility for polysulfide electrolyte, resulting in superior catalytic activity for the polysulfide electrolyte than conventional Pt CEs. The effects of nanorod length, number of successive ionic layer adsorption and reaction cycles for CdS, and chemical bath deposition time for CdSe on the photovoltaic performance were investigated, and it was found that the QDSSC assembled with CdS(6)/CdSe(4 h)/ZnO(5.4 μ m) and CuS CEs yields a maximum power conversion efficiency of 4.55%, with V OC, J SC, and FF of 0.60 V, 14.63 mA·cm–2, and 0.52, respectively, under one-sun illumination.

Synthesis and length dependent photoluminescence property of zinc oxide nanorods

One-dimensional nanostructure ZnO nanorods (NRs) with controlled lengths and diameters were synthesized by the growth of colloidal nanoparticles and then characterized by XRD, TEM, Raman, PL and UV–Vis. The growth time parameter plays an important role in the formation process of ZnO NRs. The as-prepared nanoparticles has spherical shape with size about 4nm, and formed single-crystalline NRs of length up to 150nm and 16–20nm in diameters. Raman spectra of the as-grown ZnO nanorods revealed the existence of Raman silent modes B1(low) and B1(high) at 273 and 538cm−1 respectively. Photoluminescence (PL) and UV–visible absorption measurements have been performed at room temperature. The PL spectrum showed that the relative intensity of ultraviolet (UV) and defect bands depend on the length of ZnO nanorods. The peak of photoluminescence of UV band around 395nm is strongly enhanced when the length of ZnO nanorods is reduced and the humps around 580nm decreases.