Growth Mechanism Of ZnO Nanorods Research Articles

Synthesis of ZnO Nanorods and Its Application in Zinc-Silver Secondary Batteries

In this paper, ZnO nanorods were synthesized by the hydrothermal method and used as anodes for zinc-silver batteries. The Tafel and EIS curve analysis results show that ZnO nanorods have better anti-corrosion and charge transport properties than ZnO powders. At 0.1 C discharge conditions, the ZnO electrode exhibits more stable cycle efficiency than the powder electrode; after 25 cycles, the capacity is higher by 95%. The superior electrochemical performance is due to the ZnO nanorods having the ability to conduct electrons and increase the surface area. Therefore, the possible growth mechanism of ZnO nanorods has been investigated.

Orientation and actual growth mechanism of ZnO nanorods through hydrothermal method on gold seed layer

In this study, the hydrothermal method was employed to synthesize an oriented ZnO nanorod array on an annealed gold seed layer coated on a glass substrate from different precursor concentrations. Zinc nitrate hexahydrate and hexamethylenetetramine were used as starting materials for ZnO nanorod growth. The effect of gold seed layer roughness on the orientation of ZnO nanorods is presented. The morphology of the nanorods shows that oriented ZnO nanorods were obtained after deposition on the annealed gold seed layer. Energy dispersive x-ray spectroscopy was used to identify the elemental composition and identify the elements present in the samples. The XRD pattern shows that the nanorods have a good crystalline structure, with dominant (002) peaks for all concentrations, which reflects that the c-axis of the elongated nanorods is oriented normal to the substrate. The proposed growth mechanism for the growth of ZnO nanorods is presented.

Fabriction of ZnO Nanorods with Strong UV Absorption and Different Hydrophobicity on Foamed Nickel under Different Hydrothermal Conditions.

ZnO nanorods have been grown on the surface of foamed nickel by a two-step method. Firstly, a layer of ZnO seed is sputtered on the surface of the foamed nickel by magnetron sputtering, and then the hydrothermal method is used to grow ZnO nanorods at different conditions (solution concentration, reaction time and reaction temperature). The results show that the morphology of ZnO nanorods is closely related to the solution concentration, reaction time, and reaction temperature. The energy band structure formed by the foamed nickel and ZnO seed layers and the growth mechanism of ZnO nanorods are discussed. The samples are characterized by Energy dispersive spectrometer (EDS), X-ray diffraction (XRD), and Raman spectroscopy. The absorption characteristics of samples to light are characterized by ultraviolet-to-visible (UV–VIS) absorption. The hydrophilicity of the samples is characterized by the static contact angle. By analyzing the performance characteristics of the samples at different conditions, we finally obtained the optimal growth parameters. At the optimal parameters, the morphology of the grown nanorods is regular, the ultraviolet band has strong absorption, and the surface of the samples forms a superhydrophobic surface.

Seed layer effect on different properties and UV detection capability of hydrothermally grown ZnO nanorods over SiO2/p-Si substrate

Hydrothermally grown one dimensional ZnO nanostructures are among the most widely used semiconductor materials to build high-efficiency electronic devices for various applications. Few researchers have addressed the growth mechanism and effect of ZnO seed layer on different properties of ZnO nanorods grown by hydrothermal method, instead, no one has synthesized ZnO nanorod over SiO2/p-Si substrate. The aim of this study is to study the effect of ZnO seed layer and the growth mechanism of ZnO nanorods over SiO2/p-Si substrate. To achieve the goal, we have synthesized ZnO nanorods over different thickness ZnO seed layers by using the hydrothermal method on SiO2/p-Si substrate. The effects of c-plane area ratio were identified for the growth rate of c-plane, reaction rate constant and stagnant layer thickness also calculated by using a modified rate growth equation. We have identified maximum seed layer thickness for the growth of vertical ZnO nanorod. A step dislocation in the ZnO nanorods grown on 150and200nm thick seed layers was observed, the magnitude of Burges vector was calculated for this disorder. The seed layer and ZnO nanorods were characterized by AFM, XPS, UV-visible, XRD (X-ray diffraction, and SEM(scanning electron microscope). To justify the application of the grown ZnO nanorods Ti/Au was deposited over ZnO nanorods grown over all seed layers for the fabrication of photoconductor type UV detector.

Dimethylamine Controlled Sol-Gel Process to Grow ZnO Nanorods

ZnO nanorods were prepared using dimethylamine (DMA) controlled Sol-Gel process. Dimethylamine was added as an additive to control the sol-gel process for growing ZnO nanorods. DMA would exhibit stabilizing effect, promote dissolution of precursor and control the rate of sol-gel reactions because of its basic nature and significant miscibility. The Structural and microstructural properties of the powders were characterized by X-Ray Diffractometer (XRD), Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM). FESEM and TEM analysis revealed that the ZnO powder prepared were nanorods in nature. The optical properties of powders were characterized by UV-Visible and Photoluminescence (PL) spectroscopy. The Structural, morphological, optical and photoluminescence properties of so obtained ZnO powders consisting of nanorods were studied. DMA is simple amine but found to be very effective to control the aspect ratio of nanorods. The role of DMA in growing wurtzite structured hexagonal ZnO nanorods with [0001] orientation was interpreted and growth mechanism of ZnO nanorods was explained.

Multi-angle ZnO microstructures grown on Ag nanorods array for plasmon-enhanced near-UV-blue light emitter

Metal enhanced ultraviolet light emission has been explored in ZnO/Ag hybrid structures prepared by hydrothermal growth of multi-angled ZnO nanorods on slanted Ag nanorods array fabricated by the thermal evaporation technique. Slanted Ag nanorods are realized to be the stacking of non-spherical Ag nanoparticles, resulting in asymmetric surface plasmon resonance spectra. The surface roughness of Ag nanorod array films significantly influences the growth mechanism of ZnO nanorods, leading to the formation of multi-angled ZnO microflowers. ZnO/Ag hybrid structures facilitate the interfacial charge transfer from Ag to ZnO with the realization of negative shift in binding energy of Ag 3d orbitals by ∼0.8 eV. These high quality ZnO nanorods in ZnO/Ag hybrid nanostructures exhibit strong ultraviolet emission in the 383–396 nm region without broad deep level emission, which can be explained by a suitable band diagram. The metal enhanced photoluminescence is witnessed mainly due to interfacial charge transfer with its dependence on surface roughness of bottom layer Ag nanorods, number density of ZnO nanorods and diversity in the interfacial area between Ag and ZnO nanorods. The existence of strong ultraviolet light with minor blue light emission and appearance of CIE shade in strong violet-blue region by ZnO/Ag hybrid structures depict exciting possibilities towards near UV-blue light emitting devices.

Direct growth of ZnO nanorods on biogenic hierarchical rice husk SiO2 and their application to dye degradation

ZnO nanorods/hierarchical SiO2 porous composites are successfully obtained from biogenic-template method with ZnCl2 and rice husks as raw material by a simple double-step annealing process. The structure and optical properties were characterized by XRD, SEM, TEM, XPS and UV–Vis spectra to understand the growth mechanism of ZnO nanorods on biogenic hierarchical SiO2. Vertically aligned with high regularity and density ZnO nanorods were developed on porous SiO2 when the treated temperature was 600 °C under N2 gas and post-treating in muffle furnace at 450 °C in the air. The results showed that ZnCl2 played an important role in acting as the zinc source and morphology director during the formation of ZnO nanostructures. At initial stage, ZnCl2 melted from the raw material and diffused onto the rice husk surface to formed flake structure ZnOCl2·H2O when the treated temperature was lower than 500 °C under N2 gas. The former was responsible for proto-nanorods (template) formation of ZnO nanorods. The as-prepared samples displayed high photocatalytic activity for the degradation of rhodamine B under ultraviolet (UV) irradiation.

Role of seed layer: lattice orientation attachment and structural stabilization on the lateral growth of ZnO nanorods

The role of seed layer (SL) on the growth of ZnO nanorods was investigated by preparing SL with different concentrations of zinc acetate by jet nebulizer spray pyrolysis technique at different deposition time. The ZnO nanorods were grown on the ZnO seeded substrate by hydrothermal method. The influence of SL on the growth of ZnO nanorods with respect to SL concentration and deposition time were studied with various characterization tools. The results had shown that the orientation of crystallites and alignment of rods were found to be improved with lower concentration and increasing deposition time of SL and the converse effect was found in the higher concentration. The various morphologies were obtained on the surface of SL with respect to different concentration and deposition time and they were discussed in detail from the basic nucleation theories. The growth mechanism of ZnO nanorods on the SL is effectively investigated. The lateral growth was found in nanorods, due to lattice orientation effect. The hexagonal structural stabilization was also observed and discussed in detail. The Raman measurements confirm the wurtzite phase, high crystal quality and quantum confinement in ZnO nanorods.

Local Structural Properties and Growth Mechanism of ZnO Nanorods on Hetero-Interfaces.

We investigated the growth mechanism of ZnO(001) nanorods on SrTiO3(001) substrates. In the beginning of ZnO growth, a ZnO(110) film was developed on SrTiO3 substrates and then (001)-oriented ZnO nanorods grew on the ZnO(110) film. The strain energy of ZnO(110) growth on SrTiO3(001) planes was approximately 2.7 x 10(8) J/m3 whereas it was estimated to be ~1.61 x 10(9) J/m3 for ZnO(001) directly grown on SrTiO3(001) planes using Young's modulus of elasticity. Stress due to the lattice mismatch between ZnO and SrTiO3 was mostly relaxed in several monolayers and then ZnO(001) nanorods were finally formed along their easy growth directions. Keywords: ZnO Nanorod, Hetero-Interface, Local Structural, Growth Mechanism.

Facile synthesis of ZnO nanostructures by spray pyrolysis technique and its application as highly selective H2S sensor

ZnO nanorods were facilely grown on glass substrates using spray pyrolysis technique and they were successfully used to detect hydrogen sulfide at room temperature. Desired molar concentration of zinc chloride precursor was optimized to produce high quality ZnO nanorods. The plausible growth mechanism of ZnO nanorods was schematically depicted and analyzed. Further, the influence of transition metal doping (Co, Ni and Cu) on the structural, morphological, optical and hydrogen sulfide sensing properties was investigated. Sensing response of the undoped and doped thin films were also investigated in the presence of eight different vapors. The sensing response indicated the highly selective nature of ZnO nanorods towards hydrogen sulfide. Among the doped elements, Ni-doped ZnO film showed an excellent sensing response of 321 towards 100ppm of hydrogen sulfide with the response and recovery times of 12 and 90s, respectively.

Preparation of V-doped AZO thin films and ZnO nanorods on V-doped AZO thin films by hydrothermal process

The growth mechanisms of ZnO nanorods (NRs) on sputtered Al-doped ZnO (AZO) and V-doped AZO (V:AZO) thin films are studied in this work. Firstly, the microstructure of the AZO and V:AZO thin films was investigated by XRD. We found that V-dopants retard the crystallization (grain growth) and enlarge the d-spacing of the (0002) plane of the V:AZO thin films. ZnO NRs were prepared on the AZO and V:AZO thin film substrates by the hydrothermal method. Vertically aligned ZnO NRs were grown on the pure AZO thin film substrate. With incorporating V-dopants, the growth direction of ZnO NRs grown on the V:AZO thin films is highly influenced by the concentration of the V-doping. The V-doping causes the random growth direction of ZnO NRs. XRD and SEM analysis indicate that the growth behavior of ZnO NRs depends on the microstructure of the surface grains of the AZO and V:AZO thin film substrates. A growth mechanism of ZnO NRs on the AZO and V:AZO thin film substrates is proposed in this work.

Growth of ZnO nanorods on fluorine-doped tin oxide substrate without catalyst by radio-frequency magnetron sputtering

ZnO nanorods were directly grown on fluorine-doped tin oxide (FTO)-coated glass substrate by radio frequency magnetron sputtering without a buffer layer or a catalyst. The deposition time, substrate temperature, and type of substrate were varied to investigate the growth behavior of ZnO nanorods. At an early stage of growth, nano-sized particles were locally formed on the faceted surface of FTO, which were finally grown into the nanorods. The substrate temperature of over 400°C was required for ZnO nanorod growth. ZnO nanorods were well grown on FTO, SnO2-coated Si, and SnO2-coated SiO2 substrates whereas ZnO thin film was deposited on Cu foil, stainless steel, Au-coated SiO2, and Pt-coated SiO2 substrates. Based on the obtained results, a growth mechanism for ZnO nanorods was proposed.

Preparation and enhanced photocatalytic performance of one‐dimensional ZnO nanorods

One dimensional (1D) ZnO nanorods were successfully synthesized via a facile solution route by refluxing their acetate precursors in diethylene glycol medium at 160°C. The as‐prepared ZnO nanorods were characterized by field emission scanning electron microscopy, X‐ray diffraction, and Fourier transform infrared spectroscopy. Experimental results demonstrated that the resultant products showed a 1D rod‐like hexagonal wurtzite crystal structure with diameters of about 5 nm and lengths of up to 100–200 nm. A possible growth mechanism of ZnO nanorods was tentatively proposed. Photocatalytic measurements demonstrated that the as‐prepared ZnO nanorods showed higher photocatalytic activities than the commercial photocatalyst TiO2 P25 nanoparticles. In addition, the effect of solution pH values and initial solution concentrations on the photocatalytic activities of as‐prepared ZnO nanorods was also evaluated. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 74–80, 2015

Substrate effect of hydrothermally grown ZnO nanorods and its luminescence properties

We report the hexagonal wurtzite crystalline structure of ZnO nanorod growth by hydrothermal chemical wet synthesis at low temperature (90°C). We have used p-Si (100), n-Si (100), α-quartz (0001), MgO (0001) and ITO (polycrystalline) substrates to understand the growth mechanism of ZnO nanorods with a low pressure environment. X-ray diffraction study confirms the hexagonal structure of the ZnO nanorod. Scanning electron microscopy (SEM) also shows the hexagonal structure along with different size and width of the nanorods. The substrate effect of nanorods has been explained on the basis of adatom kinetics during the growth. We observed that the nanorods were grown from a single nucleation point with 4–5 different branches on the ITO substrate with uniform length and width, whereas MgO substrate shows curled flower architecture across the whole area. The photoluminescence illustrates strong substrate effect. A wide range of UV emission bands along with visible emission has been observed from the ZnO nanorods deposited on different substrates.

Facile Hydrothermal Approach to ZnO Nanorods at Mild Temperature

In this work, ZnO nanorods are obtained through a facile hydrothermal route. The structure and morphology of the resultant products are characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The experimental results indicated that the as-synthesized ZnO nanorods have an average diameter of approximate 100 nm. A possible growth mechanism for ZnO nanorods was proposed based on the experimental results and found that Zn powder plays a critical role for the morphology of the products. Room temperature photoluminescence property of ZnO nanorods shows an ultraviolet emission peak at 390 nm.

Synthesis, photoluminescence and growth mechanism of ZnO nanorods via RTIL-assisted solid-state reaction

Well-defined ZnO nanorods were fabricated via facile solid-state reaction between zinc chloride and sodium hydroxide in the presence of room-temperature ionic liquid (RTIL) [Emim]+BF4− at a relatively low temperature. The structure and morphology of the synthetic ZnO products were characterized by X-ray diffraction and transmission electron microscopy. The effect of RTILs on the size and morphology of the as-prepared ZnO samples was studied, and the experimental results showed that RTILs in the reaction system play an important role in the synthesis of ZnO nanorods. The photoluminescence spectrum of the synthetic ZnO nanorods exhibited a strong ultraviolet emission at 376nm and a weak green emission at 536nm at room temperature. A plausible formation mechanism of ZnO nanorods was discussed in detail.

Fabrication of ZnO Nanorods in One Pot via Solvothermal Method

AbstractIn this article, we reported a low temperature solvothermal method to synthesize ZnO nanorods in one pot. In order to study the growth mechanism of ZnO nanorods, various preparative parameters, such as zinc species concentration, the molar concentration ratio of hydroxide [OH‐] to zinc species [Zn2+], and surfactants, have been systematically examined. According to the analysis, the aspect ratio of ZnO nanorods was enlarged with the increase of the concentration ratio of [OH‐] to [Zn2+]. However, the mean diameter only causes subtle change. Additionally, the influence of surfactants was studied by two different kinds of surfactant, ethylenediamine (EDA) and hexadecylamine (HDA). From transmission electron microscopy analysis, the aspect ratio of ZnO nanorods was similar to that without adding surfactant. However, the green emission caused by oxygen defects or others can be omitted while the surfactants were added into the reaction. Herein, the growth mechanism was proposed to relate to the element of coordination polyhedron presented in the interface. When terminal vertex bonds with more growth units, the interface has higher growth rate for the crystal formation. Besides, the reaction medium also affects the growth mechanism of ZnO nanorods. In an alkali medium, the larger hindrance effect of ONa‐ ions at the interface of (0001) and ( 01 1¯ 1¯ ) faces, the growth rates of (0001) and ( 01 1¯ 1¯ ) faces have a great hindrance relative to other crystal faces.

EFFECT OF PRE-HEATING AND SEED LAYER ON HYDROTHERMAL GROWTH AND OPTICAL PROPERTIES OF ZINC OXIDE NANORODS

Hydrothermal growth of highly c-axis oriented ZnO nanorods with high aspect ratio on pulsed laser deposited ZnO seed layer is reported. Effect of pre-heating time, growth time and seed layer on the structural, morphological and optical properties of ZnO nanorods is presented. The possible growth mechanism for ZnO nanorods is also discussed.

Fabrication of flower-like ZnO microstructures from ZnO nanorods and their photoluminescence properties

In the present work, we reported a novel method for the synthesis of well-dispersed flower-like ZnO microstructures derived from highly regulated, well-dispersed ZnO nanorods by using low temperature (100 °C) hydrothermal process and without using any additional surfactant, organic solvents or catalytic agent. The phase and structural analysis were carried out by X-ray diffraction (XRD) which confirms the high crystal quality of ZnO with hexagonal (wurtzite-type) crystal structure. The morphological and structural analyses were carried out by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) which indicate the formation of well-dispersed ZnO nanorods as well as flower-like ZnO. It has been shown that flower-like ZnO is made up of dozen of ZnO nanorods building block units. The high resolution transmission electron microscopy (HRTEM) and their corresponding selected area electron diffraction (SAED) pattern show that both ZnO nanorods and flower-like ZnO microstructures are single crystalline in nature and preferentially grow along [0 0 0 1] direction. Their optical property was characterized by photoluminescence spectroscopy; shows ZnO nanorods have only violet emission and no other emission while flower-like ZnO microstructures have a weak violet emission and a strong visible emission. A plausible growth mechanism of ZnO nanorods as well as flower-like ZnO microstructures has been given.

Seeded growth of ZnO nanorods from NaOH solutions

Perpendicularly aligned arrays of corrugated ZnO nanorods were grown onto gold patterned LiTaO 3 substrates, coated with a sputtered ZnO seed layer. During the growth process, these substrates were held submerged in an aqueous solution comprising a 1:40 mol ratio mix of zinc nitrate hexahydrate to sodium hydroxide. The substrates were placed in a custom apparatus residing in an autoclavable storage bottle. Scanning electron micrographs, which were taken at different deposition intervals, suggest that the growth mechanism of ZnO nanorods initiates with the etching of the ZnO sputtered seed layer into hexagonal bases (> 500 nm across), from where multiple protrusions (40 nm–100 nm in width) grow atop these hexagonal bases. Such nanoprotrusions later coalesce into larger nanorods. Uniformly distributed high density corrugated nanorods, with proximal spacing between adjacent nanorods of approximately 20 nm–50 nm, were observed over the entire surface.