Synthesis Of ZnO Nanorod Arrays Research Articles

An effective approach for hydrothermal synthesis of ZnO nanorod arrays activated under UV/Vis light: Different supporting ligands for hydrothermal precursor solutions

In this study, an effective approach is proposed for the controlled production of ZnO nanorod arrays that can be used in degradation of wastewater pollutants. Hydrothermal precursor solutions prepared using HMTA-different supporting ligands having different lengths and ends, which have not been tried before, allowed to control the type, size, and alignment of ZnO nanorods. Their physical properties were investigated by using X-ray diffraction patterns, Raman, FTIR and photoluminescence spectroscopies, UV/Vis Spectrophotometer, atomic force microscopy, field emission scanning electron microscopy and energy dispersive X-ray spectroscopy. Photoactivity tests were performed using methylene blue under UV/visible light and the reusability of ZnO nanorod arrays with the best properties was checked. The approach of using different supporting ligands led to different effects on the physical and photocatalytic properties. ZnO nanorod arrays gained the ZnO films, which became photoactive with UV light, the ability to benefit from visible light as well. Especially ZnO-HMTA-HMDA nanorod arrays will shed light on researchers as an effective strategy for the development of new functional nanomaterials having high photodegradation efficiency and fast kinetic.

Patterned synthesis of ZnO nanorod arrays for nanoplasmonic waveguide applications

We report the patterned synthesis of ZnO nanorod arrays of diameters between 50 nm and 130 nm and various spacings. This was achieved by patterning hole arrays in a polymethyl methacrylate layer with electron beam lithography, followed by chemical synthesis of ZnO nanorods in the patterned holes using the hydrothermal method. The fabrication of ZnO nanorod waveguide arrays is also demonstrated by embedding the nanorods in a silver film using the electroplating process. Optical transmission measurement through the nanorod waveguide arrays is performed and strong resonant transmission of visible light is observed. We have found the resonance shifts to a longer wavelength with increasing nanorod diameter. Furthermore, the resonance wavelength is independent of the nanowaveguide array period, indicating the observed resonant transmission is the effect of a single ZnO nanorod waveguide. These nanorod waveguides may be used in single-molecule imaging and sensing as a result of the nanoscopic profile of the light transmitted through the nanorods and the controlled locations of these nanoscale light sources.

Scalable continuous flow synthesis of ZnO nanorod arrays in 3-D ceramic honeycomb substrates for low-temperature desulfurization

Hydrothermal based continuous flow synthesis demonstrates a highly efficient strategy of integrating nanostructure arrays onto 3-D channeled honeycomb substrates.

ZnO/graphene/Ag composite as recyclable surface-enhanced Raman scattering substrates.

Surface-enhanced Raman scattering active substrates based on ZnO/Ag and ZnO/graphene/Ag were prepared via synthesis of ZnO nanorod arrays through the ZnO seed layers, followed by deposition of Ag nanoparticles onto ZnO and ZnO/graphene surfaces using photocatalytic deposition. The hybrid structures were confirmed by scanning electron microscopy and Raman spectroscopy. Rhodamine 6G (R6G) was used as the probe analyte. The experimental results indicated that the detection concentration level was 10-7 M with an enhancement factor of about 1.6×105. Additionally, the photocatalytic properties of ZnO/Ag and ZnO/graphene/Ag were exploited to recycle these substrates through UV-assisted cleaning.

Synthesis of ZnO Nanorod Arrays by Chemical Solution and Microwave Method for Sensor Application

One-dimensional ZnO semiconductor nanomaterials have been attracting increasing attention due to their outstanding properties, which are different from bulk materials. ZnO has a direct band gap of 3.37 eV and large exciton binding energy hence its nanowires and nanorods have been regarded as one of the most promising materials for nanoscale electronic and optoelectronic devices such as ultraviolet laser diodes, optical detectors and gas sensor. ZnO nanowires and nanorods have been successfully synthesized by various techniques such as evaporation, sputtering and pyrolysis. In this paper we report the preparation of nanorod arrays of ZnO on ITO glass substrates which were pre-coated with ZnO nanoparticles by using low temperature chemical solution method and the result was compared with microwave hydrolysis process. The morphology and structure of ZnO nanorod arrays were investigated using field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The ZnO nanorod arrays with a diameter of 40-70 nm were successfully synthesized. In microwave hydrolysis method, the diameter, density and surface roughness was found to depend on the microwave power. The microwave method is far superior in producing ZnO nanostructure growth.

Synthesis of ZnO nanorod arrays on Zn substrates by a gas–solution–solid method and their application as an ammonia sensor

The design of the 1D nano-structured material arrays on substrates is required for the development of conductivity sensors. A simple method, the so-called gas–solution–solid, has been developed to prepare ZnO nanorod arrays on Zn substrate. The method consists of putting Zn foils above an ammonia solution for about 24 h to obtain the aligned ZnO nanorods on substrates. The sizes of ZnO nanorod arrays could be controlled by adjusting the concentration of the ammonia–water solution and reaction time. Moreover, the growth mechanism of the nanorod arrays was studied and proposed. In the proposed mechanism, the Zn source from the Zn foil is first oxidized to ZnO and Zn2+ by oxygen. Then ZnO nanorod arrays are grown with the help of ammonia in the solution as a transporter of zinc ions. The nanorod arrays growth mechanism involves oxygen gas, ammonia solution, and Zn foil, and is, therefore, named as gas–solution–solid mechanism. Finally, the NH3 sensing properties were measured and the results showed that ZnO nano-array sensor has high sensitivity and reversibility for NH3 sensing at the room temperature and the sensitivity increases with increasing gas concentration.

Synthesis of ZnO Nanorod Arrays on Chaleted Sol-Gel-Derived ZnO Thin Films and its Optical Absorption in Visible-Light Region

Well-aligned ZnO nanorod arrays on Chaleted Sol-Gel-Derived ZnO thin films was achieved at a temperature of 90°C by a surfactant-assisted soft chemical approach. The nanorod arrays were characterized by XRD, SEM, XPS, and UV-Vis absorbance spectra. The ZnO nanorod arrays are wurtzite crystal stuctures preferentially orienting in the direction of the c-axis and ZnO nanorods are grown verticallyon the substrate. The XPS analysis shows the Zn:O ratio of ZnO nanorod arrays near is 1:1. The UV-Vis absorbance spectra indicate that ZnO nanorod arrays have absorption of visible-light as well as ultraviolet-light. Therefore, the ZnO nanorods may be good candidates for visible-light photocatalysis materials from the viewpoint of practical applications.

Low-Temperature, Ion Beam-Assisted SiC Thin Films With Antireflective ZnO Nanorod Arrays for High-Temperature Photodetection

This work demonstrates high-temperature operation of metal-semiconductor-metal photodetectors (MSM PDs) using low-temperature, ion beam-assisted deposition of nanocrystalline SiC thin films and hydrothermal synthesis of ZnO nanorod arrays (NRAs). Due to the incorporation of ZnO NRAs, the photo-to-dark current ratio of SiC MSM PDs is increased from 4.9 to 13.3 at 25 °C and from 4.9 to 7.6 at 200 °C. The enhancement in the sensitivity suggests that the ZnO NRAs could serve as an effective antireflective layer to guide more light into the SiC MSM PDs. This was confirmed through the characterization of reflectance measurements and finite-difference time-domain analysis. These results support the integration of nanocrystalline SiC thin films and ZnO NRAs for use in high-temperature photodetection applications.

Facile synthesis of ZnO nanorod arrays and hierarchical nanostructures for photocatalysis and gas sensor applications

A facile one-step hydrothermal route was demonstrated to grow ZnO nanorod arrays and hierarchical nanostructures on arbitrary substrates without any catalysts and seeds coated before the reaction, which are prerequisite in the current two-step protocol. Meanwhile, ZnO nanoflowers composed of nanorods were obtained at the bottom of the autoclaves in the absence of substrates. An in situ spontaneous-seeds-assisted growth mechanism was tentatively proposed on the basis of the experimental data to explain the growth process of ZnO nanostructures. Moreover, the obtained ZnO nanorod arrays exhibited superior photocatalytic activity for decomposing methyl orange, and the nanoflowers showed better gas sensing performance towards some flammable gases and corrosive vapors with high sensitivity, rapid response–recovery characteristics, good selectivity and long-term stability.

Controllable preferential-etching synthesis of ZnO nanotube arrays on SiO2 substrate for solid-phase microextraction

An improved route to obtain ZnO nanotube arrays and its first application to headspace solid-phase microextraction (HSSPME) as an adsorptive coating were described. The ZnO nanotube arrays were synthesized by a two-step chemical process including the hydrothermal synthesis of ZnO nanorod arrays on the surface of silica fiber (SiO(2)) in the first step, and the formation of ZnO nanotubes by selectively etching in NH(3)·H(2)O solution in the second step. The influence of NH(3)·H(2)O concentration, etching time, reaction temperature, and aging time in the ZnO nanotubes formation process was investigated, and arrays of ZnO nanotube with tailored dimensions (250 nm external diameters, 70 nm wall thicknesses and 2 μm lengths) could be obtained by varying the conditions. In addition, the feasibility of ZnO nanotube arrays adopted for HSSPME was evaluated by extracting volatile organic compounds (VOCs) by use of benzene, toluene, ethylbenzene, o-, m-and p-xylene (BTEX) as model compounds and the results showed that the coating has good extraction capability. The analytes were linear in the range of 10-600 μg L(-1) (r > 0.9960) and the detection limits were about 0.005-0.01 μg L(-1), lower than that obtained with ZnO nanorod arrays. The relative standard derivations (RSD) for the repeatability of single fiber and fiber-to-fiber were lower than 9.5% and 13.8%, respectively. The prepared coating showed good recoveries in the range of 87%-108% and long lifetime (more than 50 times), implying to be a potential absorbent for the VOCs in water samples.

Hydrothermal synthesis of ZnO nanorod arrays for photocatalytic inactivation of bacteria

Arrays of ZnO nanorods were synthesized on ZnO seed layer/glass substrates by a hydrothermal method at a low temperature of 70 °C. The effect of pH > 7 of the hydrated zinc nitrate–NaOH precursor on the morphology and topography (e.g. size, surface area and roughness), the optical characteristics (e.g. optical transmission and band-gap energy), hydrophilicity and antibacterial activity of the grown ZnO nanostructure and nanorod coatings were investigated. For pH = 11.33 of the precursor (NaOH concentration of 0.10M), a fast growth of ZnO nanorods on the seed layer (length of ∼1 µm in 1.5 h) was observed. The fast growth of the ZnO nanorods resulted in a significant reduction in the optical band-gap energy of the nanorod coating, which was attributed to the formation of more defects in the nanorods during their fast growth. The surface of the ZnO nanorod arrays was relatively hydrophilic (with a water contact angle of 16°) even after the subtraction of their surface roughness effect (with a contact angle of ca 27°). This hydrophilicity of the ZnO nanorods was assigned to the observed surface OH bonds. These characteristics caused the ZnO nanorod arrays to show an excellent UV-induced photocatalytic degradation of Escherichia coli bacteria. Furthermore, the synthesized ZnO nanorods were found to be strong photo-induced antibacterial material, even without considering their high surface area ratio.

Catalyst-free synthesis of ZnO nanorod arrays on InP (001) substrate by pulsed laser deposition

High-density well-aligned ZnO nanorod arrays were successfully fabricated on ZnO a seed-layer coated InP (001) substrate by using pulsed laser deposition (PLD) technique without metal catalyst. SEM image showed that uniformly distributed droplet-like ZnO seed-layer was formed on the InP wafer. Well-oriented ZnO nanorods were formed perpendicular to the seed-layer coated substrate and well-separated from each other. X-ray diffraction θ–2 θ scanning measurements demonstrated that the ZnO nanorods exhibited a strong c-axis orientation with high crystalline quality. The photoluminescence (PL) spectrum measurement illuminated that the ZnO nanorods produced in this work had well optical quality. The well-aligned and separated ZnO nanorods fabricated by this comparatively simple technique shed light on further applications for nanodevices.

Hydrothermal synthesis of ZnO nanorod arrays with the addition of polyethyleneimine

ZnO nanorod arrays were synthesized on glass substrates coated by a ZnO seeding layer via a hydrothermal technique by adding polyethyleneimine (PEI) to the growth solution. The XRD and SEM results show that the ZnO nanorods have the single crystal wurtzite structure with the (0 0 2) direction normal to the substrates. In 50 ml growth solution of 0.05 M zinc salts, the average diameter of the nanorods was reduced drastically from 300 nm to 40 nm with the PEI amount increasing from 0 ml to 6 ml. The diameter distribution and the polycrystalline layer at the bottom of the nanorods were improved. Longer nanorods were obtained by prolonging the growth time. Based on the results, possible mechanisms that PEI adsorbs on the non-polar facets of ZnO nanorods and its coordination to zinc ions were proposed to elucidate the effect of PEI on reducing the diameters and improving the morphologies of nanorods.

WITHDRAWN: Controllable synthesis of ZnO nanorod arrays via simple solution-based method

WITHDRAWN: Controllable synthesis of ZnO nanorod arrays via simple solution-based method

Controllable Synthesis of ZnO Nanorod Arrays via Simple Solution-Based Method

ABSTRACTHere we present a convenient solution-based method, which can afford a procedure to easily fabricate highly oriented ZnO nanorods on substrate at relatively low temperatures. The as-synthesized products have been characterized by scanning electron microscopy (SEM) and X-Ray diffraction (XRD). The results revealed that a densely packed and perpendicularly oriented single-crystalline ZnO nanorod arrays grew vertically on the fluorine-doped SnO2 transparent conducting oxide (FTO) glass substrates. In addition, we found that the length of the nanorod could be freely modified by controlling the solution temperature.