As-synthesized ZnO Nanostructures Research Articles

Bicone nanoflower evolution and multi-peak emission of polymer caped Cu doped ZnO.

A low-temperature polymer-assisted wet chemical method was used to synthesise Cu-doped ZnO bicone nanoflowers at three different PEG concentrations.The effects of PEG concentration on the structural, morphological and optical properties of Cu doped ZnO nanostructures were studied. X-ray diffraction studies revealed that the as-synthesized ZnO nanostructures are highly crystalline with a hexagonal wurtzite phase. The scanning electron microscopy (SEM) analysis showed that the prepared nanostructures have bicone-nanoflower morphology and PEG concentration has strongly influenced the size as well the shape of nanoflowers. The surface passivation effect of PEG on the band gap energies was studied by analysing UV -visible spectra of all the samples. The room-temperature fluorescent spectra of all the nanoflowers showed multiple peak emissions, both in the ultra-violet and visible regions, with varying intensities.These recasted multiple peaks are attributed to the morphological modification caused by the PEG addition.&#xD.

Antioxidant and Anti-inflammatory Applications of Aerva persica Aqueous-Root Extract-Mediated Synthesis of ZnO Nanoparticles.

In the present study, ZnO nanoparticles were synthesized by using aqueous extracts of Aerva persica roots. Characterization of as-prepared ZnO nanoparticles was carried out using different techniques, including powder X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and BET surface area analysis. Morphological analysis confirmed the small, aggregated flake-shaped morphology of as-synthesized ZnO nanostructures. The as-prepared ZnO nanoparticles were analyzed for their potential application as anti-inflammatory (using in vivo inhibition of carrageenan induced paw edema) and antioxidant (using in vitro radical scavenging activity) agents. The ZnO nanoparticles were found to have a potent antioxidant and anti-inflammatory activity comparable to that of standard ascorbic acid (antioxidant) and indomethacin (anti-inflammatory drug). Therefore, due to their ecofriendly synthesis, nontoxicity, and biocompatible nature, zinc oxide nanoparticles synthesized successfully from roots extract of the plant Aerva persica with potent efficiencies can be utilized for different biomedical applications.

Synthesis of Tower-Like ZnO Nanostructures and Its Optical Properties.

A peculiar tower-like ZnO nanostructure was synthesized using an economical and facile hydrothermal method, with zinc acetate [ZAc, Zn(CH₃COO)₂ · 2H₂O] and hexamethylenetetramine (HMTA, C6H12N₄) as the source materials. The as-synthesized tower-like ZnO was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The characterization results indicated that the tower-like ZnO nanostructures are high-quality monocrystals. The as-synthesized ZnO nanostructures may have application in sensing area due to its high specific surface areas. The growth mechanism, as well as the optical properties of the as-synthesized tower-like ZnO nanostructures was also studied.

Precursor- and Time-Dependent Morphological Evolution of ZnO Nanostructures for Comparative Photocatalytic Activity and Adsorption Dynamics with Methylene Blue Dye.

Diverse ZnO nanostructures were successfully fabricated at 700 °C by direct annealing of 1D Zn(II) coordination polymer precursors, namely, [Zn2(bpma)2(adc)2]n, [Zn2(bpea)2(adc)2]n, and {[Zn2(bpta)2(adc)2]·2H2O}n. The effect of sacrificial ligands present in the precursors as well as a variation in the retention time (6–24 h) during their synthesis resulted in 0D nanospheres, 1D microrods, and 3D polyhedra (with a diamond-like structure) of ZnO. The as-synthesized ZnO nanostructures were characterized by field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffractometry, diffuse reflectance spectroscopy, and Raman spectroscopy. The hexagonal crystal structure was confirmed for all the ZnO samples. A lattice spacing of 0.22 nm has been observed for nanospheres, whereas a lattice spacing of 0.26 nm has been observed for the polyhedra. Their Raman spectra confirm the wurtzite phase of ZnO. UV–vis spectra of ZnO nanostructures exhibit broad peaks in the range of 350–370 nm, and the band gap energies are found to be in the range of 3.02–3.20 eV. Based on the photoluminescence spectra photocatalytic activities of the as-synthesized ZnO nanostructures calcined for 12 h were tested with methylene blue (MB) as a contaminant in an aqueous solution. These results demonstrate that the photocatalytic efficiency of polyhedra is higher than those of nanospheres and microrods. The adsorption kinetics of MB dye by these nanostructures were studied by three different kinetic models—Elovich’s, intraparticle, and pseudo-second-order. The maximum rate of adsorption was observed with the intraparticle diffusion model.

Growth modulation of simultaneous epitaxy of ZnO obliquely aligned nanowire arrays and film on r-plane sapphire substrate

Simultaneous epitaxial growth of film and nanowire array on a substrate is of both scientific significance and practical importance for nanoscale optoelectronics. Nevertheless, in situ building conducting connection between individually isolated nanowires grown on insulating substrates is still challenging. Herein, we demonstrate a novel and facile strategy for the simultaneous epitaxial growth of nonpolar a-plane ZnO film and obliquely aligned nanowire array on Au-coated r-plane sapphire substrate. The morphology, structure, components, and optical properties of the as-synthesized ZnO nanostructures were investigated using field-emission scanning electron microscopy, X-ray diffraction, field-emission transmission electron microscopy, energy-dispersive spectroscopy, X-ray photo-electron spectroscopy, and photoluminescence spectroscopy. A cooperative growth mechanism is proposed: Au-catalyzed vapor transport initiates the co-occurrence of nonpolar a-plane and polar c-plane ZnO nuclei, and subsequently, the non-upward directed Au catalyst helps the nonpolar a-plane ZnO nuclei develop into a ZnO conductive film at the bottom and zinc self-catalyzed vapor–liquid–solid growth helps the polar c-plane ZnO nuclei develop simultaneously into obliquely aligned nanowire arrays. The proposed strategy realized in situ synthesis of nanowires with conductive connection and it can benefit the application of ZnO nanowires in optoelectronics.

Zinc oxide nanopillars as an electrocatalyst for direct redox sensing of cadmium

Abstract In this paper, we report an ultrasensitive and selective technique for direct electrochemical sensing of cadmium (Cd) by zinc oxide nanopillars (ZONPs) synthesized using a facile chemical method. The synthesized ZONPs have been characterized in terms of their topological, morphological, elemental, structural, and optical properties using various microscopic and spectroscopic techniques. A gold electrode was modified with the as-synthesized ZnO nanostructures and utilized for direct redox sensing of Cd using cyclic voltammetry (CV) and chronoamperometric techniques. This fabricated sensor demonstrated excellent sensitivity and selectivity for direct redox sensing of Cd in real and laboratory samples. Using chronoamperometry, the developed sensor demonstrated ultra-sensitivity (10 μA cm−2 ppb−1) with a detection limit of 4 ppb (p-value 0.99) in a linear range of 5–50 ppb. The enhanced reproducibility of the sensor in the presence of common interfering ions offers the potential for use in diagnostic applications involving food adulteration and in clinical healthcare.

Investigation of morphologies, photoluminescence and photocatalytic properties of ZnO nanostructures fabricated using different basic ionic liquids

ZnO nanostructures were synthesized in methanol-water reaction media using different basic ionic liquids [BILs] by hydrothermal approach at 150°C. ZnO nanoparticles obtained from BILs consists of different morphologies, such as, hexagonal disks, hexagonal rings assembled by nanoparticles, hexagonal disks-aggregated flower-like structure and nanospheres. The effect of these basic ionic liquids on morphology, particle size and properties of as-synthesized ZnO nanostructures was investigated. The obtained nanoparticles have been characterized by X-ray diffraction, TEM, SEM, UV–vis absorption spectroscopy and photoluminescence (PL) studies. The XRD study of as-synthesized ZnO nanostructures confirmed the existence of hexagonal wurtzite structure. The maximum around 371nm was observed in UV–vis absorption spectrum and the calculated band-gap energy is in the range of 3.07-3.10eV. The photoluminescence spectra exhibited blue and blue-green emissions. ZnO nanoparticles prepared in choline hydroxide showed higher photocatalytic activity, which was accounted for due to high surface area, the smaller size of nanoparticles and low electron-hole recombination effect.

Growth and optical properties of hierarchical flower-like ZnO nanostructures

The integration of low dimensions nanoscale building blocks into 3D architectures has attracted great scientific attention. We have obtained the novel hierarchical flower-like ZnO nanostructures self-assembled by nanorods via a facile hydrothermal method. The as-synthesized samples were characterized with various technologies. The field emission scanning electron microscope (FESEM) images indicated that hydroxide ions play a significant role on the formation of hierarchical flower-like ZnO nanostructures. The X-ray diffraction (XRD) result proved that the nanocrystals were well crystallized hexagonal wurtzite structure. A possible growth mechanism of the nanostructures was proposed based on the effects of hydroxide ions. And the TEM imagines provided some important evidence for the proposed growth mechanism. UV–vis adsorption and photoluminescence (PL) spectra results indicated that the obtained ZnO nanostructurs have a good optical-absorption and photoluminescence property. The as-synthesized ZnO nanostructures exhibited superior photocatalytic performance, which was higher than that of commercially available ZnO.

Preparation of controlled ZnO nanostructures and their optical properties

ZnO nanostructures were synthesized via a facile temple-free chemical method. The effect of different zinc sources on the morphologies and properties of ZnO nanostructures has been investigated. FESEM, XRD, UV–Vis absorption spectra and PL spectra were used to characterize the as-synthesized ZnO nanostructures. It has been found that the distinct surface morphologies of ZnO nanostructures grown by using Zn(CH3COO)2·2H2O, Zn(NO3)2·6H2O, ZnSO4·7H2O and ZnCl2 as ZnO zinc sources. The XRD patterns indicate that all the samples represent a hexagonal wurtzite structure and all diffraction peaks are indexed accordingly with the JCPDS card (No. 03-0888). The UV–Vis absorption spectra of them both exhibit a strong absorption in the ultraviolet region at band around at 400 nm. The band gaps of them are 3.17, 3.19, 3.20 and 3.27 eV, respectively. Being excited at 325 nm wavelength using a xenon lamp at room temperature, all the PL spectra consist of sharp emission in the UV range and abroad emission bands in the visible region ranging from 440 to 620 nm.

Synthesis of Zinc oxide nano flower for photovoltaic applications

In the present work, ZnO nanoflowers have been synthesized with a single precursor at relatively low temperature by using ammonia. As-prepared ZnO nanoflowers were characterized by X-Ray Diffraction, Fourier Infrared Transmission and UV–visible spectroscopy. X-raydiffraction studies confirm that as-synthesized ZnO nanostructures are highly crystalline with a hexagonal wurtzite phase. The grown nanoflowers are of immense technological applications in the field of photovoltaics.

Effects Of Solvent On Structural, Optical And Photocatalytic Properties Of ZnO Nanostructures

ZnO nanostructures were synthesized by a facile wet chemical method using water, ethanol and propanol as solvents. X-ray diffraction, field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) have been used to study the structural properties of the synthesized ZnO nanostructures, while their optical properties have been studied using UV-visible absorption spectroscopy and Raman spectroscopy. The photocatalytic activities of the as-synthesized ZnO nanostructures were evaluated by monitoring sunlight driven photocatalytic degradation of methylene blue (MB) and methyl orange (MO) dyes in water and it was observed that ZnO nanostructures prepared using propanol as a solvent exhibit highly enhanced photocatalytic activity as compared to those prepared using other solvents. The mechanism underlying the photocatalytic activity of ZnO nanostructures towards photocatalytic degradation of dyes is proposed. We attribute the highly enhanced photocatalytic activity of ZnO nanostructures prepared in propanol to the high surface area of nanosheets-like structures formed, which lead to enhanced adsorption of dye molecules resulting in efficient photocatalytic degradation of dyes upon sunlight irradiation. Copyright © 2015 VBRI Press.

Surfactant-free precipitation synthesis, growth mechanism and photocatalytic studies of ZnO nanostructures

Different morphologies of ZnO nanostructures such as spherical-like, rod-like and flower-like were successfully synthesized by a facile and surfactant-free precipitation method in different NaOH concentrations. The as-synthesized ZnO nanostructures were characterized by field-emission scanning electron microscopy, energy dispersive X-ray, X-ray diffraction and fourier transform infrared spectroscopy. The results showed that the as-synthesized ZnO nanostructures were wurtzite hexagonal phase pure ZnO and well crystalline. It was also observed that the spectral properties of the as-synthesized ZnO nanostructures can be altered at different NaOH concentrations. A possible formation mechanism of the different ZnO nanostructures was discussed in term of the crystal nucleation and crystal growth direction. The photocatalytic tests revealed that the as-synthesized ZnO nanostructures were promising photocatalysts in remediation of water contaminated of organic pollutants under UV light irradiation.

Template free large scale synthesis of multi-shaped ZnO nanostructures for optical, photocatalytical and antibacterial properties

In this article, ZnO nanostructures with diverse morphologies have been synthesized via a simple, rapid and cost effective solid state thermal decomposition method. The as-synthesized ZnO nanostructures were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy, scanning electron microscope (SEM), high-resolution transmission electron microscope (HR-TEM), UV–Vis. diffuse reflectance spectra (UV–Vis-DRS) and photoluminescence (PL). The XRD patterns and HR-TEM image indicated a hexagonal wurtzite structure of ZnO. The SEM images of ZnO samples show the different morphologies such as nanowire, nanorods, spherical and irregular microsphere at different calcination temperatures. Room temperature PL spectra of the samples exhibited characteristics blue and green emission bands in accordance with calcination temperature. Moreover, photocatalytic as well as antimicrobial activities were evaluated using ZnO synthesized at different calcination temperatures. The effects of calcination temperature, catalyst loading and pH on the photodegradation efficiency were systematically studied. A highest (99 %) photocatalytic activity of ZnO nanorods towards the Acid Green 25 (AG-25) was achieved within 35 min at optimal conditions under UV light. As-synthesized ZnO nanorods are found to be more efficient than TiO2 (P25) towards the degradation of AG-25. It was found that the antimicrobial activity of ZnO nanorods (13 mm) obtained at 300 °C showed significantly higher inhibition efficiencies than the other samples. The mineralization of AG-25 was confirmed from a reduction of 85 % the chemical oxygen demand within 35 min. In addition, ZnO nanorods could be easily reusable up to four runs without changing its photocatalytic activity.

Hydrothermal synthesis, characterization and light harvesting applications of zinc oxide nanostructures

In this manuscript, nanostructured ZnO materials have been successfully prepared via a new ammonia-assisted hydrothermal method at 70 °C with the aid of Zn(NO3)2·4H2O as a single precursor in the absence of any capping agents. The effect of the initial concentrations of Zn2+ and ammonia on the morphology and particle size of as-synthesized ZnO was investigated. The as-prepared ZnO nanostructures were characterized by X-ray diffraction patterns, electron diffraction X-ray, Fourier transformation infrared, and photoluminescence spectroscopies, and scanning electron microscopy. Furthermore, the photocatalysis results reveal that the maximum decolorization of 26.2 and 44.1 % for rhodamine-B and methylene blue occurred with ZnO samples in 120 min under ultraviolet light irradiation, respectively. Moreover, the as-synthesized ZnO nanostructures were utilized as photo-anode material for the fabrication of dye-sensitized solar cells.

Surfactant-free precipitation synthesis of lithium-doped ZnO nanopetals for degradation of phenol under UV–visible light

Pure ZnO and lithium-doped ZnO nanopetals were synthesized via a facile and surfactant-free co-precipitation method. X-ray diffraction results revealed that both synthesized pure ZnO and lithium-doped ZnO exhibited well-crystalline structure. In addition, the lithium ion was successfully doped into ZnO. Field emission scanning electron microscopy showed that the synthesized ZnO was petal-shaped. Lithium-doped ZnO enlarged the band gap of the photocatalysts which was proven by UV–vis diffuse reflectance spectra. The as-synthesized ZnO nanostructures were evaluated for the degradation of phenol under UV–visible light irradiation. The photodegradation of phenol much more rapidly in the presence of lithium-doped ZnO compared to undoped ZnO, revealing that lithium doping improved the photocatalytic activity of ZnO.

Template-free sonochemical synthesis of flower-like ZnO nanostructures

Abstract Flower-like ZnO nanostructures have been successfully synthesized via a facile and template-free sonochemical method, using zinc acetate and potassium hydroxide as reactants only. The as-synthesized flower-like ZnO nanostructures were composed of nanorods with the width of ∼ 300 – 400 nm and the length of ∼ 2 – 3 μm . The structures, morphologies and optical properties of the as-prepared products were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscopy, UV-Vis spectrophotometry and Raman-scattering spectroscopy. A plausible formation mechanism of flower-like ZnO nanostructures was studied by SEM which monitors an intermediate morphology transformation of the product at the different ultrasonic time ( t = 80 , 90 , 95 , 105 , and 120 min ).

Characterization and antibacterial activity of nanostructured ZnO thin films synthesized through a hydrothermal method

Nanostructured ZnO films have been successfully synthesized on Zn substrates by a simple hydrothermal method at 120°C in 24h. The morphologies of the products were controlled by the following alkaline precursor solutions: NaOH, LiOH and NH4OH, which played a role in the crystallization process by generating rod-like, pencil-like and star-like particles, respectively. The phase and crystallinity of the nanostructured films were characterized by X-ray diffraction and selected area electron diffraction, the vibrational modes were determined by Fourier transform infrared spectrometry and Raman spectroscopy, and their morphologies were visualized by scanning electron microscopy and transmission electron microscopy. The photoluminescence of the products exhibited a strong, green–yellow band emission at 540nm. By using the inhibition zone method, the as-synthesized ZnO nanostructures were observed to inhibit bacterial activity.

Ionic liquid-based solvent-induced shape-tunable small-sized ZnO nanostructures with interesting optical properties and photocatalytic activities

We report a simple and one-pot size- and shape-controlled synthesis of small crystalline ZnO nanostructures through the hydrolysis of zinc acetylacetonate precursor using an ionic liquid, tetrabutylphosphonium hydroxide in different organic solvents and solvent mixtures of different polarities. Transmission electron microscopy (TEM) results indeed show the formation of very small (D ∼ 5–7 nm) ZnO spheres and ZnO nanorods of very low diameters (D ∼ 8–11 nm) depending on the solvents. The size and shape of ZnO nanostructures can be easily controlled by simple variation of the solvent and reaction temperature. Protic solvents favor the growth of spherical nanoparticles, whereas the rod-shaped ZnO is formed in aprotic solvents. The spherical ZnO nanostructures exhibit excitonic absorption at lower wavelengths compared to that of rod-shaped ZnO nanostructures. Through adjustment and control of the size and shape of ZnO nanostructures, we can tune the fluorescence emission from blue to green to yellow, when dispersed in the aqueous medium. The obtained ZnO nanostructures show very high photocatalytic activities towards the degradation of different cationic organic dyes (such as rhodamine 6G, crystal violet and methylene blue) as they contain a large number of defect states, as evident from the photoluminescence study. The as-synthesized ZnO nanostructures also show very high stability towards the photocatalytic degradation of organic dyes.

Synthesis, characterization and photocatalytic recital of nest-like zinc oxide photocatalyst

3D nest-like ZnO nanostructures are synthesized via hydrothermal method operated at ambient temperature (80 °C). The as-synthesized ZnO nanostructures are assembled by numerous ultrathin nanosheets resulting into formation of many grooves which improved the photocatalytic property. The as-synthesized ZnO sample is characterized by XRD, FESEM, FT-IR, Raman spectra, BET surface area and photoluminescence spectra analysis. Moreover, the photocatalytic efficiency of as-synthesized ZnO nanostructures is evaluated for degradation of methylene blue (MB) dye degradation. A comparision with the commercial counterpart reveals that the as synthesized nest-like ZnO degrades MB dye more efficiently. The present synthetic method can provide an effective route for synthesis of other hierarchically structured metal oxides also.

Optical properties of green synthesized ZnO nanocomposites

A green synthesis route using starch as a capping agent was effectively employed to synthesize ZnO nanostructures through chemical bath deposition. Sodium borohydride was used in one of the approaches in synthesis. Broadening of X-ray diffraction peaks suggested formation of nanosize ZnO in agreement with the high resolution transmission electron microscopy images. As-synthesized ZnO nanostructures were polycrystalline having wurtzite type structure. Average size of the particles was about 8 nm which was in close agreement with measurements from optical studies. Starch was found to play a key role in bringing the strong quantum confinement in ZnO particles. Optical absorption edge was found to be around 240–275 nm which exhibited a clear large blue shift and thereby enhancement of band gap energy. A strong green photoluminescence emission at 604.5 nm was observed in ZnO nanoparticles synthesized using sodium borohydride and may be attributed to the defect controlled recombination mechanism.