ZnO Nanofiber and Nanoparticle Synthesized Through Electrospinning and Their Photocatalytic Activity Under Visible Light

In this paper, we fabricate ZnO nanofibers and nanoparticles through electrospinning precursor solution zinc acetate(ZnAc)/cellulose acetate(CA) in mixed-solvent N , N -dimethylformamide/acetone. Depending on the posttreatment of precursor ZnAc/CA composite nanofibers, both ZnO nanofibers and nanoparticles were synthesized after calcination of precursor nanofibers. The morphology and crystal structure of the ZnO nanofiber and nanoparticle were characterized by scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and X-ray diffraction. It was found that the mean diameter of the ZnO nanofiber and nanoparticle was ca. 78 and 30 nm, respectively. The photo-degradation of dye molecules such as Rhodamine B and acid fuchsin catalyzed by the ZnO nanofiber and nanoparticle was evaluated under the irradiation of visible light. Both morphological ZnO species showed strong photocatalytic activity. However, the ZnO nanofiber in the form of nanofibrous mats showed much higher efficiency than the nanoparticle although the latter has a smaller size than the former. The porous structure of ZnO nanofibrous mats is believed to improve the contacting surface areas between the catalyst and the dye molecules, while the aggregation of ZnO nanoparticle in the solution lowers the photocatalytic efficiency.     

Fabrication of Mg-doped ZnO nanofibers with high purities and tailored band gaps

The tailored doping levels towards the band gap tunability are one of the challenges to push forward the potential application of one-dimensional (1D) ZnO nanostructures in the opto/electric nanodevices. In present work, we reported the exploration of Mg-doped ZnO nanofibers via electrospinning of polyvinylpyrrolidone (PVP), Zn(CH₃COO)₂ (ZnAc) and Mg(CH₃COO)₂ (MgAc), followed by calcination in air. The resultant products were systematically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscope (HRTEM), and X-ray photoelectron spectroscopy (XPS). The optical measurements (UV–vis) of the Mg-doped ZnO nanofibers suggested that the optical band gaps of the ZnO nanofibers could be tuned from 3.33 to 3.40 eV as a function of the Mg doing levels. This tunability of the band gap of ZnO nanofibers with an intentional impurity could eventually be useful for optoelectronic applications.     

C2H2 gas sensor based on Ni-doped ZnO electrospun nanofibers

Pure and Ni-doped ZnO nanofibers were synthesized using the electrospinning method. The morphology, crystal structure and optical properties of the nanofibers were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy, respectively. It is found that Ni doping does not change the morphology and crystal structures of the nanofibers, and the ultraviolet emissions of ZnO nanofibers present red shift with increasing Ni doping concentration. C₂H₂ sensing properties of the sensors based on the nanofibers were investigated. The results show that the C₂H₂ sensing properties of ZnO nanofibers are effectively improved by Ni doping, and 5 at% Ni-doped ZnO nanofibers exhibit a maximum sensitivity to C₂H₂ gas.     

Synthesis of nanocrystalline ZnO–NiO mixed metal oxide powder by homogeneous precipitation method

Nanocrystalline ZnO–NiO mixed metal oxide powder has been successfully prepared via a simple homogeneous precipitation method in short time. The nanocrystalline sample was obtained at low calcination temperature (350 °C). Specific surface area, crystallite size and optical band gap of the samples depend on calcination temperature. The synthesized samples were characterized by means of powder X-ray diffraction, thermal gravimetric analysis, Fourier transform infrared spectroscopy, diffuse reflectance spectroscopy, surface area measurements, scanning electron microscopy coupled with energy dispersive X-ray analysis, transmission electron microscopy and magnetic measurements. The synthesized powder samples have been tested for their catalytic reduction of 4-nitrophenol to 4-aminophenol in the presence of sodium borohydride.     

ZnO纳米纤维制备及其性能表征

以PVP为前驱体溶液,采用静电纺丝法制备了PVP/Zn(CH3COO)2复合纤维,通过煅烧进一步制得了ZnO纳米纤维。并对所得样品进行了扫描电子显微镜(SEM)分析,TG-DTG分析,并对纳米ZnO纤维和纳米ZnO颗粒的抗菌性能进行了测试。     

Preparation and Optical Property of Long Single Crystalline ZnO Nanofibers

Long single crystal ZnO nanofibers were synthesized on a large-scale by a simple solvothermal method at low temperature in the presence of dodecyl benzene sulfonic acid sodium salt and hydrazine. X-ray diffraction, scanning electron microscopy, transmission electron microscopy and high-resolution transmission electron microscopy were used to characterize the product. The diameter of the single crystal nanofiber is 50–70 nm and the length is 30–50 μm. Due to the oxygen or the zinc vacancy in the nanofibers, the wide emission in the visible light region is increased, while the sharp UV emission still exists at 388.5 nm.     

Synthesis of hierarchical porous ZnO microspheres and its photocatalytic deNOx activity

Hierarchical porous metal oxide nanostructures have currently attracted much interest because their unique structures with large surface area, high porosity and low density are greatly valuable for functional applications in catalysis, biological engineering and photoelectronics device. Herein, hierarchical porous ZnO microspheres were fabricated by a facile hydrothermal method with subsequent calcination. The sample morphology has been characterized by scanning electron microscopy and transmission electron microscopy. The powder X-ray diffraction has also been used to determine the crystalline structure of the synthesized materials. The effect of calcination temperature on the crystalline structure of synthesized nanostructures has been systematically investigated. The photocatalytic activities of the obtained samples have been evaluated by means of photocatalytic decomposition of nitrogen monoxide (NO).     

Synthesis, surface modification and photocatalytic property of ZnO nanoparticles

ZnO nanoparticles were synthesized by calcination of precursor prepared by the precipitation method. Polystyrene was grafted onto the surface of ZnO nanoparticles to improve the dispersion of the particles and to reduce their photocatalytic activity. The obtained particles were characterized by Fourier transform infrared spectroscopy, X-ray powder diffraction, and transmission electron microscopy. The photocatalytic activity of bare and modified ZnO nanoparticles was studied. The influence of surface modification on the photocatalytic degradation of methyl orange has been analyzed. The composition of residual solution was determined through high performance liquid chromatography. Experimental results show that well dispersed ZnO nanoparticles were obtained after surface modification. ZnO nanoparticles possess high photocatalytic activity, whereas the photocatalytic activity can be significantly reduced when polystyrene was grafted onto the particle surface.     

ZnO纳米纤维制备及其性能表征

以PVP为前驱体溶液,采用静电纺丝法制备了PVP/Zn(CH3COO)2复合纤维,通过煅烧进一步制得了ZnO纳米纤维。并对所得样品进行了扫描电子显微镜(SEM)分析,TG-DTG分析,并对纳米ZnO纤维和纳米ZnO颗粒的抗菌性能进行了测试。     

ZnO nanocrystallites/cellulose hybrid nanofibers fabricated by electrospinning and solvothermal techniques and their photocatalytic activity

ZnO nanocrystallites have been in situ embedded in cellulose nanofibers by a novel method that combines electrospinning and solvothermal techniques. Zn(OAc)₂/cellulose acetate (CA) precursor hybrid nanofibers with diameter in the range of 160–330 nm were first fabricated via the electrospinning technique using zinc acetate as precursor, CA as the carrier, and dimethylformamide (DMF)/acetone(2 : 1) mixture as cosolvent. The precursor nanofibers were transformed into ZnO/cellulose hybrid fibers by hydrolysis in 0.1 mol/L NaOH aqueous solution. Subsequently, these hybrid fibers were further solvothermally treated in 180°C glycerol oil bath to improve the crystallite structure of the ZnO nanoparticles containing in the nanofibers. The structure and morphology of nanofibers were characterized by scanning electron microscopy, transmission electron microscopy, and X‐ray diffraction. It was found that hexagonal structured ZnO nanocrystallites with the size of ～ 30 nm were dispersed on the nanofiber surfaces and within the nanofibers with diameter of about 80 nm. The photocatalytic property of the ZnO/cellulose hybrid nanofibers toward Rhodamine (RhB) was tested under the irradiation of visible light. As a catalyst, it inherits not only the photocatalytic ability of nano‐ZnO, but also the thermal stability, good mechanical property, and solvent‐resistibility of cellulose nanofibers. The key advantages of this hybrid nanofiber over neat ZnO nanoparticles are its elasticity, dimensional stability, durability, and easy recyclability. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Enhanced CH4 sensing properties of Pd modified ZnO nanosheets

In this paper, pristine ZnO and Pd modified ZnO nanosheets have been successfully prepared via a facile hydrothermal route and the subsequent calcination process. The composition, morphology and nanostructure of the as-obtained materials were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The methane (CH₄) sensing properties of Pd/ZnO were compared with those of pure ZnO, and the materials showed the noticeable sensing capability when the loading amount of Pd was 1 at%. Moreover, the optimal working temperature of ZnO was reduced from 240 °C to 200 °C after loading Pd. The synthesized 1% Pd/ZnO nanocomposites not only showed the maximum response value 19.20 toward 5000 ppm CH₄ at 200 °C, but also exhibited the excellent selectivity and good repeatability. The improvement of CH₄ sensing performance by Pd nanoparticles could be attributed to the synergy effect with the spill-over effect and the nano-Schottky barriers.     

Photocatalytic degradation of Rhodamine B dye using ZnO–SnO2 electrospun ceramic nanofibers

ZnO–SnO₂ nanofibers were fabricated by the electrospinning technique combined with calcination at 600 °C. Their structural and morphological properties were analyzed by X-ray diffraction and scanning/transmission electron microscopy, and their photocatalytic activity was investigated by the degradation of Rhodamine B (RhB) dye by visible light irradiation. UV–vis spectral data were used to estimate the photodegradation efficiency of the metal oxide nanocomposites. All the RhB dye samples were tested for six hours of degradation the highest efficiency being obtained for a molar ratio Sn/Zn of 0.030.     

Enhanced charge transport characteristics in zinc oxide nanofibers via Mg2+ doping for electron transport layer in perovskite solar cells and antibacterial textiles

ZnO is well-known electron transport material; however, its charge carrier mobility is restricted due to lower conductivity and hysteresis losses. To overcome these issues, 1–3 wt% Mg-doped ZnO nanofibers were synthesized via electrospinning and then applied as electron transport layer (ETL) of perovskite solar cell. The structural, morphological, chemical composition, electronic structure, and optical activity of the synthesized nanofibers were studied to elucidate the role of Mg doping. X-ray diffraction of all nanofibers revealed that Mg was successfully incorporated into ZnO lattice and revealed that ZnO is present in hexagonal wurtzite structure. Optical characterization of the nanofibers revealed that with an increase in Mg²⁺ doping concentration, the bandgap energy (Eg) tuned from 3.36 eV to 2.8 eV. It was observed that doping ZnO matrix with Mg ions improved the electronic structure, hence favoring the increase in the fill factor, current density, and efficiency. By doping 1, 2, and 3 wt% Mg into ZnO, efficiency was increased up to 8.48, 10.33, and 13.52%, respectively. Thus, a significant improvement in the performance of ZnO was noted by our proposed facile Mg doping. In addition, a significant improvement in photocatalytic activity was observed in Mg doped ZnO, which was used for fabrication of antibacterial textiles.     

Diameter control of ultrathin zinc oxide nanofibers synthesized by electrospinning

Electrospinning is a versatile technique, which can be used to generate nanofibers from a rich variety of materials. We investigate the variation of a zinc oxide (ZnO)-polyvinylpyrrolidone (PVP) composite structure in morphology by electrospinning from a series of mixture solutions of ZnO sol–gel and PVP. Calcination conditions for the crystallization of ZnO nanofibers and removal of the PVP component from the ZnO-PVP composite nanofibers were also studied. The progression of the ZnO-PVP composite structure from grains to nanofibers was observed, and ZnO-PVP nanofibers as thin as 29.9 ± 0.8 nm on average were successfully fabricated. The size of the resultant ZnO-PVP composite nanofibers was considerably affected by two parameters: the concentrations of zinc acetate and PVP in the precursor solution. The concentration of zinc acetate particularly influenced the diameter distribution of the ZnO-PVP nanofibers. The ZnO-PVP nanofibers could be subsequently converted into ZnO nanofibers of a pure wurtzite phase via calcination in air at 500°C for 2 h.     

Preparation and characterization of transparent ZnO/epoxy nanocomposites with high-UV shielding efficiency

Transparent ZnO/epoxy nanocomposites with high-UV shielding efficiency were reported in this paper. First, zinc oxide (ZnO) precursor was synthesized via the homogeneous precipitation method and ZnO nanoparticles were then made by calcination of the precursor at different temperature. The structural properties of the as-prepared ZnO nanoparticles were studied in detail using thermogravimetry (TGA), differential thermal analysis (DTA), X-ray diffractometer (XRD), Fourier transform infrared spectrometer (FT-IR) and transmission electron microscopy (TEM), respectively. Transparent ZnO/epoxy nanocomposites were subsequently prepared from transparent epoxy (EP-400) and as-prepared ZnO nanoparticles via in situ polymerization. Optical properties of ZnO/epoxy nanocomposites, namely visible light transparency and UV light shielding efficiency, were studied using an ultraviolet-visible (UV-vis) spectrophotometer. The optical properties of the as-obtained nanocomposites were shown to depend on ZnO particle size and content. The nanocomposite containing a very low content (0.07% in weight) of ZnO nanoparticles with an average particle size of 26.7 nm after calcination at 350 °C possessed the most optimal optical properties, namely high-visible light transparency and high-UV light shielding efficiency, that are desirable for many important applications.     

Synthesis of Porous NiO and ZnO Submicro- and Nanofibers from Electrospun Polymer Fiber Templates

Porous nickel oxide (NiO) and zinc oxide (ZnO) submicro- and nanofibers were synthesized by impregnating electrospun polyacrylonitrile (PAN) fiber templates with corresponding metal nitrate aqueous solutions and subsequent calcination. The diameter of the NiO and ZnO fibers was closely related to that of the template fibers and larger diameters were obtained when using the template fibers with larger diameter. SEM results showed that the NiO and ZnO fibers have a large amount of pores with diameters ranging from 5 nm to 20 nm and 50 nm to 100 nm, respectively. Energy dispersive X-ray (EDX) spectra and X-ray diffraction (XRD) patterns testified that the obtained materials were NiO and ZnO with high purity.     

Bimetallic Zn/Ag doped polyurethane spider net composite nanofibers: A novel multipurpose electrospun mat

The objective of this study was to develop a new class of bimetallic ZnO/Ag embedded polyurethane multi-functional nanocomposite by a straightforward approach. Bimetallic nanomaterials, composed of two unlike metal elements, are of greater interest than the monometallic materials because of their improved characteristics. In the present study the bimetallic composite was prepared using sol–gel via the facile electrospinning technique. The utilized sol–gel was composed of zinc oxide, silver and poly(urethane). The physicochemical properties of as-spun composite mats were determined by X-ray diffraction pattern, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy and transmission electron microscopy. The antibacterial activity was tested using Escherichia coli as model organism. The antibacterial test showed that ZnO:Ag/polyurethane composite possesses superior antimicrobial activity than pristine PU and ZnO/PU hybrids. Furthermore, our results illustrate that the synergistic effect of ZnO and Ag resulted in the advanced antimicrobial action of bimetallic ZnO/Ag composite mat. The viability and proliferation properties of NIH 3T3 mouse fibroblast cells on the ZnO:Ag/polyurethane composite nanofibers were analyzed by in vitro cell compatibility test. Our results indicated the non-cytotoxic behavior of bimetallic ZnO:Ag/polyurethane nanofibers towards the fibroblast cell culture. In summary, novel ZnO:Ag/polyurethane composite nanofibers which possess large surface to volume ratio with excellent antimicrobial activity were fabricated. The unique combination of ZnO and Ag nanoparticles displayed potent bactericidal effect due to a synergism. Hence the electrospun bimetallic composite indicates the huge potential in water filtration, clinical and biomedical applications.     

硼酸镁晶须的合成及表征

以氢氧化镁和硼酸为原料,利用高温-助熔剂-湿法工艺合成了高品质的硼酸镁晶须。采用XRD、SEM、HR-TEM、SAED等手段表征,系统研究了焙烧温度、焙烧时间、硼镁物质的量比及助熔剂添加量对晶须形貌的影响。结果表明,在焙烧温度为850 ℃、焙烧时间为4 h、n（硼）∶n（镁）=3∶1、n（钠+钾）∶n（镁+硼）=4∶1的条件下,可合成直径为0.5~0.8 μm、长径比为40~240且表面光滑的硼酸镁晶须。还对硼酸镁晶须的高温-助熔剂-湿法工艺合成生长机理进行了探讨。     

PREPARATION OF ZINC OXIDE NANOPARTICLE VIA UNIFORM PRECIPITATION METHOD AND ITS SURFACE MODIFICATION BY METHACRYLOXYPROPYLTRIMETHOXYSILANE

Zinc oxide nanoparticles were prepared by uniform precipitation using urea hydrolysis. The ZnO precursor was slowly deposited from aqueous solution. Anionic surfactant was added into solution to block ZnO crystal growth and its agglomeration. Then ZnO nanoparticles were synthesized by the calcination of the precursor at high temperature. Transmission electron microscope (TEM) observation and particle size analyzer demonstrated that the ZnO nanoparticle exhibited nearly spheric shape with 10-40 nm particle size. The surface of the ZnO nanoparticle was modified by methacryloxypropyltrimethoxysilane (MPS). FT-IR (Fourier transform-infrared spectrophotometry) and XPS (X-ray photoelectron spectrophotometry) revealed that MPS was grafted onto the zinc oxide nanoparticle. XRD (X-ray diffraction) showed that the ZnO nanoparticle was a hexagonal crystal with a perfect crystalline structure, and its crystalline morphology was not altered through surface modification. The activation index (AI) of the modified ZnO nanoparticle was measured. It was found that the surface of the ZnO nanoparticle was changed from hydrophilicity into hydrophobicity via surface modification, implying the enhancement of its compatibility with organic polymers. FE-SEM (field scanning electron microscopy) showed that the modified ZnO nanoparticles were homogeneously dispersed in PVC matrices. Consequently, ZnO nanoparticles were integrated with PVC matrices by the grafting organic molecule.     

PREPARATION OF ZINC OXIDE NANOPARTICLE VIA UNIFORM PRECIPITATION METHOD AND ITS SURFACE MODIFICATION BY METHACRYLOXYPROPYLTRIMETHOXYSILANE

Zinc oxide nanoparticles were prepared by uniform precipitation using urea hydrolysis. The ZnO precursor was slowly deposited from aqueous solution. Anionic surfactant was added into solution to block ZnO crystal growth and its agglomeration. Then ZnO nanoparticles were synthesized by the calcination of the precursor at high temperature. Transmission electron microscope (TEM) observation and particle size analyzer demonstrated that the ZnO nanoparticle exhibited nearly spheric shape with 10–40 nm particle size. The surface of the ZnO nanoparticle was modified by methacryloxypropyltrimethoxysilane (MPS). FT-IR (Fourier transform-infrared spectrophotometry) and XPS (X-ray photoelectron spectrophotometry) revealed that MPS was grafted onto the zinc oxide nanoparticle. XRD (X-ray diffraction) showed that the ZnO nanoparticle was a hexagonal crystal with a perfect crystalline structure, and its crystalline morphology was not altered through surface modification. The activation index (AI) of the modified ZnO nanoparticle was measured. It was found that the surface of the ZnO nanoparticle was changed from hydrophilicity into hydrophobicity via surface modification, implying the enhancement of its compatibility with organic polymers. FE-SEM (field scanning electron microscopy) showed that the modified ZnO nanoparticles were homogeneously dispersed in PVC matrices. Consequently, ZnO nanoparticles were integrated with PVC matrices by the grafting organic molecule.