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     

原位热溶剂法制备ZnO纳米晶/PU复合纳米纤维及其吸附性能研究

通过静电纺丝法制备了直径为(320±51)nm的前驱体醋酸锌/聚氨酯(Zn(OAc)2/PU)复合纳米纤维。将前驱体先后经过0.1 mol/L NaOH乙醇溶液和甘油浴热处理,得到ZnO纳米晶/PU复合纳米纤维。讨论了甘油浴温度和时间对纳米纤维结构和形貌的影响,研究了其吸附性能。实验结果表明,经过0.1 mol/L NaOH乙醇溶液处理后,前驱体纤维Zn(OAc)2/PU转变为ZnO/PU纤维且ZnO主要以低结晶和无定型态存在;再经过甘油浴处理后,低结晶和无定型态的ZnO转变为晶型完整的六方晶系纤锌矿结构,得到了ZnO纳米晶/PU复合纳米纤维,该纤维对有机染料分子罗丹明B有良好的吸附性能。     

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.     

Silanization of ZnO nanofibers by tetraethoxysilane

Zinc oxide (ZnO) nanofibers are synthesized by electrospinning technique and then silanized to tailor its structural, optical, and electrical properties. The modification of ZnO nanofibers by chemical treatment of tetraethoxysilane (TEOS) is clearly evident from the appearance of relevant Fourier transform infrared peak at about 1000 cm^?1 corresponding to Zn? O? Si bond. The height of this peak increases linearly with increase in concentration of silane up to 400 μL, and afterward become plateau up to 500 μL. Diffuse reflectance spectroscopy measurement shows that band gap decreases from 3.35 eV for pure zinc oxide nanofibers to 3.11 eV with successive increase in concentration of TEOS from 100 to 500 μL. The electrical characteristics of modified ZnO nanofibers are analyzed by impedance spectroscopy. It is observed that impedance of ZnO nanofibers increases (resistance from 1.69 × 10⁸ to 2.618 × 10⁹ ohm and capacitance from 2.043 × 10^?12 to 7.618 × 10^?13 F) with increase of TEOS concentration. This study provides guidelines for tailoring the electrical properties of ZnO nanofibers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45378.     

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.     

Multilayered Electrospun/Electrosprayed Polyvinylidene Fluoride+Zinc Oxide Nanofiber Mats with Enhanced Piezoelectricity

Electrospun polyvinylidene fluoride (PVDF) nanofibers have been widely used in the fabrication of flexible piezoelectric sensors and nanogenerators, due to their excellent mechanical properties. However, their relatively low piezoelectricity is still a critical issue. Herein, a new and effective route to enhance the piezoelectricity of PVDF nanofiber mats by electrospraying zinc oxide (ZnO) nanoparticles between layers of PVDF nanofibers is demonstrated. As compared to the conventional way of dispersing ZnO nanoparticles into PVDF solution for electrospinning nanofiber mats, this approach results in multilayered PVDF+ZnO nanofiber mats with significantly increased piezoelectricity. For example, 6.2 times higher output is achieved when 100% of ZnO (relative to PVDF quantity) is electrosprayed between PVDF nanofibers. Moreover, this new method enables higher loading of ZnO without having processing challenges and the maximum peak voltage of ≈3 V is achieved, when ZnO content increases up to 150%. Additionally, it is shown that the samples with equal amount of material but consisting of different number of layers have no significant difference. This work demonstrates that the proposed multilayer design provides an alternative strategy to enhance the piezoelectricity of PVDF nanofibers, which can be readily scaled up for mass production.     

Growth of Nanograins in Electrospun ZnO Nanofibers

ZnO nanofibers were synthesized using an electrospinning method with polyvinyl alcohol and zinc acetate as precursor materials. The effects of the processing parameters on the microstructure of the synthesized ZnO nanofibers were investigated. X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy showed that the ZnO nanofibers were distributed uniformly over the Si substrates and had a polycrystalline nature. Individual nanofibers consisted of nanograins. Interestingly, the nanograins coalesced and grew under higher calcination temperatures and longer calcination times. The activation energy for grain-growth was estimated to be 13.126 kJ/mol, and the dominant growth mechanism was most likely to be related to lattice diffusion in pore control mode.     

ZnO Nanofiber Field-Effect Transistor Assembled by Electrospinning

A ZnO nanofiber field-effect transistor (FET) was assembled by electrospinning. Uniform ZnO nanofibers with a diameter of ∼70 nm and length over 100 μm were first synthesized by electrospinning. Using two paralleled electrodes as fiber collectors, we have successfully placed a single ZnO nanofiber on the electrodes, and an FET device was fabricated based on the assembled nanofiber. An electrical transport measurement was conducted on the FET device, showing that ZnO nanofibers are intrinsic n- type semiconductors. The present findings demonstrate that electrospinning can potentially be used as a straightforward and cost-effective means for the assembly of one-dimensional nanostuctures for building integrated nanodevices for various applications, such as transistors, sensors, diodes, and photodetectors.     

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.     

Cross-linked electrospun polyvinyl alcohol/sodium caseinate nanofibers for antibacterial applications

In this study, the polyvinyl alcohol (PVA) and sodium caseinate (SC) nanofibers were produced by a single-fluid electrospinning method from their blends. Afterward, the cross-linking process with two different methods was applied to the PVA/SC (70/30, v/v) ratio, which was selected according to the surface and mechanical properties of the electrospun mat. In the first method, different ratios (15%, 20%, 25%, and 30%) of glutaraldehyde (GLA) cross-linking agents were added to the PVA/SC solution and then, PVA/SC/GLA nanofibers were obtained. In the second method (in-situ method), the nanofibers obtained from the PVA/SC solution were cross-linked by dipping into the cross-linking solution. After, PVA/SC/GLA/Zinc oxide nanoparticles (ZnO NP) mats were obtained by adding ZnO NP at different rates to the PVA/SC/GLA (7030-25GLA) solution, which was chosen according to the results of thermal, mechanical, and moisture test. In addition, performing tests, a cytotoxicity test for fibroblast cell line (L929), and in vitro antibacterial test for Escherichia coli and Staphylococcus aureus were also applied to them. Therefore, the usability of PVA/SC/GLA/ZnO NP nanofibers as an antibacterial effective wound dressing was investigated. Due to the high toxic effect of GLA, it was found that PVA/SC/ZnO cross-linked nanofibers are not suitable for wound dressing use. However, it was determined that the PVA/SC nanofiber cross-linked by the in-situ method had high cell viability according to the cytotoxicity test result and thus could be used as a fibroblast tissue scaffold.     

Fabrication of novel p-CuO/n-ZnO heterojunction nanofibers by electrospinning for enhanced photocatalytic performance in the denitrification of fuel oil

CuO/ZnO p-n heterojunction nanofibers were fabricated by coupling p-type CuO with n-type ZnO nanofibers for efficacious elimination of pyridine in fuel oil. The structural and photoelectric characteristics of the as-synthesized nanofibers were systematically studied. The photodegradation system was appropriate for the oxidation of pyridine from fuel oil utilizing the ambient air without mixing with other oxidants. Under visible light illumination, more than 90% of the pyridine (100 mL, 100 μg/g) could be degraded within 60 min by 17.5 mg of MCuZn-0.5 (the photocatalyst with a Cu/Zn molar ratio of 0.5 at%). The visible-light-induced photocatalytic denitrification efficiency of the MCuZn-0.5 nanofibers was nearly 1.5 times as high as that of ZnO alone. The superior denitrification activity of p-CuO/n-ZnO heterojunction nanofibers could be attributed to the enhanced optical absorption capacity and efficacious separation of photoexcited charge pairs. In addition, five-cycle experiments confirmed that MCuZn-0.5 nanofibers also displayed satisfactory photocatalytic denitrification properties. Mechanistic investigations proposed that the photoexcited holes played a dominant role in the formation of reactant intermediates, while superoxide radicals promoted the ultimate mineralization process of pyridine.     

Interior synthesizing of ZnO nanoflakes inside nylon‐6 electrospun nanofibers

Doping of the polymeric electrospun nanofibers by metal oxides nanoparticles is usually performed by electrospinning of a colloidal solution containing the metal oxide nanoparticles. Besides the economical aspects, electrospinning of colloids is not efficient compared with spinning of sol–gels, moreover well attachment of the solid nanoparticles is not guaranteed. In this study, reduction of zinc acetate could be performed inside the nylon‐6 electrospun nanofibers; so polymeric nanofibers embedding ZnO nanoflakes were obtained. Typically, zinc acetate/nylon‐6 electrospun nanofibers were treated hydrothermally at 150°C for 1 h. Besides the utilized characterization techniques, PL study affirmed formation of ZnO. The produced nanofibers showed a good antibacterial activity which improves with increasing ZnO content. Overall, the present study opens new avenue to synthesize hybrid nanofibers by a facile procedure. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and Gas Sensing Properties of TiO2–ZnO Core-Shell Nanofibers

We fabricated TiO₂–ZnO core-shell nanofibers via a novel two-step process. In the first step, the TiO₂ core nanofibers were synthesized by electrospinning. Subsequently, the ZnO shell layers were grown in a controlled manner using atomic layer deposition. The methodology proposed in this work is expected to be one of most suitable methods for preparing various kinds of oxide core-shell nanofibers or nanowires. We investigated the O₂ sensing properties of the synthesized core-shell nanofibers. Good sensitivity and dynamic repeatability were observed for the sensor, demonstrating that the core-shell nanofibers hold promise for the realization of sensitive and reliable chemical sensors.     

Electrospun dendritic ZnO nanofibers and its photocatalysis application

A simple and efficient procedure has been developed to fabricate ZnO nanofibers with dendritic structure via electrospinning and subsequent calcination. The spinning solution is prepared by mixing polyvinylpyrrolidone (PVP) and zinc acetate into methanol. From SEM images, it can be observed that the ZnO product has a tendency of dendritic structure. The diameter of the dendritic branch is ～137 nm. The structure and physicochemical property of the prepared nanofibers are elucidated by TGA, SEM, XRD, FTIR, and PL, respectively. The photoluminescene measurement of the ZnO samples exhibit a broad visible emission band concentrate on around 430–580 nm. Meanwhile, the intensity is related to the content of surface oxygen vacancies, which probably influence photocatalytic activity of ZnO samples. Whereafter, the photocatalytical activity of the ZnO nanofibers is evaluated by quantifying the degradation of methyl blue. The result indicates that ZnO nanofibers annealed at 650°C show an excellent photocatalytic activity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41627.     

氨溶法制备肤色氧化锌的研究

报道了用氨水溶解氢氧化锌 ,再通过蒸氨制备肤色氧化锌的方法。氨溶法制备的肤色氧化锌呈碎薄片状聚集 ,色彩均匀     

Influence of zinc oxide nanoparticles on the crystallization behavior of electrospun poly(3-hydroxybutyrate-co-3-hydroxyvalerate) nanofibers

Pure poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and zinc oxide (ZnO)/PHBV composite nanofibers were fabricated by an electrospinning method. ZnO nanoparticles (NPs) with a diameter of about 10-20 nm were doped in the PHBV fibers and no dispersion agent was utilized. Both pure PHBV and composite electrospun fibers were smooth and uniform. ZnO NPs did not affect the basic crystalline structure of electrospun PHBV fibers. The well dispersion of NPs was attributed to the interaction of hydrogen bonds between -OH groups on the surface of ZnO and CO groups in the PHBV. ZnO NPs were not nucleating or modifying agents but retarding agents for crystallization in the polymer matrix. The crystallinity and crystallization rate was lowered by adding ZnO NPs. The well dispersion of ZnO NPs in the electrospun nanofibers was confirmed by TEM characterization. A hypothesis was developed to interpret the influence of ZnO NPs on the crystalline behavior of electrospun PHBV fibers.     

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.     

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.     

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.     

沉淀法制备纳米氧化锌的研究

通过实验和理论分析 ,对均匀沉淀法和直接沉淀法制备纳米氧化锌进行了比较 ,以硝酸锌为原料 ,尿素为均匀沉淀剂制得的氧化锌粒径小、分布窄、分散性好 ,远优于直接沉淀法制备的纳米氧化锌。