Facile fabrication of functionalized graphene sheets (FGS)/ZnO nanocomposites with photocatalytic property

Functionalized graphene sheets (FGS)/ZnO nanocomposites were fabricated via thermal treatment method, using graphene oxide as a precursor of graphene, Zn(NH(3))(4)CO(3) as a precursor of zinc oxide, and poly(vinyl pyrrolidone) as an intermediate to combine zinc with carbon materials. Thermogravimetric analysis, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), and scanning electron microscopy (SEM) were used to characterize crystal structure and morphology of FGS/ZnO nanocomposites. It was shown that the well-dispersed ZnO nanoparticles were deposited on FGS homogeneously. The composites exhibited photocatalytic activity to decompose rhodamine 6G efficiently under low-power ultraviolet (UV) light. This facile and low-cost method makes the composite a perfect candidate in applications of catalysis and other areas.     

Rapid synthesis, characterization and optical properties of TiO2 coated ZnO nanocomposite particles by a novel microwave irradiation method

A novel and rapid microwave method was used to prepare TiO₂ coated ZnO nanocomposite particles. The resulted particles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS). Results show that ZnO nanoparticles were coated with 6-10 nm amorphous TiO₂ layers. In addition, zeta potential analysis demonstrated the presence of TiO₂ layer on the surface of ZnO nanoparticles. Photoluminescence (PL) spectroscopy and UV-visible spectroscopy were used to investigate the optical properties of the nanoparticles. Compared to uncoated ZnO nanoparticles, the TiO₂ coated ZnO nanoparticles showed enhanced UV emission. The UV-visible diffuse reflectance study revealed the significant UV shielding characteristics of the nanocomposite particles. Moreover, amorphous TiO₂ coating effectively reduced the photocatalytic activity of ZnO nanoparticles as evidenced by the photodegradation of Orange G with uncoated and TiO₂ coated ZnO nanoparticles under UV radiation.     

Mesoporous titanium dioxide@ zinc oxide–graphene oxide nanocarriers for colon-specific drug delivery

In this project, TiO₂@ZnO nanoparticles core–shell nanostructured and titanium dioxide@ mesoporous zinc oxide–graphene oxide (TiO₂@ZnO–GO) hybrid nanocomposites as controlled targeted drug delivery systems were synthesized by a facile sono-chemical method. We prepared a novel mesoporous and core–shell structure as a drug nanocarrier (NCs) for the loading and pH-responsive characteristics of the chemotherapeutic curcumin. The structure, surface charge, and surface morphology of NCs were studied using with X-ray diffraction, Fourier transform infrared spectroscopy, dynamic light scattering, brunauer–emmett–teller, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The SEM and TEM images of NCs show the uniform hexagonal mesoporous morphology with average grain size of about ～ 190 nm. The drug loading was very high about 16 and 19 for TiO₂@ZnO and TiO₂@ZnO–GO, respectively. The NCs showed pH-dependent drug release behavior. Drug release from TiO₂@ZnO–GO in neutral pH were higher than in acidic medium, due to anionic charge of GO nanosheet. MTT assay results showed that the curcumin-loaded NCs showed significant toxicity due to which cell viability reduced to below 50% at 140 μg/mL concentration, thereby confirming its anticancer effects. The goal of this study is the application of water-dispersed TiO₂@ZnO–GO with pH-dependent release properties for design a new drug delivery carrier.     

High quality ZnO/CuO nanocomposites synthesized by microwave assisted reaction

Highly crystalline zinc oxide (ZnO) and ZnO/CuO nanocomposite powders have been synthesized by a facile microwave irradiation method. The resulting powders were characterized in terms of structural, optical and morphological properties by X-ray diffraction (XRD), room temperature photoluminescence (PL) spectroscopy and scanning electron microscopy (SEM), respectively. XRD patterns revealed the formation of ZnO/CuO nanocomposites with good crystalline quality. SEM images displayed the formation of hexagonal ZnO and flower shaped agglomeration of ZnO/CuO nano-flakes with uniform production. The strong UV emission peak observed at around 380 nm show enhanced intensity for ZnO/CuO nanocomposite. Compared to ZnO nanoparticles, ZnO/CuO composites exhibit good transparency with sharp absorbance edges. The simplicity of synthesis route coupled with better optical and PL emission properties propose the microwave synthesized ZnO/CuO nanocomposite powders a promising material for optoelectronic devices.     

Structural analysis of graphene oxide/silver nanocomposites: optical properties,electrochemical sensing and photocatalytic activity

In the present study, graphene oxide/silver (GO/Ag) nanocomposites were synthesized via a facile simple one pot chemical reduction method using ethylene glycol/sodium borohydrate (EG/NaBH₄) as solvent and reducing agent. GO was selected as a substrate and stabilizer to prepare GO/Ag nanocomposites. The synthesized GO/Ag nanocomposites were characterized by a series of techniques. Highly monodispersed stable crystalline silver nanoparticles having a face-centered cubic (fcc) phase were confirmed by X-ray powder diffraction (XRD) on GO signature. Scanning electron microscopy images showed that Ag nanoparticles are deposited on the GO sheet with a narrow size distribution. Transmission electron microscopy observations revealed that large numbers of Ag nanoparticles were uniformly distributed on GO sheet and well separated with an average size of 18 nm. Ultraviolet–visible (UV–Vis) spectroscopic results showed the peak of GO and surface plasmon resonance (SPR) of Ag nanoparticles. The SPR property of GO/Ag nanocomposites showed that there was an interaction between Ag nanoparticles and GO sheet. The intensities of the Raman signal of GO/Ag nanocomposites are gradually increased with attachment of Ag nanoparticles i.e. there is surface-enhanced Raman scattering activity. Electrochemical investigations indicated that the nanocomposites possessed an excellent performance for detecting towards 4-nitrophenol. An application of the obtained GO/Ag nanocomposites as a catalyst in the reduction of 4-nitrophenol to 4-aminophenol by NaBH₄ was demonstrated. The GO/Ag nanocomposites exhibited high activity and stability for the catalytic reduction of 4-nitrophenol. The prepared GO/Ag nanocomposites act as photo-catalysts.     

Synthesis and enhanced light absorption of alumina matrix nanocomposites containing multilayer oxide nanorods and silver nanoparticles

In this paper, multilayer oxide nanorods were deposited in the nanopores of anodic aluminum oxide (AAO) via solution infiltration followed by heat treatment. The nanorods have a core–shell structure. First, the shell (nanotube) with the thickness of about 40 nm was made of TiO₂ through the hydrolysis of (NH₄)₂TiF₆. Second, silver nanoparticles with the diameter of about 3 nm were added into the TiO₂ layer through thermal decomposition of AgNO₃ at elevated temperatures. Then, cylindrical cores (nanorods) of CoO and ZnO with 200 nm diameter were prepared, respectively. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the structure and composition of the nanorods. UV–vis light absorption measurements in the wavelength range from 350 to 1000 nm were performed to study the effect of nanorod and nanoparticle addition on the light absorption property of the alumina nanocomposites. It is found that CoO nanorods increase the light absorption of the alumina matrix composite in the wavelength range from 500 nm to 800 nm, but the TiO₂ shell does not increase the light absorption much. The ZnO nanorods do not change the light absorption either. However, the addition of silver nanoparticles significantly enhances light absorption of both AAO/TiO₂/Ag/CoO and AAO/TiO₂/Ag/ZnO nanocomposites. This increase in the visible light absorption reveals that there exists surface plasmon around the fine silver nanoparticles in the nanorods.     

Microwave-assisted synthesis of ZnO/MWCNT hybrid nanocomposites and their alcohol-sensing properties

Zinc oxide and multi-walled carbon nanotube (ZnO/MWCNT) hybrid nanocomposites were synthesised by microwave-assisted method using the mixed solution of zinc acetate dehydrate (Zn(CH₃COO)₂·2H₂O) and treated MWCNTs. The syntheses were carried out at various microwave irradiation powers. The characterisation of the as-synthesised nanocomposites was conducted by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD results revealed that the composites were composed of two phases of MWCNTs and hexagonal wurzite ZnO. The SEM results showed that the ZnO nanoparticles were well decorated on the surface of MWCNTs. The amount of ZnO nanoparticles and their size increased with increasing irradiation power. Thick-film sensors were fabricated onto interdigitated conducting electrodes using as-synthesised hybrid composites as sensing materials. The alcohol-sensing behaviour of the hybrid composite films was investigated. The results indicated that the irradiation power had significant influence on the sensing response of the sensors toward alcohol. The sensor fabricated from the composite synthesised at higher irradiation power exhibited an enhanced alcohol-sensing performance.     

低温剥离法制备高性能石墨烯/ZnO复合材料

采用氧化石墨和七水合硫酸锌作为初始反应物, 在低温下(80℃)合成了氧化石墨/ZnO, 然后通过低温剥离法制备了高质量石墨烯/ZnO (GNS/ZnO)复合材料. 采用X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱、热重分析仪(TG)、X射线光电子能谱(XPS)、拉曼光谱(RS)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等分析手段对石墨烯/ZnO样品进行了表征. 结果表明: 氧化石墨还原彻底, 纳米ZnO成功地负载到了石墨烯上, 有效地减少了石墨烯片层间的团聚现象. 通过对ZnO和石墨烯/ZnO荧光性能测试, 结果表明: 石墨烯/ZnO发生了荧光淬灭现象, 在光电子领域拥有广阔的应用前景.     

Interaction of chitosan capped ZnO nanorods with Escherichia coli

ZnO nanorods of around 80 nm length and 30–60 nm diameter, encapsulated in chitosan were synthesized through co-precipitation technique and was characterized by XRD, UV–VIS, SEM, HRTEM, AFM and FTIR. The aim of the study was to investigate the attachment of chitosan capped zinc oxide nanoparticles (ZnO NP) with Escherichia coli bacterial outermost cell membrane and their mode of action against these bacteria. The detailed characterization studies were carried out to develop insight into the process of influence of these nanostructures on bacterial cells. Antibiotic characteristics of chitosan capped ZnO nanoparticles have been compared with Amoxicillin by zone of inhibition through cup plate method.     

The influence of zinc oxide–cerium oxide nanoparticles on the structural characteristics and electrical properties of polyvinyl alcohol films

With the objective to investigate the influence of zinc oxide–cerium oxide (ZnO–Ce₂O₃) nanoparticles on the electrical properties of polyvinyl alcohol (PVA), PVA/ZnO–Ce₂O₃ nanocomposite films were prepared by solution intercalation method with different weight percentage viz., 0.5, 1.0, and 2.0?wt% of ZnO–Ce₂O₃ nanoparticles. The fabricated nanocomposites were characterized by Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The effect of ZnO–Ce₂O₃ nanoparticles on the dielectric constant (ε′), dielectric loss (ε″), electric modulus (M′ and M″), ac conductivity (σ _ac), and dielectric loss tangent (tan δ) over a range of frequencies at room temperature of PVA nanocomposites have been studied. FT-IR, XRD, and DSC analysis indicates the nature of ZnO–Ce₂O₃ nanoparticles interaction with the PVA matrix. The morphological behavior of the nanocomposites has been performed using scanning electron microscopy (SEM). The dielectric behaviors such as dielectric constant (ε′) and dielectric loss (ε″) increases with increase in nanoparticle concentration, but decreases with increase in frequency. But, the electric modulus (M′) increases with increase in frequency. Dielectric loss tangent (tan δ) decreases with increase in filler content at lower frequency, but at higher frequencies the tan δ increases with increase in nanoparticles content. AC conductivity (σ _ac) of PVA/ZnO–Ce₂O₃ nanocomposites increases with increasing frequency following the universal dielectric response law.     

A facile synthesis of supported amorphous iron oxide with high performance for Cr(VI) removal from aqueous solution under visible light irradiation

A series of supported iron oxide nanoparticles were prepared by impregnation with Fe(NO₃)₃ supported on TiO_2, followed by low-temperature calcination. Scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra and BET have been used to characterize the samples. These iron oxide-impregnated TiO₂ were examined for photocatalytic reduction of Cr(VI). The experiments demonstrated that Cr(VI) in aqueous solution was more efficiently reduced using Fe₂O₃/TiO₂ heterogeneous photocatalysts than either pure Fe₂O₃ or TiO₂ under visible light irradiation. All TiO₂ supported samples were somewhat active for visible light photoreduction. With an optimal mole ratio of 0.05-Fe/Ti, the highest rate of Cr(VI) reduction was achieved under the experimental conditions. We also compared the photoreactivity of TiO₂ supported iron oxide samples with that supported on Al₂O₃ and ZrO₂. It can be noted that iron oxide nanoparticles deposited on high surface area supports to increase the solid-liquid contact area renders it considerably more active. Noticeably, iron oxide cluster size and dispersion are important parameters in synthesizing active, supported Iron oxide nanoparticles. In addition, the interaction between iron oxide and TiO₂ was proposed as the source of photoactivity for Cr(VI) reduction.     

New insight for enhancing photocatalytic activity of MWCNT/TiO2 by decorating palladium nanoparticles as charge-transfer channel

A surface bond-grafted multi-walled carbon nanotube (MWCNT)/TiO₂ as supporter, palladium nanoparticles, approximately 3 nm in diameter, are uniformly deposited on the functional MWCNT surface in first, constructing a novel Pd-MWCNT/TiO₂ photocatalyst for photocatalytic solar conversion. The characterization of photocatalysts by a series of joint techniques, including BET surface area, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX), Raman spectroscopy and ultraviolet/visible (UV/vis) diffuse reflectance spectra, discloses that palladium nanoparticles has a crucial role in enhancement of photocatalytic activity of MWCNT/TiO₂, that is to act as a charge transfer channel, which helps to trap electrons from MWCNT to TiO₂.     

非织造材料表面生长ZnO薄膜的特性研究

室温下采用射频磁控溅射技术在涤纶纺粘非织造材料表面生长ZnO薄膜。通过扫描电子显微镜及原子力显微镜对ZnO薄膜的微观结构进行表征,用分光光度计测量样品的透光率。结果表明,ZnO薄膜为纳米级,其平均晶粒大小约为30 nm~55 nm。生长了ZnO透明纳米结构的非织造材料对紫外光有较强的吸收能力,在可见光区的透光率达60%以上。     

Small angle neutron scattering and photoluminescence property of wet chemistry process synthesised ZnO nanoparticles

We report the synthesis of zinc oxide (ZnO) nanoparticles from aqueous solution at 25°C and subsequent heating of the solution at 115°C by the suitable selection of the solution chemistry and the control of the alkaline conditions. The structure of the synthesised ZnO particles was studied by X-ray diffraction (XRD), confirming the formation of Wurtzite structure. The optical property of synthesised ZnO nanoparticles is investigated through room temperature photoluminescence (PL) measurement. The PL of ZnO nanoparticles shows a strong UV emission band at approximately 385 nm, a blue–green band at approximately 473 nm and a very weak green band at approximately 554 nm, although polydispersity of the sample shows no presence on the PL spectrum. Small angle neutron scattering is used to determine the size and the size distribution of ZnO nanoparticles. The SANS data analysis and model fitting predict the size as about 18–20 nm, which is closely matched with XRD and transmission electron microscopy results with Gaussian distribution.     

Optical properties of Ag doped ZnO nanocrystals prepared by hydrothermal and photodeposition method

Ag/ZnO nanocomposites have been synthesized by facile hydrothermal and photodeposition method. The effect of different concentration of Ag on the luminous intensity of ZnO was studied. The morphology, structure and optical properties of Ag/ZnO were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL), respectively. The XRD patterns show that intensities of diffraction peaks of Ag/ZnO were enhanced. The weak diffraction peak at 38.28° can be assigned to Ag₂O when the concentration of Ag increased to 0.09 M. PL results demonstrate that the UV luminous intensity of ZnO was significantly influenced by the concentration of Ag. The UV luminous intensity of Ag/ZnO nanocomposites increased by 11 times as compared with undoped ZnO when the concentration of Ag was 0.03 M due to the local surface plasma resonance effect of Ag nanoparticles.     

Synthesis and Structure of Polyethylene-Matrix Composites Containing Zinc Oxide Nanoparticles

Nanocomposites of high-pressure polyethylene and zinc oxide nanoparticles are synthesized through thermal decomposition of zinc acetate. The phase composition of the nanocomposites is determined by x-ray diffraction (XRD), and the average size of ZnO nanoparticles is evaluated by transmission electron microscopy. The average size of the nanoparticles varies from 1 to 10 nm, depending on the ZnO content of the material. Both XRD and EXAFS results indicate that the zinc oxide nanoparticles have the wurtzite structure.     

Hydrothermal synthesis of nanostructured zinc oxide and study of their optical properties

Nanostructured ZnO (nanorods, nanoshuttles) have been synthesized by hydrothermal approach using ZnCl₂ or Zn(NO₃)₂·6H₂O as zinc sources and cetyltrimethylammonium bromide as structure-directing agent. Techniques X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–visible absorption, Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy have been used to characterize the structure, morphology and composition of the nanostructured zinc oxide. The optical properties of the as-obtained materials were also studied and showing that it is possible to apply the ZnO nanoshuttles and nanorods on the UV filter, photocatalysis, and special optical devices.     

Coexistence of interfacial stress and charge transfer in graphene oxide-based magnetic nanocomposites

In this paper, the existence of both compressive stress and charge transfer process in hydrothermally synthesized cobalt ferrite–graphene oxide (CoFe₂O₄/GO) nanocomposites has been established. Transmission electron microscopy results reveal the decoration of CoFe₂O₄ nanoparticles on GO sheets. Magnetic response of nanocomposites was confirmed from superconducting quantum interference device magnetometer measurement. Optical properties of these nanocomposites were investigated by Raman spectroscopy. The interfacial compressive stress involved in this system has been evaluated from observed blue shift of characteristic G peak of graphene oxide. Increase in the full-width half-maximum value as well as upshift in D and G peaks is clear indications of involvement of charge transfer process between GO sheets and dispersed magnetic nanoparticles. The effect of charge transfer process is quantified in terms of shifting of Fermi energy level of these nanocomposites. This is evaluated from variation in contact surface potential difference using scanning Kelvin probe microscopy. XRD spectra of CoFe₂O₄/GO confirm the polycrystalline nature of CoFe₂O₄ nanoparticles. Lattice strain estimated from XRD peaks is correlated with the observed Raman shift.     

Preparation of aluminum foil-supported nano-sized ZnO thin films and its photocatalytic degradation to phenol under visible light irradiation

The zinc oxide thin films on aluminum foil have been successfully prepared by sol–gel method with methyl glycol as solvent. The film was characterized by means of XRD, TG, UV–vis, SEM and AFM, which show that the ZnO/Al film is formed by a layer of ZnO nano-sized particles with average diameter of 52.2 nm. Under the initial concentration of 20 mg/L phenol solution (500 mL) and visible light irradiation time of 3 h, more than 40% of the initial phenol was totally mineralized using two pieces of ZnO/Al thin film as photocatalyst with an efficient irradiation area of 400 cm². It is a promising visible light responded photocatalyst for the activation of O₂ at room temperature to degrade organic pollutants.     

Fabrication of ordered flower-like ZnO nanostructures by a microwave and ultrasonic combined technique and their enhanced photocatalytic activity

Ordered flower-like zinc oxide (ZnO) nanostructures were fabricated via a facile microwave and ultrasonic combined technique. The product was characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected area electron diffraction pattern (SAED). The flower-like ZnO nanostructures were assembled by a central petal and six symmetrical petals which grew radially from the center. The flower-like ZnO sample showed an enhanced photocatalytic performance compared with the ZnO microrods for the methylene blue (MB) degradation, which could be attributed to its special structure feature. Au/ZnO and Ag/ZnO nanocomposites were also synthesized and exhibited enhanced photocatalytic efficiency after decorating noble metal nanoparticles on the surface of flower-like ZnO nanostructures.