Sharif Digital Repository

An eco-friendly, simple, and effective protocol is developed for the synthesis of various multisubstituted 2-aminothiophenes. In the presence of a catalytic amount of ZnO (5 mol), ketones or aldehydes, malononitrile and elemental sulfur were converted to the corresponding 2-aminothiophene derivatives in moderate to high yields (27%-70%) under solvent-free conditions at 100 °C. Zinc oxide as an efficient, readily available, and reusable catalyst, showed very good catalytic activity for the synthesis of 2-aminothiophene derivatives. Thus far, little research has been reported on the Gewald reaction under solvent-free conditions; to the best of our knowledge, this is the first time that it has... 

Herein, a simple and novel method was used to synthesize a new structure of graphene which can be called hollow graphene. First, the ZnO-Graphene QDs synthesized by solution method and then ZnO QDs were dissolved from this structure using an acidic solution to obtain hollow structure of graphene. Afterward, this structure was used in PbS QDs solar cell in order to improve the transport of electron and decrease the recombination of the carriers. A power conversion efficiency of 5.3% was obtained using hollow graphene as a fast electron extraction layer due to the enhancement of EQE and current density. The improvement of PCE in this device was corresponded to efficient photosensitized... 

In this report, the efficacy of different factors such as temperature of reaction, time of reaction and depth of bed are investigated in a process of recovery of zinc oxide from zinc ore concentration residues in a fluidized bed furnace. Under optimum conditions, there was more than 93.5% zinc oxide in products  

In this report, the possibility of recovering zinc oxide from zinc containing wastes, also the effect of temperature, time and depth of bed on recycling has been studied. Zinc oxide with a purity of 93.5% was obtained  

ZnO nanoparticles were fabricated via hydrothermal method and an amorphous TiO2 layer was then coated on the nanoparticles via sol-gel route. X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies showed that the synthesized ZnO nanoparticles were hexagonal with wurtzite structure and an average particle size of 38 nm. The thickness of the titanium oxide layer was determined to be 20-40 nm. The photocatalytic decolorization of Methylene blue under UV irradiation indicated that as-prepared TiO 2-capped ZnO is inferior than ZnO particles. Nevertheless, calcinations of the particles at 350 °C for 24 h significantly improved the photo-activity of the ZnO/TiO2 core/shell... 

Oriented ZnO nanorods were grown directly on fluorine doped tin oxide substrates by a single bath electrodeposition process. A pulse potential at the beginning of growth improved the density and orientation of the nanorods. Pulse potential grown ZnO nanorod films showed better harvesting of visible light and enhanced the light driven water splitting performance in comparison to nanorods grown without any pulse potential. To further improve the water splitting activity, the nanorods were decorated with gold–palladium nanoparticles by sputtering. This caused visible light absorption to increase due to a plasmonic effect and the photoelectrochemical water splitting performance to further... 

This paper describes a solution-based technique for fabrication of varistor grade composite nanopowders. The method consists of coating major varistor dopants on the surface of the ZnO nanoparticles. As a result, a homogenous mixture of dopants and ZnO nanoparticles will be achieved. TEM results indicated that a composite layer of dopants with the average particle size of 9 nm on the surface of ZnO nanoparticles has been successfully prepared. Sintering of the coated powders was performed in temperatures as low as 850 °C and final specimens with average particle size of 900 nm and density of 98.5% were achieved. In comparison to conventional mixing, varistors prepared from coated nanopowders... 

The fabrication of strong photocatalysts applied to the degradation of organic pollutants is necessary in environmental applications. In a single-stage method, acetate precursor and poly vinyl pyrolydine are used to produce ZnO nanostructures with various morphologies in annealing temperatures ranging from 300 °C to 900 oC. The physical properties of the prepared nanostructures were characterized by SEM, XRD and PL spectroscopy. The SEM images exhibit a variety of the as-prepared hexagonal zinc oxides including wires, rods, particles and porous network of welded particles of ZnO nanoparticles. The results of the photocatalytic degradation of methylene blue as an organic dye in aqueous... 

This paper aims at the investigation of acoustic streaming produced by surface acoustic waves (SAWs) in a drop. Computational simulation of acoustofluidic phenomenon, using lattice Boltzmann method (LBM), presenting acoustic applications in flow control, and a relatively complete parametric study are the motivations of this work. For this purpose, a computational fluid dynamics modeling based on multi-relaxation time multi-component multiphase color gradient lattice Boltzmann method was used. The simulations were carried out at wave frequencies ranging from 20 MHz to 271 MHz and wave amplitudes ranging from 0.5 nm to about 350 nm. First, the non-dimensional form of Navier-Stokes equations... 

Large-scale K-doped ZnO nanotapers were successfully grown on an indium tin oxide (ITO) substrate using a facile electrochemical route. The structural and morphologic analysis exhibited that the K-doped ZnO nanostructures had a nanotaper morphology and strong preferential [0001] c-axis direction with a hexagonal polycrystalline structure. The optical results show that the incorporation of K+ ions as the donors in a ZnO lattice leads to substantial modulation of the band gap structure of ZnO nanotapers, which results in a redshift in the ultraviolet emission peaks. The considerable enhancement of performance in K-doped ZnO-based dye-sensitized solar cells (DSSCs) can be related to the doping... 

A novel method of oxide semiconductor nanoparticle synthesis is proposed based on high-voltage, high-current electrical switching discharge (HVHC-ESD). Through a subsecond discharge in the HVHC-ESD method, we successfully synthesized zinc oxide (ZnO) nanorods. Crystallography and optical and electrical analyses approve the high crystal-quality and outstanding optoelectronic characteristics of our synthesized ZnO. The HVHC-ESD method enables the synthesis of ZnO nanorods with ultraviolet (UV) and visible emissions. To demonstrate the effectiveness of our prepared materials, we also fabricated two UV photodetectors based on the ZnO nanorods synthesized using the subsecond HVHC-ESD method. The... 

In this article, indium doped ZnO nanoparticles (alloy nanoparticles) were investigated as inhibitors against algae growth on adobe mud and earthen artworks for surface preservation from destruction caused by micro-organisms under humid conditions, through surface modification and activation run off. Nanoparticles (NPs) were fabricated by physical vapor deposition (PVD) growth mechanism. The fabricated NPs were approximately 20 nm in size. The Chlorella vulgaris and Scenedesmus quadricauda were tested by application of indium doped ZnO nanoparticles (In/ZnO NPs) as inhibitors. As concentrations of NPs increased, the negative impacts of NPs on the algal growth were enhanced and physical... 

Curcumin incorporated polyurethanes (CPU) are gaining much attention as a biomaterial. However, challenges are still remained due to hydrophobicity and low mechanical strength of CPU. Herein, we synthesized the CPU/ZnO nanocomposites with good mechanical and improved hydrophilic properties via in-situ polymerization. A series of curcumin incorporated polyurethane with different concentrations of ZnO nanoparticles (ZnCPU) are synthesized by using the curcumin, polyethylene glycol (PEG) as the soft segment, hexamethylene diisocyanate (HDI) as the hard segment, and 1,4-butanediol (BDO) as the chain extender. The addition of ZnO nanoparticles (NPs) facilitated the soft domain of PU which is... 

A label-free electrochemical biosensor was developed for the rapid detection of the matrix metalloproteinase 9 (MMP-9) biomarker on the basis of antibody immobilizing on the zinc oxide (ZnO) nanoparticle and ZnO nanorod electrodes. The charge transfer resistance (Rct) of the electrodes was used as the indicator for MMP-9 concentration, which was obtained through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The ZnO nanorod-based biosensor exhibited linear behavior in the MMP-9 concentration range of 1–1000 ng/ml, which is a wider range than the available concentration ranges for most of the conventional methods. The biosensor sensitivity was 32.5 μA/(decade × cm2)... 

A double-tube vapor phase transport system has been used to grow ZnO nanostructures. Nanopillars, nanorods and nanowires of zinc oxide were synthesized on Au nanoparticle catalyst depending on source-substrate distance and temperature gradient in the quartz tube. In addition, influence of growth time and substrate temperature on the morphology of the nanorods and nanowires were also investigated. The scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) were employed to further understand the nanostructures growth mechanism on various temperatures and growth time steps. Longer length (>4μm) with hexagonal-cross-sectional nanowires, in [002]... 

TiO 2 nanorods, TiO 2 nanorod/TiO 2 nanoparticle and TiO 2 nanorod/ZnO nanoparticle composite structures were integrated as photoanodes in backside illuminated dye-sensitized solar cells (DSSCs). Incorporation of TiO 2 nanoparticles into the bare nanorods increased the dye loading and improved the short-circuit current density (J sc) from 2.22 mA/cm 2 to 3.57 mA/cm 2. ZnO nanoparticles electrochemically grown into the TiO 2 nanorod layer could increase the surface area. Nevertheless, this considerably reduced the J sc to 0.57 mA/cm 2 and consequently cell efficiency. Electrochemical impedance spectroscopy (EIS) results showed that ZnO incorporated samples have better effective diffusion... 

(ZnO)1-x(CdO)x nanofibers were fabricated via electrospinning of polymer precursor by subsequent annealing in air. Field emission scanning electron microscopy (FESEM) showed the smooth and beadless nanofibers and X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) showed the ZnO hexagonal and the CdO cubic structure. Diffuse reflectance spectroscopy (DRS) showed the band gap energy reduction by increasing the amount of CdO in (ZnO)1-x(CdO)x nanofibers that resulted in the photocatalytic activity under the visible light for dye degradation. Under the UV light CdO acted as both electron and hole sink in the (ZnO) 1-x(CdO)x nanofibers and a possible photocatalytic activity... 

Novel ZnO-carbon and ZnO nanofibers were fabricated by electrospinning of polymer precursor followed by subsequent annealing in nitrogen and air, respectively. Field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) indicated the smooth and beadless nanofibers with wurtzite crystal structure. X-ray photoelectron spectroscopy (XPS) showed the presence of oxygen vacancies (VO) and chemisorbed O2 on the surface of the samples. Band gap narrowing of the ZnO-carbon nanofibers in comparison to ZnO were measured by diffuse reflectance spectroscopy (DRS). Photo-degradation of azo dye under the UV and visible light was evaluated and ZnO-carbon showed an enhancement in... 

Multi wall carbon nanotube (MWCNT) doped ZnO nanofibers were fabricated by electrospinning for the first time. We have successfully demonstrated the photocatalytic activity of doped nanofibers under visible light. Scanning electron microscopy showed that the diameter of MWCNT-doped ZnO nanofibers varied from 120 to 300 nm without agglomeration of MWCNT. Fourier transform infrared spectroscopy and X-ray diffraction studies proved the formation of ZnO bond and wurtzite structure with smaller crystal size in doped nanofibers. Raman spectra demonstrated slight shift in bond position after nanofiber doping, indicating the chemical bond between MWCNT and ZnO. X-ray photoelectron spectroscopy... 

Global environmental pollution and energy supply demand have been regarded as important concerns in recent years. Metal oxide semiconductor photocatalysts is a promising approach to apply environmental remediation as well as fuel generation from water splitting and carbon dioxide reduction. ZnO nanostructures have been shown promising photocatalytic activities due to their non-toxic, inexpensive, and highly efficient nature. However, its wide band gap hinders photo-excitation for practical photocatalytic applications under solar light as an abundant, clean and safe energy source. To overcome this barrier, many strategies have been developed in the last decade to apply ZnO nanostructured...