Sharif Digital Repository

A series of reduced graphene oxide/ZnxCd1-xS (RGO/ZnxCd1-xS) nanocomposites (0 < x < 1) with different ratios of Zn/Cd were synthesized via a facile hydrothermal route under optimized experimental conditions and were carefully characterized by various techniques. Because very little is known about the morphology, specific surface area, and crystal phase effects of RGO/ZnxCd1-xS crystals on their photoresponsivity, field-emission scanning electron microscopy (FE-SEM), BET surface area analysis and X-ray diffraction (XRD) data were studied to investigate their effects on photoactivity. Based on the results, a crystal phase transition from a cubic phase in RGO/Zn0.9Cd0.1S to a hexagonal... 

RGO-α-Fe2O3/β-FeOOH ternary heterostructure composite has been developed as an active photocatalyst for photoelectrochemical water splitting. RGO-α-Fe2O3/β-FeOOH has been successfully synthesized through one-pot hydrothermal-ionic liquid assisted route using tetrabutyl ammonium L-methioninate [TBA][L-Met]and graphene oxide (GO). The electrochemical studies were carried out to demonstrate the oxygen evolution reaction (OER)and photocatalytic activities. The overpotential reduction by rGO-α-Fe2O3/β-FeOOH sample was higher than the nanobean α-Fe2O3/β-FeOOH and pristine α-Fe2O3 samples. The photocurrent density enhanced for rGO-α-Fe2O3/β–FeOOH urchin-like structure and obtained as 0.62 mA·cm−2.... 

Bead-chain-like ZnO nanoparticles (NPs) formed in colloidal solution from oriented attachment (OA) of spherical nanoparticles. Arc discharge in liquid is a cost-effective method for quick mass production of nanostructured materials without considerable environmental footprints. Applying voltage across two zinc rods as electrodes, which were immersed in water cause explosion of electrodes and plasma generation. Zn/ZnO nanocomposites produced by interaction of different active species in high-pressure and high-temperature plasma at the solid-liquid interface. Different sized nanoparticles with diameters of 26, 35, 40 and 60 nm at applied discharge currents of 150, 100, 50 and 20 A... 

Synthesis of colloidal metal oxides with controllable size and morphology is burgeoning field of research in nanoscience. Low band gap gray Zn/ZnO colloidal nanoparticles were fabricated by plasma-liquid interaction of DC arc discharge in water. Scanning electron microscopy, X-ray diffraction and UV–vis spectroscopy were employed for morphology, crystal structure and optical characterizations respectively. Optical emission spectroscopy was used to investigate the plasma properties during the synthesis and formation mechanism of nanoparticles. Nanoparticles with different size and shape were fabricated only by adjusting discharge current during synthesis without introducing any chemical... 

Inkjet-printing (IJP) technology is recognized as a significant breakthrough in manufacturing high-performance electrochemical energy storage systems. In comparison to conventional fabrication protocols, this printing technique offers various advantages, such as contact-less high-resolution patterning capability; low-cost, controlled material deposition; process simplicity; and compatibility with a variety of substrates. Due to these outstanding merits, significant research efforts have been devoted to utilizing IJP technology in developing electrochemical energy storage devices, particularly in supercapacitors (SCs). These attempts have focused on fabricating the key components of SCs,... 

Printing technologies are gaining growing attention as a sustainable route for the fabrication of high-performance and flexible power sources such as microsupercapacitors (MSCs). Here, the inkjet printing method is utilized for the fabrication of manganese dioxide (MnO2)-based, flexible all-solid-state MSCs on surface-modified A4 paper substrate. The appropriate rheology of the formulated ethanol-based ink (Fromm number <10) and the proper dimensions of MnO2 nanoflowers (average size ∼600 nm) ensure a reliable inkjet printing process. Moreover, the underlying graphene/Ag nanowire pattern serves as a primer and highly conductive (Rs < 2 Ω sq-1) layer on top of the paper to facilitate the... 

Supercapacitors store charge by ion adsorption or fast redox reactions on the surface of porous materials. One of the bottlenecks in this field is the development of biocompatible and high-rate supercapacitor devices by scalable fabrication processes. Herein, a Ti-rich anatase TiO2 material that addresses the above-mentioned challenges is reported. Tubular nanolettuces were fabricated by a cost-effective and fast anodization process of Ti foil. They attained a large potential window of 2.5 V in a neutral electrolyte owing to the high activation energy for water splitting of the (1 0 1) facet. Aqueous and all-solid-state devices showed diffusion time constants of 46 and 1700 ms, as well as... 

Preparation of the defective TiO2 nanoparticles (NPs) have been recently in particular interest for its outstanding applications in visible-light active photocatalysis. In order to make TiO2 visible-light absorber, optical band gap should be modified especially via introducing structural defects like oxygen vacancies as an effective pathway. In this research, we prepared defective rutile TiO2 NPs with highly efficient photocatalytic activity under visible light. The NPs were synthesized by electric arc discharge in water as a cost-effective and environmentally friendly method with capability of defect formation which followed by heat treatment. The photocatalytic activity improvement... 

[No abstract available]  

The Multi-walled carbon nanotube (MWCNT)/WO3 nanocomposite thin films with different MWCNT's weight percentages were prepared by sol-gel method as visible light induced photoanode in water splitting reaction. Weight percentage of MWCNT in the all nanocomposite thin films was confirmed by TGA/DSC analysis. According to XPS analysis, oxygenated groups at the surface of the MWCNT and stoichiometric formation of WO3 thin films were determined, while the crystalline structure of the nanocomposite samples was studied by XRD indicating (0 0 2) peak of MWCNT in the monoclinic phase of WO3. The influence of different weight percentage (wt%) of MWCNT on WO3 photoactivity showed that the electron... 

Two-dimensional MXenes are the newly emerging family of nanomaterials with competitive performance for nano-device development. Surface functional groups and abundant binding sites make these materials ideal candidates for sensor applications. Herein, we report the successful fabrication of a MXene-based nano-bio device for capturing, sensing, and filtering the Escherichia coli (E. coli) bacteria. Mannose carbohydrate, which binds strongly to E.coli's fimH protein via glucan multivalent interactions, is used as the bio-receptor element. MXene's structure was engineered to guarantee efficient E. coli capturing without mannose detachment. Electrochemical impedance spectroscopy (EIS) and cyclic... 

A new synergetic hybrid Ag/ZnO nanostructure was fabricated which is able to cause photocatalytic degradation (in high yields) of methylene blue under visible light as well as in the dark. In this nanostructure, ZnO was synthesized using the arc discharge method in water and was coupled with Ag via a chemical reduction method. X-ray photoelectron spectroscopy (XPS) and photoluminescence spectroscopy results confirmed the existence of defects in ZnO in the hybrid nanostructures; these defects act as electron traps and inhibit the recombination of electron-hole pairs. The absorption edge of the hybrid nanostructure shifts toward the visible region of the spectrum due to a combination of the Ag... 

Free-standing TiO2 nanotube array (TNA) films were fabricated via two-step anodization of a titanium sheet. The X-ray diffraction pattern indicated amorphous TNAs were transformed into anatase after annealing the films at 500 °C in air. The surface of TNA was modified by a sequential-chemical bath deposition (S-CBD) method to fabricate Ag2S nanoparticles and forming TNA/Ag2S-n nanostructure, by varying the number of cycles (n). Based on SEM observations, the produced films consisted of vertically ordered tubular structure arrays, each with 125 nm in diameter and 4.1 μm in length containing silver sulphide nanoparticles of ∼12 nm diameter. X-Ray photoelectron spectroscopy (XPS) confirmed the... 

Hematite is recognized as a promising photoanode for photoelectrochemical water oxidation to produce solar hydrogen due to its favorable properties. However, the high charge carrier recombination rate due to low electrical conductivity and sluggish oxygen reduction kinetics of pure hematite hinder its photocatalytic activity. This work proposed a new hematite-based heterostructure of Ti-Fe2O3/Fe2TiO5/FeOOH, synthesized through a hydrothermal method. The photoanode morphology was branched nanorods that expanded their surface area and improved charge transfer at the photoanode/electrolyte interface. In a novel and complement modification approach, a thin pseudobrookite interlayer was applied... 

This paper analyses the three-dimensional (3-D) surface texture of Co/CP/X (X = Cu, Ti, SM and Ni, CP: carbonaceous paste) nanoflakes prepared electrochemically using a conventional three electrode system. The surface chemical composition of the samples was investigated by X-ray photoelectron spectroscopy (XPS). Surface images were recorded using scanning electron microscopy (SEM) and analyzed by means of the fractal geometry. Statistical, fractal and functional surface properties of the prepared samples were computed. The statistical functions applied to the SEM data were employed in order to characterise the surfaces topographically (in amplitude, spatial distribution and pattern of... 

We used first principles calculations based on density functional theory with generalized gradient approximation to investigate and compare the structural, electronic and optical properties of two photoanode materials, ZnV2O6 and Zn2V2O7, for use in photocatalytic water splitting. After geometry optimization, the calculated structural parameters evince a satisfactory agreement with the reported experimental results indicating that the used method and conditions are suitable. The electronic structures demonstrate that both photocatalysts possess favorable band gaps (2.31 and 2.52 eV) and appropriate band edge positions for oxygen evolution reaction under solar radiation. The relatively light... 

Providing solar hydrogen as a clean energy resource is one of the human challenges for future. Controlling oxygen vacancies as well as surface morphology in metal oxide semiconductors enables developing PEC H2production in some understood ways. Here, the influence of simple change in annealing atmosphere, air and pure oxygen, on photoresponse of nanocrystalline WO3has been studied completely. Results revealed that such slight change in annealing procedure increases effective surface interface and donor density by 77 and 72%, respectively. These effects and also retarding recombination of photogenerated electro-hole pair resulted in photocurrent enhancement under solar like illumination more... 

A new plasmonic Ag hybridized CuWO4/WO3 heterostructure was successfully synthesized via a ligand-assisted sol gel method. The as-prepared plasmonic nanohybrid was thoroughly characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible spectroscopy, photoluminescence (PL) spectrometry, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, Brunauer-Emmett-Teller (BET) surface area analysis and electrochemical impedance spectroscopy (EIS). Moreover, the photocatalytic activity was evaluated by photo-degradation of methylene blue (MB) under visible light irradiation. The results indicate that the as-prepared plasmonic Ag-CuWO4/WO3 nanohybrid (compared to pure... 

In this research, we investigate the effect of alkali metal cations including Li, Na and Cs in hydrothermal solution on the morphology, stability, and photoactivity of nanostructured TiO2 nanoflakes as a photoanode. The TiO2 nanoflakes are formed through hydrothermal treatment of Ti foil in 1.0 M LiOH, NaOH or CsOH at 100 °C for 3 h. By subsequent thermal reduction of the structure in an optimized Ar/H2 environment, conductive TiO2 nanoflakes were formed. The reduction treatment remarkably improves the photocurrent density of the TiO2 nanoflakes and has the highest impact on the sample treated in the NaOH alkali solution. For the nanoflakes produced in NaOH alkali solution, the bandgap is... 

Iron(III) oxide (hematite, Fe2O3) nanofibers, as visible light-induced photoanode for water oxidation reaction of a water splitting process, were fabricated through electrospinning method followed by calcination treatment. The prepared samples were characterized with scanning electron microscopy, and three-electrode galvanostat/potentiostat for evaluating their photoelectrochemical (PEC) properties. The diameter of the as-spun fibers is about 300nm, and calcinated fibers have diameter less than 110nm with mesoporous structure. Optimized multilayered electrospun α-Fe2O3 nanostructure mats showed photocurrent density of 0.53mA/cm2 under dark and visible illumination conditions at voltage 1.23V...