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[en] Graphical abstract: Rosalike CuSe hierarchical nanostructures modified TiO2 NTs were firstly synthesized by a facile photo-assisted chemical bath deposition method. The p-type CuSe with the average diameter of 2–4 μm were well well-proportionedly grown on the top surface of n-type TiO2 NTs, forming the p–n heterojunction. And the morphology of an individual CuSe looks like a beautiful flower of rosa in nature. The rosalike hierarchical nanostructures with high surface area will facilitate the adsorption and photocatalysis of reactants. Thus, the resulting hybrid materials exhibit improved photocatalytic activities in degrading anthracene-9-carboxylic acid compared with the unmodified TiO2 nanotubes under simulated solar light. Highlights: ► CuSe hierarchical nanostructures were grown on TiO2 nanotubes using photo-assisted chemical bath deposition. ► The fabrication technique of CuSe operated at room temperature and room pressure. ► The hierarchical nanostructures with high surface area facilitated the adsorption and photocatalysis of reactants. ► The hybrid materials exhibited improved photocatalytic activities compared with the unmodified TiO2 nanotubes. ► A possible mechanism was proposed to explain the formation of rosalike architecture CuSe at low temperature. - Abstract: Highly crystalline CuSe hierarchical nanostructures made of nanosheets have been successfully synthesized on the surface of TiO2 nanotube arrays (NTs) pre-loaded with Cu2O nanowires using a photo-assisted chemical bath deposition. The pre-synthesized Cu2O nanowires served as copper precursor and nucleation centers for the crystal growth, resulting in the rapid formation of CuSe crystals at low temperature. This novel material held the advantages of both p–n junction and hierarchical nanostructures which provided high specific surface areas, thus facilitating the transfer of the electrons and inhibiting the recombination of the photogenerated hole-electron pairs, which were demonstrated by photoelectrochemistry measurements. Meanwhile, UV–vis diffuse reflectance spectra (DRS) showed the modified TiO2 significantly enhanced the absorption in the visible light region. X-ray diffractometer (XRD) and high resolution transmission electron microscopy (HRTEM) were employed to demonstrate that the resulting CuSe was single crystalline. A possible mechanism was proposed to explain the formation of rosalike architecture CuSe at low temperature. In addition, this novel material exhibited remarkable photocatalytic performance on the degradation of anthracene-9-carboxylic acid (ACA).
[en] Highlights: • Cu-Ni-W/SiC nano composite coatings were electrodeposited on steel. • Effects of the concentration nano SiC particles, stirring rate and current density on incorporation of nano SiC particles were investigated. • Effects of incorporation SiC particles in the coatings on microstructure and mechanical properties of the nano composite coatings were investigated. • The incorporation of nano SiC particles in the coatings leads to increasing wear resistance and microhardness of the coatings. - Abstract: In this work Cu-Ni-W/SiC nanocomposite coatings were prepared by electrodeposition method and the effects of incorporation of silicon carbide (SiC) nanoparticles on microstructure and wear resistance of Cu-Ni-W coatings were investigated. In this regard, the effects of various parameters such as concentration of SiC nanoparticles, stirring rate and current density on incorporation of SiC nanoparticles were examined by scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX) to reach the optimum composition for the bath. In addition, the effects of SiC nanoparticles on the wear resistance of the coatings was examined by pin on disk wear technique. It was found that in comparison with other coatings, the coating electrodeposited from the bath containing 15 g/L SiC nanoparticles at a current density of 20 mA.cm"−"2 and stirring rate of 400 rpm has the highest microhardness and wear resistance
[en] Due to the high isoelectric point of the ZnO quantum dots (QDs), ZnO QDs were employed as biolabels for carbohydrates to construct a biosensor for determination of the carcinoembryonic antigen (CEA), which act as the carbohydrate. The assay was based on the competition between a quantum dots labeled CEA and analyte CEA using concanavalin A (Con A) as the recognition element. The extent of completion was monitored by the square wave stripping voltammetry. The displacement assay results showed that there are two changes model of the current response to the analyte CEA concentration (0–30 ng/mL and 30–80 ng/mL). The most likely reason for this was also discussed in the paper.
[en] Graphical abstract: - Highlights: • In_2S_3 quantum dots are adsorbed on TiO_2 by a repeated deposition technique. • The In_2S_3 loading and electron density on CB of TiO_2 are elevated. • A promising power conversion efficiency of 1.30% is recorded in QDSSC. - Abstract: As a branch of dye − sensitized solar cell, quantum dot − sensitized solar cells (QDSSCs) have attracted growing interests because of promisingly theoretical electron density on conduction band of TiO_2 nanocrystallite. Here we report the synthesis of efficient In_2S_3 sensitized solar cells. The adsorption cycles are repeated to optimize In_2S_3 loading and therefore photovoltaic performances. A promising power conversion efficiency of 1.30% (under AM 1.5G) is recorded at 24 cycles of In_2S_3 adsorption. The relatively high conversion efficiency in combination with simple preparation demonstrates the potential use of In_2S_3 quantum dots in QDSSCs
[en] Highlights: ► A ZnS/CdSe/CdS/TiO2 nanotube film was prepared by anodization and chemical bath deposition. ► The film showed that the optical absorption range is shifted to the visible region significantly. ► The film could produce highly efficient photocathodic protection for 403 stainless steel. - Abstract: A ZnS/CdSe/CdS/TiO2 composite nanotube film on titanium substrates was prepared by an anodic oxidation method and a chemical bath deposition technique in succession. This CdSe/CdS co-sensitized TiO2 nanotube film was used as a photoanode to achieve a special photocathodic protection effect for metals. The ZnS shell was deposited onto the film to cover the CdS and CdSe quantum dots so as to improve their stabilities. The results indicated that the photoabsorption of the composite film shifted to the visible region and the photocurrent intensity was greatly enhanced due to the modification of CdS and CdSe quantum dots. Especially when 403 stainless steel in a 0.5 M NaCl solution was coupled to the ZnS/CdSe/CdS/TiO2 film photoanode, its potential decreased by 1100 mV under white light illumination, which indicated that the composite film could produce highly efficient photocathodic protection for the steel.
[en] The electrochemical deposition of sodium and lithium from their respective molten chlorides onto a graphite cathode as the first step of carbon nanotube electrolytic production has been investigated. It has been shown that in the case of both sodium and lithium, as the cathodic current density increases, the cathode weight first increases and then decreases, i.e. the dependence of cathode weight change vs. cathodic current density passes through a maximum. The value of cathodic current density corresponding to the maximum increase in the cathode weight in the case of sodium is approximately 4 times as high as that in the case of lithium, which is explained by a higher solubility of sodium metal in molten sodium chloride compared to that of lithium metal in molten lithium chloride. The higher sodium metal solubility causes a higher electronic conductivity of the molten electrolyte, while the ratio of intercalated to dissolved sodium will be lower as compared to lithium. Curved multi-walled carbon nanotubes of an outer diameter of 20-50 nm with a wall thickness of 5-10 nm (molten NaCl) and of 20-100 nm with a wall thickness of 5-40 nm (molten LiCl) have been synthesized.
[en] Poor crystallined α-MnO2 grown on multi-walled carbon nanotubes (MWCNTs) by reducing KMnO4 in ethanol are characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and Brunauer-Emmett-Telle (BET) surface area measurement, which indicate that MWCNTs are wrapped up by poor crystalline MnO2 and BET areas of the composites maintain the same level of 200 m2 g-1 as the content of MWCNTs in the range of 0-30%. The electrochemical performances of the MnO2/MWCNTs composites as electrode materials for supercapacitor are evaluated by cyclic voltammetry (CV) and galvanostatic charge-discharge measurement in 1 M Na2SO4 solution. At a scan rate of 5 mV s-1, rectangular shapes could only be observed for the composites with higher MWCNTs contents. The effect of additional conductive agent KS6 on the electrochemical behavior of the composites is also studied. With a fixed carbon content of 25% (MWCNTs included), MnO2 with 20% MWCNTs and 5% KS6 has the highest specific capacitance, excellent cyclability and best rate capability, which gives the specific capacitance of 179 F g-1 at a scan rate of 5 mV s-1, and remains 114.6 F g-1 at 100 mV s-1.
[en] Thin Cu films of microelectronic quality and low electrical resistivity were created by electroless deposition (ELD) onto SiO2 surface modified first with self-assembled monolayer (SAM) of 3-aminopropyltrimethoxysilane (APTMS) and activated then by 5 nm gold nano-particles (AuNPs). The presence of highly oriented amino-terminated SAM was revealed by XPS and ToF-SIMS analyses. The Cu films were deposited in boron- and phosphorous-free tartrate/formaldehyde electrolyte. Controlling the deposition rate via the solution pH permitted a minimum value in resistivity ρ. XPS depth profile revealed that diffusion of Cu into SiO2 modified by APTMS did not take place after annealing at 220 deg. C, 4 h. Moreover, annealing resulted in the drop of electrical resistivity to ρ = 4 ± 0.4 μΩ cm for the films with the thickness of 35-100 nm. This value of ρ is several times smaller than those reported in literature for sub-100 nm Cu films deposited by electroless on different SAMs. It is speculated that nano-scale porosity and corrugated structure observed by HRTEM and AFM in the ELD Cu films contribute to the resistivity. The obtained results demonstrate a viable route for formation of low resistivity, sub-100 nm Cu films on dielectrics for microelectronic application.
[en] The kinetics of O2 reduction on novel electrocatalyst materials deposited on carbon substrates were studied in 0.5 M H2SO4 and in 0.1 M NaOH solutions using the rotating disk electrode (RDE) technique. Pt nanoparticles (PtNP) supported on single-walled (PtNP/SWCNT) and multi-walled carbon nanotubes (PtNP/MWCNT) were prepared using two different synthetic routes. Before use, the CNTs were cleaned to minimize the presence of metal impurities coming from the catalyst used in the synthesis of this material, which can interfere in the electrochemical response of the supported Pt nanoparticles. The composite catalyst samples were characterised by transmission electron microscopy (TEM) showing a good dispersion of the particles at the surface of the carbon support and an average Pt particle size of 2.4 ± 0.7 nm in the case of Pt/CNTs prepared in the presence of citrate and of 3.8 ± 1.1 nm for Pt/CNTs prepared in microemulsion. The values of specific activity (SA) and other kinetic parameters were determined from the Tafel plots taking into account the real electroactive area of each electrode. The electrodes exhibited a relatively high electrocatalytic activity for the four-electron oxygen reduction reaction to water.
[en] Magnesium alloy, although valuable, is reactive and requires protection before it can be applied in many fields. In this study, a novel protective environmental-friendly gradient coating was performed on AZ91D magnesium alloy by non-chromate surface treatments, which consisted of phytic acid chemical conversion coating and the sol-gel-based CeO2 thin film. The surface morphologies, microstructure and composition of the coatings were investigated by scanning electron microscopy (SEM), energy disperse spectroscopy (EDS) and X-ray diffraction (XRD), respectively. The corrosion resistance of the coatings was evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in 3.5 wt.% NaCl solution. The effects of the concentration, layers, temperature of heat treatment of CeO2 sol on the anti-corrosion properties of the gradient coating for magnesium were also investigated. The results showed that the gradient coating was mainly composed of crystalline CeO2. According to the results of electrochemical tests, the corrosion resistance of AZ91D magnesium alloy was found to be greatly improved by means of this new environmental-friendly surface treatment.