Highly dispersible and uniform size Cu2ZnSnS4 nanoparticles for photocatalytic application

Highly dispersible, uniform size (～7 nm) single-phase Cu₂ZnSnS₄ nanoparticles have been synthesized by hydrothermal method using non-toxic surfactant (oleic acid). High resolution transmission electron microscopy image indicates good crystallinity of the Cu₂ZnSnS₄ nanoparticles with the growth along (1 1 2) plane. X-ray photoelectron spectroscopy analyses suggested that the formation of with Cu, Zn, and Sn in +1, +2 and +4 oxidation states. The optical absorption spectrum of Cu₂ZnSnS₄ nanoparticles exhibits an absorption in the visible region and its optical band gap was found to be ～1.72 eV, which could be much more appropriate for photocatalytic application under visible light irradiation. These Cu₂ZnSnS₄ nanoparticles have been shown high photocatalytic degradation activity of methylene blue (MB) dye in the presence of visible light irradiation. The rate constant (k) value of Cu₂ZnSnS₄ nanoparticles is found to be 0.0144 min^?1. We have discussed the mechanism of dye degradation process that drives the photocatalytic degradation process. The reusability of the Cu₂ZnSnS₄ nanoparticles for the dye degradation is also demonstrated.     

Synthesis of dispersed PrBaCo0.9Cu0.1O5+δ cathode nanopowders with layered perovskite structure for intermediate temperature solid oxide fuel cells

PrBaCo_1.9Cu_0.1O_5+δ (PBCCO) nanopowders were synthesized by an EDTA-citrate complexing process using water and ethanol as solvents, and their structures and electrochemical properties were characterized. PBCCO precursor gels were highly oxidized at 450 °C, using either water (PBCCO-W) or ethanol (PBCCO-E) as the solvent. PBCCO powders calcined at 450 °C had a second phase, while those calcined at 850 °C for 4 h were obtained as single phase PBCCO with a layered perovskite structure in the P4mm space group. PBCCO-E primary particles were approximately 5–10 nm in size and were well-dispersed compared with those of the PBCCO-W powder. We hypothesized that the enhanced dispersibility of the PBCCO-E powder was caused by a decrease in bridging hydrogen bonds on the chelate surface, which prevents chelate agglomeration in sol state. It causes the larger specific surface area of PBCCO-E powders and thus a lower polarization resistance (R_p) than that of PBCCO-W powders at the measured temperature. The R_p value of PBCCO-E powder was 0.041 Ω cm² at 750 °C, which is about 1.5 times lower than that of PBCCO-W at the same temperature.     

Chemical synthesis of Cu2Se nanoparticles at room temperature

A simple and rapid method has been developed to synthesize cuprous selenide (Cu₂Se) nanoparticles by the reaction of selenium nanoparticles sol with copper sulfate solution containing ascorbic acid at room temperature. Cu₂Se nanoparticles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy dispersive X-ray analysis (EDX). The results indicated that Cu₂Se nanoparticles were cubic crystal structure and spherical with the diameter about 75 nm. The ultraviolet–visible absorption spectrum (UV–vis) and cyclic voltammetry of Cu₂Se nanoparticles were also investigated. The optical band gap energy of Cu₂Se nanoparticles was 1.94 eV. On the basis of a series of experiments and characterizations, the formation mechanism of Cu₂Se nanoparticles was discussed.     

Water driven enhanced photoluminescence of Ln (=Dy3+, Sm3+) doped LaVO4 nanoparticles and effect of Ba2+ co-doping

Well-dispersed Dy³⁺ and Sm³⁺ doped LaVO₄ nanoparticles have been synthesized at a relatively low temperature of 140 °C in ethylene glycol (EG), water, N,N′-dimethyl formamide (DMF) and mixed solvents. The samples prepared in water show mixed tetragonal and monoclinic phase where tetragonal planes are found to be dominated over the monoclinic planes. However, the samples prepared in EG and DMF show monoclinic phase. Due to the phase transformation of the samples prepared in water the luminescence intensity of these samples is highly enhanced than that of the samples prepared in EG and DMF. The mixed phase of the samples prepared in water transformed to pure monoclinic phase when heated at 900 °C. The luminescence intensity of Dy³⁺ and Sm³⁺ doped LaVO₄ prepared in EG are also enhanced when large divalent Ba²⁺ ions is used as co-activator. The optimum concentration for Ba²⁺ ions was found to be 1 at.% in both Dy³⁺ and Sm³⁺ doped systems. The prepared nanoparticles are subsequently dispersed in methanol and incorporated in polymer films of PVA which showed the characteristic emissions of Dy³⁺ and Sm³⁺ when irradiated under UV light.     

Preparation of w–cu nano-composite powders with high copper content using a chemical co-deposition technique

A novel chemical co-precipitation was used to produce W-70%Cu nanocomposite powders with coating structure. The precursors consisting of CuC₂O₄·xH₂O and WO₃·2H₂O were first synthesized using copper nitrate, ammonium metatungstate(AMT) and oxalic acid as the raw materials at 80?°C for 1.5?h when the concentrations of the reactants were 0.8?mol/L and the hydrogen ion concentration was 1.2?mol/L. The precursors were calcined to produce the powders with different phase components and microstructure at various temperatures. The CuWO₄ and CuO nano-powders were obtained at 300?°C, which is colder than the traditional reaction temperature (1000?°C) of CuO?+?WO₃ = CuWO₄. However, the cubic Cu₂O and Cu₂WO₄ could be formed when the calcining temperature was 600?°C. The hydrogen reduction results show that the calcined powder is reduced to obtain W-Cu composite powder at 750?°C and 800?°C. In reduction process, volatile WO₂(OH)₂ through chemical vapor transport(CVT) continuously spreads to the copper surface and is reduced to form W and the coated particle is eventually formed. This particle is Cu particle coated by W phase and the interface between W and Cu phases is semi-coherent. It is found that the average particle size of the reduced powder is 30–50?nm observed by TEM images.     

Synthesis and characterization of novel magnetically separable NiFe2O4@AlMCM-41-Cu2O core-shell and its performance in removal of dye

The synthesis of magnetic NiFe₂O₄@AlMCM-41-Cu₂O core-shell as a new class of visible light driven photocatalyst was suggested. The magnetic NiFe₂O₄ core was prepared by solvothermal method. The intermediate AlMCM-41 shell was prepared by the method of liquid crystal templating mechanism and subsequently cuprous oxide (Cu₂O) nanoparticles (NPs) were synthesized in NiFe₂O₄@AlMCM-41core-shell via colloidal chemistry approach. The properties of prepared magnetic core-shell were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), nitrogen adsorption–desorption measurement and vibration sample magnetometer (VSM). Based on EDX results, the weight percentage (wt%) of NiFe₂O₄ core, MCM-41 shell and Cu₂O NPs were calculated to be 68.89, 30.55 and 0.56%, respectively. It consisted of mesoporous structure with a surface area of 687.00 m² g^?1, an average pore size of 2.95 nm and possessed excellent magnetic properties of 4.74 emu g^?1. The TEM results indicated that the NiFe₂O₄ as core were regular spheres with diameter of 68 nm, and the average thickness of AlMCM-41 shells was ～35 nm. The particles size of Cu₂O incorporated in core-shell was less than 5 nm. The photocatalytic activity was evaluated under visible light irradiation using the removal of methylene blue (MB) dye as a model reaction. The removal rate of MB achieved up to 90% after 60 min under visible light irradiation, and the NiFe₂O₄@AlMCM-41-Cu₂O can be recycled and reused.     

Synthesis and magnetic properties of shuriken-like nickel nanoparticles

Shuriken-like nickel nanoparticles were successfully synthesized by a thermal decomposition method at 200 °C with Nickel(II) acetylacetonate (Ni(acac)₂) as the precursor and oleylamine (OAm) as the solvent and reductant, respectively. The phase structures, morphologies and sizes, and magnetic properties of the as-synthesized nickel products were characterized in detail by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission-scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and vibrating sample magnetometer (VSM). Some key reaction parameters, such as the reaction time, reaction temperature and surfactants, have important influence on the morphology of the final products. XRD pattern indicated that the products are well-crystallized face-centered cubic (fcc) nickel phase. SEM images demonstrated that the nickel nanoparticles are shuriken-like morphology with average size around 150 nm. The mechanism of shuriken-like Ni nanoparticles (NPs) is proposed. The magnetic hysteresis loops of shuriken-like and spherical nickel products illustrated the ferromagnetic nature at 300 K, indicating its potential applications in magnetic storage.     

Fabrication and characterization of Ag/calcium silicate core-shell nanocomposites

The Ag/calcium silicate nanocomposite with core-shell nanostructure has been successfully synthesized using Ag solution, Ca(NO₃)₂·4H₂O and Na₂SiO₃·9H₂O in ethanol/water mixed solvents at room temperature for 48 h. Ag solution was previously prepared by microwave-assisted method in ethylene glycol (EG) at 150 °C for 10 min. The nanocomposites consisted of Ag core and an amorphous calcium silicate shell. The XRD and EDS results confirmed that the product was the Ag/calcium silicate nanocomposite. The TEM micrographs indicated that the Ag/calcium silicate nanocomposite was core-shell nanoparticles. The effects of Ca(NO₃)₂·4H₂O and Na₂SiO₃·9H₂O concentration on the shells of Ag/calcium silicate nanocomposite were investigated. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and energy-dispersive X-ray spectra (EDS). This method is simple, fast and may be extended to the synthesis of the other kinds of core-shell nanocomposites.     

Co2(OH)3Cl nanoparticles as new-type electrode material with high electrochemical performance for application in supercapacitor

In this work, we report the preparation of Co₂(OH)₃Cl nanoparticles with average size of ～20 nm and well-defined cubic shape at room temperature by an epoxide precipitation route. It was found that the as-prepared Co₂(OH)₃Cl nanoparticles could be used as a promising new electrode material for application in redox supercapacitors due to its high electrochemical performance. It presented superior specific capacitance of 783 F g^?1 at low current density of 2.8 A g^?1, while it had a high value of 604 F g^?1 at high current density of 56.6 A g^?1, proving its excellent high rate performance. Its 75% capacitance retention after 10,000 cycles of charge–discharge demonstrated its long-life span. According to characterization results, the possible mechanism for the electrochemical process that Co₂(OH)₃Cl nanoparticles underwent was proposed as a process of Co₂(OH)₃Cl → β-Co(OH)₂ → CoOOH ? Co₃O₄.     

Synthesis and characterization of CuInSe2 nanoparticles via a solution method

Pure CuInSe₂ nanoparticles have been successfully synthesized via a solution method in the solvent of oleylamine. Anhydrous InCl₃, CuCl, and Se powder were used as the starting materials. The CuInSe₂ samples were characterized by XRD, TEM, and XPS techniques. It was found that tetragonal chalcopyrite structured CuInSe₂ nanoparticles were obtained with temperature above 230 °C. Sample prepared at 200 °C possesses triangular morphology and a minute amount of In₂Se₃ coexists as intermediate. CuInSe₂ nanoparticles with size of 20.2 ± 0.4 nm were prepared at 230 °C and the narrow size distribution was ascribed to the employment of hot injection, which was better for homogeneous nucleation. Stable “ink” can be formed when the as-synthesized CuInSe₂ nanoparticles were dispersed in organic solvents such as hexane and tolune, and such “ink” might have a practical application in CuInSe₂-based solar cells.     

Magnetic separation and adsorptive performance for methylene blue of mesoporous NiFe2O4/SBA-15 nanocomposites

Magnetic NiFe₂O₄/SBA-15 nanocomposites were synthesized by a facile impregnation method, and NiFe₂O₄ nanoparticles presented spinel phase structure and existed in the mesopores of SBA-15. Partial mesopores were blocked by NiFe₂O₄ nanoparticles and micropores formed, which the capillarity of micropores played a decisive role for methylene blue (MB) adsorption. The saturation magnetization increased from 2.34 emu g^?1 to 10.03 emu g^?1 with the NiFe₂O₄ content, while the specific surface area decreased from 552.18 m² g^?1 to 260.40 m² g^?1 and pore volume decreased from 1.13 cm³ g^?1 to 0.49 cm³ g^?1. MB adsorption could be improved by optimizing the NiFe₂O₄ content of the nanocomposites. MB could be adsorbed completely in 60 min with the optimum nanocomposites and could be separated easily from water by magnetic separation technique.     

Basic zinc carbonate as a precursor in the solvothermal synthesis of nano-zinc oxide

ZnO nanoparticles were synthesized solvothermally in various diols (ethylene glycol, di(ethylene glycol), tetra(ethylene glycol), 1,2-propanediol, 1,4-butanediol), using basic zinc carbonate (2ZnCO₃·3Zn(OH)₂) as a precursor for the first time. Since ZnCO₃ was sparingly soluble in diols the transformation reaction proceeded at a low reaction rate. Ethylene glycol was found as the most suitable medium among five diols studied yielding the smallest ZnO particles (~ 55 nm) and short reaction time, t_r (2 h). Diols with shorter chain length produced smaller ZnO particles. p-Toluene sulfonic acid (p-TSA) acted as a catalyst and reduced t_r from 8 h to 2 h in concentration of 0.02 M. Optimum reaction conditions for the synthesis in ethylene glycol were 185 °C and 2 h. At higher p-TSA concentrations (0.04–0.08 M) the size of ZnO particles was reduced from 500–800 nm to 50–100 nm and crystallite size to 25–30 nm. Benzene sulfonic acid (BSA) and inorganic bases (LiOH, NaOH, and KOH) also showed catalytic activities. Raman and photoluminescence spectroscopies revealed high concentration of defects on ZnO surface causing the emission of visible light and giving this type of ZnO higher potential in various (opto)-electronic application in comparison to Zn(II) acetate based ZnO.     

Pt/TiO2 composite nanoparticles synthesized by electron beam irradiation for preferential CO oxidation

This paper describes a novel synthesis method of stabilizer-free Pt/TiO₂ composite nanoparticles using electron beam irradiation. The chemical compositions were analyzed by inductively coupled plasma-atomic emission spectroscopy. The microstructures of the samples were observed by using transmission electron microscope. Pt nanoparticles with the sizes of 2–4 nm were deposited on TiO₂ without any use of stabilizers. The concentrations of Pt ions and 2-propanol notably affected the size and shape of Pt nanoparticles. Their reactions of preferential CO oxidation were measured in temperature region from 60 to 140 °C. The Pt/TiO₂ catalyst with spherical Pt nanoparticles exhibited a 67% of CO conversion rate and 100% of selectivity at a low temperature of 60 °C.     

Reaction mechanisms,resultant microstructures and tensile properties of Al-based composites fabricated in situ from Al-SiO2-Mg system

Reaction mechanisms, microstructures and tensile properties of the aluminum matrix composites made from Al-SiO₂-Mg system were investigated. When the temperature increased from room temperature to around 761 K, Mg dissolved into Al to form Mg-Al alloy. As the temperature increased to about 850 K, the remaining Mg reacted with SiO₂ to form MgO, Mg₂Si and Si as expressed in step reaction I: 6Mg + 2SiO₂ → 4MgO + Mg₂Si + Si. Finally, with a further increase in temperature, the remaining SiO₂ reacted with Al to produce Al₂O₃ and Si, while MgO reacted with Al₂O₃ to form MgAl₂O₄ as expressed in step reaction II: 4Al + 3SiO₂ + 2MgO → 2MgAl₂O₄ + 3Si. The Si also dissolved into matrix Al to form Al-Si alloy. Accordingly, its reaction process consisted of two steps and their apparent activation energies were 218 kJ/mol and 192 kJ/mol, respectively. As compared to the composites prepared by Al-SiO₂ system, its density increased from 2.4 to 2.6 g/cm³, and its tensile strength and elongation increased from 165 MPa and 3.95% to 187 MPa and 7.18%, respectively.     

Vitis vinifera peel polyphenols stabilized gold nanoparticles induce cytotoxicity and apoptotic cell death in A431 skin cancer cell lines

Gold nanoparticles (AuNPs) are considered beneficial in the field of biomedicine and in the development of therapeutic nanomedicine products. In the present study, Vitis vinifera. L (grapes) peel polyphenols were utilized as reducing and stabilizing agents for the biosynthesis of gold nanoparticles, and their cytotoxicity and apoptotic effects were assessed. The synthesized gold nanoparticles were characterized using UV-Visible spectroscopy, Transmission electron microscopy (TEM), X-ray diffraction (XRD), Particle size distribution, Fourier transform infrared spectroscopy (FTIR) and zeta potential analysis. TEM analysis confirmed that the nanoparticles were spherical with ～20–40 nm in size. Particle size distribution revealed ～50 ± 5 nm nanoparticles and FTIR confirmed the presence of polyphenols capped onto the peel gold nanoparticles. The V. vinifera peel gold nanoparticles were studied for their antiproliferative activities and induction of apoptosis at the inhibitory concentration (IC₅₀) of 23.6 µM. A431 cell lines incubated with V. vinifera peel gold nanoparticles for 24 h exhibited cytotoxicity activity mediated by increased reactive oxygen species (ROS) production, apoptotic morphological changes and loss of membrane potential significantly (p < 0.01). Thus, the cytotoxicity of the gold nanoparticles could be attributed to the synergistic effects of the phenolic moieties of the V. vinifera peels and the efficiency of the bioconjugated gold nanoparticles causing apoptosis and secondary necrosis.     

Physical and optical properties of HfO2 NPs – Synthesis and characterization in finding its feasibility in opto-electronic devices

HfO₂ nanoparticles (HfO₂ NPs) with different precursors (NaOH, H₂O, ethanol) were synthesized by a simple co-precipitation method. FTIR and EDX spectroscopy analysis shows the Stoichiometries composition of HfO₂ NPs. X-ray diffraction pattern analysis revealed that the as prepared and calcined HfO₂ NPs are respectively amorphous and polycrystalline nature. TEM analysis confirms that the morphology of the calcined HfO₂ NPs is spherical in shape with less agglomeration. The crystallite size was evaluated to be 51 nm, 37 nm and 30 nm respectively, for the precursors NaOH, H₂O and ethanol used for HfO₂ NPs. SEM analysis shows spherical, rock and sponge like surface morphology respectively, for the precursors NaOH, H₂O and ethanol used for HfO₂ NPs. UV–visible spectroscopy analysis revealed that the optical band gap energy of NaOH, H₂O and ethanol precursors used HfO₂ NPs were respectively 5.50 eV, 5.52 eV and 5.50 eV. The observed optical properties indicated the feasibility of utilizing these NPs as anti reflection layers in solar cells and for the construction of poultry farms to save energy. The estimated dielectric constant value indicated that these NPs could be used to prepare dielectric layers in thin film transistor.     

Sol-gel synthesis,structural and enhanced photocatalytic performance of Al doped ZnO nanoparticles

In this research ZnO and Zn_1?x Al_xO (x = 1, 3, 5, 7% mol) nanoparticles were synthesized by sol-gel method. The effect of Al concentration on the structure, morphology, absorption spectra and photocatalytic properties investigated by using X-ray, TEM, EDS and UV–Vis spectrophotometer approaches. Hexagonal, spherical and rod-like structure was achieved as the dominant structure for undoped nanoparticles, low and high concentrations of doped Al, respectively. Photocatalytic activity of nanoparticles was measured by degradation of methyl orange as a pollutant under radiation of ultraviolet (UV). The experimental test results indicate that the best photocatalytic performance is at of 5% of Al. Furthermore, the doped ZnO nanoparticles have more activity in visible area compared with undoped nanoparticles. The absorption amount in this area increases by raising the Al concentrations. Furthermore, the band gap of the particles decreases from 3.22 eV to 2.93 eV by increasing Al percentage.     

Low-cost chemical fabrication of Cu2ZnSnS4 microparticles and film

In this study, ball cactus-like kesterite Cu₂ZnSnS₄ microparticles were successfully and rapidly fabricated by chemical solution with microwave irradiation using ethylene glycol as a solvent. And then CZTS thin film was prepared by ink-print method. The samples were characterized by means of X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, energy dispersive spectrometer, scan electron microscopy, transmission electron microscopy, and UV–vis-NIR spectroscopy. The results showed that the as-prepared microparticles had single phase, stoichiometric composition, a ball cactus-like shape with a diameter about 300 nm and that CZTS thin film had large grains and high crystallinity.     

Doughnut-shaped hierarchical Cu2ZnSnS4 microparticles synthesized by cyclic microwave irradiation

For the first time, hierarchical doughnut-shaped Cu₂ZnSnS₄ (CZTS) microparticles were synthesized by microwave-assisted solution method. N,N-dimethylformamide and polyvinylpyrrolidone (PVP) were used as solvent and stabilizing agent respectively, and the results showed that PVP played an important role in the formation of hierarchical nanostructures. Structural analysis by X-ray diffraction and Raman studies confirmed the formation of single phase kesterite CZTS. Morphological analysis by scanning electron microscope showed doughnut-shaped CZTS microparticles composed of large number of interpenetrating nanoplates. Optical analysis by UV–Vis diffused reflectance spectra showed strong absorption in the visible region with an optical band gap of 1.54 eV. Asymmetric broad emission bands around 1.55 eV and 1.30 eV were observed in the photoluminescence spectrum. A possible formation mechanism for doughnut-shaped CZTS microparticles was put forward and discussed briefly.     

Synthesis and properties of magnetic multi-walled carbon nanotubes loaded with Fe4N nanoparticles

High saturation magnetization (>90 emu/g) multi-walled carbon nanotubes (MWCNTs) and Fe₄N nanoparticles composite were successfully synthesized by gas nitriding at 550 °C. Almost all Fe₄N nanoparticles were evenly distributed inside the carbon nanotubes and formed a special composite microstructure. This composite microstructure shows excellent soft magnetic property, structural stability, and chemical stability at room temperature. The investigations of electromagnetic and microwave absorption performances indicate that microwave absorbing capacity of low frequency band of MWCNTs were greatly improved by addition of Fe₄N nanoparticles.