Synthesis of MoSe2/Reduced graphene oxide composites with improved tribological properties for oil‐based additives

In this work, we developed a facile and effective hydrothermal method synthesis of MoSe₂ nanoflowers on reduced graphene oxide (RGO) sheets. The as‐prepared MoSe₂/reduced graphene oxide (MoSe₂/RGO) composites are characterized by X‐ray diffractometer (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicated that MoSe₂ nanoflowers were successfully deposited on RGO nanosheets to form a well interconnected hybrid structure. The tribological properties of MoSe₂/RGO composites as lubricating oil additive were investigated by a UMT‐2 ball‐on‐plate friction and wear tester. By the addition of MoSe₂/RGO composites in paraffin oil, the antiwear ability was improved and the friction coefficient was decreased. The based oil with MoSe₂/RGO composites showed better tribological properties than the oil with MoSe₂ and pure oil. The good friction and wear properties of MoSe₂/RGO composites as additives were attributed to the formation of a thin physical tribofilm on the substrate.     

Hydrothermal synthesis of MoO3 nanobelt‐graphene composites

A composite of graphene sheets decorated with molybdenum trioxide (MoO₃) nanobelts has been fabricated via a facile and efficient hydrothermal route in the presence of NaCl. The structure, morphology of these promising composites were investigated by means of field‐emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), Raman spectroscopy and thermogravimetric (TG) analysis. FESEM and TEM studies suggest the presence of uniform crystalline MoO₃ nanobelts and graphene sheets in as‐prepared hybrid materials. XRD and Raman results confirm the reduction of graphite oxide (GO) sheets to graphene sheets accompanying by the formation of MoO₃ nanobelts. Moreover, thermal properties of GO and MoO₃ nanobelt‐graphene composites reveal that thermal stability of the obtained MoO₃ nanobelt‐graphene composites is obviously higher than that of GO due to the transformation of GO sheets to highly stable graphene sheets in the hybrids. This work could provide new insights into the fabrication of high quality MoO₃‐graphene hybrid nanomaterials and facilitate their potential applications in different fields. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Mixed metal oxide nanocomposites derived from layered double hydroxides as photocatalysts for C.I. Basic Blue 3 degradation under UV light

In this research we report synthesis of the heterostructure Mg‐Al‐Zn mixed metal oxide (ZnO/MMO) nanocomposite photocatalysts derived from Zn(OH)₂/Mg‐Al‐layered double hydroxides (ZLDHs) precursors. The obtained samples were characterized by the X‐ray diffraction (XRD), FT‐IR, BET surface area, ICP and TG/DTG methods. The chemical compositions and morphology of the synthesized materials were investigated by the energy dispersive X‐ray analysis (EDX) and the transmission electron microscopy (TEM). The results reveal that at the reaction time 96 h, ZLDH has the highest crystalinity which was confirmed by the X‐ray diffraction spectra. The calcined samples at 500, 600 and 700 °C for 4 h show that the crystallinity of the nanocomposite improves with the increase of calcination temperature. The photocatalytic activities of synthesized nanocomposites were compared for the degradation of C. I. Basic Blue 3 (BB3) dye under UV illumination in aqueous solution. Among the synthesized nanocomposites, ZnO/MMO calcined at 700 °C shows the highest efficiency towards the removal of dye. The effect of UV illumination on the stability of ZnO in ZnO/MMO nanocomposite and pure ZnO was also investigated. The results showed that the photostability of ZnO in ZnO/MMO nanocomposite is increased compared to the pure ZnO.     

Synthesis of nanoflakes‐based self‐assembling crossed structure of stannous oxide and photocatalysis property

Self‐assembling nanoflakes‐based crossed architectures of stannous oxide (SnO) were successfully synthesized via template‐free hydrothermal growth method by using SnCl₂·2H₂O and KOH as precursors. Crystal structures, morphology, chemical composition and optical properties were examined by X‐ray diffraction (XRD), field‐emission scanning electron microscopy (FESEM), energy dispersive X‐ray analysis, and Raman spectroscopy, respectively. The results indicate that the as‐synthesized product belongs to tetragonal phase SnO with crossed morphology self‐assembled by nanoflakes. Furthermore, UV‐vis spectrophotometry was used to determine optical band gap of the SnO nanostructures and the direct band gap of 2.90 eV was obtained. The photocatalysis of the product has been evaluated with methyl orange and the high degradation ratio of 87% is obtained in 240 minutes under the measuring condition which is attributed to the wide band gap and large specific surface area of the nanoflakes‐based crossed SnO architectures. A possible growth mechanism is proposed in the end.     

Synthesis and characterization of semiconductor metal sulfide nanocrystals using microemulsion technique

The semiconductor nanocrystals ZnS, PbS, CdS and CuS were synthesized via microemulsion technique involving metal acetate, reducing agent (Na₂S) and Triton X‐100 as surfactant. Nanocrystals were characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM) and dynamic light scattering (DLS). The average size of ZnS, PbS, CdS and CuS nanocrystals were found to be 5.6 nm, 13.3 nm, 11.4 nm and 6.2 nm, respectively. Different parameters like surfactant (Triton X‐100) concentration, water‐to‐surfactant ratio (ω), precursor concentration [zinc acetate, (Zn(AC)₂], reducing agent concentration [sodium sulphide, (Na₂S)] were optimized to synthesize ZnS quantum dots.     

Electrospinning synthesis and photocatalytic property of CaFe2O4/MgFe2O4 heterostructure for degradation of tetracycline

CaFe₂O₄/MgFe₂O₄ nanowires with heterostructure had been successfully synthesized by electrospinning method. The obtained samples were systematically characterized by scanning electron microscopy (SEM), X‐Ray diffraction (XRD), UV–Vis diffuse reflectance spectra (UV‐Vis DR) and Environment scanning electron microscopy (ESEM). The novel CaFe₂O₄/MgFe₂O₄ nanowires exhibit an enhanced photocatalytic activity for degrading of tetracycline (TC) under visible light. Compared with bare CaFe₂O₄ or MgFe₂O₄ samples, the prepared CaFe₂O₄/MgFe₂O₄ (Ca:Mg:Fe = 3:2:10) composited nanowires show the best photocatalytic performance with a degradation efficiency of 40% after 150 min reaction time. This enhancement is attributed to the heterostructure of CaFe₂O₄/MgFe₂O₄ nanowires, which effectively repress the recombination of photo‐generated electrons and holes. Based on heterostructure and energy band positions, the enhancement of mechanism under visible‐light enhances the photocatalytic activity.     

One‐step green synthesis by organic molten salt method and optical properties of CdS nanosheets

Cadmium sulfide (CdS) nanosheets were synthesized by an environment friendly, “green” organic molten salt (OMS) method at 220 °C. The as‐synthesized products were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS), respectively. The XRD results reveal that the as‐synthesized CdS nanosheets are of the hexagonal wurtzite structure and the CdS nanosheets grow along the c‐axis. The SEM results indicate that the diameters and thickness of the CdS nanosheets are about 20–40 nm and 5–10 nm, respectively. The optical properties of the CdS nanosheets were investigated by ultraviolet–visible (UV‐Vis) spectroscopy and photoluminescence (PL) spectroscopy. The ultraviolet–visible spectrum exhibits two excitonic peaks with a step‐like absorption and the photoluminescence spectrum shows a green emission peak centered at around 524 nm. A possible growth mechanism of CdS nanosheets was discussed.     

α‐Fe2O3 nanospindles loaded with ZnO nanocrystals: Synthesis and improved gas sensing performance

ZnO/α‐Fe₂O₃ nanocomposites were fabricated through a two‐step hydrothermal method. The morphology and composition of the as‐synthesized products were characterized by X‐ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), energy‐dispersive X‐ray spectroscopy (EDS), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). The gas sensing properties of the fabricated products were investigated towards ethanol, acetone, propanol, isopropanol, formaldehyde, chloroform and so on. The results demonstrated that the ZnO/α‐Fe₂O₃ nanocomposites exhibited excellent sensing properties and showed remarkably higher sensing responses and much lower optimum operating temperature compared to individual ZnO and α‐Fe₂O₃. In addition, the ZnO/α‐Fe₂O₃ nanocomposites have some selectivity for ethanol, propanol and isopropanol. The possible gas sensing mechanism was also proposed. Our studies demonstrate that our fabricated materials could be widely used in the future.     

Highly efficient photocatalytic degradation of methyl orange and Rhodamine B by hierarchical BiOBr microspheres

Hierarchical BiOBr microspheres were successfully synthesized via a solvothermal method by using the diethylene glycol(DEG) as the solvent and soft‐template. The as‐obtained products were characterized by X‐ray powder diffraction (XRD), scanning electron microscopy (SEM), selected area electron diffraction (SAED), high resolution transmission electron microscopy (HRTEM), N₂ adsorption–desorption and UV–Vis diffuse reflectance spectroscopy(DRS) techniques. The formation mechanism for the growth of hierarchical BiOBr microspheres has been studied. The possible mechanism of photocatalysis has been discussed. Remarkably, the as‐prepared BiOBr microspheres has a large specific surface area, which can reach a maximum surface area of 55.9307 m²/g. In addition, the superior enhanced photocatalytic activities of BiOBr microspheres were evaluated by the photodegradation of methyl orange (MO) and Rhodamine B (RhB) under visible‐light illumination, which presented the efficiency up to 98.10% just within 50 min and 98.64% within 30 min, respectively. BiOBr microspheres can be a promising candidate as highly efficient photocatalyst for decompositing of organic contaminants for environmental remediation.     

Synthesis and characterization of inorganic‐organic ZnS(aminopropane)n composite materials

The main goal of our work was the synthesis and characterization of ZnS(aminopropane)_n hybrid inorganic‐organic layered materials. The basic material of our investigation was ZnS(1,3‐dap)_1/2, (where dap denotes diaminopropane). Its crystal structure has been solved by X‐ray powder diffraction methods. This layered compound was prepared using 1,3‐diaminepropane, zinc sulphate (ZnSO₄) and tioacetamide (CH₃CSNH₂). We have also tried to obtain and characterize other materials: ZnS(1‐ap) and ZnS(1,2‐dap), where ap denotes aminopropane. But in these last two cases diffraction patterns were of much poorer quality, which prevented a full structural survey; thus we cannot directly prove that hybrid lamellar materials were obtained. All compounds were studied using X‐ray diffraction, chemical analysis, UV‐vis spectroscopy and scanning electron microscopy. Additionally, using X‐ray diffraction as a function of temperature, we obtained information about structural changes of obtained composite materials under temperature treatment. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Elliptic NdCrO3 microplate by a simple one‐step hydrothermal synthesis route and its characterization and magnetic properties

Elliptic NdCrO₃ microplates were synthesized by a simple and facile one‐step hydrothermal method of processing temperature 280 °C for 3 days. The products prepared in this paper have been characterized by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), X‐ray fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR) and field‐emission scanning electron microscopy (FESEM). The magnetic properties of the final sample are also studied. The XRD pattern indicates the pure orthorhombic phase for NdCrO₃ particles, the XPS, XRF and FTIR results further demonstrate the composition and purity of the final product. A possible growth mechanism for elliptic NdCrO₃ microplates is proposed. Through the investigation of magnetic properties, it can be generally concluded that the orthorhombic elliptic NdCrO₃ microplates exhibit typical behaviors of magnetic transition, spin reorientation transition and magnetic exchange bias. The Néel temperature is 218 K and the spin reorientation transition temperature is 46 K. The hysteresis loop under 5 K shows that the value of exchange bias field (H_ex) is 12 Oe and the shift of remanent magnetization (ΔM) is 0.008 emu/g, respectively.     

Synthesis of rhombohedral strontium carbonate aggregates at the water/hexamethylene interface with cetyltrimethylammonium bromide

Unusual rhombohedral strontium carbonate (SrCO₃) aggregates have been synthesized in situ from strontium nitrate by the slow release of carbon dioxide by alkaline hydrolysis of diethyl carbonate at the water/hexamethylene interface in the presence of cetyltrimethylammonium bromide (CTAB). Transmission electron microscopy, Fourier transform infrared spectroscopy and X‐ray powder diffractometry were used to characterize the products. The results indicate that rhombohedral SrCO₃ aggregates are obtained with weaker crystallinity and sizes of several micrometers. The possible formation mechanism of the SrCO₃ aggregates at the interface is discussed, which can be interpreted by particle‐aggregation based non‐classical crystallization laws. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of citric acid and starch as emulsifier on phase formation and crystallite size of lanthanum oxide nanoparticles

Lanthanum oxide nanoparticles were synthesized via thermal decomposition method of the lanthanum nitrate in the presence of citric acid or starch as emulsifier. The effects of emulsifier and calcination temperature were investigated on the phase transformation and particle size distribution of the products. La₂O₃ nanoparticles were synthesized by drying lanthanum precursor and emulsifier solution, followed by calcination process at 600 and 900°C, respectively. Products were characterized by Fourier Transform Infrared (FT‐IR) spectroscopy, X‐ray diffraction (XRD), thermal analysis (TG/DTA) and nitrogen adsorption method (porous characteristics). The morphology of the samples analyzed using scanning electron microscopy (SEM). Average crystallite size of the products was calculated by XRD data and average particle size was measured from the TEM micrographs. Lanthanum dioxycarbonate in different forms of the tetragonal and monoclinic is crystallized in the presence of citric acid and starch during the calcination at 600°C, respectively. The hexagonal structure, however, is detected as the only crystalline phase formed by calcination at 900°C.     

Magnetic properties and X‐ray photoelectron spectroscopy of nanocrystalline Ho3Al5O12

Nanocrystalline holmium aluminium garnet (Ho₃Al₅O₁₂) has been prepared for the first time by modified Pechini's reaction after sintering the precursor gel at 1223 K. The nanomaterial has been characterized by X‐ray diffraction (XRD), selected area electron diffraction (SAED) and high resolution transmission electron microscopy (HRTEM). The XRD pattern confirms the formation of single‐phase Ho₃Al₅O₁₂; the average size of the nanoparticles has also been determined. X‐ray photoelectron spectroscopy (XPS) has been used to study the chemical composition and bonding in the as‐prepared samples. The binding energies of core‐level electrons in Ho, Al and O in the title material have been found slightly shifted compared to the values of the respective elements. DC magnetic susceptibility has been measured in the temperature range 2 – 260 K. Low effective magnetic moment of Ho³⁺, μ_eff = 1.35 µ_B and Weiss constant have been derived from the inverse magnetic susceptibility–temperature linear plot. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Zr‐doped CeO2 Hollow slightly‐truncated nano‐octahedrons: One‐pot synthesis,characterization and their application in catalysis of CO oxidation

Zirconium‐doped ceria hollow slightly‐truncated nano‐octahedrons (HTNOs) (Ce_1‐xZr_xO₂) were synthesized by a one‐pot, facile hydrothermal method. The morphology and crystalline structure were characterized with powder X‐ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and the high resolution transmission electron microscopy (HRTEM). The composition and chemical valence on the surface of the as‐prepared Ce_1‐xZr_xO₂ powders were detected by X‐ray photoelectron spectroscopy (XPS) and energy dispersive spectrometry (EDS). The surface area and pore size distribution of as‐obtained Zr‐doped ceria HTNOs were measured by N₂ adsorption‐desorption measurement. Mechanisms for the growth of Zr‐doped ceria HTNOs are proposed as both oriented attachment and Ostwald ripening process and the formation of the hollow structure is strongly dependent on the addition of Zr⁴⁺ ions. Furthermore, the as‐obtained Zr‐doped ceria HTNOs revealed superior catalytic activity and thermal stability toward CO oxidation compared to pure ceria. It may provide a new path for the fabrication of inorganic hollow structures on introducing alien metal ions.     

Vanadium pentoxide nanobelts: One pot synthesis and its lithium storage behavior

In this paper, we report a synthesis, characterization and electrochemical properties of V₂O₅ nanobelts. V₂O₅ nanobelts have been prepared via hydrothermal treatment of commercial V₂O₅ in acidic (HCl/H₂SO₄) medium at relatively low temperature (160 °C). The hydrothermally derived products have been characterized by powder X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), Raman spectroscopy, X‐ray photo electron spectroscopy (XPS), UV‐Vis spectroscopy, Scanning/Transmission electron microscopy (SEM/TEM). XRD pattern of V₂O₅ nanobelts show an orthorhombic phase. From the FTIR spectrum, the peak observed at 1018 cm⁻¹ is characteristic of the stretching vibration mode of the terminal vanadyl, V = O. The UV‐Vis absorption spectrum of V₂O₅ nanobelts show maximum absorbance at 430 nm, which was blue‐shifted compared to that of bulk V₂O₅. TEM micrographs reveal that the products consist of nanobelts of 40‐200 nm in thickness and several tens of micrometers in length. The electrochemical analysis shows an initial discharge capacity of 360 mAh g⁻¹ and its almost stabilized capacity is reached to 250 mAh g⁻¹ after 55 cycles. A probable reaction mechanism for the formation of orthorhombic V₂O₅ nanobelts is proposed.     

Room‐temperature synthesis and characterization of cross‐like Pr2(C2O4)3·10H2O micro‐particles

Cross‐like Pr₂(C₂O₄)₃·10H₂O micro‐particles were synthesized through a simple precipitation method at room temperature. The products were characterized by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), field‐emission scanning electron microscopy (FESEM), thermogravimetry–differential thermal analysis (TG‐DTA) and photoluminescence (PL). The possible formation mechanism of the cross‐like Pr₂(C₂O₄)₃·10H₂O micro‐particles was discussed, and Pr₆O₁₁ with similar morphology was obtained by calcining the oxalate precursor. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Nanosized barium carbonate particles stabilized by cetyltrimethylammonium bromide at the water/hexamethylene interface

Nanoparticles of barium carbonate (BaCO₃) have been synthesized in situ from barium chloride by the slow release of carbon dioxide by alkaline hydrolysis of diethyl carbonate, and stabilized by cetyltrimethylammonium bromide (CTAB) at the water/hexamethylene interface. Transmission electron microscopy, Fourier transform infrared spectroscopy and X‐ray powder diffractometry were used to characterize the products. The results indicate that spherical BaCO₃ nanoparticles are obtained with poor crystallinity and diameters ranging from 30 to 300 nm. The possible formation mechanism of the nanoparticles at the interface is discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and properties of α‐Fe2O3 nanorods

We report synthesis of α‐Fe₂O₃ (hematite) nanorods by reverse micelles method using cetyltrimethyl ammonium bromide (CTAB) as surfactant and calcined at 300 °C. The calcined α‐Fe₂O₃ nanorods were characterized by X‐ray diffraction (XRD), high‐resolution scanning electron microscopy (HRSEM), transmission electron microscopy (TEM), energy dispersive spectrometer (EDS), fourier transform infrared spectroscopy (FTIR) and vibrating sample magnetometer (VSM). The result showed that the α‐Fe₂O₃ nanorods were hexagonal structure. The nanorods have diameter of 30‐50 nm and length of 120‐150 nm. The weak ferromagnetic behavior was observed with saturation magnetization = 0.6 emu/g, coercive force = 25 Oe and remanant magnetization = 0.03 emu/g. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Self‐template hydrothermal synthesis ZnS microspheres

Zinc sulfide (ZnS) microspheres were synthesized by a self‐template hydrothermal route using thiourea as sulphur source. The formation of these hollow spheres was mainly attributed to the oriented aggregation of ZnS nanocystals around the gas‐liquid interface between gas (H₂S, NH₃, or CO₂) and water followed by an Ostwald ripening process. The gas bubbles of H₂S, NH₃, or CO₂ produced during the reaction might play a soft‐template to form ZnS hollow microspheres. The products were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), electron diffraction (ED), and photoluminescence (PL). The crystal structure of prepared ZnS microspheres is hexagonal phase polycrystalline. The average microspheres diameter is 1.5 ‐ 6 µm. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)