Synthesis of carbon nitride powder by selective etching of TiC0.3N0.7 in chlorine-containing atmosphere at moderate temperature

We reported the synthesis of carbon nitride powder by extracting titanium from single inorganic precursor TiC_0.3N_0.7 in chlorine-containing atmosphere at ambient pressure and temperature not exceeding 500 °C. The TiC_0.3N_0.7 crystalline structure acted as a template, supplying active carbon and nitrogen atoms for carbon nitride when it was destroyed in chlorination. X-ray diffraction data showed that the obtained carbon nitride powders were amorphous, which was in good agreement with transmission electron microscope analysis. The composition and structure of carbon nitride powders were analyzed by employing Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. Results indicated that disorder structure was most likely for the carbon nitride powders and the N content depended greatly on the chlorination temperature. Thermal analysis in flowing N₂ indicated that the mass loss started from 300 °C and the complete decomposition occurred at around 650 °C, confirming the low thermal stability of the carbon nitride material.     

Sonochemical synthesis,characterization, and electrochemical properties of MnMoO4 nanorods for supercapacitor applications

In this article, we reported the preparation of manganese molybdate (MnMoO₄) nanorods by a facile sonochemical method and investigated its electrochemical properties for supercapacitor applications. The microstructure, surface morphology and composition were characterized by using field emission scanning electron microscope (FE-SEM), high resolution-transmission electron microscopy (HR-TEM), X-ray diffraction analysis (XRD), Raman spectroscopy and X-ray photo electron microscopy (XPS). The cyclic voltammetry (CV) curves of sonochemically synthesized α-MnMoO₄ nanorods revealed the presence of redox pairs suggesting the pseudocapacitive nature of MnMoO₄. A maximum specific capacitance of the α-MnMoO₄ nanorods was about 168.32 F g⁻¹ as observed from the galvanostatic charge–discharge (GCD) analysis at a constant current density of 0.5 mA cm⁻². Long term cyclic stability study revealed that about 96% of initial capacitance was retained after 2000 cycles.     

Enhanced performance of Al2O3 coated ZnO nanorods in CdS/CdSe quantum dot-sensitized solar cell

CdS/CdSe quantum dot-sensitized solar cells (QDSCs) based on ZnO nanorods, 4.55 μm in length, were studied. Many studies have shown that the performance of QDSCs is limited by a recombination process. Therefore, the interface layer was fabricated on the surface of the ZnO nanorods to retard recombination at the interface between the semiconductor and electrolyte. Overall, the performance of the QDSCs was improved by a surface coating of aluminum isopropoxide (Al₂O₃) on the ZnO nanorod, which facilitates a decrease in electron recombination and increased adsorption of CdS/CdSe QDs on the ZnO nanorods.     

Improved photodegradation activity of TiO2 via decoration with SnS2 nanoparticles

The particles of TiO₂ modified with various amounts of SnS₂ nanoparticles (TiO₂/SnS₂) were synthesized via the hydrothermal method by reacting SnCl₄·5H₂O with thioacetamide in 5% (vol.) acetic acid aqueous solution in the presence of TiO₂. The obtained products were characterized by using X-ray diffraction, X-ray photoelectron spectroscopy, UV–Vis diffuse reflection spectra, scanning and transmission electron microscopy. The photodegradation activities of TiO₂/SnS₂ composites have been investigated by using methyl orange as target in water under the light irradiation of 250–400, 360–600 and 400–600 nm. It was found that the photodegradation activity of TiO₂/SnS₂ composites depended on the mass ratio of SnS₂ and the wavelength of the irradiating light. The composites containing 33% SnS₂ exhibited the maximum activity under the light irradiation of 250–400 and 360–600 nm. However, the more SnS₂ in the composites, the higher activity appeared under the irradiation of 400–600 nm light. All the results reveal that the composites possess much better activity than the pristine TiO_2.     

NO2 gas sorption studies of Ge33Se67 films using quartz crystal microbalance

A study on the NO₂ gas sorption ability of amorphous Ge₃₃Se₆₇ coated quartz crystal microbalance (QCM) is presented. The thin films have been characterized before and after sorption/desorption processes of NO₂ by energy-dispersive X-ray spectroscopy (EDS), grazing angle X-ray diffraction (GAXRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and atom force microscopy (AFM) measurements. These studies indicated that physisorption occurs when NO₂ gas molecules are introduced into the chalcogenide film and the thin film composition or structure do not change. The mass loading due to NO₂ gas sorption was calculated by the resonator’s frequency shift. At the conditions of our experiment, up to 6.8 ng of the gas was sorbed into 200 nm thick Ge₃₃Se₆₇ film at 5000 ppm NO₂ concentration. It has been established that the process of gas molecules sorption is reversible.     

CuS:Ni flowerlike morphologies synthesized by the solvothermal route

CuS:Ni flowerlike morphologies composed of nanosheets were fabricated by the solvothermal route with polyvinyl pyrrolidon as surfactant and ethylene glycol as solvent. The as-prepared CuS:Ni morphologies were characterized by means of X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The size of CuS:Ni flowerlike morphologies was about 2 and 5 μm corresponding to the Ni doping concentration of 3.7 and 7.1 at.%, respectively. The thickness of the nanosheets changes with changing Ni doping. The magnetic properties of the CuS:Ni products have been investigated in detail.     

Preparation, magnetic and microwave absorption properties of La0.5Sr0.5MnO3/La(OH)3 composites

La_0.5Sr_0.5MnO₃/La(OH)₃ composites with different weight ratio of La_0.5Sr_0.5MnO₃ particles and La(OH)₃ nanowires have been prepared by tuning the reaction time under hydrothermal conditions. The structure, morphology and magnetic properties have been investigated. Additionally, by the measurements of the complex permittivity, permeability and microwave absorption properties in the frequency range of 1-12 GHz, the results shown that the weight ratio of La(OH)₃ nanowires has great influence on reflection loss. Excellent absorption property can be obtained when the ratio is 1.4%, which is attributed to the enhanced electromagnetic match as well as the proper dielectric loss and magnetic loss. The enhanced electromagnetic match is originated from the improved frequency dispersion of the complex permittivity and permeability due to the presence of dielectric La(OH)₃ nanowires.     

Photoactive Zn(II)Porphyrin–multi-walled carbon nanotubes nanohybrids through covalent β-linkages

Donor–acceptor nanohybrids by a covalent linkage between the β-position of a Zn(II)Porphyrin and multi-walled carbon nanotubes are reported for the first time, in a closer analogy to the natural light harvesting systems, which are based on β-substituted porphyrinoid structures, the chlorophylls. An unique and direct connection was established through the immobilization of the Zn(II)(β-NH₂-tetraphenylporphyrin), using diazonium chemistry, in order to afford i) a short and conjugated linkage between the two aromatic systems and ii) an amide bond resulting from a three-step functionalization synthesis. Electronic and steady-state fluorescence spectroscopies confirmed high photoinduced electron communication through the β-linkage when compared to analogous meso-phenyl linkers, stating its positive effect. The procedure involving the amide linkage allowed higher chromophore loadings; however, the direct conjugated bond showed improved photoinduced activity and a different emission pattern that can be associated with intense communication within the expanded π-system MWCNT–metalloporphyrin.     

Photochemical synthesis and characterization of Bi2S3 nanofibers

Bismuth sulfide (Bi₂S₃) nanofibers have been successfully prepared by a photochemical method from an aqueous solution of bismuth nitrate (Bi(NO₃)₃) and thioacetamide (TAA) in the presence of complexing agents of nitrilotriacetic acid (NTA) at room temperature. It was found that the irradiation time, the pH of the solution, and the species of complexing agents play important roles in the morphology control of the bismuth sulfate (Bi₂S₃) nanomaterials. The nanofibers were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), electron diffraction (ED), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectra (XPS), and UV-Visible absorption spectra (UV-Vis). Probable mechanisms for the photochemical formation of Bi₂S₃ nanofibers in aqueous solutions are proposed. The photochemical method is a convenient approach for controlling the shape for other metal sulfide semiconductor nanocrystals.     

In2O3 hollow spheres: One-step solvothermal synthesis and gas sensing properties

Hollow In₂O₃ spheres were prepared via a P123-assisted one-step solvothermal process for the first time. Ethanol medium played a key role in the direct cubic In₂O₃ phase formation whereas the triblock copolymer acted as a structure directing agent in the formation of the hollow spheres. The gas sensing properties of the as-prepared In₂O₃ hollow spheres were investigated. Compared to the products synthesized without P123, the In₂O₃ hollow spheres exhibited much faster response and higher sensitivity toward HCHO vapor.     

Thickness dependent transport and magnetotransport in CSD grown La0.7Pb0.3MnO3 manganite films

We report the effect of film thickness on transport and magnetotransport in La_0.7Pb_0.3MnO₃ (LPMO) manganite films grown on single crystalline LaAlO₃ substrate using chemical solution deposition (CSD) technique. AFM measurements show the island type grain growth responsible for the strain at the film-substrate interface, while structural studies using XRD shows the presence of thickness dependent compressive strain in the films which modifies the transport and magnetotransport in LPMO/LAO films. The observation of low temperature resistivity minima behavior in all the LPMO films has been explained in the context of electron-electron scattering mechanism. The ZFC-FC magnetization measurements show the glassy state behavior below T_min.     

Synthesis of sub-5 nm Co-doped SnO2 nanoparticles and their structural,microstructural, optical and photocatalytic properties

A swift chemical route to synthesize Co-doped SnO₂ nanopowders is described. Pure and highly stable Sn_1−xCo_xO_2−δ (0 ≤ x ≤ 0.15) crystalline nanoparticles were synthesized, with mean grain sizes <5 nm and the dopant element homogeneously distributed in the SnO₂ matrix. The UV–visible diffuse reflectance spectra of the Sn_1−xCo_xO_2−δ samples reveal red shifts, the optical bandgap energies decreasing with increasing Co concentration. The samples' Urbach energies were calculated and correlated with their bandgap energies. The photocatalytic activity of the Sn_1−xCo_xO_2−δ samples was investigated for the 4-hydroxylbenzoic acid (4-HBA) degradation process. A complete photodegradation of a 10 ppm 4-HBA solution was achieved using 0.02% (w/w) of Sn_0.95Co_0.05O_2−δ nanoparticles in 60 min of irradiation.     

Spin-dependent tunnelling in La0.7Sr0.3MnO3/SrTiO3 superlattices

La_0.7Sr_0.3MnO₃ is predicted to show half-metallic behaviour at low temperature, which gives rise to a metallic character for one spin direction and an insulating character for the other. This 100% polarisation of the conduction band should enhance the spin dependent tunnelling in manganite-based tunnel junctions. La_0.7Sr_0.3MnO₃/SrTiO₃ epitaxial superlattices were grown on LaAlO₃(001) substrates by metal–organic chemical vapour deposition (MOCVD). These multilayers consist of 15 epitaxial bilayers of La_0.7Sr_0.3MnO₃ and SrTiO₃. The junctions were patterned using UV lithography and Ar ion milling to carry out transport measurements in the current perpendicular-to-plane geometry (CPP). A temperature-independent non-linear I–V curve, which is characteristic of a tunnelling conduction mechanism, was observed below 50 K. At higher temperatures, the I–V curves are found to become linear and temperature-dependent. Up to 30 K, a constant tunnel magnetoresistance (TMR) (3%) is measured. The switching field is consistent with the film coercive field (a few 10s of mT). At higher temperatures, the TMR decreases rapidly. This temperature dependence is compared to the expected behaviour of a spin tunnel junction with half-metallic electrodes, with thermal activation or the loss of spin polarisation taken into account.     

Combustion synthesis of La0.7Sr0.3Co0.5Fe0.5O3 (LSCF) porous materials for application as cathode in IT-SOFC

La_0.7Sr_0.3Co_0.5Fe_0.5O₃ (LSCF) porous materials have attracted a substantial interest for application as cathode in solid oxide fuel cells of intermediate temperature (IT-SOFC). This work investigates the effect of different propellants (urea, glycine, citric acid and sucrose) in the preparation of LSCF powders by the combustion method and also the influence of the sintering temperature on the porosity and electrical conductivity. TGA profiles of the as-prepared samples showed a lower weight loss for the sample prepared with glycine, associated with the higher combustion temperature. XRD patterns presented characteristic reflections of LSFC perovskite and a small formation of secondary phases, with nanometric crystallite sizes (9-20 nm). SEM analysis revealed the loose and porous structure of the powder materials. Densification studies were carried within 950-1100 °C, showing that porosity decreased with increasing sintering temperature. Electrical conductivity was measured in the temperature range 300-800 °C and correlated with the sintering temperature.     

Photoconductivity in BiFeO3/La0.7Sr0.3MnO3 heterostructure

In this letter, an oxide heterostructure has been fabricated by successively growing La_0.7Sr_0.3MnO₃ (LSMO) and BiFeO₃ (BFO) layers on LaAlO₃ (100) by pulsed laser deposition. Analysis of the leakage current at different temperature demonstrated that the Poole-Frenkel dominated the leakage current mechanism. Additionally, the BiFeO₃/La_0.7Sr_0.3MnO₃ heterostructure exhibits a positive colossal magnetoresistance (MR) effect over a temperature range of 50-320 K. The maximum MR values are determined to be about 45.32% at H = 0.5 T and 28.34% at H = 0.3 T. At last, we report photoconductivity in BiFeO₃/La_0.7Sr_0.3MnO₃ film under illumination from 160 mW/cm² and 200 mW/cm² green-light source, and photoconductivities increase with the intensity of light enhanced.     

Magneto-electrical transport in V-patterned La0.7Sr0.3MnO3 nanostructures

We investigate the electrical transport and magnetic field dependence of nano-patterned La_0.7Sr_0.3MnO₃ devices. We find that the resistivity versus temperature dependence is the same as that observed in thin films, indicating that our nano-patterning preserves the fundamental properties of the material. At temperatures below 20 K there is resistivity upturn of ~ 5 % in the smallest and thinnest device. Structures in a “V” pattern were fabricated in order to investigate domain wall resistance. We find a much smaller resistance area product as compared to previous reports observed in nanoconstrictions and also that the switching field matches that in micromagnetic simulations.     

Microstructure and nano-scratch behaviors of La0.7Sr0.3MnO3 films

The La_0.7Sr_0.3MnO₃ (LSMO) films were prepared at various substrate temperatures on si(100) by DC magnetron sputtering method. The microstructure and nano-scratch behaviors of the films were investigated. The results indicate that the films are single phase with perovskite distorted cubic structure and the texture orientation changes obviously with the increase of substrate temperature. A smooth and dense nanocrystalline LSMO film is obtained at high substrate temperature. The (110) preferred orientation growth is beneficial to the improvement of nano-scratch resistance of the films. The friction coefficient between the films and the diamond tip depends on the critical load (L_c). Elastic deformation is the dominant deformation mechanism and the friction coefficient is about 0.08-0.14 for all the films when the loading normal load is less than L_c. When the loading load is larger than L_c, the delamination or detachment of the films occur and the friction coefficient increases abruptly near the L_c. The films deposited at 480 °C and 680 °C possess higher L_c which is about 77 mN due to lower hardness. The suitable decrease in hardness can enhance cohesion strength and scratch resistance of the films.     

Synthesis and characterization of zirconium oxynitride ZrOxNy coatings deposited via unbalanced DC magnetron sputtering

A study of structure, morphology, and corrosion resistance was performed on zirconium oxynitride thin films deposited on 304 and 316 stainless steels by the DC sputtering magnetron unbalance technique. Structural analysis was carried out using X-ray diffraction (XRD), while morphological analysis was performed by scanning electron microscopy (SEM), atomic force microscopy (AFM), and transmission electron microscopy (TEM). These studies were performed as a function of deposition time via DC sputtering at room temperature (287 K) with an Ar/air flow ratio of 3.0 and a total deposition time of 30 min. The oxynitride films were grown with cubic crystalline structures Zr₂ON₂ and preferentially oriented along the (222) plane. Chemical analysis determined that in the last 5.0 nm, the Zr coatings present the following spectral lines: Zr3d_3/2 (184.6 eV) and 3d_5/2 (181.7 eV), O1s (531.3 eV), and N1s (398.5 eV).     

La0.7Sr0.3FeO3纳米晶薄膜的制备及FET式气敏元件的研制

采用溶胶凝胶工艺,合成出纳米晶La07Sr03FeO3薄膜,薄膜为钙铁矿结构,平均粒径在40nm左右。利用该薄膜采用平面工艺制作出微米尺寸、室温工作的La07Sr0.3FeO3纳米薄膜栅OSFET式气敏元件,并对其气敏性能进行了测试,发现器件的漏电流在乙醇气体中zk大,在氮氧化物中降低。     

Synthesis and characterization of In2O3 nanocube via a solvothermal-calcination route

In₂O₃ nanocubes have been generated by a two-step process, a simple solvothermal technique for In(OH)₃ nanocubes and subsequent reaction with O₂ to form the In₂O₃ nanocubes, which exhibit morphologies identical to the original In(OH)₃ nanocube. The In(OH)₃ nanocubes and the In₂O₃ nanocubes are well-crystallized single-crystal nanostructure. Under optimal conversion conditions, the final geometry features of In₂O₃ are predetermined by the size and morphology of the In(OH)₃ nanocubes. The size of In(OH)₃ nanocubes is effected by pH value of solution.