Synthesis and characterization of mercury oxide unusual nanostructures by ultrasonic method

A facile direct synthesis has been done to prepare HgO nanocrystallites of different shapes. The effect of different parameters such as the presence of alkali salts or stabilizers, power of the ultrasound, time of sonicating, and the starting materials on the size, morphology and crystallinity degree of the products were studied. Scanning electron microscopy observations revealed that using of polyvinyl alcohol (PVA) or alkali salts led to different shapes of product.     

Synthesis and characterization of BaMoO4 nanostructures prepared via a simple sonochemical method and their degradation ability of methylene blue

Rod-like and sphere-like barium molybdate (BaMoO₄) nanostructures have been synthesized by a large scale and simple sonochemical method by using Ba(Sal)₂ (Sal=salicylidene) and Na₂MoO₄·2H₂O for the first time. The effects of sonochemical irradiation time, sonochemical power, temperature, solvent, surfactant and barium source were considered to obtain a controlled shape. It was established that morphology, particle size and phase composition of the final products could be greatly affected by these parameters. The photocatalytic activity of the synthesized products has been compared for the photodegradation activity of methylene blue (MB).     

In situ monitoring of the adsorption of Co2+ on the surface of Fe3O4 nanoparticles in high-temperature aqueous fluids

Developing an understanding of the reaction processes occurring at the surface⿿fluid interface at the atomic level of nanostructured materials in high-temperature aqueous environments is necessary for establishing general principles of behavior of nanomaterials operating in such extremes. In situ Co K-edge X-ray absorption spectroscopy (XAS) measurements were made on Fe₃O₄ nanoparticles in the presence of Co²⁺ ions in aqueous fluids to 500 °C and approximately 220 MPa. The results from analysis of the in situ EXAFS data, along with SEM-EDX spectra measured from reacted nanoparticles, indicate that adsorption of Co²⁺ ions on the surface of Fe₃O₄ nanoparticles is negligible at temperatures below 200 °C but becomes significant in the 250⿿500 °C temperature range. The low reaction temperature threshold of the Co²⁺ aqua ion with Fe₃O₄ nanoparticles is consistent with a relatively low value of the crystal field stabilization energy (CFSE) of Co²⁺ in octahedral site symmetry in spinels. Modeling of the pre-edge feature of the XANES and analysis of the extended X-ray absorption fine structure (EXAFS) shows that Co²⁺ adsorbs predominantly on octahedral sites of the surface of nanoparticles in aqueous fluids. Structural analyses using EXAFS and high resolution TEM show that the inverse spinel structure is preserved in the Co-incorporated surface atomic layers of the Fe₃O₄ nanoparticles. Our results suggest that the dissolved radioactive isotope ⁶⁰Co in the primary cooling loop of supercritical water-cooled nuclear reactors have a high likelihood of precipitating on the surfaces of spalled ferrite nanomaterial.     

Solvothermal Synthesis, Structure and Optical Property of Nanosized CoSb(3) Skutterudite

Binary skutterudite CoSb₃ nanoparticles were synthesized by solvothermal method. The nanostructuring of CoSb₃ material was achieved by the inclusion of various kinds of additives. X-ray diffraction examination indicated the formation of the cubic phase of CoSb₃. Structural analysis by transmission electron microscopy analysis further confirmed the formation of crystalline CoSb₃ nanoparticles with high purity. With the assistance of additives, CoSb₃ nanoparticles with size as small as 10 nm were obtained. The effect of the nanostructure of CoSb₃ on the UV–visible absorption and luminescence was studied. The nanosized CoSb₃ skutterudite may find application in developing thermoelectric devices with better efficiency.     

Synthesis and characterization of microspheres composed of SnO2 nanoparticles processed via a chemical route

SnO₂ microspheres were synthesized by a chemical route, heating the mixed Sn²⁺ and sulfuric acid solution in the presence of pressurized oxygen at 900 °C in a designed calorimetric pump. Phase analysis was carried out by X-ray diffraction (XRD) and the results confirmed the SnO₂ microspheres as a single-phase tetragonal structure. Scanning electron microscopy (SEM) images indicated that these microspheres with average diameters of 0.9 μm were composed of SnO₂ nanoparticles with a diameter of about 4.7 nm and a crystallite size of 3.7 nm, as observed by transmission electron microscope (TEM) and calculated by Scherrer's equation from diffractograms, respectively. The formation mechanism of microspheres composed of SnO₂ nanoparticles and the influence of changes in processing are proposed and explained.     

Synthesis of photoluminescent polycrystalline SiC nanostructures via a modified molten salt shielded method

Polycrystalline SiC (3C-, 6H-, 24R- and 27H-) nanostructures are synthesized via a modified molten salt shielded synthesis method (m-MS³) in open air using Si and carbon black as the starting materials. The influences of salt species and their amount, and the sintering temperature, are discussed and optimized. Well crystalline SiC nanopowders composed of bountiful microstructures (nanoparticles, nanowires, nanosheets and nanoblocks) are successfully synthesized by m-MS³ at 1250 °C, with KCl and NaCl as the shielding salt. The polycrystalline SiC powders showed excellent photoluminescence property at an excitation wavelength of 330 nm and relatively small band gaps of 2.57–2.74 eV, which are quite attractive among reports for SiC-based materials. The investigation in this paper may provide a prototype strategy for protection-free synthesis of nanostructured SiC powders applicable for ultraviolet luminescence devices.     

A facile and reliable route to prepare of flower shaped lead sulfide nanostructures from a new sulfur source

Flower shaped PbS nanostructures were prepared by the solvothermal method using propylene glycol and a new sulfuring agent. Novelty of this work is application of a new thio Schiff-base as complexing and sulfuring agent for synthesizing of PbS nanostructures. SEM and TEM was used to examine the surface morphology of the grown samples; also the products were characterized by XRD, SEAD, UV–vis and FT-IR spectra. The results of this paper indicate that the shape and size of lead sulfide nanocrystals can be controlled systematically by setting certain reaction parameters.     

Synthesis,microstructure and optical characterization of zirconium oxide nanostructures

Zirconium oxide (ZrO₂) nanostructures were synthesized by hydrothermal route. Surface morphology analysis depicts the formation of the nanobars and hexagonal-shaped nanodiscs at different synthesis conditions. The structural analysis confirms that the as-synthesized ZrO₂ product is of pure monoclinic phase (m-ZrO₂) with crystallite size of about 25 nm. The product consists of monodispersed nanoparticles of uniform composition, high purity, and crystallinity. The Raman spectra are quantitatively analyzed and the observed peaks are attributed to various vibration modes of the m-ZrO₂. The UV–vis absorption spectrum showed a strong absorption peak at about 292 nm and the estimated optical band gap was around 3.57 eV. Photoluminescence (PL) spectrum of ZrO₂ nanostructure showed a strong and broad emission peak at around 410 nm at room temperature, which can be attributed to the ionized oxygen vacancy in the material.     

Synthesis and characterization of MgAl2O4 micro-rods by a molten salt method

Large amounts of MgAl₂O₄ micro-rods were successfully synthesized using the molten-salt technology. The effect of KCl contents on the formation of MgAl₂O₄ micro-rods was investigated. The structure and morphology of MgAl₂O₄ were investigated by means of powder X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy, respectively. The experimental results showed that the contents of KCl significantly influenced the formation of MgAl₂O₄ micro-rods. MgAl₂O₄ micro-rods could be prepared at 1150 °C with a weight ratio of 100:1 between the salt and the starting materials. The formation of MgAl₂O₄ micro-rods could be suggested to be due to the inhomogeneous nucleation and orientated growth perpendicularly to the surfaces of Al₂O₃ grains. An impedance-type humidity sensor was finally fabricated based on the as-prepared MgAl₂O₄ micro-rods. According to tests of the humidity performance, MgAl₂O₄ micro-rods might be suitable for high-performance humidity sensors.     

Synthesis and characterization of a bi-functional hydroxyapatite/Cu-doped TiO2 composite coating

In the present work, a two-layer hydroxyapatite (HA)/Cu-doped TiO₂ composite coating was prepared via one-step micro-arc oxidation in an aqueous electrolyte containing calcium acetate, sodium di-hydrogen phosphate and ethylene diamine tetraacetic acid cupric disodium (CuNa₂-EDTA) at a constant current density of 100?mA/cm². After micro-arc oxidation for 20?min, Cu species incorporate into the TiO₂ as CuO and Cu₂O, resulting in the formation of Cu-doped TiO₂-based coating. In addition, spherical-shaped HA phase of nanometre scale is also present on the Cu-doped TiO₂-based coating. With HA phase boosting osseointegration and Cu species killing pathogenic microbes, a bi-functional coating fabricated by one-step micro-arc oxidation is of promising potential application in the bio-medical field.     

A single-step method for synthesis of CuInS2 nanostructures using cyclic microwave irradiation

Pure and well-crystalline CuInS₂ nanostructures were successfully synthesized via a cyclic microwave irradiation method at low microwave power using cupric chloride dihydrate (CuCl₂·2H₂O), indium chloride tetrahydrate (InCl₃·4H₂O) and thioacetamide as starting reagents. The effects of processing cycles (2–75 cycles) and microwave heating powers (180–600 W) on purity, crystallinity, particle size and morphology of the synthesized products were investigated. The synthesized products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and UV–vis spectroscopy. Increasing processing cycles and microwave heating power improved the purity and crystallinity of the synthesized products. Using the microwave powers of 450 and 600 W with 75 cycles, pure CuInS₂ nanocrystallites were obtained. The CuInS₂ crystallites displayed nanoparticles in clusters with decreasing in the diameter sizes from 1.6 to 0.9 µm when the microwave power was increased from 180 to 600 W. The reaction mechanism of the CuInS₂ formation was also provided. A CuInS₂ solar cell, made from FTO/TiO₂/CuInS₂/CdS/Pt-FTO layers, was fabricated to explore the potential use of the CuInS₂ nanoparticles in photovoltaic devices. The photovoltaic properties of the CuInS₂ solar cell including open-circuit voltage (V_oc), short-circuit current density (J_sc) and fill factor (FF) were 281.10 mV, 0.072 mA/cm² and 0.47, respectively, with cell conversion efficiency (η) of 0.01% under 1.5 AM illumination.     

Synthesis and characterization of multiferroic BiFeO3 powders fabricated by hydrothermal method

The influence of processing parameters on phase formation and particle size of hydrothermally synthesized BiFeO₃ powders was investigated. BiFeO₃ powder was synthesized by dissolving bismuth nitrate and iron nitrate in KOH solution at temperatures ranging from 150 to 225 °C. X-ray diffraction patterns and scanning electron microscopy observation indicated that rod-like α-Bi₂O₃ phase was formed at initial stage of reaction and dissolved into ions to form thermodynamically stable BiFeO₃ phase. Single-phase perovskite BiFeO₃ has been formed using a KOH concentration of 8 M at a temperature of ≥175 °C in a 6 h reaction period. BiFeO₃ particle growth was promoted by lowering the KOH concentration, or increasing the duration time or reaction temperature. The effects of processing conditions on the formation of crystalline BiFeO₃ powders were discussed in terms of a dissolution–precipitation mechanism. The magnetization of the BiFeO₃ powders at room temperature showed a weak a ferromagnetic nature.     

Synthesis and characterization of (S)-3-benzoylthio-2-methylpropionic acid

以硫代乙酸、甲基丙烯酸为原料,经过缩合、水解-酯化得到3-苯甲酰巯基-2-甲基丙酸的消旋体,经化学拆分得到(S)-3-苯甲酰巯基-2-甲基丙酸。综合考察了缩合、水解-酯化、拆分过程中影响反应的因素,结果表明：硫代乙酸与甲基丙烯酸摩尔比为1.4︰1,反应时间为2 h、反应温度为93 ℃条件下,可以得到收率为95.6%的3-乙酰巯基-2-甲基丙酸（缩合物A）;控制釜温不超过20 ℃,将缩合物A加入11.8%的氢氧化钠水溶液中进行水解,水解完成后将下层钠盐投回釜内,然后在低温下滴加苯甲酰氯,反应进行2 h后将釜液调至酸性,产品逐渐析出,计算得水解-酯化总收率为96.7%;利用拆分剂D-(+)-N-苄基-α-苯乙胺对产品拆分,拆分收率为36.0%,综合以上三步总收率可达33.3%。其结构经核磁、质谱、红外分析确认且由X射线衍射分析结晶度非常高。     

Synthesis and characterization of mesoporous anatase TiO2 nanostructures via organic acid precursor process for dye-sensitized solar cells applications

Titania (TiO₂) nanoparticles have been synthesized using organic precursor technique. The titania nanoparticles were characterized. The results indicated that the prepared titanium oxalate and citrate precursors were transformed to anatase TiO₂ phase at temperature 400 °C for 2 h. Dye-sensitized solar cells were assembled using the prepared nanocrystalline TiO₂ with large surface area. The specific surface area S_BET was 80.9 and 78.6 m²/g using oxalic and citric acids, respectively. The power efficiency was 3.5 and 2.4%. A brief discussion on the possible reasons behind the low power conversion efficiency observed for these type of solar cells was reported.     

Multiple nanostructures in high performance Cu2S0.5Te0.5 thermoelectric materials

Cu₂(S,Te) solid solution material has shown excellent thermoelectric performance with a maximum zT value up to 2.1. Previous work has observed specific mosaic nanocrystals in this solid solution which is considered to be responsible for its ultra-low thermal conductivity. In the present study, we performed in-depth microstructural examinations by transmission electron microscopy and revealed additional multiform nanostructures in Cu₂S_0.5Te_0.5 solid solution. Apart from widely existed mosaic nanocrystals, nano-domains of ordered structure, nanoscale periodic antiphase domains, stacking faults and polytype have been observed. Formation of such abundant nanoscale substructures could be related to the large mismatch in atomic size between S and Te solute elements. These nanostructures are all coherently embedded in the matrix lattice. Thereafter, continuous carrier transportation is still guaranteed while in the meantime phonon scattering is enhanced by such high density of structural imperfection. Thus, solid solution strategy in Cu₂S_0.5Te_0.5 matches well with the phonon-glass electron-crystal concept for high performance thermoelectric materials.     

Synthesis of high surface area Al2O3-CeO2 composite nanopowder via inverse co-precipitation method

In the present work, Al₂O₃-CeO₂ composite nanopowder was synthesized by inverse co-precipitation method using metal chlorides, aluminum powder and NH₄OH as precipitant agent. The thermal decomposition of the precipitate and subsequent formation of Al₂O₃-CeO₂ were investigated by X-ray diffractometery, scanning electron microscopy, thermogravimetric and differential thermal analysis, Brunauer-Emmett-Teller surface area measurement and Fourier transform infrared spectroscopy. The results showed that the presence of ceria suppressed the formation of α-Al₂O₃. The BET-specific surface area was 173 m²/g for powders calcined at 800 °C. The particle size examined by using scanning electron microscopy was in the range 30-70 nm. The activation energy of Al₂O₃-15 wt.% CeO₂ nanocrystallite growth during calcination was measured to be 32.4 kJ/mol whereas that of Al₂O₃ was about 23.8 kJ/mol.     

Synthesis and characterization of compound-curved graphite

Crystalline graphite with compound curvature has been produced by precipitation of carbon from metal carbide solutions. Nearly spherical graphitic shells hundreds of microns thick have been synthesized on top of millimeter-sized spherical transition metal cores in high vacuum. Raman spectroscopy, backscatter electron diffraction and X-ray analysis shows the shell to be composed of highly crystalline graphite. Upon cooling, these graphite-like shells routinely undergo a reversible transformation in which the initially smooth surface forms striking geometric facets bounded by ridges of triangular cross section. Evaporation rates and other factors suggest that this transformation represents a phase transition from graphite composed of randomly oriented layers of graphene to fully crystalline graphite having layers in registry.     

Synthesis and characterization of Al2O3 nanopowders by a simple chitosan-polymer complex solution route

Al₂O₃ nanopowders were synthesized by a simple chitosan-polymer complex solution route. The precursors were calcined at 800–1200 °C for 2 h in air. The prepared samples were characterized by XRD, FTIR and TEM. The results showed that for the precursors prepared with pH 3–9 γ-Al₂O₃ and δ-Al₂O₃ are the two main phases formed after calcination at 800–1000 °C. Interestingly, when the precursor prepared with pH 2 was used, α-Al₂O₃ was formed after calcination at 1000 °C, and pure α-Al₂O₃ was obtained after calcination at 1200 °C. The crystallite sizes of the prepared powders were found to be in the range of 4–49 nm, as evaluated by the XRD line broadening method. TEM investigation revealed that the Al₂O₃ nanopowders consisted of rod-like shaped particles and nanospheres with particle sizes in the range of 10–300 nm. The corresponding selected-area electron diffraction (SAED) analysis confirmed the formation of γ- and α-Al₂O₃ phases in the samples.     

γ-Ray assisted synthesis of silver nanoparticles in chitosan solution and the antibacterial properties

In the present study, chitosan had been utilized as a “green” stabilizing agent for the synthesis of spherical silver nanoparticles in the range of 5–30 nm depending on the percentage of chitosan used (0.1, 0.5, 1.0 and 2.0 wt%) under γ-irradiation. X-ray diffractometer identified the nanoparticles as pure silver having face-centered cubic phase. Ultraviolet–visible spectra exhibited the influence of γ-irradiation total absorbed dose and chitosan concentration on the yield of silver nanoparticles. The antibacterial properties of the silver nanoparticles were tested against Methicillin-resistant Staphylococcus aureus (MRSA) (gram-positive) and Aeromonas hydrophila (gram-negative) bacteria. This work provides a simple and “green” method for the synthesis of highly stable silver nanoparticles in aqueous solution with good antibacterial property.