Synthesis and evaluation of lead telluride/bismuth antimony telluride nanocomposites for thermoelectric applications

Heterogeneous nanocomposites of p-type bismuth antimony telluride (Bi_2−xSb_xTe₃) with lead telluride (PbTe) nanoinclusions have been prepared by an incipient wetness impregnation approach. The Seebeck coefficient, electrical resistivity, thermal conductivity and Hall coefficient were measured from 80 to 380 K in order to investigate the influence of PbTe nanoparticles on the thermoelectric performance of nanocomposites. The Seebeck coefficients and electrical resistivities of nanocomposites decrease with increasing PbTe nanoparticle concentration due to an increased hole concentration. The lattice thermal conductivity decreases with the addition of PbTe nanoparticles but the total thermal conductivity increases due to the increased electronic thermal conductivity. We conclude that the presence of nanosized PbTe in the bulk Bi_2−xSb_xTe₃ matrix results in a collateral doping effect, which dominates transport properties. This study underscores the need for immiscible systems to achieve the decreased thermal transport properties possible from nanostructuring without compromising the electronic properties.     

Sonochemical synthesis and characterization of CuInS2 nanostructures using new sulfur precursor and their application as photocatalyst for degradation of organic pollutants under simulated sunlight

In this research, we investigated the photocatalytic activity of CuInS₂ nanoparticles in visible light during the decomposition of three toxic dyes (Eriochrome Black T, Rhodamine B, and Erythrosine). The CuInS₂ nanostructures were synthesized by a rapid and simple sonochemical method using dithiooxamide as a sulfur reagent and various capping agents, including SDS, CTAB, and PVP, were applied to achieve a pure structure with fine morphology. The flower-like structure was observed through FESEM images, implying different capping agents and fabrication had a considerable influence on the morphology of samples. The suitable bandgap of CuInS₂ (1.53 eV) was obtained from DRS analysis and resulted in higher photodegradation efficiency. The fabricated CuInS₂ revealed better photodegradation efficiency (74.8%) to the anionic dyes than cationic dye. A possible photodegradation mechanism was suggested based on scavenger tests of active species.     

Additive assisted hydrothermal synthesis,characterization and optical properties of one dimensional DyPO4:Ce3+ nanostructures

One dimensional nanostructures of cerium doped dysprosium phosphate (DyPO₄:Ce³⁺) were synthesized via hydrothermal route in the presence of different surfactants [sodium dodecyl sulfate (SDS), dodecyl sulfosuccinate (DSS), polyvinyl pyrollidone (PVP)] and solvent [ethylene glycol and water]. The prepared nanostructures were characterized by Powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FE-SEM), Transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), UV-VIS-NIR absorption spectrophotometer and photoluminescence (PL) studies. The PXRD and FTIR results indicate purity, good crystallinity and effective doping of Ce³⁺ in nanostructures. SEM and TEM micrographs display nanorods, nanowires and nanobundles like morphology of DyPO₄:Ce³⁺. Energy-dispersive X-ray spectra (EDS) of DyPO₄:Ce³⁺nanostructures confirm the presence of dopant. UV-VIS-NIR absorption spectra of prepared compounds are used to calculate band gap and explore their optical properties. Luminescent properties of DyPO₄:Ce³⁺ was studied by using PL emission spectra. The effect of additives and solvents on the uniformity, morphology and optical properties of the nanostructures were studied in detail.     

Two lead coordination polymers with nitrilotriacetic acid and oxydiacetic acid: synthesis,characterization, and crystal structure

Two lead coordination compounds [Pb₂(nta)]NO₃ (1) and [Pb(oda)] (2) have been synthesized by slow evaporation or hydrothermal conditions using nitrilotriacetic acid (nta) and 2,2′-oxydiacetic acid (oda) as ligands, respectively. Their structures were determined by single-crystal X-ray diffraction and further characterized by X-ray powder diffraction, infrared absorption spectrum, and thermogravimetric analysis. Compound 1 is a 2-D honeycomb-like layer structure with (6,3) topology. When the bonding limit of Pb–O extends from 2.76 to 2.90 Å, potential weak Pb–O bonds can be found in 1, and the 2-D layer structure can be further linked to generate a 3-D 4-connected supramolecular sra net with the (4².6³.8) Schläfli symbol. Compound 2 contains a 1-D infinite Pb–O chain which is connected through µ₃-, µ₄-, and µ₅-coordination modes of oda to form a new 3-D structure.     

Two dinuclear Schiff-base complexes: synthesis,characterization, and biological activity

Two complexes, [Zn₂L(µ-OAc)](ClO₄) (1) and [Mn₂L(OAc)₂]?·?4H₂O (2), were synthesized by [2?+?2] cyclo-condensation between 2,6-diformyl-4-fluorophenol and 1,3-propyldiamine in the presence of metal ions M(II) (M?=?Zn and Mn), and were characterized by chemical analyses, IR spectra, electrospray mass spectra, and X-ray determinations. The results show that 1 forms dimers through hydrogen bonding. In 2, lattice waters, forming a 1-D water chain, function as glue to form a 3-D supramolecular network through extended hydrogen bonding. pBR322 plasmid DNA can be transformed to nicked form in air by 1 or nicked and linear forms in air by 2. Moreover, their antibacterial activities against S. aureus were investigated using penicillin as reference system.     

PbTe colloidal nanocrystals: synthesis, characterization, and multiple exciton generation

We report an alternative synthesis and the first optical characterization of colloidal PbTe nanocrystals (NCs). We have synthesized spherical PbTe NCs having a size distribution as low as 7%, ranging in diameter from 2.6 to 8.3 nm, with first exciton transitions tuned from 1009 to 2054 nm. The syntheses of colloidal cubic-like PbSe and PbTe NCs using a PbO "one-pot" approach are also reported. The photoluminescence quantum yield of PbTe spherical NCs was measured to be as high as 52 +/- 2%. We also report the first known observation of efficient multiple exciton generation (MEG) from single photons absorbed in PbTe NCs. Finally, we report calculated longitudinal and transverse Bohr radii for PbS, PbSe, and PbTe NCs to account for electronic band anisotropy. This is followed by a comparison of the differences in the electronic band structure and optical properties of these lead salts.     

Room temperature ferromagnetism in undoped and Fe doped ZnO nanorods: Microwave-assisted synthesis

One-dimensional (1D) undoped and Fe doped ZnO nanorods of average length ∼1 μm and diameter ∼50 nm have been obtained using a microwave-assisted synthesis. The magnetization (M) and coercivity (H_c) value obtained for undoped ZnO nanorods at room temperature is ∼5×10⁻³ emu/g and ∼150 Oe, respectively. The Fe doped ZnO samples show significant changes in M -H loop with increasing doping concentration. Both undoped and Fe doped ZnO nanorods exhibit a Curie transition temperature (T_c) above 390 K. Electron spin resonance and Mössbauer spectra indicate the presence of ferric ions. The origin of ferromagnetism in undoped ZnO nanorods is attributed to localized electron spin moments resulting from surface defects/vacancies, where as in Fe doped samples is explained by F center exchange mechanism.     

Precipitation and characterization of uniform submicrometer lead titanate particles. Part II: Reaction mechanism

The chemical mechanism of the precipitation of lead titanium peroxohydroxide particles in a solution of nitrilotriacetate (NTA) complexes of lead and titanium peroxo-hydroxide is envisioned as the interaction between cations of lead hydroxide and anions of polymeric titanium peroxo-hydroxide.     

Microwave-assisted synthesis of ethyl laurate using immobilized lipase: Optimization,mechanism and thermodynamic studies

Microwave-assisted synthesis of ethyl laurate using lauric acid and ethanol catalyzed by Fermase CALB has been investigated. The effect of operating parameters like molar ratio (lauric acid: ethanol), enzyme loading, temperature, and molecular sieves was systematically studied. A maximum conversion of 98.2% was obtained in 10 ​min compared to the conventional method, where the reaction required 4 ​h to achieve 92.4% conversion. The optimum parameters for the microwave-assisted synthesis were 1:2 ​M ratio of lauric acid to ethanol, 45 ​°C temperature, 1.8% (w/w) enzyme amount, 1.5% (w/w) molecular sieves. The enzyme lipase was reused for up to seven successive cycles under microwave irradiation. The thermodynamic study was carried out to determine various thermodynamic parameters for the reaction. The esterification mechanism was proposed, and the impact of microwave irradiation on the immobilized enzyme after several reuse was studied by scanning electron microscopy.     

Metal oxide nanoparticles: synthesis, characterization and application

The synthesis of metal oxide nanoparticles is described in terms of precursor formation, nucleation, growth, and aging processes. The main parameters governing these processes are the solution properties, including the solvent viscosity, dielectric constant and the presence of adsorbing anions, the solubility of the metal oxide, and the metal oxide surface energy.     

Polyaniline nanobelts, flower-like and rhizoid-like nanostructures by electrospinning

Nanobelts, flower-like and rhizoid-like nanostructures of pure polyaniline （PANI） doped with sulfuric acid or hydrochloric acid were prepared via electrospinning by using a coagulation bath as the collector after optimizing the fabrication parameters. The morphologies of these nanostructures were characterized by scanning electron microscope （SEM）. The possible formation mechanisms were discussed.     

The influence of co-doping Ag and Sb on microstructure and thermoelectric properties of PbTe prepared by combining hydrothermal synthesis and melting

Ag and Sb co-doped PbTe (AgPb₁₈SbTe₂₀) and pure PbTe nanopowders were hydrothermally synthesized. The synthesized nanopowders were heated at 1173-1223 K in vacuum for 5 h followed by a slow cooling. The nanopowders and the bulk samples were characterized by X-ray diffraction and electron microscopy, respectively. Electrical transport properties of the bulk samples were measured from room temperature to ∼773 K. The results showed that co-doping Ag and Sb into PbTe has significant effects on both the nanopowders and bulk samples. Bulk AgPb₁₈SbTe₂₀ sample showed n-type conduction in the whole temperature range measured, while bulk PbTe sample exhibited a transition from p- to n-type conduction at ∼500 K. The thermoelectric properties of PbTe were markedly improved after co-doping of Ag and Sb. The AgPb₁₈SbTe₂₀ sample has a dimensionless figure of merit of ∼0.94 at 723 K.     

Rare-earth-rich tellurides: Gd4NiTe2 and Er5M2Te2 (M=Co, Ni)

Three new rare earth metal-rich compounds, Gd₄NiTe₂, and Er₅M₂Te₂ (M=Ni, Co), were synthesized in direct reactions using R, R₃M, and R₂Te₃ (R=Gd, Er; M=Co, Ni) and single-crystal structures were determined. Gd₄NiTe₂ is orthorhombic and crystallizes in space group Pnma with four formula units per cell. Lattice parameters at 110(2) K are a=15.548(9), b=4.113(2), . Er₅Ni₂Te₂ and Er₅Co₂Te₂ are isostructural and crystallize in the orthorhombic space group Cmcm with two formula units per cell. Lattice parameters at 110(2) K are a=3.934(1), b=14.811(4), , and a=3.898(1), b=14.920(3), , respectively. Metal-metal bonding correlations were analyzed using the empirical Pauling bond order concept.     

Rare-earth hexaborides nanostructures: Recent advances in materials, characterization and investigations of physical properties

Nanostructured rare-earth hexaborides (REB₆) are promising materials for photonic and electronic applications due to their unique characteristic. These include high melting point, hardness, chemical stability, low work function, low volatility at high temperatures, superconductivity, magnetic properties, efficiency, thermionic emission, and narrow band semiconductivity. This article focuses on recent developments regarding the synthesis, characterization, and applications of REB₆ nanostructures. We first summarize information regarding the classification and crystal chemistry of REB₆. Next, we examine the means by which researchers have successfully synthesized REB₆. We consider the structural properties and morphology of REB₆, and the growth mechanism involved in their fabrication. Finally, we offer suggestions for the use of REB₆ nanostructures in photonic and electronic applications, and identifying four areas for further research.     

Sb2S3 with various nanostructures: controllable synthesis, formation mechanism, and electrochemical performance toward lithium storage

The size- and shape-controlled synthesis of Sb(2)S(3) nanostructures has been successfully realized by a facile hydrothermal route. A range of dimensional nanostructures, such as one-dimensional nanorods, two-dimensional nanowire bundles, three dimensional sheaf-like superstructures, dumbbell-shaped superstructures, and urchin-like microspheres, could be obtained through introducing different organic complex reagents or ionic liquids to the reaction system. The formation mechanisms of various Sb(2)S(3) nanostructures have been rationally proposed based on the crystal structure and the nature of the complex reagents and the ionic liquid. The effects of experimental parameters on the final product are also discussed in detail. In addition, electrochemical measurements demonstrate that the as-synthesized Sb(2)S(3) nanostructures have higher initial Li intercalation capacity and excellent cyclic performances, which indicates that the as-synthesized Sb(2)S(3) nanostructures could have potential applications in commercial batteries.     

Copolymer nanosphere encapsulated CdS quantum dots prepared by RAFT copolymerization: synthesis,characterization and mechanism of formation

Cadmium sulfide (CdS) quantum dots (QDs) encapsulated in block copolymer spheres were synthesized by an aqueous emulsion polymerization process. First, stable dispersions of CdS QDs in water were prepared using a polymer dispersant, either poly(acrylic acid) or a random copolymer having an average of ten acrylic acid and five butyl acrylate units. These polymer dispersants were prepared by reversible addition-fragmentation chain transfer polymerization. Then, the CdS QDs dispersed in water were encapsulated in a polystyrene shell using an emulsion polymerization process. Spectroscopic and microscopic techniques were used to characterize the resulting nanocomposites. Optical properties of QDs in polymer microspheres were investigated by UV-vis and fluorescence spectroscopic studies. Particle sizes of all CdS QD samples were calculated from absorption edges using Henglein's empirical curve. Transmission electron microscopy was used to determine the size and morphology of CdS QD samples. These observations were used to elucidate the mechanism of formation of the resulting well-defined polymer-encapsulated CdS nanoparticles.     

微波辅助消解-原子荧光法测定玻璃中的镉砷铅

光学玻璃中的各种元素对玻璃的光学性能有不同的影响。如加入镉可以提高玻璃折射率;砷的引入能增加玻璃的透光度,含铅玻璃具有低成本、高折射性等优点。但是镉、砷、铅均为有毒元素,玻璃加工和处理过程以及毒废弃物的处理都可能引起水、土壤、大气的污染并给人体带来一定的危害     

Rapid and solvent-free solid-state synthesis and characterization of Zn3V2O8 nanostructures and their phenol red aqueous solution photodegradation

Zinc vanadate (Zn₃V₂O₈) nanostructures have been successfully synthesized via simple, rapid and solvent-free solid-state method by using different complex precursors of Zn and NH₄VO₃ as novel starting materials. Effects of various zinc (II) Schiff base complex precursors and calcination temperatures were investigated to reach optimum condition. It was found that particle size and optical property of the as-prepared products could be greatly influenced via these parameters. The products were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectra, energy dispersive X-ray microanalysis (EDX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Photoluminescence and ultraviolet-visible (UV–Vis) spectroscopy. The photocatalytic activity of zinc vanadate nano and bulk structures were compared by degradation of phenol red aqueous solution.     

Synthesis,characterization and impregnation of lead sulphide semiconductor nanoparticles on polymer matrix

Lead sulphide nanoparticles were prepared using a precursor and dual sources methods. The composites were fabricated by stabilizing chemically synthesized semiconductor PbS nanocrystals into laurylmethacrylate and ethyleneglycol dimethacrylate matrix in the presence of tri-n-octylphosphine. PbS nanocrystals were dispersed in toluene as a compatible medium for the polymerization and cross-linking of poly laurylmethacrylate networks. The nano-sized particles and polymer composites were characterized by XRD and TEM. Possible formulations and incorporation of these PbS nanoparticles in polymer matrix have been discussed. The reported lead sulphide nanoparticles into tailered polymeric system show greater uniformity and stability.     

One-pot synthesis,characterization, and drug loading of polysaccharide-based nanoparticles with carboxy functional groups

Herein, various polysaccharide-based nanoparticles were synthesized from dextran, hydroxypropyl cellulose, and hydroxyethyl cellulose, respectively, by a self-assembly assisted approach. This approach enables us to prepare stable polysaccharide-based nanoparticles with carboxy functional groups directly from monomers without using any surfactant and organic solvent. The existence of abundant carboxyls in these polysaccharide-based nanoparticles provides them obvious pH sensitivity as verified by ¹H nuclear magnetic resonance as well as the potential in loading cationic drug.