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.     

Fabrication and characterization of ‘self-binding’ nanocrystalline SnO2 powder based thick film ethanol sensor

Sensing response of ‘self-binding’ nanoparticles of tin dioxide powder deposited on alumina substrate has been investigated. The nanocrystalline SnO₂ powder has been derived from stannic chloride. It has been prepared through fine crystallization in liquid phase. SnO₂ powder has been characterized using SEM, TEM and XRD techniques, which reveal that the average crystallite size is of 12 nm. The slurry blobs deposited on alumina substrate of the powder-thus-prepared have been studied for sensing response to ethanol at various temperatures and concentrations. The observations reveal that the material prepared is ‘self-binding’ and is very sensitive even without catalyst.     

Green synthesis by diethylene glycol based solution process and characterization of SnS nanoparticles

Uniform near‐spherical SnS nanoparticles were prepared by a hydrazine hydrate‐assisted diethylene glycol solution synthesis based on the reaction of tin dichloride (SnCl₂·2H₂O) with thioacetamide (H₃CCSNH₂). The as‐prepared SnS nanoparticles were characterized by XRD, FETEM, EDS, XPS and UV‐vis‐NIR spectrophotometer. The results showed that the SnS nanoparticles had orthorhombic crystal structure, good stoichiometry and indirect bandgap of ∼1.1 eV. The nanoparticle size could be controlled by changing injection temperature. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth of spindle‐shaped silver nanoparticles in SDS solutions

Spindle‐shaped silver nanoparticles were successfully prepared in high yield by a simple wet chemical approach using citric acid (CA) as reducant in the presence of sodium dodecyl sulfate (SDS) at room temperature. Transmission electron microscopy (TEM), UV‐vis absorption spectroscopy and X‐ray diffraction (XRD) have been used to characterize the obtained products. It is found that the spindle‐shaped architecture of siver nanoparticles is drastically influenced by the mass ratio of SDS to CA and the concentration of silver nitrate (AgNO₃). It is revealed that SDS is not as a template but as a capping agent. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Size‐dependent spectroscopic,optical, and electrical properties of PbSe nanoparticles

Stable crystalline Lead Selenide nanoparticles (PbSe NPs) were prepared with a cubic (sphalerite) phase in polyvinyl alcohol (PVA) matrix. Moreover, XRD was used to characterize the PbSe NPs in PVA. The size were controlled by Pb:Se ions ratio in which the particle size was found to be inversely proportional to this ratio up to 16:1. FT‐Raman and FT‐IR measurements indicated the decrease of crystallization of PVA due to doping with PbSe NPs as indicated by the appearance of a peak at 1124 cm^‐1 that increases by size reduction of PbSe NPs. The Photoluminescence and electrical measurements monitored the interaction of PbSe NPs with PVA which increased by decreasing the particle size. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis of highly ordered hBN in presence of group I/IIA carbonates by solid state reaction

This comprehensive study declares experimentally the effects of IA/IIA metal carbonates on the formation of hexagonal boron nitride (hBN) with the aid of the available experimental methods as regards Fourier transform infrared spectroscopy (FT‐IR), powder X‐ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (TEM). hBN is synthesized in the existence of the metal carbonates at the low temperature by modified O'Connor method. The experimental findings of FT‐IR and XRD investigations show that the addition of metal carbonates affects considerably the crystallization of hBN powder during the synthesis process. The presence of the high concentration level of the additions improves harshly the crystallinity. In this respect, the graphitization index deduced from the XRD patterns reduces with the enhancement in the amount of the dopant content. At the same time, the differentiation between the products is analyzed by the SEM surveys. According to the results, the materials synthesized by the Li₂CO₃ powder exhibit both the tubular form and rod‐like while the other samples prepared by the CaCO₃ chemical dopant display the homogeneous plates. Even, the TEM images confirm the nanowires and nanotubes structures such as multi‐walled cylindrical, bamboo nanotubes in all the materials studied in this work.     

Preparation of PbS nano‐microcrystals with different morphologies and their optical properties

PbS nano‐microcrystals were prepared from Pb(OAc)₂·3H₂O and sulfur in a solution without any surfactant using the solvothermal process. Different morphologies, mainly including polyhedron microcrystals and sphere‐like assemblies, were characterized using a scanning electron microscope (SEM) and a transmission electron microscope (TEM). PbS nano‐microcrystals with cubic crystal structure were detected using X‐ray diffraction (XRD), electron diffraction (ED) and high resolution transmission electron micrograph (HRTEM) techniques. The optical properties were investigated by ultraviolet‐visible (UV‐vis) spectroscopy, and photoluminescence spectroscopy (PL). The UV‐vis absorption peaks of PbS exhibited a large blue‐shift and the PL spectra had a strong and broad emission bands centered at 408 nm. The crystal growth mechanism of PbS was also discussed.     

Dependence of nanocrystalline SnO2 particle size on synthesis route

Very fine SnO₂ powders were produced by (a) slow and (b) forced hydrolysis of aqueous SnCl₄ solutions and (c) hydrolysis of tin(IV)-isopropoxide dissolved in isopropanol (sol-gel route) and then characterized by X-ray powder diffraction, Fourier transform infrared and laser Raman spectroscopies, TEM and BET. The XRD patterns showed the presence of the cassiterite structure. As found from XRD line broadening the crystallite sizes of all powders were in the nanometric range. TEM results also showed that the sizes of SnO₂ particles in all powders are in nanometric range. Very fine SnO₂ powders showed different features in the FT-IR spectra, depending on the route of their synthesis. The reference Raman spectrum of SnO₂ showed four bands at 773, 630, 472 and 86 (shoulder) cm⁻¹, as predicted by group theory. Very fine SnO₂ powders showed additional Raman bands, in dependence on their synthesis. The broad Raman band at 571 cm⁻¹ was ascribed to amorphous tin(IV)-hydrous oxide. The additional Raman bands at 500, 435 and 327 cm⁻¹ were recorded for nanosized SnO₂ particles produced by forced hydrolysis of SnCl₄ solutions. However, these additional Raman bands were not observed for nanosized SnO₂ particles produced by slow hydrolysis of SnCl₄ solution or the sol-gel route. The aggregation effects of nanosized particles were considered in the interpretation of the Raman band at 327 cm⁻¹. The method of low frequency Raman scattering was applied for SnO₂ particle size determination. On the basis of these measurements it was concluded that the size of SnO₂ particles was also in the nanometric range and that, the sol-gel particles heated to 400 °C consisted of several SnO₂ crystallites.     

The effects of solvent and microwave on the preparation of Magnesium Oxide Precursor

Four methods including hydrothermal method, glycol‐hydrothermal method, microwave‐hydrothermal method and glycol‐microwave‐hydrothermal method were used to prepare magnesium oxide precursor by the reaction of MgSO₄·7H₂O with (NH₄)₂CO₃. The composition, crystallinity, morphology, aspect ratio, yield, functional groups, atom distribution, and interplanar spacing of the sample were investigated by X‐ray diffraction (XRD), Scan Electron Microscope (SEM), Fourier Transform Infrared Spectroscopy (FT‐IR), and High Resolution Transmission Electron Microscope (HRTEM). The properties of Magnesium Oxide precursor were compared with each other. The results of FT‐IR and XRD showed that the crystals were all nesquehonite. However, it was shown by FT‐IR results that the crystals prepared by glycol‐microwave‐hydrothermal method contained OH⁻ and HCO₃⁻ groups, which indicated that the Mg(OH)(HCO₃)·2H₂O type crystals would be facilitated by this method. The glycol‐hydrothermal method can create high quality Magnesium Oxide precursor with a high degree of crystallinity, high purity, high aspect ratio, smooth surface, and good dispersibility.     

Effect of La doping on microstructure of SnO2 nanopowders prepared by co-precipitation method

A series of La-doped SnO₂ nanopowders with various dopant concentrations were prepared by chemical co-precipitation technique, and the nanopowders prepared were characterized by differential scanning calorimeter (DSC), thermo-gravimetric (TG), X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The results show that La doping can obviously prevent the growth of nanosized SnO₂ crystallites. When the La concentration reaches and surpasses 5 at.%, SnO₂ crystallite size reaches a minimum value and remains almost constant. With the increase of La concentration, La tends to dissolve in the bulk phase of SnO₂ to form solid solution below 10 at.% addition and then starts to disperse onto the surface of the solid solution as a monolayer above 10 at.%. The effect of La doping on hindering crystallite growth can be attributed to the solute drag and lattice distortion resulting from La dissolving in the bulk phase of SnO₂ to form solid solution, rather than the monolayer of La on the surfaces of the SnO₂ powders.     

Structural evolution of SnO2 nanostructure from core–shell faceted pyramids to nanorods and its gas-sensing properties

Tin oxide (SnO₂) nanorods were synthesized through an aqueous hexamethylenetetramine (HMTA) assisted synthesis route and their structural evolution from core–shell type faceted pyramidal assembly was investigated. Structural analysis revealed that the as-synthesized faceted SnO₂ structures were made of randomly arranged nanocrystals with diameter of 2–5 nm. The shell thickness (0–80 nm) was dependent on the molar concentration of HMTA (1–10 mM) in aqueous solution. It was revealed that the self-assembly was possible only with tin (II) chloride solution as precursor and not with tin (IV) chloride solution. At longer synthesis hours, the pyramidal nanostructures were gradually disintegrated into single crystalline nanorods with diameter of about 5–10 nm and length of about 100–200 nm. The SnO₂ nanorods showed high sensitivity towards acetone, but they were relatively less sensitive to methane, butane, sulfur dioxide, carbon monoxide and carbon dioxide. Possible mechanisms for the growth and sensing properties of the nanostructures were discussed.     

Synthesis and characterization of strontium chloroborate whiskers

Single crystalline strontium chloroborate (Sr₂B₅O₉Cl) whiskers with uniform diameter have been synthesized by a facile route based on the calcination of precursor. The precursor was prepared by the sedimentation reaction between SrCl₂ and Na₂B₄O₇ aqueous solution. The products were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared spectrum (FT‐IR). An optimal synthesis temperature for preparing Sr₂B₅O₉Cl whiskers was obtained, and the possible formation process was also presented.     

Particle size of powders under hydrothermal conditions

Various non‐oxide (CuI, AgI, AgCl, PbS, CuS and ZnS) and oxide (ZnO, TiO₂, SnO₂, CeO₂ and ZrO₂) powders were prepared under hydrothermal conditions to investigate the effects of temperature, pH and precursors on the particle size of powders. It was found that the particle sizes of PbS, CuS and ZnS powders were much smaller than that of CuI, AgI and AgCl powders prepared under the same conditions. The particle sizes of TiO₂, SnO₂, CeO₂ and ZrO₂ powders are much smaller than that of ZnO powders prepared under the same conditions. It is concluded that the solution conditions have a certain effect on the particle size of powders under the hydrothermal conditions. The particle size of powders increased with the rising of temperature. Additional factors affecting the particle size were uncovered through studying the nucleation mechanism. The particle size was mainly related to the Madelung constant and the electric charge number of ions. Powders with smaller particle size resulted from systems that possessed the larger Madelung constant and ionic charge number. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Bioinspired synthesis of morphologically controlled SrCO3 superstructures by natural gum acacia

Crystallization of strontium carbonate is performed in aqueous solution using Gum Acacia (GA) as crystal growth modifier. A novel study of hierarchical assembly, specifically interacting inorganic and natural component without introduction of other additives was studied. SrCO₃structures exhibiting the morphologies of well defined nanocrystallites in the form of clusters of hexagonal rods, flower shaped, cross like, doughnut shaped and rice grain shaped are identified by optimizing the conditions and concentration of GA. In continuation, morphology was also examined for mixed metal carbonates (Sr‐LaCO₃, Sr‐TbCO₃). The results indicate that –OH, –COOH and ‐NH₂ functional group moieties of GA play a remarkable role in inhibiting growth morphology of metal carbonates and mixed metal carbonates. Structural characterization of the synthesized materials was investigated by Powder X‐ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive analysis (EDAX), Transmission electron microscopy (TEM), Thermogravimetric analysis (TGA) coupled Mass (MS) and Fourier transform infrared spectroscopy (FT‐IR). This synthesis method can be easily extended to a variety of inorganic nanoparticles, thereby enabling exact control over material properties. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Optical and magnetic properties of Nd‐doped ZnO nanoparticles

Nd‐doped ZnO nanoparticles with different concentration were synthesized by sol‐gel method. The structures, magnetic and optical properties of as‐synthesized nanorods were investigated. X‐ray diffraction (XRD) and x‐ray photoelectron spectroscopy (XPS) results demonstrated that Nd ions were incorporated into ZnO lattice; but Zn_1‐xNd_xO nanoparticles with Nd concentration of x = 0.05 showed Nd₂O₃ phase, so the saturation concentration of Nd in Zn_1‐xNd_xO is less than 5 at%. Vibrating sample magnetometer (VSM) measurements indicated that Nd doped ZnO possessed dilute ferromagnetis behaviour at room temperature. Photoluminescence spectroscopy (PL) showed that Nd ions doping induced a red slight shift and decrease in UV emission with increase of Nd concentration.     

Novel electrospun SnO2@carbon nanofibers as high performance anodes for lithium‐ion batteries

SnO₂@carbon (SnO₂@C) nanofibers (NFs) have been prepared by electrospinning method and evaluated as anodes in lithium‐ion battery half cells. XRD were carried out to provide further information about the structure of the as‐prepared NFs, and all the peaks can be readily indexed to the rutile phase SnO₂ (JCPDS No. 41–1445). Electrochemical characterization by galvanostatic charge‐discharge tests shows that the NF anodes have first discharge capacities of 1375.5 mA h g⁻¹ at 80 mA g⁻¹current density. This excellent Li‐ion storage capability of SnO₂ NFs is probably resulting from protection of amorphous carbon and the synergy arising from that the ultrafine SnO₂ particles embedded in the carbon nanofiber (CNF) matrix: the nanometer‐sized SnO₂@C NFs can provide not only negligible diffusion times of ions thus faster phase transitions but also enough space to buffer the volume changes during the lithium insertion and extraction reactions. The highly dispersed NFs are expected to be applied as attractive anodes for lithium‐ion batteries.     

Microwave-assisted green synthesis of SnO2 nanoparticles and their optical and photocatalytic properties

Abstract

In this study, SnO₂ has been synthesized using Andrographis Paniculata (A. Paniculata) by microwave-assisted method. It is also characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). It exhibits the tetragonal structure with average crystallite size of 27?nm. The stretching vibration peak of Sn-O-Sn is 670?cm^?1. SEM reveals the formation of nanoparticles. The bandgap was estimated by the tauc’s relation as 3.52?eV from the UV-Visible (UV-Vis) spectra. Biosynthesized SnO₂ nanoparticles show excellent photocatalytic activity against Congo red dye under sunlight irradiation.     

Controlled synthesis of ZnO nanostructures with different morphologies in microemulsions

ZnO nanostructures with different morphologies were prepared in microemulsions with ZnSO₄ and ammonia as raw materials. The effects of microemulsion types, concentration of reactants, W values, co‐surfactants, surfactants, oil phases and calcination temperatures were systematically studied. The products were characterized by X‐ray diffraction (XRD), differential scanning calorimetry and thermogravimetry (DSC‐TG), transmission electron microscopy (TEM), high‐resolution TEM (HRTEM), and photoluminescence (PL) spectrum. Results show that ZnO nanoparticles were obtained in water‐in‐oil microemulsions while ZnO nanorods are gained in bicontinuous microemulsions. Water‐in‐oil microemulsions and long carbon chains of surfactants can prevent the preferential growth of ZnO. The particle size of the products increased with the increase of W values, calcination temperatures and the concentration of reactants but decreased with the increase of the carbon chain length of surfactants, co‐surfactants and oil phases. PL spectrums show that the UV emission peak weakened and visible emission peak increased with the decrease of particle size. Meanwhile, the PL spectrums have a little red‐shifted.     

Controlled synthesis of PAN/Ag2S composites nanofibers via electrospinning-assisted hydro(solvo)thermal method

The Ag₂S nanoparticles embedded in polyacrylonitrile (PAN) fibers matrix were successfully prepared by the combining electrospinning with the hydro(solvo)thermal process, without the presence of any templates or organic surfactants. What's more, the size and content of Ag₂S nanoparticles was tunable through proper controlling of the reaction conditions. Consequently, the Ag₂S nanoparticles with 10-100 nm diameter could be obtained via this two-step synthetic route. The as-synthesized composites nanofibers were investigated by X-ray diffraction(XRD), field-emission scanning electronic microscopy (FE-SEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), Fourier transform infrared spectroscopy (FT-IR), and photoluminescence( PL), respectively. What's more, a possible formation mechanism of Ag₂S nanoparticles grown on PAN nanofibers was also proposed.     

A novel sonochemical synthesis and nanostructured assembly of polyvinylpyrrolidone-capped CdS colloidal nanoparticles

Nanoparticles of cadmium sulfide (nano-CdS) have been successfully prepared from an aqueous solution of cadmium chloride and sodium sulfide by a novel sonochemical method. Through adding polyvinylpyrrolidone K30 (PVP) as the dispersant, a yellow translucent colloidal solution of cadmium sulfide which was considerably stable within at least one month was obtained. The characterizations of nanoparticles by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscope (SEM) and FT-IR spectroscopy showed good properties of small size, high surface area and crystal structure. The size of the prepared nanoparticles was about 3–5 nm according to XRD spectra and TEM images. Poly(diallyldimethylammonium chloride) (PDDA) has been employed to fabricate multilayer films on quartz wafer and indium tin oxide (ITO) electrode in a layer-by-layer manner. Atomic force microscopy (AFM) displayed the dense coverage of the substrate surface by the nanoparticles. UV–vis absorption spectroscopy confirmed the consecutive growth of PDDA/nanoparticles layer pairs. The photoelectrochemical and the electrochemical behaviors of the prepared CdS particle were examined as well.