Hydrothermal synthesis of PbS hollow spheres with single crystal-like electron diffraction patterns

PbS hollow spheres were successfully prepared by a sodium citrate-assisted hydrothermal process at 120 degrees C for 12 h, employing lead acetate trihydrate, thiourea and sodium citrate as precursors. The diameter of PbS hollow spheres is 200-400 nm, which is composed of about 50-80 nm nanoparticles. The synthesized product was characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), electron diffraction (ED), Fourier transform-infrared (FT-IR) spectroscopy, ultraviolet-visible spectrometer (UV-vis) and near-infrared absorption spectrometer (NIR). The effects of the reaction conditions on morphologies of PbS structures were investigated. Star-shaped and flat PbS crystals were obtained by changing some experiment conditions. The results show that temperature, sodium citrate concentration, sulfur sources and solvent play key roles on the final morphologies formation of PbS crystals. Especially, ED result indicates that PbS hollow spheres hold single crystal-like electron diffraction patterns. And the possible formation mechanism of hollow spheres was proposed.     

反应介质对二氧化硅在碳球表面包覆效果的影响

为了改善碳球表面惰性,利用溶胶-凝胶法在碳球表面包覆二氧化硅,考察了介质条件对包覆效果的影响。通过场发射扫描电子显微镜和透射电子显微镜等手段对不同介质中得到的样品进行对比分析表征。结果表明,碱性介质更有利于二氧化硅在碳球表面的包覆,所得复合物球表面光滑、包覆层厚且厚度均一,焙烧除去碳球核后得到空心二氧化硅球,并分析了碳球表面二氧化硅的包覆机理。     

Directly ultraviolet photochemical deposition of silver nanoparticles on silica spheres: Preparation and characterization

A simple method was developed to directly deposit silver nanoparticles on the surface of silica spheres. The photochemical reduction was carried out by ultraviolet irradiation in air atmosphere at room temperature. The [Ag(NH₃)₂]⁺was reduced to silver atoms upon ultraviolet irradiation. Silver atoms subsequently deposited on the surface of silica spheres and agglomerated into silver nanoparticles. Silica spheres with silver nanoparticles of different size and density can be simply controlled by adjusting the UV-light irradiation time. The silver nanoparticles deposited on silica spheres were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscopy, and field emission scanning electron microscopy.     

CdSe/CdS/SiO2 core/shell/shell nanoparticles

Quantum dots (QD) of a CdSe-ZnS core-shell structure are coated with silica spheres to improve their stability in biological buffers and biocompatibility in fluorescence imaging. We found that it was critical to transfer quantum dots from organic phase to aqueous phase before the silica shell growth process. As a result, high quality CdSe-ZnS-SiO2 core-shell-shell nanoparticles were prepared in high yields and their size and distribution are characterized with transmission electron microscopy and dynamic light scattering, which yielded uniform sizes and narrow polydispersity. Single particle fluorescence spectroscopy on the silica-protected quantum dots showed they were stronger emitters with consistent fluorescence intensity and "on-off" behaviors than bare CdSe-ZnS nanocrystals.     

Fabrication of hollow silver spheres by MPTMS-functionalized hollow silica spheres as templates

In this study, we provide a strategy to prepare the hollow silver spheres by accumulating the silver nanoparticles on the surface of 3-mercaptopropyltrimethoxysilane (MPTMS)-functionalized silica as templates, which was accomplished by the chemisorption between silver nanoparticles and thiol groups. Then, the resulting hollow silver spheres were obtained through the chemical wet etching process with 10 M HF solution. In conventional method, the fabrication of hollow silver spheres from core-shell spheres was not easy due to the difficulties in retaining the shell structures during core removal. The method in this paper could overcome this limitation. The major focus of study is on understanding the mechanism of formation of the hollow silver spheres through the self-assembly behavior by chemisorption between silver nanoparticles and thiol groups. The silver-coated silica and hollow silver spheres were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high-resolution TEM (HR-TEM), and X-ray photoelectron spectroscopy (XPS).     

Antibacterial activity of hybrid chitosan–cupric oxide nanoparticles on cotton fabric

In this study, cupric oxide (CuO) nanoparticles were prepared using sonochemical method. The prepared nanoparticles were studied using X‐ray diffraction (XRD) pattern, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) methods. The colloidal chitosan (CS) solution was prepared using ultrasound irradiation method and simultaneously mixed with CuO nanoparticles. The coatings of colloidal solution with and without CuO nanoparticles were studied through TEM images. The cotton fabrics were separately soaked in the prepared nanoparticle‐containing (hybrid) solutions by sonication method followed by pad‐dry‐cure method. The structural, functional, and morphological analyses of the coated and uncoated fabrics were performed using XRD, FTIR‐attenuated total reflectance, and SEM analyses, respectively. The hybrid‐coated cotton fabrics showed better antibacterial activity against Staphylococcus aureus and Escherichia coli. The bioactivity performance of the coated fabrics was in the order of CuO‐coated fabric > CS‐coated fabric.Inspec keywords: cotton fabrics, nanoparticles, antibacterial activity, transmission electron microscopy, Fourier transform spectroscopy, infrared spectroscopy, scanning electron microscopy, copper compoundsOther keywords: antibacterial activity, hybrid chitosan‐cupric oxide nanoparticles, cotton fabric, cupric oxide nanoparticles, sonochemical method, X‐ray diffraction, XRD pattern, Fourier transform infrared spectroscopy, FTIR spectroscopy, scanning electron microscopy, SEM, transmission electron microscopy, TEM methods, colloidal chitosan solution, ultrasound irradiation method, colloidal solution, TEM images, cotton fabrics, nanoparticle‐containing solutions, sonication method, pad‐dry‐cure method, morphological analyses, structural analyses, functional analyses, FTIR‐attenuated total reflectance, SEM analyses, hybrid‐coated cotton fabrics, Staphylococcus aureus, Escherichia coli, bioactivity performance, CuO     

Fabrication of superparamagnetic hydroxyapatite with highly ordered three-dimensional pores

Hydroxyapatite (HA) with highly ordered three-dimensional pores, whose size is about 300 nm, was prepared by colloidal template method. The effect of the surface modification of silica spheres on the order degree of porous structure was investigated by field emission scanning electron microscopy (FESEM). Then, superparamagnetic Fe₃O₄ nanoparticles were fabricated via redox reaction, followed by coating with silica via a sol–gel process, in which a certain amount of TEOS was used in order to control the thickness of the silica shell. X-ray diffraction (XRD), transmission electron microscopy (TEM), and magnetometry were applied to characterize the properties. Finally, Fe₃O₄ magnetic nanoparticles coated with silica were adsorbed in the mesopores of HA with highly ordered three-dimensional pores by capillarity. The influence of dispersing agent on the adsorption results has been studied. Magnetometry was applied to characterize the magnetic properties of superparamagnetic HA. The quantities of adsorbed SiO₂/Fe₃O₄ nanoparticles with core–shell have been compared by variation of saturation magnetization before and after adsorption.     

Synthesis and characterization of silica–lead sulfide core–shell nanospheres for applications in optoelectronic devices

Nanoscale miniaturization of chalcogenide semiconductors such as lead sulfide (galena) can generate interesting quantum confinement effects in the field of optoelectronic applications. In this work, we developed a process in order to obtain SiO₂ nanospheres coated with Galena, as the denominated core–shell system; this process is based on Stöber’s method, where the magnetic stirring was replaced by an ultrasonic bath to achieve well rounded and highly stable silica nanoparticles with diameters average of 70 nm. The PbS shell cover presents a thickness of 10 nm around. The nanostructures’ chemical composition, morphology, and optical properties were determined by transmission electron microscopy and UV–Vis spectroscopy. As a result, the nanoshells correspond to cubic PbS, presenting some interplanar distances of 2.95 Å and 3.41 Å; this nanoshell also shown an optical spectrum shift toward blue and a remarkable increase of 3.75 eV in its band gap, compared with the PbS bulk value. The chemical composition is studied by energy scattering spectroscopy and X-ray photoelectron spectroscopy analysis.

     

Fabrication of PbS nanoparticle coated amorphous carbon nanotubes: Structural, thermal and field emission properties

A simple chemical route for the synthesis of PbS nanoparticle coated amorphous carbon nanotubes (aCNTs) was described. The nanocomposite was prepared from an aqueous suspension of acid functionalized aCNTs, lead acetate (PbAc), and thiourea (TU) at room temperature. The phase formation and composition of the samples were characterized by X-ray diffraction and energy dispersive analysis of X-ray studies. The Fourier transformed infrared spectra analysis revealed the attachment of PbS nanoparticles on the acid functionalized aCNT surfaces. Morphology of the samples was analyzed with a field emission scanning electron microscope. UV-Vis study also confirmed the attachment of PbS nanoparticles on the walls of aCNTs. Thermal gravimetric analysis showed that the PbS coated aCNTs are more thermally stable than functionalized aCNTs. The PbS coated aCNTs showed enhanced field emission properties with a turn-on field 3.34 V μm⁻¹ and the result is comparable to that of pure crystalline CNTs.     

A facile approach to fabrication of PbS hollow spheres with improved polystyrene templates

This paper provides a simple route to produce monodisperse PbS hollow spheres by using cationic polystyrene (PS) micro-particles as templates. The templates used in our experiment, were prepared via emulsifier-free polymerization by using the cationic monomer 2-(methacryloyloxy) ethyltrimethylammonium chloride as co-monomer. X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTRI) were used to characterize the structure of the obtained PbS/PS composites and hollow PbS spheres. It was found that the as-produced samples are well-defined core-shell structures with an average diameter of about 0.98 μm. TEM showed that after the removal of the templates, the hollow structures were perfectly retained.     

Nanotexturing of GaN light-emitting diode material through mask-less dry etching

We describe a new technique for random surface texturing of a gallium nitride (GaN) light-emitting diode wafer through a mask-less dry etch process. This involves depositing a sub-monolayer film of silica nanospheres (typical diameter of 200 nm) and then subjecting the coated wafer to a dry etch process with enhanced physical bombardment. The silica spheres acting as nanotargets get sputtered and silica fragments are randomly deposited on the GaN epi-layer. Subsequently, the reactive component of the dry etch plasma etches through the exposed GaN surface. Silica fragments act as nanoparticles, locally masking the underlying GaN. The etch rate is much reduced at these sites and consequently a rough topography develops. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) inspections show that random topographic features at the scale of a few tens of nanometres are formed. Optical measurements using angle-resolved photoluminescence show that GaN light-emitting diode material thus roughened has the capability to extract more light from within the epilayers.     

单分散SiO_2/TiO_2/SiO_2多层复合微球的制备

采用一种以醇盐水解法为基础的生长硅溶胶的方法,制备了粒径为２００ｎｍ的单分散二氧化硅球形颗粒,并将其作为核心,利用常温连续进料的钛酸丁酯水解的多步法,在二氧化硅核心外经多次包覆形成厚层二氧化钛;在正硅酸乙酯的水解和陈化环境下,将上述ＴｉＯ２／ＳｉＯ２复合颗粒外再包覆一薄层二氧化硅,形成一种高折射率,可用于组装光子晶体的ＳｉＯ２／ＴｉＯ２／ＳｉＯ２多层复合微球．对该复合微球用重力沉降法、透射电镜法（ＴＥＭ）、Ｘ射线能谱分析法（ＥＤＳ）进行了表征．其中,重力沉降法是一种将Ｓｔｏｋｅｓ公式为基础推导的复合颗粒的粒径与沉降速度关系式所得的一系列数据进行拟合外延,来测定复合颗粒的粒径及包覆厚度的方法．     

Size-controllable preparation of bovine serum albumin-conjugated PbS nanoparticles

Protein-conjugated PbS nanocrystals with the average sizes of 15, 25, and 35 nm have been synthesized by adjusting the concentration of the bovine serum albumin (BSA) solution at room temperature. The obtained BSA-conjugated PbS nanoparticles have been characterized by powder X-ray diffraction, transmission electron microscopy, selected-area electron diffraction, high-resolution transmission electron microscopy, thermal analyses and photoluminescence. The quantum-confined effect of the BSA-conjugated PbS nanoparticles has been confirmed by the UV–vis spectra. The results indicated that the BSA not only induced the nucleation, but inhibited the further growth of PbS nanocrystals. The effect of Pb²⁺ on BSA and the change of BSA conformation were studied through Fourier transform infrared spectroscopy and circular dichroism spectroscopy. The possible mechanism of BSA-conjugated PbS nanoparticles growth was also discussed.     

From CdS aggregate spheres to PbS hollow spheres: a case study of the growth mechanism in chemical conversion

Monodisperse PbS hollow spheres were successfully prepared via using CdS aggregate spheres as template. The present strategy is based on the different solubilities of CdS and PbS. This process was intensively studied by time-dependent trails which were monitored by transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and photoluminescence spectroscopy (PL). Reaction temperature was found to play an important role in controlling the diffusion rate of Pb²⁺ ions and the quality of as-prepared PbS crystals, which finally leads to different shape evolution processes from the starting aggregate spheres to the final hollow spheres. Two growth mechanisms defined as kinetics-controlled process (KCP) and thermodynamics-controlled process (TDCP) were, respectively, proposed for the two conversion patterns observed at 30 and 90 °C. Moreover, specific structural evolution including primary crystal size, diameter growth, and shell thickness were also discussed in detail. This work is of great significance in elucidating the underlying mechanism of chemical conversion and could be potentially applied to synthesize other hollow architectures.     

Influence of pluronic P123 in modifying the morphological and optical properties of PbS nanocomposite

Pluronic (P123) capped lead sulphide (PbS) nanoparticles were synthesized for the first time by simple wet chemical method. Series of experiments were conducted by changing the concentration of P123 to establish the most suitable conditions for obtaining different morphologies of PbS nanoparticles. The synthesized product has been characterized by powder X-ray diffraction (XRD), UV–Vis spectrophotometry, scanning electron microscopy (SEM), transmission electron Microscopy (TEM), energy dispersive X-ray spectroscopy (EDX) and photoluminescence studies. The particle size observed from XRD analysis is around 44–3 nm. Significant “blue shift” from bulk material was observed on the PbS nanoparticles using UV–Vis spectra. A sevenfold increase in photoluminescence intensity has been observed from PbS nanoparticles after surface passivation by P123 agent.     

Mesoporous silica-magnetite nanocomposite synthesized by using a neutral surfactant

Magnetite nanoparticles coated by mesoporous silica were synthesized by an alternative chemical route using a neutral surfactant and without the application of any functionalization method. The magnetite (Fe(3)O(4)) nanoparticles were prepared by precipitation from aqueous media, and then coated with mesoporous silica by using nonionic block copolymer surfactants as the structure-directing agents. The mesoporous SiO(2)-coated Fe(3)O(4) samples were characterized by x-ray diffraction, Fourier-transform infrared spectroscopy, N(2) adsorption-desorption isotherms, transmission electron microscopy, (57)Fe M?ssbauer spectroscopy, and vibrating sample magnetometry. Our results revealed that the magnetite nanoparticles are completely coated by well-ordered mesoporous silica with free pores and stable (～8?nm thick) pore walls, and that the structural and magnetic properties of the Fe(3)O(4) nanoparticles are preserved in the applied synthesis route.     

Ultrasonic-assisted synthesis and magnetic studies of iron oxide/MCM-41 nanocomposite

Iron oxide nanoparticles were stabilized within the pores of mesoporous silica MCM-41 amino-functionalized by a sonochemical method. Formation of iron oxide nanoparticles inside the mesoporous channels of amino-functionalized MCM-41 was realized by wet impregnation using iron nitrate, followed by calcinations at 550 °C in air. The effect of functionalization level on structural and magnetic properties of obtained nanocomposites was studied. The resulting materials were characterized by powder X-ray diffraction (XRD), high-resolution transmission electron microscopy and selected area electron diffraction (HRTEM and SAED), vibrating sample and superconducting quantum interface magnetometers (VSM and SQUID) and nitrogen adsorption–desorption isotherms measurements. The HRTEM images reveal that the most of the iron oxide nanoparticles were dispersed inside the mesopores of silica matrix and the pore diameter of the amino-functionalized MCM-41 matrix dictates the particle size of iron oxide nanoparticles. The obtained material possesses mesoporous structure and interesting magnetic properties. Saturation magnetization value of magnetic iron oxide nanopatricles stabilized in MCM-41 amino-functionalized by in situ sonochemical synthesis was 1.84 emu g⁻¹. An important finding is that obtained magnetic nanocomposite materials exhibit enhanced magnetic properties than those of iron oxide/MCM-41 nanocomposite obtained by conventional method. The described method is providing a rather short preparation time and a narrow size distribution of iron oxide nanoparticles.     

Preparation of silica coated iron oxide nanoparticles using non-transferred arc plasma

Silica coated iron oxide nanoparticles were prepared using non-transferred arc plasma. The plasma was discharged with argon. Vapors of iron pentacarbonyl (Fe(CO)₅) and tetraethyl orthosilicate (TEOS, Si(OC₂H₅)₄) were injected into a plasma torch with carrier gas and reacted in the plasma chamber. In addition, two types of reaction chambers that are a hot wall reactor and a cold wall reactor were used to investigate the effect of temperature gradient on the synthesis of silica coated iron oxide nanoparticles. The synthesized nanoparticles were collected on the chamber wall and bottom. Phase compositions of the obtained nanoparticles were characterized by X-ray diffractometer (XRD) and the morphologies and the size distributions of the synthesized particles were analyzed by scanning electron microscopy (SEM) and transmission electron microscope (TEM). Additionally, elements mapping of the coated particles was performed by energy dispersive spectroscopy (EDS). The phase composition of the prepared particles was mainly composed of amorphous silica and polycrystalline Fe₃O₄. It was confirmed that the silica was adsorbed on iron oxide particles or encapsulated iron oxide particles. Furthermore, the mechanism of the formation of silica coated iron oxide in the plasma chamber was predicted.     

Fabrication of nanoscaled silica layer on the surfaces of submicron SiO2-Ag core-shell spheres

A two-step silica deposition process, including prefunctionalization with poly(vinylpyrrolidone) and the following silica deposition, has been used to fabricate silica layer on the surface of nanoscaled silver shell. The influencing parameters of silica coating process were optimized to prevent the precoated silver nanoparticles from desquamating from silica spheres, finally to obtain mono-dispersed silica spheres with silver and silica multilayer films. The resulted silica layer was dense and uniform, its thickness was controllable in the range of 20–50 nm. Such coated silica layer can provide improved thermal stability of the SiO₂-Ag core-shell structural spheres.     

Optical and surface morphological properties of triethylamine passivated lead sulphide nanoparticles

The triethylamine capped lead sulphide (PbS) nanoparticles were successfully synthesized by simple wet chemical method. The synthesized product has been characterized by powder X-ray diffraction (XRD), UV–vis spectrophotometry, FTIR spectroscopy, atomic force microscopy (AFM), transmission electron microscopy (TEM) and photoluminescence studies. The size of the PbS nanoparticles was determined from AFM, TEM, XRD and from these studies it is found that the size of the particles of the order of 10–15 nm. Significant “blue shift” from bulk material was observed on the PbS nanoparticles using UV–vis and photoluminescence spectrum.