One-pot synthesis and optical properties of monodisperse ZnSe colloidal microspheres

Monodisperse ZnSe colloidal microspheres were fabricated by a green one-pot wet chemical strategy through aggregation of primary nanoparticles without expensive organic additives or reductants involved. The as-prepared products were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectrum, X-ray photoelectron spectroscopy (XPS), UV–vis absorption and room-temperature photoluminescence techniques. The size-dependent optical spectra of as-obtained microspheres were blue-shifted in comparison with that of bulk ZnSe and exhibit near band edge luminescence, indicating the quantum confinement effect. The strong and stable blue emission band from the ZnSe colloidal microspheres indicates their potential applications as building blocks in photonic crystals.     

Synthesis, optical, structural and thermal characterization of Mn doped ZnS nanoparticles using reverse micelle method

Mn²⁺­doped ZnS nanoparticles have been prepared through the reverse micelles method using sodium bis (2-ethylhexyl) sulfosuccinate (AOT) as a surfactant. The prepared particles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infra-red spectrometer (FT-IR), UV-vis spectrometry, photoluminescence (PL), electron spin resonance (ESR) and thermogravimetry-differential scanning calorimetry (TG-DSC).     

Template-free solution approach to synthesize ZnSe hollow microspheres

Uniform hollow spherical assemblies of ZnSe nanoparticles have been synthesized through a template-free hydrothermal route at low temperature. The product was characterized by means of X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and the Raman spectrum. The two strong Raman vibrational peaks of the ZnSe hollow microspheres indicate a clear shift towards lower frequency, which may be associated with the small size and large surface effects. Also, the ZnSe hollow microspheres show a strong luminescence at about 652 nm. PACS 61.46.+w; 78.67.Bf; 81.05.Dz; 81.05.Hd; 81.10.Dn     

Study of Structural and Photoluminescent Properties of Ca8Eu2(PO4)6O2

In this work it is presented for the first time the nanostructured hydroxyapatites doped with 0.5, 1.0 and 2.0 wt% of Eu³⁺ prepared at room temperature by the mechanical alloying technique. X-ray diffraction powder (XRD), infrared (IR) and Raman scattering spectroscopy, scanning electron microscopy (SEM), microhardness measurements as well as luminescent data of Eu³⁺ were used to investigate the structural and optical properties of these nanomaterials. The electrical and dielectrical analyses were used with the intention of having a better comprehension about the electromagnetic fields in pure and doped hydroxyapatites.     

Preparation of nanodiamonds by laser irradiation of graphite

Graphite powders were irradiated by pulsed laser at room temperature and normal pressure and then boiled in perchloric acid. Samples were characterized by high-resolution transmission electron microscopy (HRTEM), electron diffraction pattern (EDP), X-ray diffraction (XRD) pattern, and Raman spectroscopy.The analyses on the HRTEM images, EDP, and XRD show that the diamond particles with a size of about 5 nm are obtained. The shifting and broadening of the diamond peak in Raman spectrum indicate that there are high defect density and residual internal stress in synthetic diamond.     

Visible-light photocatalytic degradation of methylene blue with laser-induced Ag/ZnO nanoparticles

The preparation of Ag doped ZnO nanoparticles conducted through the method of laser-induction is presented in this work. The Ag/ZnO nanoparticles attained from various weight percentages of added AgNO₃ relative to ZnO were applied under visible-light irradiation for evaluating the heterogeneous photocatalytic degradations of methylene blue (MB) solutions. It was shown that the catalytic behavior of Ag/ZnO nanoparticles in the visible-light range is notably improved through the Ag deposition onto ZnO nanoparticles by the method of laser-induction with a maximum effectiveness of 92% degradation. The properties of the nanoparticles were characterized by the employments of UV-vis spectroscopy (UV-vis), X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), and selected-area electron diffraction (SAED).     

Different effects of cerium ions doping on properties of anatase and rutile TiO2

Pure and Ce⁴⁺ doped anatase and rutile TiO₂ were prepared by hydrothermal methods and characterized by XRD, TEM, UV-vis diffusion spectroscopy, and XPS measurements. The photocatalytic reactivity of the catalysts was evaluated by the photodegradation of Rhodamine B (RB) under ultraviolet irradiation. The photocatalytic efficiency of the rutile sample doped with an appropriate amount of Ce⁴⁺ was enhanced while all Ce⁴⁺ doped anatase samples showed a much lower activity than pure anatase. The reasons were discussed     

Enhanced photocatalytic activity and stability of nano-scaled TiO2 co-doped with N and Fe

Titanium dioxide (TiO₂) nanoparticles co-doped with N and Fe were prepared via modified sol-gel process. The products were characterized by transmission electron microscopy (TEM), N₂ adsorption, X-ray diffraction (XRD), Raman spectroscopy, UV-vis spectroscopy, photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS). It is shown that the prepared TiO₂ particles were less than 10 nm with narrow particle size distribution. The addition of MCM-41 caused the formation of Ti-O-Si bond which fixed the TiO₂ on MCM-41 surface, thus restricted the agglomeration and growth of TiO₂ particles. The photocatalytic performance in the degradation of methylene blue showed that N, Fe co-doped TiO₂ exhibited much higher photocatalytic activity than doped sample with nitrogen or Fe³⁺ alone under both UV and visible light. N, Fe co-doping decreased the loss of doping N during the degradation reaction, thus increased the photocatalytic stability. It was also found that the nitridation time had significant influence on the photocatalytic activity of prepared TiO₂ catalysts.     

Study of the growth of CeO2 nanoparticles onto titanate nanotubes

We report the study of the growth of CeO₂ nanoparticles on the external walls and Ce⁴⁺ intercalation within the titanate nanotubes. The materials were fully characterized by multiple techniques, such as: Raman spectroscopy, infrared spectroscopy (FTIR), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The ion exchange processes in the titanate nanotubes were carried out using different concentrations of Ce⁴⁺ in aqueous solution. Our results indicate that the growth of CeO₂ nanoparticles grown mediated by the hydrolysis in the colloidal species of Ce and the attachment onto the titanate nanotubes happened and get it strongly anchored to the titanate nanotube surface by a simple electrostatic interaction between the nanoparticles and titanate nanotubes, which can explain the small size and even distribution of nanoparticles on titanate supports. It was demonstrated that it is possible to control the amount and size of CeO₂ nanoparticles onto the nanotube surface, the species of the Ce ions intercalated between the layers of titanate nanotubes, and the materials could be tuned for using in specific catalysis in according with the amount of CeO₂ nanoparticles, their oxygen vacancies/defects and the types of Ce species (Ce⁴⁺ or Ce³⁺) present into the nanotubes.     

Biomimetic synthesis of HgS nanoparticles in the bovine serum albumin solution

HgS nanocrystals conjugated with protein were synthesized in aqueous solution of Bovine Serum Albumin (BSA) at room temperature. The obtained HgS nanoparticles with average diameter about 20–40 nm were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), selected-area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM). The quantum-confined effect of the HgS nanoparticles is confirmed by the ultraviolet-visible (UV-vis) and photoluminescence (PL) spectrum. The rescults indicate that the BSA not only induce the nucleation, but inhibit the further growth of HgS nanoparticles. The effect of Hg²⁺ on BSA and the change of BSA conformation were studied through Fourier transform infrared (FTIR) spectroscopy and Circular dichroism (CD) spectroscopy. The possible mechanism of HgS nanoparticles growth in the BSA solution was also discussed.     

White light emission from sonochemically synthesized rare earth doped ceria nanophosphors

Undoped CeO₂, and single and triple doped CeO₂:M (where M=Dy³⁺, Tb³⁺and Eu³⁺) nanophosphors were synthesized through a simple sonochemical process and characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), EDS and photoluminescence (PL) spectrophotometry. The TEM micrographs show that resultant nanoparticles have flower-like shape. The doped samples showed multicolor emission on single wavelength excitation. Energy transfer was observed from host to the dopant ions. Characteristic blue emission from Dy³⁺ ions, green from Tb³⁺ ions and red from Eu³⁺ ions were observed. The CIE coordinates of the triple doped Ce_0.86Dy_0.005Tb_0.055Eu_0.08O₂ nanoflowers lie in the white light region of the chromaticity diagram and show promise as good phosphor materials for new lighting devices.     

CdSe/ZnSe核-壳结构纳米粒子合成新方法

报道用“一步”合成新方法制备了CdSe/ZnSe核-壳结构的发光纳米粒子.该方法是将锌的前驱体注入表面Se富集的CdSe发光纳米粒子溶液中,通过Zn²⁺与Se共价键结合,从而在CdSe发光纳米粒子的表面形成ZnSe壳.分别通过X射线粉末衍射、光电子能谱、透射电镜、紫外-可见吸收光谱和光致发光光谱,对核-壳结构的发光纳米粒子的结构及光学性质进行了表征.结果表明,以较宽带隙的ZnSe在较窄带隙的CdSe纳米粒子表面形成的壳层有效地钝化了CdSe纳米粒子的表面缺陷,明显地提高了室温下CdSe纳米粒子的光致发光效率.X射线粉末衍射表明随着Zn²⁺的不断注入,CdSe/ZnSe的衍射峰逐渐移向ZnSe衍射峰.光电子能谱数据显示,Zn2p的双峰分别位于1020,1040eV附近,通过与体材料ZnO相比,确定为Zn²⁺的光电子发射,说明Zn是以共价键形式存在于CdSe纳米粒子的表面.透射电镜照片显示纳米粒子具有良好的单分散性,核-壳结构的发光纳米粒子直径较CdSe核的直径明显增加.     

Compatibility and optoelectronic of ZnSe nano crystalline thin film

We report the room temperature synthesis of zinc selenide (ZnSe) nano crystalline thin film on quartz by using a relatively simple and low cost closed space sublimation process (CSSP). The compatibility of the prepared thin films for optoelectronic applications was assessed by X-ray diffraction (XRD), atomic force microscope (AFM), scanning electron microscope (SEM), Raman spectroscopy, photoluminescence, and Fourier transform infrared spectroscopy (FT-IR). The XRD confirmed that the films were polycrystalline with the preferential orientation along the (111) plane corresponding to the cubic phase (2θ = 27.28 ). The AFM indicated that the ZnSe film presented a smooth and compact morphology with RMS roughness 19.86 nm. The longitudinal optical phonon modes were observed at 247 cm 1 and 490 cm 1 attributed to the cubic structured ZnSe. The Zn-Se stretching band was confirmed by the FT-IR. The microstructure and compositional analysis was made with the SEM. The grain size, dislocation density, and strain calculated were co-related. All these properties manifested a good quality, high stability, finely adhesive, and closely packed structured ZnSe thin film for optoelectronic applications.     

Optimization of ZnSe film growth conditions for p-type doping

Wide bandgap semiconductors such as ZnSe and ZnO have attracted great interest due to their applications in solar cells, light emitting diodes, and lasers. However, these wide bandgap semiconductors are frequently difficult to be doped to heavy concentrations, greatly limiting their application. A substrate holder with a natural temperature gradient was developed for batch growth of films at different deposition temperatures, in order to investigate ZnSe film growth and doping challenges. Thin ZnSe films were grown by pulsed laser deposition and characterized using X-ray diffraction, optical transmission and reflection, Raman spectroscopy, and Energy Dispersive X-ray analysis. Deposition temperature and film stoichiometry (Zn:Se) are shown to be significant factors affecting ZnSe growth and doping. ZnSe films with improved crystallinity have been obtained by enriching with selenium and depositing at an optimized temperature. Heavily p-type ZnSe films with hole concentrations of ~2.7 × 10¹⁹ cm^?3 and resistivities of ~0.099 Ohm cm have been obtained (compared with previous reports of ~1 × 10¹⁸ cm^?3 and ~0.75 Ohm cm). The results, which are consistent with previous theoretical prediction of compensating defects in ZnSe films, can help to optimize ZnSe growth conditions and understand doping challenges in wide bandgap semiconductors.     

A novel precursor for synthesis of metallic copper nanocrystals by thermal decomposition approach

[Bis(2-hydroxy-1-naphthaldehydato)copper(II)] complex, as a novel precursor, was employed in thermal decomposition process to synthesize metallic copper nanoparticles using oleylamine (C₁₈H₃₇N) as capping agent. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible (UV-vis) spectroscopy. The synthesized copper nanoparticles have a fcc structure with average size 20-35 nm.     

Syntheses of optically efficient (La1−x−yCexTby)F3 nanocrystals via a hydrothermal method

Optically efficient cerium and terbium doped lanthanide fluoride (La_1−x−yCe_xTb_y)F₃ nanocrystals with different doping concentrations have been synthesized by a hydrothermal route in the presence of ethylenediamine tetraacetic acid disodium salt (EDTA). The results showed that the formation of nanocrystals with different morphologies depends on terbium ion Tb³⁺ doping concentration, but independent of cerium ion Ce³⁺ doping concentration. With increase in Tb³⁺ doping concentration, the morphologies of nanocrystals evolved from a spherical shape to a plated-like one. In addition, both the photoluminescence quantum yield (PL QY) and the fluorescence lifetime of nanocrystals increased with the increase in Ce³⁺ doping concentration in cerium and terbium co-doped system. The PL QY reached up to 55%, and the lifetime up to 7.3 ms. Transmission electron microscopy (TEM), X-ray diffraction (XRD), selected area electron diffraction (SAED), X-ray fluorescence (XRF), energy dispersive spectroscopy (EDS), ultraviolet-visible (UV-vis) absorption, photoluminescence (PL) and infrared (IR) spectroscopies were employed to characterize the properties of nanocrystals. The growth mechanism of nanocrystals with different morphologies and optical properties of nanocrystals with different doping concentrations were investigated.     

Structure and photocatalytic properties of copper-doped rutile TiO2 prepared by a low-temperature process

Copper-doped titania with variable Cu/Ti ratios have been prepared via a simple aqueous-phase method at 85 °C. The obtained products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and UV-vis absorption spectra analysis. The photocatalytic properties of the products were tested by photocatalytic degradation of aqueous brilliant red X-3B solution. The results showed that the sample with 2% copper doping has the best photocatalytic activity, which is 3 times that of undoped rutile titania. The effect of the doped copper on the structure and property of TiO₂ has also been discussed.     

Tin-doped indium oxide nanobelts grown by carbothermal reduction method

This communication discusses the formation of doped nanobelts produced by a simple route. Tin-doped indium oxide (ITO) nanobelts were obtained by a carbothermal reduction method. The nanostructures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX) and wavelength-dispersive X-ray spectroscopy (WDX). The results show that the nanobelts have a cubic structure, are single crystalline and doped with tin and grow in the [400] direction. PACS 81.07.-b; 61.46.+w; 68.37.Hk; 68.37.Lp     

Synthesis and characteristics of natural zeolite supported Fe-TiO2 photocatalysts

Natural zeolite supported Fe³⁺-TiO₂ photocatalysts were synthesized for the sake of improving the recovery and photocatalytic efficiency of TiO₂. The as-prepared materials were characterized by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflection spectroscopy (UV-vis DRS), scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDX). Methyl orange was used to estimate the photocatalytic activity of the samples. The results showed that zeolite inhibited the growth of TiO₂ crystallite sizes. The Fe³⁺ concentration played an important role on the microstructure and photocatalytic activity of the samples. The iron ions could diffuse into TiO₂ lattice to the form Fe-O-Ti bond and gave TiO₂ the capacity to absorb light at lower energy levels. The photocatalytic activity of the samples could be enhanced as appropriate dosages of Fe³⁺ were doped.     

Catalytic synthesis of single-crystalline gallium nitride nanobelts

Single-crystalline gallium nitride nanobelts have been synthesized through the reaction of gallium vapor with flowing ammonia using nickel as a catalyst. The as-synthesized products were characterized using X-ray powder diffraction (XRD), scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and selected-area electron diffraction (SAED). XRD and SAED results revealed that the products are pure, single-crystalline GaN with hexagonal structure. The widths and thickness of the nanobelts ranged from 80 to 200 nm, and 10 to 30 nm, respectively. The lengths were up to several tens of micrometers. The nanobelts had smooth surface with no amorphous sheath, and a sharp-tip end. The growth mechanism of nanobelts was discussed.