Enhanced photoluminescence properties of ZnS:Cu2+ nanoparticles using PMMA and CTAB surfactants

ZnS nanoparticles with Cu²⁺ doping have been synthesized at 80 °C through a soft chemical route, namely the chemical co-precipitation method at air atmosphere. The water soluble PMMA and CTAB were used as capping agents. The nanostructures of the synthesized nanoparticles have been analyzed using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transform infrared spectrometer (FT-IR), UV–vis and fluorescence spectrophotometer. The sizes of as-prepared nanoparticles are found to be below 3.4–5.2 nm range. Room temperature photoluminescence (PL) spectrum of the undoped sample exhibits emission in the blue region with multiple peaks under UV excitation. On the other hand, in the Cu²⁺ doped ZnS samples enhanced visible light emissions with emission intensities of ∼2 times larger than that of the undoped sample are observed for CTAB capped sample. The phase changes were observed in different temperatures by TG-DTA.     

Synthesis and optical property of ZnO nano-/micro-rods

A series of zinc oxide (ZnO) nano-/micro-rods had been synthesized via solution-based routes. In the hydrothermal route, the obtained ZnO nano-/micro-rods had two topographies. In refluxing procedures, spindly ZnO nanorods were obtained in the presence of poly(vinyl-pyrrolidone) (PVP) and ellipsoid-like nanorods were obtained in the absence of PVP. The products were characterized using X-ray powder diffraction (XRD),scanning electron microscope (SEM), transmission electron microscope (TEM), and electron diffraction (ED)analysis. Room temperature photoluminescence (PL)spectra of the ZnO products demonstrated a weak UV emission and a broad visible emission for each of the sample. The growth mechanism of 1-D ZnO crystals was discussed briefly.     

Characteristics and optical properties of MgO nanowires synthesized by solvothermal method

Magnesium oxide (MgO) nanowires were synthesized by solvothermal method using magnesium nitrate hexahydrate and sodium hydroxide. Field emission scanning electron microscopy (FE-SEM) and transmission scanning electron microscopy (TEM) measurements indicate that the product consists of a large quantity of nanowires with average diameter of 20 nm and average length of several micrometers. Explorations of X-ray diffraction (XRD), energy dispersive analysis of X-ray (EDAX), Fourier transformer infrared spectroscopy (FTIR), selected area electronic diffraction (SAED) and high-resolution transmission electron microscope (HRTEM) indicate that the product is high-quality cubic single-crystalline nanowires. The optical properties of the samples are investigated using UV–visible spectroscopy to study the refractive index and optical dielectric constant. The photoluminescence (PL) measurement suggests that the product has an intensive emission centered at 437 nm, showing that the product has potential application in optical devices. The advantages of our method lie in high yield, the easy availability of the starting materials and allowing their large-scale production at low cost.     

Phase transformation from cubic ZnS to hexagonal ZnO by thermal annealing

We have investigated the mechanism of phase transformation from ZnS to hexagonal ZnO by hightemperature thermal annealing. The ZnS thin films were grown on Si(001) substrate by thermal evaporation system using ZnS powder as source material. The grown films were annealed at different temperatures and characterized by X-ray diffraction(XRD), photoluminescence(PL), four-point probe, scanning electron microscope(SEM) and energy dispersive X-ray diffraction(EDX). The results demonstrated that as-deposited ZnS film has mixed phases but high-temperature annealing leads to transition from ZnS to ZnO. The observed result can be explained as a twostep process:(1) high-energy O atoms replaced S atoms in lattice during annealing process, and(2) S atoms diffused into substrate and/or diffused out of the sample. The dissociation energy of ZnS calculated from the Arrhenius plot of 1000/T versus log(resistivity) was found to be 3.1 eV. PL spectra of as-grown sample exhibits a characteristic green emission at 2.4 eV of ZnS but annealed samples consist of band-to-band and defect emission of ZnO at 3.29 eV and 2.5 eV respectively. SEM and EDX measurements were additionally performed to strengthen the argument.     

Optical properties of undoped and cobalt doped ZnS nanophosphor

In the present study, the optical properties of ZnS and cobalt (Co) doped ZnS nanoparticles were investigated at room temperature. ZnS and ZnS:Co nanophosphors were prepared through chemical route, namely the chemical precipitation method and the formation of the nanoparticles were confirmed by X-ray diffraction and field emission scanning electron microscope (FESEM). Band gap energy of the prepared samples is determined by using a UV–vis–NIR spectrophotometer. The photoluminescence property of ZnS and ZnS:Co sample is determined by fluorescence spectroscopy. The sizes of as prepared nanoparticles are found to be in the 8–9 nm range. The FESEM morphology shows the formation of nanostructure of ZnS samples. The value of optical band gap has been found to be in the range 4.30–4.03 eV. Room temperature photoluminescence (PL) spectrum of the undoped sample exhibits emission in the blue region with multiple peaks under UV excitation. On the other hand, Co²⁺ doped ZnS samples show enhanced visible light emissions under the same UV excitation wavelength of 310 nm.     

The role of oxidizing agents in the structural and morphological properties of CeO2 nanoparticles

Cerium oxide (CeO₂) nanoparticles with good crystallinity and smooth surface are prepared by chemical precipitation method with different bases (NH₃, NaOH and KOH) using cerium nitrate as a source material. The effect of precipitating agents on the growth of cerium oxide nanoparticles are investigated by Photoluminescence (PL), X-ray diffraction (XRD), Fourier transform-infra red spectroscopy (FTIR), thermo gravimetric–differential thermal analysis (TG-DTA), Scanning electron microscope (SEM), Transmission electron microscope (TEM), and X-ray Photoelectron Spectroscopy (XPS). Cubic fluorite crystallites are detected by XRD pattern with preferred orientation along (1 1 1) direction. PL spectra revealed the presence of a strong and broad emission band at425 nm due to the blue shift in the visible region. The broad band below 700 cm⁻¹ is due to the envelope of the phonon band of metal oxide (Ce–O) network as revealed by the IR spectra. The TG-DTA curves revealed that the total weight loss of the samples is 19.67% when the samples are heated upto 800 °C. SEM images exhibits weakly agglomerated spheroid crystallites are obtained with the typical size in the range 10–50 nm. TEM images display that the particles are nearly spherical and square in shape with diameter 8–12 nm. XPS spectrum confirms the existence of Ce⁴⁺ oxidation states in CeO₂samples.     

氧化锌纳米棒中自发辐射的回音壁模腔增强

应用气相传输法制备了氧化锌纳米线和具有六方对称截面的纳米棒,利用电子扫瞄显微镜,X-射线衍射仪等进行形貌与结构表征。室温下,用355nm激光脉冲,以260 W/cm2相同光强激励条件,分别测量其光致发光(PL)谱,在棒状样品中发现393nm有发光峰,而线状样品是在382nm处。二者相比,棒状样品的紫光波段自发辐射光强增加、频谱展宽、中心波长红移和绿光波段辐射被显著抑制。基于半导体材料的能带理论、激子复合发光理论和费米黄金定则等,对样品PL谱差异原因进行理论分析,结果表明上述现象源于棒状样品中回音壁模谐振腔(WGMRs)的自发辐射增加。利用强激励条件下样品光致发光谱,验证了实验结果与理论分析结果较好吻合。     

One-step, solid-state reaction to ZnO nanoparticles in the presence of ionic liquid

ZnO nanoparticles have been synthesized in ionic liquids (1-butyl-3-methylimidazolium chloride, [BMIM]Cl) by one-step solid-state reaction at room temperature for short time. The structure and morphology of the products were characterized by means of X-ray powder diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM), whose results indicated that the sample was spherical in morphology with diameters of 15–20 nm. The room temperature photoluminescence spectra (PL) showed strong and broad green light emission. In addition, [BMIM]Cl could be collected and reused for subsequent reactions. This method provides a facile, one-step and low-cost route for the synthesis of nanostructures of metal oxides with potential photo-catalysis.     

High Purity and Large-scale Preparation of β-Ga2O3 Nanowires and Nanosheets by CVD and Their Raman and Photoluminescence Characteristics

Ga2O3 nano-structures,nanowires and nanosheets are produced on Au pre-coated(111) silicon substrates with chemical vapor deposition(CVD) technique.By evaporating pure Ga powder in the H2O atmosphere under ambient pressure the large-scale preparation of β-Ga2O3 with monoclinic crystalline structure is achieved.The crystalline structures and morphologies of produced Ga2O3 nano-structures are characterized by means of scanning electron microscope(SEM),X-ray diffraction(XRD),selected area electron diffraction(SAED) and transmission electron microscope(TEM).Raman spectrum reveals the typical vibration modes of Ga2O3.The vibration mode shifts corresponding to Ga2O3 nano-structures are not found.Two distinguish photoluminescence(PL) emissions are found at about 399 nm and 469 nm owing to the VO-VGa excitation and VO-VGa-O excitation,respectively.The growth mechanisms of Ga2O3 nanowires and nanosheets are discussed with vapor-liquid-solid(VLS) and vapor-solid(VS) mechanisms.     

Large-scale and facial fabrication of PbS nanorods by sulfuration of a Pb sheet

PbS nanostructures were synthesized by sulfuration of lead sheets in a tube furnace under sulfur ambiance. The lead sheets were placed in different temperature zones, between 330 and 470 °C. Field emission scanning electron microscope (FESEM) images showed that only the lead sheet placed at 330 °C showed nanorods morphology. The prepared nanorods exhibited a rectangular shape with an average diameter of 95 nm and an average length of 400 nm. The phase and composition of the product were identified by x-ray diffraction (XRD) pattern and x-ray photoelectron spectra (XPS). The pattern indicated that these PbS nanorods were with a cubic phase and the XPS result showed binding energy for lead and sulfur that belonged to PbS structure. In addition, Raman measurements confirmed the XRD pattern and XPS results and indicated three Raman active modes, which belonged to PbS phase for the nanorods. The optical properties of the products were characterized by UV–visible and room temperature photoluminescence (PL) spectrometers. The optical characterization results showed a band gap for the PbS nanorods in the infrared region.     

Studies on structural,morphological, magnetic and optical properties of chromium sesquioxide (Cr2O3) nanoparticles: Synthesized via facile solvothermal process by different solvents

Chromium sesquioxide (Cr₂O₃) nanoparticles have been successfully synthesized via the facile solvothermal process, by using CrO₃ in different solvents. The as-synthesized nanoparticle sizes are calculated and confirmed to be 25–45 nm, by using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The functional groups of the samples were tested by the Fourier transform infrared (FTIR) spectroscopy. Fine and spherical-like morphologies and compositional elements of the products were observed by the scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy. A weak ferromagnetic (WFM) property was observed for sample by the vibrating sample magnetometer (VSM). The observed band gap values (E_g=4.33–3.54 eV) higher than that of bulk Cr₂O₃ (~3.4 eV) indicated that the particles had been successfully synthesized in the nano region, and measured by ultra-violet visible (UV–vis) absorption spectroscopy. The broad visible emission at ~399 nm, in the photoluminescence spectroscopy revealed the high purity and perfect crystallinity of the samples.     

SnO2纳米棒阵列的制备及光学、场发射性能研究

采用简单的一步水热法直接在不锈钢基底上制备了不同形貌的SnO2纳米棒阵列。利用X射线衍射（XRD）,扫描电镜（SEM）、透射电镜（TEM）、 分光光度计、场发射装置对材料的结构、形貌、光致发光谱和场发射特性进行了表征。XRD结果表明不锈钢基底上制备的样品为四方晶系金红石结构。SEM和TEM结果表明不同的反应条件下都能够在基底上大面积的垂直生长单晶SnO2纳米棒阵列,但是形貌和尺寸发生了改变（A:针尖状,B:铅笔状）。室温下的光致发光光谱（PL）表明两种样品在367、392、419 nm处分别存在较强的发射峰,并且紫外光峰强与可见光峰强比值较大,说明样品的结晶质量较好。场发射测试结果表明:两种样品的场发射都是通过电子隧道效应进行的,且样品A的场发射性能优于样品B。     

Visible light active TiO2–ZnO composite films by cerium and fluorine codoping for photocatalytic decontamination

The visible light active Ce/F codoped TiO₂–ZnO composite films with a bad gap of 1.82 eV were successfully prepared though a simple sol–gel method. Experimental results indicated that the composite films showed excellent photocatalytic performance towards photocatalytic oxidation of organic pollutants including formaldehyde, acid naphthol red (ANR) and methyl green (MG). The catalysts were characterized by photoluminescence (PL) spectra, UV–vis diffraction reflectance absorption spectra (DRS), X-ray diffraction (XRD), differential thermal analysis-thermogravimetry (DTA-TG), field emission scanning electron microscopy (FE-SEM) equipped with energy-dispersive spectroscopy (EDS), and N₂ adsorption/desorption isotherms. The DRS and PL spectra results showed that multi-modification not only induced strong visible light absorption but also reduced the recombination rate of electron–hole pairs. The DTA-TG and XRD results indicated that the crystal type of the TiO₂-based catalyst was mostly stabilized in anatase. The FE-SEM and BET surface area results revealed that the nanocrystalline Ce/F codoped TiO₂–ZnO composite samples with the larger specific surface area were composed of smaller nanoparticles compared to pure TiO₂. The mechanism of the enhanced photocatalytic activity was discussed in this study.     

Defect-related visible luminescence of ZnO nanorods annealed in oxygen ambient

ZnO nanorods prepared by a solution-phase method are annealed at different temperatures in oxygen ambient.The luminescence properties of the samples are investigated.In the same excitation condition,the photoluminescence(PL) spectra of all samples show an ultraviolet(UV) emission and a broad strong visible emission band.The asymmetric visible emis-sion band of annealed samples has a red-shift as the annealing temperature increasing from 200 ℃ to 600 ℃ and it can be deconvoluted into two subband emissions centered at 535 nm(green emission) and 611 nm(orange-red emission) by Gaussian-fitting analysis.Analyses of PL excitation(PLE) spectra and PL spectra at different excitation wavelengths reveal that the green emission and the orange-red emission have a uniform initial state,which can be attributed to the electron transition from Zn interstitial(Zni) to oxygen vacancy(Vo) and oxygen interstitial(Oi),respectively.     

Structural and optical properties of functionalized multi-walled carbon nanotubes

Herein, we report the functionalization of multiwalled carbon nanotubes (MWCNTs) using meta-Chloroperoxybenzoic acid (mCPBA) as an oxidizing agent. Epoxy groups are incorporated into the sidewall of MWCNTs and the prepared functionalized multiwalled carbon nanotubes (F-MWCNTs) were characterized using FT-IR spectroscopy, X-ray diffraction, Raman spectroscopy and UV–visible spectroscopy. Morphology of MWCNTs and F-MWCNTs was determined using Scanning electron microscopy (SEM) and transmission electron microscopy (TEM). TEM results clearly indicated that the diameter of F-MWCNTs is increased by 120% as compared to neat MWCNTs. From UV–visible spectroscopy data, band gap of F-MWCNTs was calculated using Tauc equation and it was found to be 3.9 eV. Photo emission property of F-MWCNTs was analyzed using photoluminescence spectroscopy. F-MWCNTs showed nice emission in the visible region and it depended upon the excited wavelength. These functionalized carbon nanotubes could find use as tunable optoelectronic devices in future nanotechnology.     

Electron microscopy characterization of airborne micro- and nanoparticulate matter

The aim of this work was to offer a state-of-the-art critical survey for characterizing airborne nano- and microparticles by means of electron microscopy (EM) techniques and to highlight advantages and limits of different possible operation modes. Procedures of collection and sample preparation are revisited and improved to analyse airborne particles deposited on filtering membranes by using various sampling methods. Three kinds of electron microscopes are used to this end: scanning electron microscope (SEM), field emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM). Following and extending previous studies, we optimized procedures by varying both the sample collection/preparation and the operational parameters of the microscopes. In particular, we diversified the sampling methods applied, using ad hoc filters as well as common filters for standard gravimetric measures. This approach enabled us to achieve a simple and clean procedure allowing direct SEM or TEM observation of the collected particulate matter.     

AlN/GaN/AlN heterostructures grown on Si substrate by plasma-assisted MBE for MSM UV photodetector applications

The AlN/GaN/AlN heterostructures were successfully grown on silicon substrate by plasma-assisted molecular beam epitaxy (MBE). High purity gallium (7N) and aluminum (6N5) were used to grow GaN and AlN, respectively. The structural and optical properties of the samples have been investigated by high-resolution X-ray diffraction (HR-XRD), photoluminescence (PL), Raman spectroscopy, transmission electron microscopy (TEM), selected area electron diffraction (SAED), dark field scanning transmission electron microscopy (DF STEM), and high-angle annular dark field scanning transmission electron microscopy (HAADF STEM). HR-XRD measurement showed that the sample has a typical diffraction pattern of hexagonal AlN/GaN/AlN heterostructures. Raman spectra revealed all four Raman-active modes, i.e., GaN-like E₂ (H), AlN-like A₁ (TO), AlN-like E₂ (H), and AlN-like A₁ (LO) inside the AlN/GaN/AlN heterostructures. Good thickness uniformity of the layers and high-quality hetero-structures without cracking were confirmed by TEM, SAED, DF STEM and HAADF STEM. The fabricated AlN/GaN/AlN heterostructures based metal-semiconductor-metal (MSM) for the UV photodetector shows a rise and fall of photoresponses, suggesting that the AlN/GaN/AlN heterostructures have good carrier transport and crystallinity properties.     

Optical properties of ZnS nanoparticles prepared by high energy ball milling

In this work, we synthesized zinc sulfide (ZnS) nanoparticles by the mechanochemical route using zinc acetate and sodium sulfide as source materials in a high energy planetary ball mill at rotation speed of 300 rpm with ball to powder ratio 5:1 for 30–120 min. Powder samples were collected at duration of 30 min for different analyses. The milled powders were washed with methanol to remove impurity and dried at 50 °C for 2 h. ZnS nanoparticles are characterized by X-ray diffraction, transmission electron microscopy, field-emission scanning electron microscopy, UV–vis–NIR spectrophotometry and fluorescence spectrophotometry. The crystallite size of synthesized ZnS nanoparticles is found to be approximately 2 nm. The optical band gap of the ZnS nanoparticles is found to be in the range of 4.71–5.17 eV. Room temperature photoluminescence (PL) spectra of the samples exhibit blue-light emission using UV excitation wavelength of 280 nm.     

Cadmium selenide@sulfide nanoparticle composites: Facile precipitation preparation,characterization, and investigation of their photocatalyst activity

We report a two-step synthesis and structural characterization of CdSe/CdS core/shell nanoparticles by the precipitation method. Besides, the effects of preparation parameters such as reaction temperature, the speed of the reaction stirrer, and the rate of adding sulfide source on the size, morphology, and photocatalyst activity of CdSe/CdS core–shell nanoparticles were studied by SEM images and degradation of methyl orange (MO) dye test. The structure and composition of the obtained products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution field-emission transmission electron microscope (HRTEM), photoluminescence spectroscopy (PL), scanning electronic microscopy (SEM), spectra energy dispersive analysis of X-ray (EDS), and ultraviolet–visible (UV–vis) techniques.     

Facile preparation of Sn-doped BiOCl photocatalyst with enhanced photocatalytic activity for benzoic acid and rhodamine B degradation

A series of Sn-doped BiOCl photocatalysts were successfully synthesized at room temperature via a facile oxidation-reduction method. The as-synthesized products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoemission spectroscopy (XPS), UV–vis diffuse reflectance spectra (DRS) and photoluminescence (PL) emission spectroscopy measurements. The results showed that the as-prepared samples exhibited tetragonal crystal structure, lamellar morphology and band gap energy of 3.12 eV and 2.91 eV for BiOCl and Sn(10%)-doped BiOCl, respectively. XPS results showed that Sn was in the form of tetra-valence. The photocatalytic activities of as-synthesized samples were evaluated by the degradation of benzoic acid (BA) and rhodamine B (RhB) in an aqueous solution. The results revealed that the Sn doping could enhance the photocatalytic performance of BiOCl and the highest photocatalytic activity was achieved by the Sn(10%)-doped BiOCl, in addition, the optimum dosage of Sn(10%)-doped BiOCl was 0.4 mg/L in degrading BA. The improved photocatalytic activity of Sn-doped BiOCl could be attributed to the narrower band gap energy (2.91 eV) than pure BiOCl. Furthermore, scavenger experimental results indicated that h⁺ played the pivotal role in BA photocatalytic degradation. What is more, the as-synthesized Sn(10%)-doped BiOCl photocatalyst exhibited a good stability during the photodegradation of BA and RhB, revealing its promising prospect in the practical application of the treatment of organic wastewaters.