Search results for "High-resolution"
showing 10 items of 208 documents
Quenching and blue shift of UV emission intensity of hydrothermally grown ZnO:Mn nanorods
2015
Abstract ZnO:Mn alloyed nanorods (Mn nominal concentration – 3–5 wt%) were synthesized by using hydrothermal process at an optimized growth temperature of 200 °C and a growth time of 3 h. The XRD, SEM and Raman, FTIR investigations reveal that ZnO:Mn (Mn – 3–5 wt%) retained hexagonal wurtzite crystal structure with nanorod morphology. The HRTEM and SAED analysis confirm the single crystalline nature of hydrothermally grown ZnO and ZnO:Mn (5 wt%) nanorods. The ZnO:Mn nanorods (Mn – 0–5 wt%) displayed optical band gap in the range 3.23–3.28 eV. The blue shift of UV emission peak (PL) from 393 (ZnO) to 386 nm and quenching of photoluminescence emission in ZnO:Mn is due to the Mn incorporation …
Near band edge and defect emissions in wurtzite Cd0.025Mg0.10Zn0.875O nanocrystals
2021
Abstract We report on near band edge and local defects emissions in Cd0·025Mg0·10Zn0·875O (CdMgZnO) nanoparticles (NPs) as a function of temperature, where a strong temperature-dependent near-infrared emission around 1.7 eV (~730 nm) has been observed. The NPs were synthesized by a modified sol-gel method and were annealed at 750 °C after growing. The crystallographic parameters have been determined by 2-dimensional synchrotron x-ray diffraction (XRD) and conventional XRD analysis, confirming their growth within the wurtzite phase with a preferred orientation along the (101) plane and an apparent crystallite size of 52.72 ± 0.18 nm. This apparent crystallite size is consistent with the near…
Luminescence mechanisms of defective ZnO nanoparticles.
2016
ZnO nanoparticles (NPs) synthesized by pulsed laser ablation (PLAL) of a zinc plate in deionized water were investigated by time-resolved photoluminescence (PL) and complementary techniques (TEM, AFM, μRaman). HRTEM images show that PLAL produces crystalline ZnO NPs in wurtzite structure with a slightly distorted lattice parameter a. Consistently, optical spectra show the typical absorption edge of wurtzite ZnO (Eg = 3.38 eV) and the related excitonic PL peaked at 3.32 eV with a subnanosecond lifetime. ZnO NPs display a further PL peaking at 2.2 eV related to defects, which shows a power law decay kinetics. Thermal annealing in O2 and in a He atmosphere produces a reduction of the A1(LO) Ra…
Synthesis of cubic ZnS microspheres exhibiting broad visible emission for bioimaging applications
2015
Biocompatible ZnS microspheres with an average diameter of 3.85 µm were grown by solvo-hydrothermal (S-H) method using water-acetonitrile-ethylenediamine (EDA) solution combination. ZnS microspheres were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform (FT)-Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR) techniques. The broad photoluminescence (PL) emissions from 380-580 nm that were seen from the ZnS microspheres attributed to the increase in carrier concentration, as understood from the observed intense Raman band at 257 cm(-1). Cytotoxicity and haemocompatibility…
Low melting Metal Catalysed Growth of Tin Disulfide Nanotubes
2009
AbstractWe report here the synthesis of tin disulfide nanotubes by a vapour liquid solid growth using bismuth, a low melting metal, as a catalyst. The reaction was carried out in a single step process by heating SnS2 and bismuth in a horizontal tube furnace at 800oC. TEM analysis allowed proposing a plausible mechanism for the formation of SnS2 nanotubes. Pure material could be obtained by optimizing the reaction based on a product analysis using powder X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) combined with energy dispersive X-ray spectroscopy (EDX).
Preparation of magnetic composites of MIL-53(Fe) or MIL-100(Fe) via partial transformation of their framework into γ-Fe2O3
2016
A novel two-step approach is proposed to obtain magnetically active composite materials consisting of MIL-53(Fe) or MIL-100(Fe) and γ-Fe2O3 particles. The first step consists in a partial transformation of the framework into a layer of γ-FeO(OH) (lepidocrocite) covering the MOF particles. We found that such a transformation can be realized under air-free conditions by hydrolysing the MOFs at pH 6.2 in the presence of FeSO4. In the second step the obtained γ-FeO(OH)/MOF composite is heated under an air flow at 250 °C in order to transform γ-FeO(OH) to γ-Fe2O3. The thus prepared composites containing 40 wt% of the magnetic phase were characterized in detail by XRD, HRTEM, FESEM, N2 adsorption…
Morphology and structure of electrospun CoFe2O4/multi-wall carbon nanotubes composite nanofibers
2010
CoFe2O4/multiwall carbon nanotubes (MWCNTs) composite nanofibers were produced by electrospinning a dispersion of MWCNTs in a solution of polyvinylpyrrolidone, iron(III) nitrate nonahydrate, cobalt (II) acetate tetrahydrate, absolute ethanol and H2O. Microstructure was examined by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HR-TEM). Thermal behaviour was studied by thermogravimetry and differential thermal analysis (TG-DTA) and phase analysis of calcined fibers was performed by X-ray diffraction (XRD). Upon thermal treatment at 450 °C defect-free, randomly oriented composite fibers having a mean diameter of 60 ± 10 nm were obtained. The results s…
Real-space imaging with pattern recognition of a ligand-protected Ag374 nanocluster at sub-molecular resolution
2018
High-resolution real-space imaging of nanoparticle surfaces is desirable for better understanding of surface composition and morphology, molecular interactions at the surface, and nanoparticle chemical functionality in its environment. However, achieving molecular or sub-molecular resolution has proven to be very challenging, due to highly curved nanoparticle surfaces and often insufficient knowledge of the monolayer composition. Here, we demonstrate sub-molecular resolution in scanning tunneling microscopy imaging of thiol monolayer of a 5 nm nanoparticle Ag374 protected by tert-butyl benzene thiol. The experimental data is confirmed by comparisons through a pattern recognition algorithm t…
Interfacial reaction during MOCVD growth revealed by in situ ARXPS.
2006
International audience; Angle-resolved X-ray photoelectron spectroscopy (ARXPS) experiments were performed to study in situ the reaction at the film–substrate interface during metal organic chemical vapor deposition (MOCVD) growth of TiO2 thin films deposited on the silicon substrate. The in-depth distribution of chemical species was determined using several ARXPS thickness calculation models considering either single or bilayer systems. By the comparison of two single-layermodels, the presence of a second layer composed of silicon oxidewas evidenced. High-resolution transmission electron microscopy (HRTEM) observations confirmed the stratification of the film in two layers, as well as the …
Unraveling the Formation of Core−Shell Structures in Nanoparticles by S-XPS
2010
The combination of the surface sensitivity of X-ray photoelectron spectroscopy (XPS) with the high flux and variable photon energy excitation of Synchrotron radiation (S-XPS) is used to probe the atomic distribution of bimetallic nanoparticles. Based on the energy dependence of the photoemission differential cross section of core level photoelectrons, we propose a methodology to monitor the formation and to evaluate sizes of the core−shell structure. We have successfully applied it to unveil the mechanism involved in the atomic rearrangement of thermally treated Pt0.7Pd0.3 nanoparticles.