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1.
Ling Huang Maolin L. Zhai Dewu W. Long Jing Peng Ling Xu Guozhong Z. Wu Jiuqiang Q. Li Genshuan S. Wei 《Journal of nanoparticle research》2008,10(7):1193-1202
The silver nanoparticles (AgNPs) were synthesized in an alkalic aqueous solution of silver nitrate (AgNO3)/carboxymethylated chitosan (CMCTS) with ultraviolet (UV) light irradiation. CMCTS, a water-soluble and biocompatible chitosan
derivative, served simultaneously as a reducing agent for silver cation and a stabilizing agent for AgNPs in this method.
UV–vis spectra and transmission electron microscopy (TEM) images analyses showed that the pH of AgNO3/CMCTS aqueous solutions, the concentrations of AgNO3 and CMCTS can affect on the size, amount of synthesized AgNPs. Further by polarized optical microscopy it was found that
the CMCTS with a high molecular weight leads to a branch-like AgNPs/CMCTS composite morphology. The diameter range of the
AgNPs was 2–8 nm and they can be dispersed stably in the alkalic CMCTS solution for more than 6 months. XRD pattern indicated
that the AgNPs has cubic crystal structure. The spectra of laser photolysis of AgNO3/CMCTS aqueous solutions identified the early reduction processes of silver cations (Ag+) by hydrated electron formed by photoionization of CMCTS. The rate constant of corresponding reduction reaction was 5.0 × 109 M−1 s−1. 相似文献
2.
In this work, the fungus Penicillium was used for rapid extra-/intracellular biosynthesis of gold nanoparticles. AuCl4
− ions reacted with the cell filtrate of Penicillium sp. resulting in extracellular biosynthesis of gold nanoparticles within 1 min. Intracellular biosynthesis of gold nanoparticles
was obtained by incubating AuCl4
− solution with fungal biomass for 8 h. The gold nanoparticles were characterized by means of visual observation, UV–Vis absorption
spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy-dispersive
X-ray spectroscopy (EDX). The extracellular nanoparticles exhibited maximum absorbance at 545 nm in UV–Vis spectroscopy. The
XRD spectrum showed Bragg reflections corresponding to the gold nanocrystals. TEM exhibited the formed spherical gold nanoparticles
in the size range from 30 to 50 nm with an average size of 45 nm. SEM and TEM revealed that the intracellular gold nanoparticles
were well dispersed on the cell wall and within the cell, and they are mostly spherical in shape with an average diameter
of 50 nm. The presence of gold was confirmed by EDX analysis. 相似文献
3.
Nanocrystalline gadolinium monoaluminate (GdAlO3) has been synthesized by sol–gel method after sintering the precursor gel at 950°C. The microstructural features have been
proved by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive
X-ray analysis (EDX). The XRD pattern confirms the formation of single-phase GdAlO3 while EDX shows that this nanomaterial is stoichiometric; the average size of the nanoparticles is 40 nm. X-ray photoelectron
spectroscopy (XPS) has been used to study the chemical composition and bonding in the as-prepared samples. The binding energies
of core-level electrons in Gd, Al and O in GdAlO3 nanopowder have been found slightly shifted compared to the corresponding values of the same elements. The electron paramagnetic
resonance (EPR) spectra at 9.23 GHz (X-band) and different temperatures indicate the existence of magnetically concentrated
solid containing Gd3+ ions. Nèel temperature, T
N
=3.993 K, effective Bohr magneton number, μ
eff=8.18, and constant of magnetic exchange interaction, J
ex=−0.069 cm−1, have been determined from DC magnetic susceptibilities measured in the range 2–300 K. 相似文献
4.
ZnCo2O4 nanomaterial was prepared by co-precipitation method and characterized by X-ray diffraction (XRD), scanning electron microscope
(SEM), transmission electron microscopy (TEM), cyclic voltammetry (CV), and galvanostatic charge–discharge tests at various
current densities. It is shown that the crystal structure and surface morphology play an important role in the enhancement
of the specific capacitance. The TEM results clearly indicate that the prepared material shows aggregated particles. The particle
size powder was about 50 nm, and SEM pictures indicate a porous morphology. The electrochemical behavior of ZnCo2O4 was characterized by mixing equal proportion of carbon nanofoam (CNF). From CV, it is concluded that the combination of redox
and pseudo-capacitance increases the specific capacitance up to 77 F g−1 at 5 mV s−1 scan rate. The ZnCo2O4-based supercapacitor cell has good cyclic stability and high coulombic efficiency. 相似文献
5.
J. C. Cruz V. Baglio S. Siracusano R. Ornelas L. Ortiz-Frade L. G. Arriaga V. Antonucci A. S. Aricò 《Journal of nanoparticle research》2011,13(4):1639-1646
Nanosized IrO2 electrocatalysts (d ~ 7–9 nm) with specific surface area up to 100 m2 g−1 were synthesized and characterized for the oxygen evolution reaction in a solid polymer electrolyte (SPE) electrolyzer. The
catalysts were prepared by a colloidal method in aqueous solution and a subsequent thermal treatment. An iridium hydroxide
hydrate precursor was obtained at ~100 °C, which was, successively, calcined at different temperatures from 200 to 500 °C.
The physico-chemical characterization was carried out by X-ray diffraction (XRD), thermogravimetry–differential scanning calorimetry
(TG–DSC) and transmission electron microscopy (TEM). IrO2 catalysts were sprayed onto a Nafion 115 membrane up to a loading of 3 mg cm−2. A Pt catalyst was used at the cathode compartment with a loading of 0.6 mg cm−2. The electrochemical activity for water electrolysis of the membrane-electrode assemblies (MEAs) was investigated in a single
cell SPE electrolyzer by steady-state polarization curves, impedance spectroscopy and chrono-amperometric measurements. A
maximum current density of 1.3 A cm−2 was obtained at 1.8 V and 80 °C for the IrO2 catalyst calcined at 400 °C for 1 h. A stable performance was recorded in single cell for this anode catalyst at 80 °C. The
suitable catalytic activity and stability of the most performing catalyst were interpreted in terms of proper combination
between nanostructure and suitable morphology. 相似文献
6.
Teresa Roncal-Herrero Juan Diego Rodríguez-Blanco Eric H. Oelkers Liane G. Benning 《Journal of nanoparticle research》2011,13(9):4049-4062
The precipitation of lanthanum and neodymium phosphate phases from supersaturated aqueous solutions at pH ~1.9 was studied
at 5, 25, 50, and 100 °C in batch reactors for up to 168 h. Crystalline La and Nd–rhabdophane phases precipitated immediately
upon mixing of the initial aqueous La or Nd and PO4 solutions. Changes in aqueous PO4 and Rare Earth Element (REE) concentrations during the experiments were determined by ICP-MS and UV–Vis spectrophotometry,
while the resulting solids were characterized via powder XRD, SEM, TEM, and FTIR. All precipitated crystals exhibited a nano-rod
morphology and their initial size depended on temperature and REE identity. At 5 °C and immediately after mixing the La and
Nd–rhabdophane crystals averaged ~44 and 40 nm in length, respectively, while at 100 °C lengths were ~105 and 94 nm. After
168 h of reaction, the average length of the La and Nd rhabdophanes increased by 23 and 53% at 5 °C and 11 and 59% at 100 °C,
respectively. The initial reactive solutions in all experiments had activity quotients for rhabdophane precipitation:
\textREE 3+ + \textPO43 - + n\textH2 \textO = \textREEPO4 · n\textH2 \textO {\text{REE}}^{ 3+ } + {\text{PO}}_{4}^{3 - } + n{\text{H}}_{2} {\text{O}} = {\text{REEPO}}_{4} \cdot\;n{\text{H}}_{2} {\text{O}} of ~10−20.5. This activity quotient decreased with time, consistent with rhabdophane precipitation. The rapid equilibration of rhabdophane
supersaturated solutions and the progressive rhabdophane crystal growth observed suggests that the REE concentrations of many
natural waters may be buffered by rhabdophane precipitation. In addition, this data can be used to guide crystallization reactions
in industrial processes where monodisperse and crystalline La or Nd rhabdophane materials are the target. 相似文献
7.
In this paper, data concerning the effect of pH on the morphology of Ag–TiO2 nanocomposite during photodeposition of Ag on TiO2 nanoparticles is reported. TiO2 nanoparticles prepared by sol–gel method were coated with Ag by photodeposition from an aqueous solution of AgNO3 at various pH levels ranging from 1 to 10 in a titania sol, under UV light. The as-prepared nanocomposite particles were
characterized by UV–vis absorption spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), and N2 adsorption/desorption method at liquid nitrogen temperature (−196 °C) from Brunauer–Emmett–Teller (BET) measurements. It
is shown that at a Ag loading of 1.25 wt.% on TiO2, a high-surface area nanocomposite morphology corresponding to an average of one Ag nanoparticle per titania nanoparticle
was achieved. The diameter of the titania crystallites/particles were in the range of 10–20 nm while the size of Ag particles
attached to the larger titania particles were 3 ± 1 nm as deduced from crystallite size by XRD and particle size by TEM. Ag
recovery by photo harvesting from the solution was nearly 100%. TEM micrographs revealed that Ag-coated TiO2 nanoparticles showed a sharp increase in the degree of agglomeration for nanocomposites prepared at basic pH values, with
a corresponding sharp decrease in BET surface area especially at pH > 9. The BET surface area of the Ag–TiO2 nanoparticles was nearly constant at around a value of 140 m2 g−1 at all pH from 1–8 with an anomalous maximum of 164 m2 g−1 when prepared from a sol at pH of 4, and a sharp decrease to 78 m2 g−1 at pH of 10. 相似文献
8.
Amurisana Bao Hua Lai Yuming Yang Zhilong Liu Chunyan Tao Hua Yang 《Journal of nanoparticle research》2010,12(2):635-643
We report an efficient process for preparing monodisperse SiO2@Y0.95Eu0.05VO4 core–shell phosphors using a simple citrate sol–gel method and without the use of surface-coupling silane agents or large
stabilizers. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy
(TEM), and photoluminescence (PL) spectra were used to characterize the resulting SiO2@Y0.95Eu0.05VO4 core–shell phosphors. The XRD results demonstrate that the Y0.95Eu0.05VO4 particles crystallization on the surface of SiO2 annealing at 800 °C is perfectly and the crystallinity increases with raising the annealing temperature. The obtained core–shell
phosphors have a near perfect spherical shape with narrow size distribution (average size ca. 500 nm and an average thickness
of ~50 nm), are not agglomerated, and have a smooth surface. The thickness of the YVO4:Eu3+ shells on the SiO2 cores could be easily tailored by changing the mass ratio of shell to core (W = [YVO4]/[SiO2]) (~50 nm for W = 30%). The Eu3+ shows a strong PL luminescence (dominated by 5D0 − 7F2 red emission at 618 nm) under the excitation of 320 nm UV light. The PL intensity of Eu3+ increases with increasing the annealing temperature and the values of W. 相似文献
9.
Eu doped BaSO4 was prepared by the recrystallization method and characterization of the material was done by using X-ray diffraction (XRD),
scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR)
techniques. From the XRD pattern of Eu doped BaSO4 compound, it was found that the prominent phase formed was BaSO4 and traces of other phases were very weak and the result of FTIR spectrum of BaSO4:Eu shows that the sulfur-oxygen stretch was found at around 1100 cm−1. The room-temperature PL spectra of the Eu doped BaSO4 sample showed one peak centered at 374 nm, which is the characteristic emission of Eu2+ ion. This emission band at 374 nm corresponds to the 4f6 5d→4f7 (8S7/2) transitions of Eu2+ ions. The excitation spectrum taken at the wavelength 374 nm extends over a wide range of wavelengths from 220–350 nm with
a strong peak at around 260 nm. Furthermore, the present sample shows good crystal quality and high photoluminescence sensitivity.
Hence our results suggest possible potential applications of Eu doped BaSO4 phosphor in optoelectronic devices. 相似文献
10.
Mamata Mohapatra K. Rout S. K. Gupta P. Singh S. Anand B. K. Mishra 《Journal of nanoparticle research》2010,12(2):681-686
The present article describes a novel synthesis route for nano-sized goethite (α-FeOOH) using hydrazine sulphate as an additive.
The X-ray diffraction (XRD) peaks of synthesized powder matched well with those of α-FeOOH. Transmission electron microscopy
(TEM) showed the particles of irregular shape in the range of 1–10 nm. Batch adsorption experiments for fluoride uptake were
performed to study the influence of various experimental parameters such as contact time (10 min to 7 h), initial fluoride
concentration (10–150 mg L−1), pH (2–11.6) and the presence of competing anions. The time data fitted well to pseudo-second-order kinetic model. The fluoride
removal passed through broad maxima in pH ranges of 6–8. High adsorption capacity of 59 mg g−1 goethite was obtained. The isothermic data fitted well to Freundlich model. The presence of other ions namely chloride and
sulphate adversely affected fluoride removal. Fluoride from contaminated water sample could be successfully brought down from
10.25 to 0.5 mg L−1. 相似文献
11.
Ashok Kumar Baral V. Sankaranarayanan 《Applied Physics A: Materials Science & Processing》2010,98(2):367-373
The nanocrystalline material of 15 mol% Gd-doped ceria (Ce0.85Gd0.15O2−δ
) was prepared by citrate auto ignition method. The electrical study and dielectric relaxation technique were applied to investigate
the ionic transport process in this nanocrystalline material with an average grain size of 13 nm and the dynamic relaxation
parameters are deduced in the temperature range of 300–600°C. The ionic transference number in the material is found to be
0.85 at 500°C at ambient conditions. The oxygen ionic conduction in the nanocrystalline Ce0.85Gd0.15O2−δ
material follows the hopping mechanism. The grain boundary relaxation is found to be associated with migration of charge
carriers. The frequency spectra of modulus M″ exhibited a dielectric relaxation peak corresponding to defect associates
(Gd-Vo\blacksquare \blacksquare)\blacksquare(\mathrm{Gd}\mbox{-}\mathrm{V}_{\mathrm{o}}^{_{_{{\blacksquare\,\blacksquare}}}})^{_{_{{\blacksquare}}}}. The material exhibits very low values of migration energy and association energy of the oxygen vacancies in the long-range
motion, i.e., 0.84 and 0.07 eV, respectively. 相似文献
12.
The spectral dependence of Stern–Volmer constants (KSVlK_{SV}^{\lambda} ) for fluorescence quenching by Cu2+ ions in a standard sample of humic acid (HA) (IHSS) with monochromatic excitation (λex = 337.1 nm) conditions has been studied in the spectral range 400–600 nm. This is interpreted within a concept implying that
HA macromolecules possess the property of polydispersity, which means that fluorophore-containing sites are different in terms
of chemical nature and spatial accessibility. Modeling data show that the minimum number of spectral components required for
the simulated spectral dependence of KSVlK_{SV}^{\lambda} to agree as closely as possible with that observed experimentally is three. 相似文献
13.
P. Ortwein W. Woiwode S. Wagner M. Gisi V. Ebert 《Applied physics. B, Lasers and optics》2010,100(2):341-347
A high-resolution spectrometer based on a vertical-cavity surface-emitting laser (VCSEL) was developed and used to determine
the line strength S(T
0)=12.53(11)×10−21 cm−1/(molec cm−2) and the self-broadening coefficient
g0HCl=0.021787(61)\gamma^{0}_{\mathrm{HCl}}=0.021787(61)
cm−1/atm of the R(3) absorption line in the first rovibrational overtone (2←0) band of H35Cl. Furthermore, the first laser-based high-pressure study on the pressure broadening of HCl by He, N2 and
O2(g0N2=0.07292(5)\mathrm{O}_{2}(\gamma^{0}_{\mathrm{N}_{2}}=0.07292(5)
cm−1/atm,
g0He=0.02113(1)\gamma^{0}_{\mathrm{He}}=0.02113(1)
cm−1/atm,
g0O2=0.03978(6)\gamma^{0}_{\mathrm{O}_{2}}=0.03978(6)
cm−1/atm) is presented covering pressures of up to 1 MPa. The results are compared to previously available low-pressure data. 相似文献
14.
This paper describes the preparation and conductivity studies of polyindole–ZnO composite polymer electrolyte (CPE) with LiClO4. Polyindole–ZnO-based polymer nanocomposites were prepared by chemical method and characterized by XRD, infrared (IR), scanning
electron microscope (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The IR spectrum confirms
the intermolecular interaction between polyindole and ZnO. The significant spectral changes of polyindole and ZnO nancomposites
reveal the strong interaction between polyindole and ZnO nanoparticles. The structural morphologies of the ZnO, polyindole,
and polyindole–ZnO are obtained from SEM. The TEM image of polyindole nanocomposite shows that ZnO is embedded in polyindole
matrix. An enhanced conductivity of 4.405 × 10−7 S cm−1 at 50 °C for the CPE was determined from impedance studies. 相似文献
15.
Hydrothermal synthesis and photoluminescent properties of YV1
− xPxO4:Eu3+ (x = 0–1.0) nanophosphors
Hongliang Zhu Hong Yang Dalai Jin Zhengkai Wang Xiaoyun Gu Xiaohui Yao Kuihong Yao 《Journal of nanoparticle research》2008,10(7):1149-1154
A simple hydrothermal process has been proposed to systematically synthesize europium-doped yttrium phosphate-vanadates with
general formula YV1 − xPxO4:Eu3+ (x = 0–1.0). All the YV1 − xPxO4:Eu3+ products were characterized by x-ray diffraction (XRD) and transmission electron microscopy (TEM), the results of which revealed
they were single-phase tetragonal-structured nanocrystals with diameter of 20 nm and their cell parameter a exhibited a linear relationship with the x value. Photoluminescence (PL) excitation and emission intensities of the products
were sensitive to the x value and the change of the PL intensity with x was a wave-like curve which reached the peak at x = 0.4
and 0.8. In addition, the x value had an obvious influence on the (5D0–7F2)/(5D0–7F1) intensity ratio of Eu3+. 相似文献
16.
S. K. El-Labany W. M. Moslem Kh. A. Shnishin S. A. El-Tantawy 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,61(2):409-420
By using the hydrodynamic equations of positive and two negative ions,
Boltzmann electron density distribution, and Poisson equation with immobile
positive/negative dust particles, a cylindrical Korteweg-de Vries (CKdV)
equation is derived for small but finite amplitude ion-acoustic waves. At the
critical total negative ion concentration and/or the critical density rate of
the second-negative ions, the pulses collapse at this limit as nonlinearity
fails to balance dispersion. Then the CKdV equation is not appropriate to
describe the system. Therefore, the modified CKdV (MCKdV) and extended CKdV
(ECKdV) equations are derived at the critical plasma compositions and in the
vicinity of the critical plasma compositions, respectively. The physical
parameters of two plasma environments (e.g., Xe+–F-–SF6-_{6}^{-} and
Ar+–F-–SF6-_{6}^{-} plasmas) are examined on the wave phase velocity and
the nonlinear localized pulse profile. The latter should satisfy necessary
condition to exist. The localized pulse of Ar+–F-–SF6-_{6}^{-} plasma is
much spiky than Xe+–F-–SF6-_{6}^{-} plasma. Thus, the mass ratio of the
negative-to-positive ions is focused upon and it emphasizes to play an
important role on the pulse profile. Dependence of the geometrical divergence
on the pulse profile is also investigated, which indicates that the localized
pulse damps with time. The implications of our results agrees with the
experimental observations. 相似文献
17.
Metallic gold nanoparticles have been synthesized by the reduction of chloroaurate anions [AuCl4]− solution with hydrazine in the aqueous starch and ethylene glycol solution at room temperature and at atmospheric pressure.
The characterization of synthesized gold nanoparticles by UV–vis spectroscopy, high resolution transmission electron microscopy
(HRTEM), electron diffraction analysis, X-ray diffraction (XRD), and X-rays photoelectron spectroscopy (XPS) indicate that
average size of pure gold nanoparticles is 3.5 nm, they are spherical in shape and are pure metallic gold. The concentration
effects of [AuCl4]− anions, starch, ethylene glycol, and hydrazine, on particle size, were investigated, and the stabilization mechanism of Au
nanoparticles by starch polymer molecules was also studied by FT-IR and thermogravimetric analysis (TGA). FT-IR and TGA analysis
shows that hydroxyl groups of starch are responsible of capping and stabilizing gold nanoparticles. The UV–vis spectrum of
these samples shows that there is blue shift in surface plasmon resonance peak with decrease in particle size due to the quantum
confinement effect, a supporting evidence of formation of gold nanoparticles and this shift remains stable even after 3 months. 相似文献
18.
B. Sitamtze Youmbi Serge Zékeng Samuel Domngang Florent Calvayrac Alain Bulou 《Ionics》2012,18(4):371-377
To date, the fastest lithium ion-conducting solid electrolytes known are the perovskite-type ABO3 oxide, with A = Li, La and B = Ti, lithium lanthanum titanate (LLTO)
Li3x La( 2 \mathord