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1.
The approximate barium X‐ray atomic absorption in the energy region of L‐edges is reconstructed from the absorption spectrum of an aqueous solution of BaCl 2. The result is corroborated by comparison with pure atomic absorption spectra of neighbour elements Xe and Cs. The application of the atomic absorption signal as a proper EXAFS background is demonstrated and discussed in the analysis of Ba hexaferrite nanoparticles with a very weak structural signal. The essential gain is found in the decrease of uncertainty intervals of structural parameters and their correlations. A simple analytical model of the absorption background for the practical EXAFS analysis is demonstrated. 相似文献
2.
This paper reports on the study of the evolution of 4-mercaptoaniline ( p-HSC 6H 4NH 2) functionalized platinum nanoparticles in solution by coupling the Langmuir-Blodgett technique and X-ray photoelectron spectroscopy (XPS). The spectra are recorded on mixed LB films containing fatty acid and platinum particles in proportion 50/50. Several samples built from fresh and aged solutions of particles are analyzed. Comparison of the Pt 4f, S 2p and N 1s regions in each case points to the time dependant chemical evolution of the functionalized particles involving at once platinum, thiolate and amine components. The particle aging in solution is reported during several months, until the complete flocculation of the functionalized platinum nanoparticles. Using the compared XPS analysis of the LB layers obtained from the different particle solutions, unstability of the storage looks then clearly related to the chemical evolution of the bifunctional organic crown. 相似文献
3.
Polymeric matrices with stabilized metallic nanoparticles constitute an important class of nanostructured materials, because
polymer technology allows fabrication of components with various electronic, magnetic and mechanical properties. The porous
cellulose matrix has been shown to be a useful support material for platinum, palladium, silver, copper and nickel nanoparticles.
In the present study, nanosized cobalt particles with enhanced magnetic properties were made by chemical reduction within
a microcrystalline cellulose (MCC) matrix. Two different chemical reducers, NaBH 4 and NaH 2PO 2, were used, and the so-formed nanoparticles were characterized with X-ray absorption spectroscopy, X-ray diffraction, scanning
electron microscopy and transmission electron microscopy. These experimental techniques were used to gain insight into the
effect of different synthesis routes on structural properties of the nanoparticles. Magnetic properties of the nanoparticles
were studied using a vibrating sample magnetometer. Particles made via the NaBH 4 reduction were amorphous Co-B or Co oxide composites with diminished ferromagnetic behaviour and particles made via the NaH 2PO 2 reduction were well-ordered ferromagnetic hcp cobalt nanocrystals. 相似文献
4.
Copper complex nanoparticles were fabricated from bulk copper using picosecond laser ablation in water and chloroform. We found that composition of the nanoparticles was CuCl and Cu 2OCl 2 in chloroform at three different input fluences; Cu 2O in water which was confirmed from the data of EDAX, UV-Visible absorption spectra, and selected area electron diffraction pattern. We have also performed nonlinear optical studies of colloidal nanoparticles using Z-scan technique at 800 nm and ~2 ps laser pulses. Cu 2O NPs exhibited two-photon absorption at lower peak intensities while three-photon absorption was observed at higher peak intensities. Other samples exhibited two-photon absorption at all peak intensities. 相似文献
5.
ABSTRACT In the present study, Zn 1?xNi xS (x = 0.0–0.8 mol%) nanoparticles were prepared through the chemical route and the synthesis involved the mixing and drying of zinc acetate and sodium sulphide in an appropriate ratio with the addition of Ni 2+ at a proper concentration. The structural and spectroscopic studies are investigated by X-ray diffraction (XRD), absorption spectra, emission and excitation spectra, and Raman spectra. Compared with that of the pristine materials, the absorption band-edge demonstrates an apparently blue shift, which is attributed to the quantum size effect. The average particle size of ZnS nanoparticles is in the range of 2–4 nm deduced from the XRD line broadening. Excited at about 330 nm, a blue emission band at 425 nm can be observed, which corresponds to Ni 2+ luminescent center; this result is consistent with the postulation that Ni 2+ replaced the Zn 2+ ions in the lattice of ZnS nanocrystals. Excitation spectra also confirm the above postulation. The effect of different concentrations of nickel is also studied by Raman spectra. 相似文献
6.
TiO 2 nanoparticles doped with two different concentrations of Cobalt, 0.02 and 0.04 mol, are prepared by sol–gel method. The crystalline phase of the doped and undoped nanoparticles and particle sizes are observed with X-ray diffraction and transmission electron microscope. FTIR confirms the bonding interaction of Co 2+ in TiO 2 lattice framework. The UV absorption spectra of the doped material shows two absorption peaks in the visible region related to d–d electronic transitions of Co 2+ in TiO 2 lattice. Compared to undoped TiO 2 nanoparticles, the cobalt doped samples show a red shift in the band gap. Steady state photoluminescence spectra give emission peaks related to oxygen defects. The decrease in the intensity ratio of UV/visible emission peaks confirms distortion of structural regularity and formation of defects after doping. The intensity ratio of different visible emission peaks is nearly same for undoped and 0.02 Co 2+. However, this ratio decreases profoundly at 0.04 Co 2+, due to concentration quenching effect. Photoluminescence excitation spectra, recorded at 598 nm emission wavelength, give different excitation peaks associated with oxygen vacancies and Co 2+. Time resolved photoluminescence spectra give longer decay time for doped samples, indicating longer relaxation of conduction band electrons on the defect and on dopant sites. 相似文献
7.
Tin dioxide nanoparticles of different sizes and platinum doping contents were synthesized in one step using the flame spray pyrolysis (FSP) technique. The particles were used to fabricate semiconducting gas sensors for low level CO detection, i.e. with a CO gas concentration as low as 5 ppm in the absence and presence of water. Post treatment of the SnO 2 nanoparticles was not needed enabling the investigation of the metal oxide particle size effect. Gas sensors based on tin dioxide with a primary particle size of 10 nm showed signals one order of magnitude higher than the ones corresponding to the primary particle size of 330 nm. In situ platinum functionalization of the SnO 2 during FSP synthesis resulted in higher sensor responses for the 0.2 wt% Pt-content than for the 2.0 wt% Pt. The effect is mainly attributed to catalytic consumption of CO and to the associated reduced sensor response. Pure and functionalized tin dioxide nanoparticles have been characterized by Brunauer, Emmett and Teller (BET) surface area determination, X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and scanning transmission electron microscopy (STEM) while the platinum oxidation state and dispersion have been investigated by X-ray photoelectron spectroscopy (XPS) and extended X-ray absorption fine structure (EXAFS). The sensors showed high stability (up to 20 days) and are suitable for low level CO detection: <10 ppm according to European and 50 ppm according to US legislation, respectively. 相似文献
8.
The synthesis, morphological characterization, and optical properties of colloidal, Eu(III) doped Gd2O3 nanoparticles with different sizes and shapes are presented. Utilizing wet chemical techniques and various synthesis routes, we were able to obtain spherical, nanodisk, nanotripod, and nanotriangle-like morphology of Gd2O3:Eu3+ nanoparticles. Various concentrations of Eu3+ ions in the crystal matrix of the nanoparticles were tested in order to establish the levels at which the concentration quenching effect is negligible. Based on the luminescence spectra, luminescence lifetimes and optical parameters, which were calculated using the simplified Judd–Ofelt theory, correlations between the Gd2O3 nanoparticles morphology and Eu3+ ions luminescence were established, and allowed to predict the theoretical maximum quantum efficiency to reach from 61 to 98 %. We have also discussed the impact of the crystal structure of Gd2O3 nanoparticles, as well as coordinating environment of luminescent ions located at the surface, on the emission spectra. With the use of a tunable femtosecond laser system and the Z-scan measurement technique, the values of the effective two-photon absorption cross-section in the wavelength range from 550 to 1,200 nm were also calculated. The nonlinear optical measurements revealed maximum multi-photon absorption in the wavelength range from 600 to 750 nm. 相似文献
9.
The sulfur-doping (S-doping) effects in TiO 2 nanoparticles are investigated by means of Raman spectroscopy and UV–Vis spectroscopy with different S-doping levels (10
and 50%). Raman spectra indicate that the rutile and anatase phases dominate for the low S-doped (10%) and high S-doped (50%)
TiO 2 nanoparticles, respectively. The variation of phase with different S-doping levels has been ascribed to the different S-doping
processes into TiO 2 nanoparticles. In addition, an extra absorption band is observed in both the S-doped TiO 2 nanoparticles. With increasing S-doping level from 10 to 50%, the extra absorption band shows a blue-shift from 470 to 445 nm,
which may be ascribed to the variation of phase from rutile to anatase for TiO 2. 相似文献
10.
Deposited electrocatalysts with different distributions of components in PtCu bimetallic nanoparticles involved in their composition were synthesized by simultaneous and sequential reduction of Cu(2+) and Pt(IV) in a carbon suspension. The dependence of the atomic structure of PtCu nanoparticles on the synthesis conditions and the degree of influence of post-treatment was established from analysis of the changes in Fourier transforms of the experimental Pt and Cu EXAFS spectra, as well as the structural parameters obtained by their fitting before and after the treatment of the materials in an acid solution. A technique was proposed for visualizing the atomic structure of synthesized bimetallic nanoparticles. This technique made it possible to determine the character of the distribution of the components over the nanoparticle volume in accordance with the component composition and local atomic structure parameters determined from EXAFS spectroscopy and to obtain the visualization of the distribution of the components in PtCu nanoparticles synthesized by the aforementioned methods. 相似文献
11.
借助时域有限差分法,对几种常见金属纳米颗粒影响有机太阳能电池光吸收效率的因素及其内部物理机制进行了研究.首先对金属纳米颗粒激发局域表面等离子共振的场分布特点进行分析,对比其在电池不同功能层中对光吸收率的影响;其次基于米氏理论与电共振效应,得出金属纳米颗粒的结构参量对局域表面等离子共振位置及强度的影响规律,并以此进行优化设计.结果表明,具有高对称性形貌的金属纳米颗粒以小尺寸密堆积结构引入电池活性层,能够促进电池光吸收增强三倍以上. 相似文献
12.
借助时域有限差分法,对几种常见金属纳米颗粒影响有机太阳能电池光吸收效率的因素及其内部物理机制进行了研究.首先对金属纳米颗粒激发局域表面等离子共振的场分布特点进行分析,对比其在电池不同功能层中对光吸收率的影响;其次基于米氏理论与电共振效应,得出金属纳米颗粒的结构参量对局域表面等离子共振位置及强度的影响规律,并以此进行优化设计.结果表明,具有高对称性形貌的金属纳米颗粒以小尺寸密堆积结构引入电池活性层,能够促进电池光吸收增强三倍以上. 相似文献
13.
The reflection and absorption spectra of gallium phosphide (GaP) nanoparticles were measured. The radiative transfer equation (RTE) for the medium with scattering and absorption is solved by three different solutions. The ratio of the absorption and scattering coefficients ( E a/ E s) of the GaP nanoparticles layer is calculated from the reflection spectrum via the three solutions, respectively, and the result derived with the three-flux model is closest to the exact solution given by Giovanelli. The E a/ E s curves all exhibit the energy band gaps of GaP nanoparticles, which are consistent with the absorption spectrum measurement. The shape of the reflection spectrum is mainly determined by the absorption, and the scattering only influences its intensity. The energy band structure of the powder sample plays an important role in the reflection phenomenon, and the reflectance data can be used for quantitative analyses. 相似文献
14.
Nanoaluminum combined with an oxidizing polymer binder is representative of a new class of nanotechnology energetic materials
termed “structural energetic materials” that can be laser initiated by near-infrared heating of the Al particles. The visible
and near-IR absorption spectra of Al nanoparticles passivated by the native oxide Al 2O 3, embedded in nitrocellulose (NC) binder, are simulated numerically using a model for the metallic dielectric function that
incorporates the effects of interband transitions. The effects of oxide thickness, nanoparticle size and size distribution,
and particle shape on the absorption characteristics are investigated. The nanoparticle spectra evidence an absorption peak
and valley in the 550–1,100 nm range that redshift with decreasing nanoparticle size. Calculations indicate that this peak-valley
structure results from interband transitions, and the unusual redshift cannot be explained without using an interband transition
onset frequency that varies with nanoparticle size. 相似文献
15.
The chaperonin protein GroEL was mixed with varying concentrations of K 2PtCl 4 followed by a 20-fold concentration of sodium borohydride to afford GroEL–platinum nanoparticle complexes in a ratio of between
1:25 and 1:2,000. Typical colour change, from colourless or pale yellow to brown, occurred that was dependent on the amount
of platinum present. These complexes were characterised by UV/Vis, inductively coupled plasma optical emission spectroscopy,
Fourier transform infra red, transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy. TEM analysis
revealed that the size of nanoparticles increased as the molar ratio of platinum to GroEL increased with an average size diameter
of 1.72–3.5 nm generated with GroEL–platinum molar ratios of 1:125–1:2,000. Fourier-transform infrared spectroscopy (FTIR)
spectra showed no distinct changes in the structure of GroEL but confirmed that the nanoparticles were attached to the protein.
The effect of platinum nanoparticles on the ATPase activity of GroEL showed an activity of 5.60 μmol min −1 ml −1 (87 % increase over a control) at the molar ratio of GroEL–platinum nanoparticles of 1:25. 相似文献
16.
PbS molecular clusters and quantum dots are formed by heat treatment in fluorophosphate glasses of the Na 2O 3–Р 2O 5–Ga 2O 3–AlF 3–ZnO(S)–PbF 2 system with different lead concentrations. PbS molecular clusters are characterized by optical absorption in the range of 300–800 nm and low quantum yields, which decrease from 8.9 to 2.7% with a semiconductor component concentration. It is shown that the parameters of formation of quantum dots luminescing in the wavelength range of 1000–1500 nm are considerably different at different semiconductor component concentrations. The influence of silver ion exchange on the formation of PbS nanoparticles is studied. Introduction of silver stimulates the growth of molecular clusters, which is seen in the absorption spectra. A possible mechanism of interaction of silver nanoparticles with PbS quantum dots is presented. 相似文献
17.
Cobalt-doped ceria nanoparticles were synthesized using the polyol method under co-precipitation hydrolysis. The structural, morphological, optical and redox properties were observed to investigate the influence of different concentration of cobalt ion doping on the prepared CeO 2 nanomaterials in terms of X-ray diffraction, field-emission transmission electron microscopy, thermogravimetric analysis, Fourier-transform infrared spectroscopy, UV/vis absorption spectroscopy and temperature program reduction techniques. The optical band gap energy was calculated from the optical absorption spectra for doped ceria nanoparticles, which have been found to be 2.68, 2.77, and 2.82 eV for the 2, 4, and 7 mol% Co ion-doped CeO 2 nanoparticles, respectively. As observed, the band gap energies increases as the doping Co ion concentrations increased, which could be due to significant increased oxygen vacancies with Co doping. The synergistic interaction between Co and CeO 2 was the main factor responsible for high catalytic activity of cobalt-doped CeO 2 model catalysts. 相似文献
18.
利用新合成的复合纳米结构银/二氧化钛核壳纳米颗粒,研究了金属银纳米颗粒对碲化镉纳米晶层荧光的增强情况.结果表明,这种新型复合金属纳米结构能极大地增强发光纳米晶层的荧光强度.银/二氧化钛核壳纳米颗粒是以水合肼、硝酸银和四异丙氧基钛为原材料,利用胶体化学法在水溶液中合成.透射电子显微镜图片表明这种新合成的银/二氧化钛纳米材料基本上呈球形,有较为明显的核壳结构,中间黑色的核是银纳米颗粒,外层颜色较浅部分是二氧化钛壳层.另外,包裹二氧化钛壳层后,银纳米颗粒的表面等离子吸收带从409 nm红移至430 nm,也证实了这种新型核壳纳米材料的形成.将此合成方法得到的银/二氧化钛纳米颗粒和碲化镉纳米晶用旋转涂覆方法进行直接组合后,得到了银纳米颗粒对碲化镉纳米晶荧光的明显增强,并对其增强的物理过程进行了讨论.这种能够增强荧光团发光的新型复合银纳米结构将在发光器件、荧光成像、生物探测等方面具有一定的应用价值. 相似文献
19.
ZnO nanoparticles embedded in the PMMA matrix were prepared by wet chemical synthesis. The optical band gap of the ZnO nanoparticles decreases with increase in NaOH concentration. The photoluminescence spectra of the ZnO colloids show strong UV, green and blue emissions. The optical absorptive nonlinearity of the ZnO:PMMA composites was analyzed using an open aperture Z-scan technique which shows optical limiting type nonlinearity due to the two photon absorption in ZnO. The efficiency of limiting is found to increase with decrease in the band gap. ZnO:PMMA shows a negative value for nonlinear refractive index n2 and the magnitude of n2 increases with decrease of band gap. Stability as well as the mechanical properties of the nanoparticles embedded in the PMMA matrix makes it more suitable for device fabrication as compared to the ZnO nanoparticles dispersed in solution. 相似文献
20.
The dielectric, structural, and kinetic properties of (GaN) 54(SiO 2) 50 nanoparticles of the following two types are studied using the method of molecular dynamics: particles of GaN covered by a SiO 2 layer and particles of SiO 2 with a GaN layer deposited onto it. The absorption and reflection spectra of these nano-particles are considerably different in the respective frequency ranges 0 ≤ ω ≤ 1500 cm ?1 and ω > 700 cm ?1. The single-centered functions of the radial distribution of the nanoparticles differ in their peak positions and intensities, including the “tail” part for r > 0.9 nm. The structure of nanoparticles with the SiO 2 nucleus is completely tetrahedral, while the nearest six-atom environment is dominant in the structure of a particle with the GaN nucleus. The mobility of gallium atoms in the nanoparticles is lower by two orders than that of other elements constituting them. 相似文献
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