共查询到20条相似文献,搜索用时 15 毫秒
1.
Schneider R 《Analytical and bioanalytical chemistry》2002,374(4):639-645
This paper briefly reviews the potential applicability of analytical transmission electron microscopy (TEM) to elucidate both structural and chemical peculiarities of materials at high lateral resolution. Examples of analytical TEM investigations performed by energy-dispersive X-ray spectroscopy (EDXS), electron energy loss spectroscopy (EELS), and energy-filtered TEM (EFTEM) are presented for different materials systems including metals, ceramics, and compound semiconductors. In particular, results are given of imaging the element distribution in the interface region between gamma matrix and gamma' precipitate in the nickel-based superalloy SC16 by energy-filtered TEM. For core-shell structured BaTiO(3) particles the chemical composition and even the chemical bonding were revealed by EELS at a resolution of about 1 nm. A sub-nanometer resolution is demonstrated by energy-selective images of the Ga distribution in the surrounding of (In,Ga)As quantum dots. Moreover, the element distribution in (Al,Ga)As/AlAs multilayers with linear concentration gradients in a range of about 10 nm was investigated by EDXS line-profile analyses and EFTEM. 相似文献
2.
Guan-Ping Jin Li-Li Chen Guo-Pei Hang Shan-Zhong Yang Xiao-Jing Wu 《Journal of Solid State Electrochemistry》2010,14(7):1163-1169
Silver nanoparticles coat polyquercetin (Qu) and multi-walled carbon nanotube (MWCNT) complex films were prepared using an
electrochemical coupling strategy on platinum electrode (Ag/Qu/MWCNT/Ch/Pt). The new composite material was characterized
by means of field emission scanning electron microscopy, X-ray photoelectron spectroscopy spectra, X-ray diffraction, and
electrochemical techniques, which confirmed that polyquercetin plays an important role to obtain a great deal of uniformly
dispersed silver nanoparticles and MWCNT complex film with a diameter of 10 ± 6 nm. The resulting Ag/Qu/MWCNT/Ch/Pt electrode
shows a significant electrocatalysis for the redox of cysteine (CysH). The stripping chronopotentiometric analysis of CysH
has been successfully used with a satisfying effect. A linear range of 1 × 10−10 to 9 × 10−8 M was obtained with a detection limit of 3 × 10−11 M (3σ) and sensitivity of 35 μA/nM. The films were also robust, surviving up to 100 consecutive cyclic voltammograms and
sonication. 相似文献
3.
Energy-filtering transmission electron microscopy (EFTEM) was employed for investigating interactions between rubber and ZnO particles in the accelerated vulcanization process. Combining elemental mapping and electron energy loss spectroscopy (EELS) by EFTEM enabled the characterization of the interfaces with spatial resolutions of less than 10 nm and with high elemental detection sensitivity. We found that a sulfur- and zinc-rich compound was generated around ZnO particles, and that product was then revealed to be ZnS-generated as a byproduct in the accelerated vulcanization process. Through this study, it is indicated that the accelerated vulcanization with ZnO does not occur uniformly in the rubber matrix; it occurs locally around ZnO particles at a higher reaction rate, implying that the rubber network structure is not uniform on the nanoscale. 相似文献
4.
Luis H. Mendoza-Huizar Clara H. Rios-Reyes 《Journal of Solid State Electrochemistry》2011,15(4):737-745
An electrochemical study of cobalt electrodeposition onto a polycrystalline platinum electrode from an aqueous solution (10−2 M CoCl2 + 1 M NH4Cl (pH 9.5)) was carried out through cyclic voltammetry and potential step techniques. Analysis of the voltammetric data clearly
showed that a cobalt adlayer is formed during the application of potential in the underpotential deposition (upd) region.
Formation of this cobalt adlayer involved the simultaneous presence of both adsorption and 2D nucleation processes. Cobalt
adlayers obtained by linear voltammetry in upd region were analyzed employing diffuse reflectance spectroscopy (DRS). By using
theoretical quantum studies at PM6//HF/LANL1MB level, it was possible to assign the peaks obtained by DRS at 328 and 337 nm
to the cobalt adsorption on Pt(111) and Pt(100), respectively, while the signals recorded at 355 and 362 nm were related with
the clean platinum surfaces Pt(100) and Pt(111). Also, quantum calculations at the PM6 level indicated that the energy formation
order is Co-Pt(100) > Co-Pt(111) > Co-Pt(110) > Co-Co(surface). 相似文献
5.
Jian-Shan Ye Hui-Fang Cui Ying Wen Wei De Zhang Guo Qin Xu Fwu-Shan Sheu 《Mikrochimica acta》2006,152(3-4):267-275
Platinum (Pt) nanoparticles were deposited at the surface of well-aligned multi-walled carbon nanotubes (MWNTs) by potential
cycling between +0.50 and −0.70 V at a scanning rate of 50 mV · s−1 in 5 mM Na2PtCl6 solution containing 0.1 M NaCl. The electrocatalytic oxidation of methanol at the nanocomposites of Pt nanoparticles/nanotubes
(Ptnano/MWNTs) has been investigated using 0.2 M H2SO4 as supporting electrolyte. The effects of various parameters, such as Pt loading, concentration of methanol, medium temperature
as well as the stability of Ptnano/MWNTs electrode, have been studied. Compared to glassy carbon electrode, carbon nanotube electrode significantly enhances
the catalytic efficiency of Pt nanoparticles for methanol oxidation. This improvement in performance is due not only to the
high surface area and the fast electron transfer rate of nanotubes but also to the highly dispersed Pt nanoparticles as electrocatalysts
at the tips and the sidewalls of nanotubes. 相似文献
6.
Ilse Papst Gerald Kothleitner Ferdinand Hofer Leo Binder 《Monatshefte für Chemie / Chemical Monthly》2001,132(4):541-549
Summary. Energy-filtering transmission electron microscopy (EFTEM) and electron energy-loss spectrometry (EELS) have been used to
measure the distribution of titanium in titanium-doped electrolytic manganese dioxide, which consists of large particle agglomerates
of some micrometer diameter. In contrast to previous investigations, where the distribution of the doping elements can only
be investigated at the thinnest regions of the agglomerates, we describe an improved procedure which allows to measure the
concentration of the dopant not only at the thinner edges of the particle agglomerate, but also in the interior. The titanium
distribution maps showed that titanium is enriched on the surface of the agglomerates and in pores penetrating into their
interior. Within the agglomerates, titanium is evenly distributed, and in manganese dioxide the titanium concentration could
be analyzed quantitatively by EELS spectrometry. Based on these results, suggestions for possible improvements of the doping
process and for the preparation of the product are given.
Received November 29, 2000. Accepted (revised) December 12, 2000 相似文献
7.
Christopher J. G. Plummer Rudolf Gensler Hans-Henning Kausch 《Colloid and polymer science》1997,275(11):1068-1077
Melt crystallized isotactic polypropylene thin films of thickness between 30 and 100 nm have been investigated by high-resolution
transmission electron microscopy at room temperature. The c-axis projection of the 2*31 helices and their packing in the lattice were clearly visible in flat-on lamellae of the α-phase following reconstruction
from the components of the image Fourier transform corresponding to the (1 1 0) and (0 4 0) lattice planes, and the image
power spectra also indicated contributions from (1 3 0) and (0 6 0) relfections, corresponding to a line resolution of about
0.35 nm. These results are discussed in terms of Bloch wave calculations based on the generally accepted structure for the
α-phase. Attempts to obtain lattice images of the β-phase in isotactic polypropylene and melt crystallized syndiotactic polypropylene
under similar operating conditions are also briefly discussed, although these provided relatively little structural information.
Received: 27 June 1997 Accepted: 15 August 1997 相似文献
8.
Juliet D Risner Thomas P Nolan James Bentley Erol Girt Samuel D Harkness Robert Sinclair 《Microscopy and microanalysis》2007,13(2):70-79
For this analytical TEM study, nonmagnetic oxygen-rich boundaries were introduced into Co-Pt-alloy perpendicular recording media by cosputtering Co and Pt with TiO2. Increasing the TiO2 content resulted in changes to the microstructure and elemental distribution within grains and boundaries in these films. EFTEM imaging was used to generate composition maps spanning many tens of grains, thereby giving an overall depiction of the changes in elemental distribution occurring with increasing TiO2 content. Comparing EFTEM with spectrum-imaging maps created by high-resolution STEM with EDXS and EELS enabled both corroboration of EFTEM results and quantification of the chemical composition within individual grain boundary areas. The difficulty of interpreting data from EDXS for these extremely thin films is discussed. Increasing the TiO2 content of the media was found to create more uniformly wide Ti- and O-rich grain boundaries as well as Ti- and O-rich regions within grains. 相似文献
9.
R. Valledor J. Pisonero N. Bordel J. I. Martín C. Quirós A. Tempez A. Sanz-Medel 《Analytical and bioanalytical chemistry》2010,396(8):2881-2887
Nanometer depth resolution is investigated using an innovative pulsed-radiofrequency glow discharge time-of-flight mass spectrometer
(pulsed-rf-GD-TOFMS). A series of ultra-thin (in nanometers approximately) Al/Nb bilayers, deposited on Si wafers by dc-magnetron
sputtering, is analyzed. An Al layer is first deposited on the Si substrate with controlled and different values of the layer
thickness, t
Al. Samples with t
Al = 50, 20, 5, 2, and 1 nm have been prepared. Then, a Nb layer is deposited on top of the Al one, with a thickness t
Nb = 50 nm that is kept constant along the whole series. Qualitative depth profiles of those layered sandwich-type samples are
determined using our pulsed-rf-GD-TOFMS set-up, which demonstrated to be able to detect and measure ultra-thin layers (even
of 1 nm). Moreover, Gaussian fitting of the internal Al layer depth profile is used here to obtain a calibration curve, allowing
thickness estimation of such nanometer layers. In addition, the useful yield (estimation of the number of detected ions per
sputtered atom) of the employed pulsed-rf-GD-TOFMS system is evaluated for Al at the selected operating conditions, which
are optimized for the in-depth profile analysis with high depth resolution. 相似文献
10.
A new technique of analytical transmission electron microscopy has been developed for determining accurately the amount of
solute atoms incorporated into well-defined planar defects in solids, such as stacking faults, special grain boundaries or
interfaces. The method is based on recording series of analytical spectra taken with different electron beam diameters on
the same position centred above a defect that is oriented nearly edge-on. The matrix/solute ratio is then plotted as a function
of the electron beam radius, linear regression is performed and the segregation level is determined from the slope of the
best fit. This method can be applied to energy-dispersive X-ray (EDX) or electron energy-loss spectroscopy (EELS) in a transmission
electron microscope. It necessitates a nano-probe mode but no scan unit. Reliability and accuracy have been tested numerically.
Simulations suggest an accuracy in the determination of the Gibbsian solute excess at a special grain boundary down to ±0.1 atoms nm−2 under typical experimental conditions, with a maximum error about twice as large. 相似文献
11.
Berendes A Brunkahl O Angelkort C Bock W Hofer F Warbichler P Kolbesen BO 《Analytical and bioanalytical chemistry》2004,379(4):554-567
The nitridation of niobium films approximately 250 and 650 nm thick by rapid thermal processing (RTP) at 800 °C in molecular nitrogen or ammonia was investigated. The niobium films were deposited by electron beam evaporation on silicon substrates covered by a 100 or 300 nm thick thermally grown SiO2 layer. In these investigations the reactivity of ammonia and molecular nitrogen was compared with regard to nitride formation and reaction with the SiO2 substrate layer. The phases formed were characterized by X-ray diffraction (XRD). Depth profiles of the elements in the films were recorded by use of secondary neutral mass spectrometry (SNMS). Microstructure and spatial distribution of the elements were imaged by transmission electron microscopy (TEM) and energy-filtered TEM (EFTEM). Electron energy loss spectra (EELS) were taken at selected positions to discriminate between different nitride, oxynitride, and oxide phases. The results provide clear evidence of the expected higher reactivity of ammonia in nitride formation and reaction with the SiO2 substrate layer. Outdiffusion of oxygen into the niobium film and indiffusion of nitrogen from the surface of the film result in the formation of oxynitride in a zone adjacent to the Nb/SiO2 interface. SNMS profiles of nitrogen reveal a distinct tail which is attributed to enhanced diffusion of nitrogen along grain boundaries. 相似文献
12.
Torsten Barfels Bernd Schmidt Andreas von Czarnowski Hans-Joachim Fitting 《Mikrochimica acta》2002,139(1-4):11-16
For investigation of the luminescent center profile cathodoluminescence measurements are used under variation of the primary
electron energy E
0 = 2…30 keV. Applying a constant incident power regime (E
0·I
0 = const), the depth profiles of luminescent centers are deduced from the range of the electron energy transfer profiles dE/dx.
Thermally grown SiO2 layers of thickness d = 500 nm have been implanted by Ge+-ions of energy 350 keV and doses (0.5–5)1016 ions/cm2. Thus Ge profiles with a concentration maximum of (0.4 – 4) at% at the depth of dm≅240 nm are expected. Afterwards the layers have been partially annealed up to T
a = 1100 °C for one hour in dry nitrogen. After thermal annealing, not only the typical violet luminescence (λ = 400 nm) of
the Ge centers is strongly increased but also the luminescent center profiles are shifted from about 250 nm to 170 nm depth
towards the surface. This process should be described by Ge diffusion processes, precipitation and finally Ge nanocluster
formation. Additionally, a Ge surface layer is piled-up extending to a depth of roughly 25 nm. 相似文献
13.
Pollak C Hutter H Warbichler P Reichmann K 《Fresenius' Journal of Analytical Chemistry》2001,371(1):54-57
A chemical solution-deposited multilayer system of SrTiO3 ("STO")/La0.5Sr0.5CoO3 ("LSCO") on a platinized wafer with a layer sequence Pt/TiO2/SiO2/Si(bulk) has been investigated by dynamic SIMS (secondary ion mass spectroscopy) and TEM (transmission electron microscopy); element determination was performed with EELS (electron energy-loss spectroscopy). The STO layer is intended to serve as a dielectric layer for a microelectronic capacitor; the conducting LSCO layer is a buffer layer intended to eliminate fatigue effects which usually occur at the STO/Pt interface. The SIMS depth profiles obtained for the main components revealed intense diffusion processes which must have occurred during the deposition/crystallization processes. Ti is found to diffuse from the (insulating) STO layer into the conductive LSCO layer where a region of constant concentration is observable. TEM-EELS experiments showed that these Ti plateaus are caused by precipitates approximately 20-80 nm in diameter. 相似文献
14.
Photoelectrochemical measurements have been performed at a polybithienyl (PBT) film (doping level of 1 × 1018/cm3) deposited on a platinum electrode. The cathodic photocurrents and negative slope of the Mott-Schottky plot indicate that
the PBT film has the features of a p-type semiconductor. The cathodic photocurrents are interpreted in terms of the Gaertner-Butler
model on the basis of the theory of the semiconductor|solution interface. The (i
ph
hν)2/n vs. hν plots taken from the photocurrent spectra show two linearities for n=1 in the wavelength range from 460 nm to 490 nm and for n=4 in the wavelength range λ > 490 nm. The band gaps of the PBT film were determined to be 2.05 ± 0.05 eV for n=1 and 1.55 ± 0.05 eV for n=4. The flat-band potential is 0.33 V (vs SCE). From the slope of the Mott-Schottky plot at the modulation frequency of 3 kHz,
the dielectric constant ɛ of the film and the thickness of the depletion layer W
0 of the PBT film were determined to be 7.4 and 0.29 μm, respectively.
Received: 6 January 1999 / Accepted: 6 June 1999 相似文献
15.
Z. H. Zhou W. S. Li P. P. Guo H. Y. Yang X. D. Xiang L. Z. Zeng Z. Fu 《Journal of Solid State Electrochemistry》2010,14(2):191-196
In this paper, we reported an improved process for the preparation of PtRu/CNTs, which involves the adsorption of Pt and Ru
ions on CNTs in aqueous solution and the reduction of the adsorbed Pt and Ru ions on CNTs in ethylene glycol. The surface
morphology, structure, and compositions of the prepared catalyst were studied by transmission electron microscopy (TEM), X-ray
diffraction (XRD), and energy-dispersive spectrometer. TEM observation showed that the particles size of the prepared PtRu
alloy was in the range of 2–5 nm, XRD patterns confirmed a face-centered cubic crystal structure. The activity and stability
of the prepared catalyst toward methanol oxidation were studied in 0.5 M H2SO4 + 1 M CH3OH solution by cyclic voltammetry, chronoamperometry, and chronopotentiometry. The electrochemical results showed that the
prepared catalyst exhibited higher activity and stability toward methanol oxidation than commercial PtRu/C with the same loading
amount of Pt and Ru. 相似文献
16.
T. Werninghaus A. Schneider D. Drews D. R. T. Zahn 《Analytical and bioanalytical chemistry》1997,358(1-2):32-35
Micro-Raman spectroscopy measurements in a cross-sectional sample geometry were performed for three heterosystems (3C-SiC/Si(100),
diamond/Si(100), and ZnSxSe1-x/GaAs(100)). Using an automated xy-stage with a minimum step width of 100 nm one-dimensional scans across the interface were
taken. It is demonstrated that sufficient sensitivity for the detection of ultra-thin layers with thicknesses in the nanometer
range can be achieved. Thus surface and interface layers not accessible in a plane-view geometry can be identified. In addition,
the depth-resolved variation of sample properties like interfacial reactions, stress, and stoichiometry will be discussed.
Received: 24 June 1996/Revised: 9 December 1996/Accepted: 13 December 1996 相似文献
17.
Cornelia Weiss Joachim Knoth Heinrich Schwenke Holm Geisler Jürgen Lerche Rüdiger Schulz Hans-Jürgen Ullrich 《Mikrochimica acta》2000,133(1-4):65-68
The actual detection limits of total reflection X-ray fluorescence (TXRF) are determined and compared to those of destructive
physical analytical methods like secondary ion mass spectrometry (SIMS) and chemical methods like vapour phase decomposition
in combination with inductively coupled plasma-mass spectrometry (VPD-ICP-MS). The elements Ca, Ti, Cr, Fe, Cu were analyzed
on a Si wafer with 10 nm thermal oxide using TXRF and VPD-ICP-MS. The deviation of the TXRF and the VPD-ICP-MS results is
less than 30%. The thickness, composition and density of a Co/Ti two-layer stack were determined using angle dependent total
reflection and grazing incidence X-ray fluorescence (A-TXRF). The obtained data were compared with X-ray reflectometry (XRR)
and energy filtered transmission electron microscopy (EFTEM). The agreement between TEM and A-TXRF is excellent for the determination
of the thickness of the metal layers. From these results we conclude, that A-TXRF permits the accurate determination of composition,
thickness and density of thin metallic layers.
The results are discussed regarding detection efficiency, acquisition time, accuracy and reproducibility. 相似文献
18.
Y. Kobayashi H. Kakinuma D. Nagao Y. Ando T. Miyazaki M. Konno 《Journal of Sol-Gel Science and Technology》2008,47(1):16-22
This paper describes a method for fabrication of silica-coated Co–Pt alloy nanoparticles in a liquid phase process. The Co–Pt
nanoparticles were prepared from CoCl2 (4.2 × 10−5 M), H2PtCl6 (1.8 × 10−5 M), citric acid (4 × 10−4 M) and NaBH4 (1.2 × 10−2 M) with a Co:Pt mole ratio of 7:3. The silica coating was performed in water/ethanol solution with a silane coupling agent,
3-aminopropyltrimethoxysilane (8 × 10−5 M), and a silica source, tetraethoxyorthosilicate (7.2 × 10−4 M) in the presence of the Co–Pt nanoparticles. Observations with a transmittance electron microscope and a scanning transmission
electron microscope revealed that the Co-rich and Pt-rich nanoparticles were coated with silica. According to X-ray diffraction
measurements, core particles were crystallized to metallic Co crystallites and fcc Co–Pt alloy crystallites with annealing
in air at 300–500 °C. Magnetic properties of the silica-coated particles were strongly dependent on annealing temperature.
Maximum values of 11.4 emu/g-sample for saturation magnetization and 365 Oe for coercive field were obtained for the particles
annealed at 300 and 500 °C, respectively. Annealing at a temperature as high as 700 °C destroyed the coating structures because
of crystallization of silica shell, resulting in reduction in saturation magnetization and coercive field. 相似文献
19.
N. Karthikeyan V. V. Giridhar D. Vasudevan 《Journal of Solid State Electrochemistry》2010,14(5):877-881
The role of surfactants, cetyl trimethyl ammonium bromide (CTAB), sodium dodecyl sulphate (SDS) and Triton X-100 (in the catalyst),
on methanol oxidation at commercial 50:50 Pt–Ru/C catalyst-coated glassy carbon has been studied using cyclic voltammetry,
scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). Surfactant containing catalysts showed
a considerable reduction in the methanol oxidation potential. In terms of oxidation potential, better results (lower methanol
oxidation potential) were observed in the order SDS > Triton X-100 > CTAB > no surfactant. SEM studies on the catalyst ink
showed better homogeneity in the sample prepared using surfactant. This indicates better Pt Pt contact, which is likely to
favour methanol adsorption and its oxidation. Hence, lowering of oxidation potentials for methanol oxidation could be seen
with use of surfactants. Results of FT-IR on the catalyst ink showed definite changes in the frequencies in the case of Pt–Ru/C
containing surfactants indicating definite interaction between catalyst and surfactant. Catalysts, with and without surfactants,
yielded linear plots of concentration vs peak currents for methanol oxidation (0–2 M). With surfactant containing catalysts,
reduction in methanol oxidation current was observed, and the order followed was the reverse of the above. 相似文献
20.
Yeon-Tae Yu Jae-Chang Song Jeong-Hyun Kim Yoon-Su Kim Hong-Gi Lee 《Journal of Solid State Electrochemistry》2012,16(4):1377-1381
A Pt-loaded carbon black electrode was prepared by pulsed electrophoresis deposition in a Pt colloid solution as a plating
bath to overcome the growth problem of a Pt catalyst during deposition in an electrochemical process. This method is a promising
technique for preparing Pt catalyst layers at the polymer electrolyte/electrode interface. The particle size of the Pt catalyst
loaded by electrophoresis deposition was the same as that of Pt nanoparticles (3–4 nm) in a colloid and the particle size
was maintained even during deposition. The loading of the Pt catalyst was controlled by the pH of the Pt colloid and deposition
time. The Pt nanoparticles were deposited on a carbon black electrode to a depth of 2.5 μm. 相似文献