Absorption copper particles

Yanase, A., Komiyama, H. 1991. In situ observation of oxidation and reduction of small supported copper particles using optical absorption and x-ray diffraction. Surface Science 248 11-19. 

By differentiating the XANES spectra, it was identified that the intensity of the edge absorption for the catalyst was lower than that for copper foil, consistent with the nanosized dimension of the copper particles. Moreover, the positive shift of the derivative peaks at ca. 8990 and 8984 eV relative to those of copper foil suggested some alterations in the chemical environment around the copper species. Combined with the XRD results, the positive shift was tentatively assigned to a distortion of the copper lattice due to the presence of microstrain at the interface between Cu NPs and ZnO NRs. Consequently, the superior catalytic performance of the ZnO NR Cu NPs catalyst in methanol reforming was attributed to the enhanced dispersion of Cu NPs and the existence of the SMSl effect. 

A1(N03)3 in the reverse-micellar core with NH3. More recently, Cason and Roberts prepared copper nanoparticles via the hydrazine reduction of copper ions in reverse micelles based on the C u +-substituted AOT, Cu(AOT)2, as surfactant in subcritical and supercritical ethane (245). The particle size was estimated to be 9-10 nm on the basis of in situ UV-vis absorption spectral analysis and the characterization of the recovered particles. The recovery involved a transfer from the microemulsion in high-pressure propane to a liquid-micelle emulsion. Results of TEM analysis of the recovered copper particles indicated agglomeration of the particles during recovery. 

Figure 1.13 (a) Simulated absorption spectrum of copper particles having different shapes nanodisks (size = 23 nm, aspect ratio = 1.8, truncature = 0), solid line elongated particles (length = 22, width = 13, aspect ratio = 1.8), dotted line cubo-octahedra (19nm), dashed line (b) Simulated... 

MeV a-particles and used the Au/Ir source after annealing without any further chemical or physical treatment. Commercially available sources are produced via Pt(p, n) Au. The most popular source matrix into which Au is diffused is platinum metal although it has the disadvantage of being a resonant matrix - natural platinum contains 33.6% of Pt. Using copper and iridium foils as host matrices for the Au parent nuclide, Buym et al. [327] observed natural line widths and reasonable resonance absorption of a few percent at 4.2 K. 

There have been many recent studies in support of this mechanistic approach. Stepwise reductive formation of Ag3+ and Ag4+ clusters has been followed using spectroscopic methods by Henglein [33], Reduction of copper (II) to colloidal Cu protected by cationic surfactants (NR4+) through the intermediate Cu+ prior to nucleation of the particles [36] as monitored by in situ x-ray absorption spectroscopy is another example. The seed-mediated synthesis also serves as evidence in support of this mechanism [38-41],... 

The dielectric function of a metal can be decomposed into a free-electron term and an interband, or bound-electron term, as was done for silver in Fig. 9.12. This separation of terms is important in the mean free path limitation because only the free-electron term is modified. For metals such as gold and copper there is a large interband contribution near the Frohlich mode frequency, but for metals such as silver and aluminum the free-electron term dominates. A good discussion of the mean free path limitation has been given by Kreibig (1974), who applied his results to interpreting absorption by small silver particles. The basic idea is simple the damping constant in the Drude theory, which is the inverse of the collision time for conduction electrons, is increased because of additional collisions with the boundary of the particle. Under the assumption that the electrons are diffusely reflected at the boundary, y can be written... 

Absorption resonances resulting from excitation of surface modes are accompanied by scattering resonances at approximately the same frequencies this was pointed out following (12.26). In most experiments transmission is measured to determine extinction, which is nearly equal to absorption for sufficiently small particles. However, surface mode resonances have been observed in spectra of light scattered at 90° by very small particles of silver, copper, and gold produced by nucleation of vapor in an inert gas stream (Eversole and Broida, 1977). The scattering resonance peak was at 3670 A, near the expected position of the Frohlich mode, for the smallest silver particles. Although peak positions were predictable, differences in widths and shapes of the bands were concluded to be the result of nonsphericity. 

Until now, little attention has been given to the analysis of ancient copper alloys with LA-ICP-MS. This type of material is usually analyzed with fast or instrumental neutron activation analysis (FNAA or INAA), particle induced X-ray emission (PIXE), X-ray fluorescence (XRF), inductively coupled plasma-atomic emission spectrometry or inductively coupled plasma-atomic absorption spectrometry (ICP-AES or ICP-AAS). Some of these techniques are destructive and involve extensive sample preparation, some measure only surface compositions, and some require access to a cyclotron or a reactor. LA-ICP-MS is riot affected by any of these inconveniences. We propose here an analytical protocol for copper alloys using LA-ICP-MS and present its application to the study of Matisse bronze sculptures. 

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