Spectra of Cu

The electronic absorption spectrum of the CuS nanotubes given in Fig. 5a shows the characteristic broad band of CuS in the near IR region, peaking at 1200 nm. The band is attributed to an electron-acceptor state lying within the band gap [17]. A similar broad band has been reported for CuS nanocrystals [27], The photoluminescence spectrum of CuS nanostructures given in Fig. 5b shows a broad band peaking at 560 nm with a shoulder at 480 nm. Bulk CuS is reported to show a broad band centered at 560 nm with a shoulder at 587 nm [17], The absence of any appreciable blue-shift of the emission bands of the CuS nanostructures prepared by us might be due to the formation of chains of nanorods by self-assembly. 

Figure 5 UV- %ible transmittance spectrum of CuS dispersed films with precursor film composition of a, CuCl2-2H2O/HPC=0.253/0.5(g/g) b,CuCl2-2H20/HPaSi02 sol=0.5/0.4/0.29(g/g) c, CuCl2-2H20/HPCySi02 sol/AlCl3=0.5/0.5/0.29/0.2(g/g).

Copper-63 NMR/NQR spectra for CuS, from 4.2K up to ambient temperatures, show two distinct lines based on the abrupt change in the spectrum at 55K. This is ascribed to a structural phase transition for both the powder and the oriented CuS. A more recent study of powdered samples at temperatures as low as 1.5K under a magnetic field of 6.5 T revealed more detail. An intense resonance with satellites was observed at all temperatures up to the ambient. This peak consisted of two resonance lines above 60K and four lines below 50K. The splittings observed correspond to crystal distortions below 55K. The central peaks with satellites were assigned to the metallic Cu(l) and Cu(2) in the crystal structure of CuS, for which spin-lattice relaxation times of 4 ms and 55 ms, respectively, were measured at 15K. The authors suggest that the anomalously short Ti for Cu(l) is indicative of the metallic character in the plane formed by Cu(l)-S bonds. 

In a germanium sample from an As-doped crystal pulled in vacuo and contaminated with Cu, the PTIS spectrum of a CuX centre has been reported by Sirmain et al. [156]. Its first ionization energy is 10.05 meV and the ther-malized energy is 9.15 meV. Piezospectroscopic measurements indicate a C v symmetry and the dissociation conditions of this complex have led to the tentative attribution of CuX to a (Cus, As) acceptor complex, which should normally behave as a double acceptor. 

To test this prediction the surface of CuS membranes, dissolved anodically in the media discussed above, was analyzed for the presence of sulphur by using SEM/EDAX technique with sulphur probe. In 1 M HCl the sulphur presence can clearly be seen already after one anodic half-cycle (Fig. 10). In 1x10 M HCl no sulphur could be detected. In 1x10 M HCl + 1 M KCl the result of the analysis was not definite, the surface analyzed by XRD, however, provided the strong indication of sulphur presence, because of the characteristic low-angle spectrum. Fig.9. To facilitate sulphur formation under these conditions potentiostatic dissolution at +600 mV (SCE) for 72 h was attempted. The presence of sulphur was quite evident (Fig.ll) which is opposite to the observation of CuS membrane surface dissolved under the same conditions in lxlO M HCl, (Fig.5). Finally, the surface of CuS disc left in... 

FIGURE 2.a) Experimental K-band ESP spectrum of deuterated Synechococ-cus lividus. Solid line spectrum at early times. Broken line spectrum of nutations at late times. For full data set see /lO/. b) Solid line ... 

Their wide spectrum of biolc cal activities provides numerous classes of useful medicinal agents, and yet, at the same time, they provide a global paradox. In spite of many health beneficent effects, two alkaloids, cocaine and morphine (and its derivative heroin), are the ft)cus of a counter culture of illicit use of biological powerful alkaloids, and many alkaloids, because of their profound toxicity, are to be feared. On the other hand, the xanthine alkaloids, caffeine and threobromine, are an integral aspect of providing pleasure in the daily lives of most of the world in the consumption of tea, coffee, and chocolate. 

Figure 9.17 (A) HRTEM image of CuS NPs. (B) Optical absorption spectrum of...

This group published a number of other papers on Cu S, using the same basic deposition solution, with emphasis on variations of their spectral properties for possible use in solar control coatings. Some examples are given in Refs. 44, 45, and 53 (the last deals with films deposited on Kapton foil). This last showed some weak CuS (covellite) peaks in the XRD spectrum no inference of whether this was the major phase or not could be made. 

The constitution (XXI) was confirmed by a synthesis of dl-cus-pareine, which was identical with the alkaloid in boiling point, in ultraviolet absorption spectrum, and in its sensitivity to hot mineral acid which caused reddening and resinification. dl-Norcuspareine (XXIV) was formed by the catalytic reduction of the products obtained by the condensation of veratric aldehyde with quinalcfine or with o-nitrobenzal-acetone, or of o-nitrobenzaldehyde with veratralacetone, and on methyla-... 

Further significant developments of the EXAFS technique are envisaged. Energy-dispersive X-ray absorption tine structure (DXAFS) allows collection of a spectrum in much less than 1 s, and its extension to the fj,s or even the ns time scale is not impossible. Polarisation-dependent total-reflection fluorescence X-ray absorption fine structure (PTRF-XAFS) permits high spatial resolution and has been applied to the copper trimer Cus on a Ti(llO) surface. The use of time-and space-resolved XAFS observation for studies of dynamic aspects of the local structure at catalyst surfaces under working conditions is forseen . Note that the acronym XAFS is used, rather than EXAFS. 

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