UV-VIS-NIR absorption

Spectroscopic methods are often used as in-line or off-line analytical tools to identify chemical species or determine chemical concentrations. Optical spectroscopy may cover the entire spectral range of wavelengths from the ultraviolet (UV, 1>10 run) to the infrared (IR, A<1 mm). Spectra can be recorded in either absorption (UV, Vis, NIR, IR) or emission (IR, Raman, fluorescence). These methods are used in supercritical media and especially, but not exclusively, in supercritical carbon dioxide (SCCO2). 

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Optical absorption (OA) absorption spectra for all the samples were collected with a CARY 5E UV-VIS-NIR or a Jasco V570 dual-beam spectrophotometers in the 200-800 nm wavelength range at the Department of Mechanical Engineering (Materials Division) in Padova (Italy). 

In order to follow progress of elimination, reactions were also performed on thin films in a special sealed glass cell which permitted in situ monitoring of the electronic or infrared spectra at room temperature (23°C). Typically, the infrared or electronic spectrum of the pristine precursor polymer film was obtained and then bromide vapor was introduced into the reaction vessel. In situ FTIR spectra in the 250-4000 cm-- - region were recorded every 90 sec with a Digilab Model FTS-14 spectrometer and optical absorption spectra in the 185-3200 nm (0.39-6.70 eV) range were recorded every 15 min with a Perkin-Elmer Model Lambda 9 UV-vis-NIR spectrophotometer. The reactions were continued until no visible changes were detected in the spectra. 

Fig. 7 UV-vis-nIR absorption spectra of 3+ trimer 46 (line), neutral trimer 46a (dots) and 2+ trimer 46b (dashes) containing ortho-metallated pyq, measured in dichloromethane solutions...

Figure 7. UV-vis-NIR absorption spectra of RC60+ generatedfrom the corresponding fuller enols in CF3SO3H at room temperature. The inset shows the absorptions in the vis-NIR region. (Reproduced from reference 13. Copyright 1999 American Chemical Society.)...

Fullerenes can be easily chemically reduced by the reaction with electropositive metals [1, 97-99], for example, alkali- and alkaline earth metals. The anions Cjq"" (n = 1-5) can be generated in solution by titrating a suspension of in liquid ammonia with a solution of Rb in liquid ammonia [100], whereupon the resulting anions dissolve. Monitoring of this titration is possible by detecting the characteristic NIR absorption of each anion by UV/Vis/NIR spectroscopy. The solubility of the alkali metal fullerides in the polar solvent NHj demonstrates their salt character. 

The Instrumental Criteria Sub-committee of the Analytical Methods Committee has been active for many years in producing Guidelines for the Evaluation of Analytical Instrumentation. Since 1984, they have produced reports on atomic absorption, ICP, X-ray spectrometers, GLC, HPLC, ICP-MS, molecular fluorescence, UV-Vis-NIR, IR and CE. These are excellent source documents to facilitate the equipment qualification process. A current listing of these publications is given in Section 10.2. 

UV-VIS-NIR diffuse reflectance (DR) spectra were measured using a Perkin-Elmer UV-VIS-NIR spectrometer Lambda 19 equipped with a diffuse reflectance attachment with an integrating sphere coated by BaS04. Spectra of sample in 5 mm thick silica cell were recorded in a differential mode with the parent zeolite treated at the same conditions as a reference. For details see Ref. [5], The absorption intensity was calculated from the Schuster-Kubelka-Munk equation F(R ,) = (l-R< )2/2Roo, where R is the diffuse reflectance from a semi-infinite layer and F(R00) is proportional to the absorption coefficient. 

The reflecting surface can be a mirror or a membrane with a light-scattering surface. In any case, the sensor has the appearance of a monolithic probe (i.e., a dip-stick probe). Optical sensors based on absorption, fluorescence, phosphorescence, and luminescence can employ such a configuration. Various highly optimized fiberoptic probes for UV-Vis, NIR, and IR ranges are now commercially available, and their designs are shown in Fig. 9.23. 

The UV-vis-NIR spectrum of TBPDA-(C60)2 is a superposition of the spectra of TBPDA and Cgo. A broad band in the 700-1100 nm range and the maximum at 896 mn can be attributed to charge transfer (CT) from TBPDA to Cg0 at the absorption of light quantum. However, the IR and EPR spectra of TBPDA-(Cg0)2 indicate the absence of any charge transfer from TBPDA to Cg0 in the ground state. Thus, TBPDA-(Cgo)2is a neutral CT complex. 

Pristine SWCNTs and their fluorinated derivatives, F-SWCNTs, were reacted with organic peroxides to functionalize their sidewalls covalently by attachment of free radicals (Scheme 1.15). The tubes reactivity towards radical addition was compared with that of corresponding polyaromatic and conjugated polyene JT-systems [150, 151]. The characterization of the functionalized SWCNTs and F-SWCNTs was performed by Raman, FT-IR and UV/Vis/NIR spectroscopy and also by TGA/MS, TGA/FT-IR and with TEM measurements. The solution-phase UV/Vis/NIR spectra showed complete loss of the van Hove absorption band structure, typical of functionalized SWCNTs [150]. 

Abstract. The synthesis, isolation and multistage chromatographic separation of the Y2 C84, Ce2 C78 n M C82 (M = Y, La, Ce, Gd) was carried out. All these newly synthesized metallofullerenes are characterized by S8-MALDI mass spectrometry and UV-vis-NIR absorption spectroscopy. 

The UV-vis-NIR absorption spectra of newly isolated EMFs Ce2 C78 and Y2 C84 were recorded between 300 and 1100 nm in toluene solution. The spectrum of Y2 C84 (Fig. 4) is remarkably rich with characteristic absorption bands at 355, 482, 625, 710 and 785 nm. The onset of the absorption spectrum is at 785 nm and corresponds to the lowest energy electronic transition approximately the HOMO-LUMO energy gap. Figure 3 shows the UV-vis spectra of Ce2 C78 with several... 

For the first time the possibility of the use of metal (La, Y) hydrides to prepare composite graphite electrodes was studied. The yield of DCB extracts of C2n/M C82 (M = Y, La, Ce, Gd) from soot obtained by evaporation of composite electrodes based on YH3, LaH3, CeH3 or GdH3 is 2-3 % higher (4-5 wt. % of the primary soot) than the yield of the extracts from soot synthesized using the electrodes based on metallic yttrium, lanthanum, cerium or gadolinium. EMF.v Y2 C84 and Ce2 C78 were produced, separated, and isolated for the first time. Their purity was justified by S8-MALDI mass spectrometry and they were characterized by UV-Vis-NIR absorption spectroscopy. 

The most characteristic spectroscopic feature of CT complexes is a new absorption band in their electronic (UV/vis/NIR) spectra that is not seen in the individual spectra of either the... 

Photoluminescence spectra were recorded with a Perkin-Elmer LS-55 spectrometer while the UV-vis absorption spectra were recorded with UV/VIS/NIR Perkin-Elmer spectrometer. Transmission electron microscope (TEM) images were obtained using a JOEL JEM 3010 instrument. Infrared spectra were recorded with a Bruker IFS-66v spectrometer. 

Volumes 50 and 51 of the Advances, published in 2006 and 2007, respectively, were the first of a set of three focused on the physical characterization of solid catalysts in the functioning state. This volume completes the set. The six chapters presented here are largely focused on the determination of structures and electronic properties of components and surfaces of solid catalysts. The first chapter is devoted to photoluminescense spectroscopy it is followed by chapters on Raman spectroscopy ultraviolet-visible-near infrared (UV-vis-NIR) spectroscopy X-ray photoelectron spectroscopy X-ray diffraction and X-ray absorption spectroscopy. 

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