UV-vis absorption spectra

Billmers and Smith recorded the UV-Vis absorption spectra of sulfur vapor at various pressures (9-320 Torr or 1.2-42.7 kPa) and temperatures (670-900 K) but failed in obtaining the correct reaction enthalpy for the interconversion of S3 and S4 from the absorption intensities [19]. The molar extinction coefficient of S3 at 400 nm exceeds that of S4 at 520 nm by more than one order of magnitude. While the S3 absorption band at 360-440 nm exhibits a vibrational fine structme, the two broad S4 absorption bands at... 

The UV-Vis absorption spectra of the homocyclic molecules S with n = 6-10, 12, 15, and 20 have been recorded in methylcyclohexane and/or methanol solutions at 20 °C in the range 200-360 nm [42]. Representative examples of the spectra are shown in Fig. 1. Their molar extinction coefficients (e) at 254 nm in methylcyclohexane solution linearly increase with the ring size as the following data demonstrate (20 °C) ... 

Fig. 1. UV-Vis absorption spectra of the precatalyst Scheme 2. Possible working model for the HKR chiral Co(salen) and monomer and dimer complex. of terminal epoxides catalyzed by C0-AIX3...

Therefore no trustworthy results for kinetic analysis conld be obtained from the UV-vis absorption spectra due to the formation of bixin isomers and degradation products at different rate constants. " ... 

The maximum absorption wavelengths in different solvents of many carotenoids can be found in the literature, and the % III/II values are also available for some carotenoids. It is common to find variations of 1 to 3 nm in for the same carotenoid in the same solvent cited in different publications. No identification based simply on the matching of recorded UV-Vis spectra with tabulated data can be done without considering the relationships of structures and the factors influencing light absorption. The principal factors that influence carotenoid UV-Vis absorption spectra are discussed below. 

Au2(dcpm)2]X2 complexes with weakly interacting counterions (X = C104, PFg, Cp3S03, Au(CN)2 ) exhibit similar UV/Vis absorption spectra in acetonitrile. They show an intense absorption band at 277 nm ( = 2.6-2.9 x cm ) and a weak shoulder at 315 nm ( w400 cm ), which are assigned to... 

Figure 3.30. (a) UV-vis absorption spectra of the HPAA product (solid line) and the HPDP substrate (dash line) in a H20/MeCN (1 1) mixed solvent, (b) Picosecond time-resolved resonance Raman (ps-TR ) spectra of HPDP obtained with a 267 nm pump and 200 nm prohe wavelengths in a HjO/MeCN (1 1) mixed solvent. Resonance Raman spectrum of an authentic sample of HPAA recorded with 200 nm excitation is displayed at the top. (Reprinted with permission from reference [49]. Copyright (2006) American Chemical Society.)... 

Fig. 6.10 UV-vis absorption spectra of gold - ruthenium bimetallic nanoparticles prepared by the sonochemical co-reduction method using (a) 1 1 and (b) 1 5 gold - ruthenium compositions, respectively [45]...

Fig. 6 UV-Vis titration of the D-A-D receptor BHPN (1 x 10 5 M in Me2SO/H20, 1 1) with various amounts of Hg2+ ion (1 x 10-2 M in distilled water). The ratiometric visual detection of Hg2+ ion can thus be demonstrated by UV-Vis absorption spectra (reprint from ref. [58], Copyright 2005 American Chemical Society)...

Electronic (UV-Vis) spectroscopy has not been utilized in a routine manner. This is perhaps due to the fact that the nature of heterocycles is rather difficult to correlate correctly, with the chromophoric absorption. The UV-Vis absorption spectra of 23b (Table 2) have been studied in detail with R = H, C6H13, CgH17, C20H21, C4H9, and 4-( I, 11. With the exception of 23 (R = 4-C6Hi3C6H4) and which contains conjugated A -phenyl ring, the... 

Various spectroscopic methods have been used to probe the nature of the copper centers in the members of the blue copper oxidase family of proteins (e.g. see ref. 13). Prior to the X-ray determination of the structure of ascorbate oxidase in 1989, similarities in the EPR and UV-vis absorption spectra for the blue multi-copper oxidases including laccase and ceruloplasmin had been observed [14] and a number of general conclusions made for the copper centers in ceruloplasmin as shown in Table 1 [13,15]. It was known that six copper atoms were nondialyzable and not available to chelation directly by dithiocarbamate and these coppers were assumed to be tightly bound and/or buried in the protein. Two of the coppers have absorbance maxima around 610 nm and these were interpreted as blue type I coppers with cysteine and histidine ligands, and responsible for the pronounced color of the protein. However, they are not equivalent and one of them, thought to be involved in enzymatic activity, is reduced and reoxidized at a faster rate than the second (e.g. see ref. 16). There was general concurrence that there are two type HI... 

Transient UV-vis absorption spectra showed that theTi02/Ru(II) films yield prompt electron injection upon photolysis ( >108s 1) These same films displayed photoluminescence decays with parallel first- and second-order components, the first-order component having a rate constant of about lxl06s-1. These two sets of results provide further support for the existence of at least two populations of adsorbed Ru(II), one of which injects electrons rapidly and another which does not inject electrons and is thus capable of luminescing on a longer time scale. The second-order component of the luminescence decay is attributed to bimolecular triplet-triplet annihilation of surface-bound Ru(II). (Note that the second-order rate constants reported for luminescence decay have units of s-1 because they are actually values for k2(Asi))... 

A suggestion for the existence of at least three populations of adsorbed Ru(II) comes from the time evolution of the transient UV-vis absorption spectra. These spectra show that the recovery of the initial Ru(II) spectra occurs with two parallel (fast and slow) second-order components. The rate constants for these two components show remarkably little dependence on the nature of the coordinating ligands. Both of these components are attributed to recombination of the adsorbed Ru(III) with the injected electrons. Thus there is a small luminescent population of Ru(II) that does not engage in electron injection, a non-luminescent population that injects and recombines rapidly, and a third population that injects rapidly and recombines slowly. A detailed picture of the nature of the ligand/semiconductor interaction and how it affects the behavior of these systems awaits further study. 

Figure 2 UV/vis absorption spectra of DDA deposited four monolayers thick on each side of a quartz plate (solid line) and 0.01 mM of DDA in n-hexane (dotted line).

Due to the electronegative atom, polypyridines are good electron acceptors from UPS and UV-vis absorption spectra, Yamamoto and coworkers [669] estimated /iA 3.5 eV, /P = 6.3eV. Chen and coworkers [670] reported L a 2.9 cV, /p = 5.7 eV based on electrochemical measurements. For the double-layer ITO/PPV/562/A1 device, in which 562 acts as electron transport and hole-blocking layer, Chen and coworkers [670] reported a EL efficiency of 0.12cd/A that is 17 times higher than for an single-layer PPV-based PLED. The improvement in d by a factor of 60 (from 0.004 to 0.25%) for this device configuration was demonstrated by Monkman and coworkers [665]. 

Electronic Spectra. The UV-vis absorption spectra of these porphyrazines show absorbances that are common to all S functionalized porphyrazines, for example, the magnesium porphyrazines all have an intense Soret band -370 nm, a weak shoulder at 510-538 nm, and an intense Q band at 656-664 nm. 

Fig. 4 Temperature dependant UV-vis absorption spectra of a PMBMT thin film [1]...

SnC>2 nanoparticles have been successfully synthesized by chemical co-precipitation method using ethanol, acetone, tetrahydrofuran (THF) and ether as solvents. X-ray Diffraction (XRD), Field Emission Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM) have been used to study the crystallographic and morphological properties of synthesized SnC>2 nanoparticles, while their optical properties have been studied by UV-Visible absorption spectroscopy. UV-Vis absorption spectra shows a weak quantum confinement in all the synthesized SnCL samples. The photo-catalytic activity of as-synthesized SnC>2 nanoparticles under UV irradiation has been evaluated using Methylene Blue (MB) dye as a test contaminant in water. The results showed that solvents played a key role to control the morphology and photo-catalytic activity of SnCE nanoparticles. 

The most convenient method for the evaluation of fullerene molecules aggregation is the comparison of UV-VIS absorption spectra in various solvents and for Langmuir-Blodgett films (Bensasson et al., 1994). Some preliminary conclusions about the state of aggregation can be made basing only the absorption maximum of fullerene C60 in the region of 3 30-340 nm concern. 

Further loss of the other signals occurs in three much slower steps. The uv/vis absorption spectra of the complex remains unchanged and no resonances due to the free bpy are observed during this time. The nmr of free bpy does not undergo any changes in the same conditions. Suggest what may be happening and any implications of the results. 

UV/Vis absorption spectra of the polymers and the model complexes show four absorption maxima in acetonitrile. The absorption maxima in the visible region (around 450 and 440 nm, respectively) are similar to those of Ru(bpy) +, and therefore correspond to the metal-to-hgand charge-transfer (MLCT) band of ruthenium(II) complex units. The high molar absorptivity can therefore be explained by the fact that the MLCT band is hkely buried under the considerably more intense hgand-centered tt-tt transition. 

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