Absorption peak shift

Fig. 12. Absorption spectra of perchloric acid extracts of whole blood from normal subject and a patient with pyrimidine 5 -nucleotides (P5N) deficiency. Absorption peak shift occurs in P5N deficiency, reflecting intracellular accumulation of pyrimidine nucleotides.

The absorption spectra for all these dyes are composed of intense cyanine-like bands attributed to the, S 0 S) absorption, with the main absorption peaks shifted by fslOO nm to longer wavelengths upon lengthening of the main conjugation... 

A third example can be taken from analytical chemistry. Absorption and resonance Raman spectra of phenol blue were measured in liquid and supercritical solvents to determine the solvent dependence of absorption bandwidth and spectral shifts. Good correlation between absorption peak shift and resonance Raman bands and between Raman bands and bandwidth of C-N stretching mode were observed while anomalous solvent effect on the absorption bandwidth occnrred in liquid solvents. Large band-widths of absorption and resonance Raman spectra were seen in supercritical solvents as compared to liquid solvents. This was dne to the small refractive indices of the supercritical solvents. The large refractive index of the liqnid solvents only make the absorption peak shifts withont broadening the absorption spectra (Yamaguchi et al., 1997). 

The inclusion of 5 wt% PCBM [l-(3-methoxycarbonyl)propyl-l-phe-nyl-[6,6]C6i] in the spin-coating solutions resulted in efficient polymer emission quenching for all the polythiophenes studied. The transient absorption spectra of the amorphous poly(541)/PCBM blend film. At 10 ps exhibited an absorption peak around 700 nm, similar to that observed for the poly(541) pristine film. The shape of the transient spectrum varied with time, with the absorption peak shifting from 700 nm at 10 is to 900 nm for time delays >100 (is, demonstrating the formation of two distinct transient species in the blend film. The monoexponential lifetime was t = 8 (is under Ar atmosphere and significantly shortened under 02 atmosphere. Monoexponential phase is therefore assigned to the decay of poly(541) triplet excitons. 

The chemical and spectroscopic properties of the cofactor F-430 have been reviewed [98,99], The structure of the macrocycle (Figure 4) was elucidated by x-ray crystallography and NMR spectroscopy [100], The free cofactor, which is present in substantial amounts in the cells, has an absorption maximum at 430 nm, hence its name. In the enzyme, the absorption maximum is blue shifted to 420 nm. The pentamethyl ester of F-430 is soluble in organic solvents and can be reduced to the Ni(I) state under aprotic conditions, resulting in an absorption peak shift to 382 nm [101], or can be oxidized to the Ni(III) state, giving an absorption peak at 368 nm [102],... 

The UV-vis spectra of the colloids/sols of TAA-OL-1 and DA-OL-1 diluted to concentrations of 10 10 moH" manganese were measured. One strong absorption band centered at 368 nm and one weak absorption band centered at 216 nm were found for TMA-OL-1 colloids. Based on the Beer-Lambert law, the molar absorption coefficients of TMA-OL-1 colloids with Mn concentrations of 3.60 x 10 moi r were 2.41 x lo" M cm" and 1.89 x lO" M cm for the two absorption bands centered at 368 nm and 216 nm, respectively. Similar results were found for the other TAA-OL-l colloids. The molar absorption coefffcients of TAA-OL-1 colloids bectune smaller along with the longer alkyl chain TAA species intercalated into OL-1 layers. These results are similar to those of TAA manganese oxides reduced from TAA permanganate, whose UV-vis absorption peaks shift from lower to higher... 

These results support current interpretations of the bathochromic shifts observed in dialkyl-substituted poly silane. Experimental results for poly(di-n-hexylsilane) indicate that as the temperature is cooled below a transition temperature of roughly -35 °C, the major absorption peak shifts from a broad peak at about 310-320 nm (3.9-4.0 eV) to a narrower peak at about 350-370 nm (3.3-3.5 eV), with the red shift being attributed to a transition from a disordered system with a large population of gauche bond twists in the silicon backbone and in the alkyl substituent to a planar dll-trans backbone conformation (5-8, 15). Results from polarized absorption spectra of stretch-oriented samples for the cooled samples exhibit absorbance only for polarizations parallel to the stretch (and presumably the chain axis) direction (22). 

The produced intensity of the plasmon resonance band of silver nanoparticles essentially upraises and shifts down for lOnm (up to 410 nm). Hence, the presence of polymer that forms the stabilizing layer on silver nanoparticles and simultaneously reduces metal ions can provide the rise of electronic density of metal cores. This can increase the intensity of absorption band and shift it. The variation of silver ion / arabinogalactan ratios have shown a possibility to shift the plasmon absorption maximum [2]. This ratio in the range of 0.01-0.39 (g/g) leads to the increase of silver content from 1 to 19% in the composites accompanied by the absorption peak shift. 

Figure 7 Absorption peak shift of PEG upon the addition of PAA(890K)...

The deprotonation pathway in the CL reaction of Ln is proposed as follows Ln (Neutral) —> M440 ( Anion-2 , Anion-0+K+ or Anion-2+2K+ ) —> M420 ( Anion-3+DMSO+K+ ). The DMSO molecule between K+ and Anion-3 makes absorption peaks shift to shorter wavelengths. Furthermore, we are going to study the ionized states of M440 and M420 by experimental techniques of IR and H-NMR. 

Figure C2.17.13 presents a model ealeulation of the absorption of gold nanoerystals, using the formalism outlined above. The qualitative result is that, as metal eolloids beeome smaller, the primary absorption peak shifts to lower energy, and broadens signifieantly. The peak shifts predieted are small, of the order of 0.1 eV for a 2 nm gold crystallite. In eontrast, the peak widths are far more sensitive to size. This simple theory, and its variations, have been successful at explaining many experimental observations, espeeially for elusters greater than 3 nm in size...

The decrease in the value of was also observed for the fluorescent probe 1-anilino-8-naphthalene sulfonate (ANS) in presence of apomyoglobin. In fact, the absorption peak shift from 265 mu when free in solution to 271 mu in presence of apomyoglobin while the extinction coefficient decreases from 19200 to 13000 cm / mmole L, (Fig. 1.15). 

Random copolymer. Figures 5 and 6 show the absorption and fluorescence spectra of the random copolymers consisting of (A) and (D) units. The absorption peak shifts proportionally to the ratio of (A) and (D), while the absorption edge shifts less than the peak. Similar shifts in absorption and fluorescence spectra were observed in the copolymers of A /B, and A/C. 

Fig. 5.20 [169]. One can see that with a decrease in X, the spectrum evolves from that of a-Si H to that of a-Sii-xQ.K as the SiC stretching band shifts from 760 to 800 cm" and becomes more asymmetric in the higher frequency region and the Si-H stretching absorption peak shifts from 2000 cm (as in pure a-Si H) to 2090 cm (as in an a-SiC H alloy). The gradual shift of the Si-H stretching absorption band may be a result of the induction effect as the number of (more electronegative) carbon atoms attached to Si—H increases [149]. Variations in the IR absorption spectra are accompanied by the growth of the optical band gap from 1.7 eV (pure a-Si H) to 2.6 eV (a-Sii cCx H alloy with X = 0.17) [169]. The carbon content in the film can be calculated from the SiC stretching absorption band at 760 cm by using Eqs. (5.13) and (5.14) and the coefficient Ai = 2.1 X lOi cm-2 [171].

The ultraviolet (UV) - visible spectrophotometer is another important tool in the characterisation of vegetable oil-based polymer nanocomposites and is particularly effective for metal nanocomposites. The formation of metal nanoparticles in the matrix can be easily detected by UV-visible spectroscopy. Every metal nanoparticle has its own characteristic surface plasmon resonance value. This band is attributed to the collective oscillation of electron gas in the nanoparticles, with a periodic change in the electronic density at the surface. Parameters such as particle size, shape and dielectric constant of the medium and surface adsorbed species determine the position and shape of the plasmon absorption. When the particles become significantly smaller than the mean free path of electrons in the bulk metal, the plasmon oscillation is dampened. The plasmon absorption peak shifts to a higher wavelength than expected with an increase in aggregation of the nanoparticles. The sharpness of the peak indicates the narrow size distribution. 

From their study of the reactions of organic halides with organosodium complexes in dioxane solution, Morantz and Warhurst (97) concluded that the measurements could be reconciled only with the concept of ion pairing. They concluded that the solutions contained exclusively the monomeric form of the radical anion paired with the alkali metal cation. The influence of the alkali ion on the electronic spectra was investigated by Carter et al. (100). They measured the absorption spectra in the region 10,000-25,000 cm of a number of alkali metal complexes in dioxane solution and found that for a given radical anion the frequency of the maximum of an absorption peak shifted towards the red as the radius of the alkali metal cation increased. A relation was found between this frequency and the radius of the cation... 

Figure 9.1 Effect of polymer matrix on the spectra of spiropyran. The absorption peak shifts toward lower wavelength in polar matrix. Larger blueshifts are observed for the poly(n-butyl methacrylate) (PnBMA) compared to poly(methyl methacrylate) (PMMA), and styrene-butadiene-styrene (SBS) matrices.

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