Fluorescence band blue shift

Figure 1 shows 77K absorption and fluorescence spectra of PSII RC suspended in the absence (A) or presence (B) of Triton X-100 in the buffer. Addition of small quantities of detergent causes significant changes in the spectra. The amplitude of the 680 nm absorption band decreases and the 673 nm band blue shifts to 670 nm (a small absorption shoulder at about 680 nm is also observed in PSII RC at 293K). The fluorescence intensity increases when Triton is added (fluorescence spectra are normalized in Fig. 1), and the main peak at 686 nm blue-shifts to 684 nm and broadens. Furthermore, the shoulder at 692 nm (not due to CP47 contamination) disappears. The CD spectra (Fig 1C) do not change qualitatively however, the amplitude of the 682 nm CD peak was... 

Solvent Influence. Solvent nature has been found to influence absorption spectra, but fluorescence is substantiaHy less sensitive (9,58). Sensitivity to solvent media is one of the main characteristics of unsymmetrical dyes, especiaHy the merocyanines (59). Some dyes manifest positive solvatochromic effects (60) the band maximum is bathochromicaHy shifted as solvent polarity increases. Other dyes, eg, highly unsymmetrical ones, exhibit negative solvatochromicity, and the absorption band is blue-shifted on passing from nonpolar to highly polar solvent (59). In addition, solvents can lead to changes in intensity and shape of spectral bands (58). 

Red shift of fluorescence band with the increase of dye concentration due to directed nonradiative energy homotransfer (DHT) (owing to FRET mechanism) from the blue to the red centers of sample (see panel b in Fig. 5). 

ZnTPPS/ZnTTAP] (17). It is found that dimerization is accompanied by (a) a blue shift of the Soret band, (b) red shifts of the Q bands, (c) red shift of the fluorescence maximum, and (d) strong quenching of fluorescence. Optical spectra of face-to-face covalently linked diporphyrins show the same trends (20,21). However, in one instance formation of a covalently-linked diporphyrin does not lead to a Soret band shift ( ). Of the systems considered here, [TPPS]2 and [ZnTPPSl2 also fail to show a Soret shift even though the visible absorption bands and fluorescence show clear evidence of dimer formation (10). A summary of observed dimerization induced... 

Fluorescence and Phosphorescence. Essentially the same effects that influence absorption of radiation are found to perturb the emission processes. Fluorescence spectra are red- or blue-shifted along with the corresponding band of the absorption spectrum. 

New absorption shoulders appear strongly at 250 and 345 nm. Given this evidence of ground-state interaction, the fluorescence band of the noneclipsed naphthalenophanes should be red-shifted below the peak emission of the dimethylnaphthalene solution excimer. In fact, the emission of chiral [2.2](2,6) naphthalenophane is blue-shifted 900 cm 1, and the emissions of the onh -[2.2](l,4), onfi-[3.3](l,4), and chiral [2.2](1,5)... 

The stationary red fluorescence (versus blue fluorescence see below) and fluorescence excitation spectra of Pr [76] are characterized by relatively narrow long-wavelength emission and excitation (=absorption) bands, a small blue/red intensity ratio of the excitation maxima (/380//666 = 0.5), and a small Stokes shift between the absorption and emission 0-0 bands of 180kJ mol"1 (Figure 7 top Hendricks, Butler and Siegelman [85] were the first in 1962 to report on the fluorescence of 64-kDa Pr). All three criteria are appropriate to differentiate between the helicaloid and the diverse stretched conformations of linear bilatrienes [44,47]. They confirm the proposed stretched alignment of the bilatriene chromophore in Pr (see Section I.B). The... 

Figure 3.55 Examples of solvatochromic plots in solvent mixtures, (a) The fluorescence of 4-aminophthalimide in ether/dimethylformamide shows a much steeper non-linearity than its absorption band because of the large dipole moment of the emitting state, (b) The absorption spectrum of an aminobenzene in dioxan/water displays a red shift followed by a steep blue shift at high water concentrations...

In the case of the hexaadduct where the symmetry is increased to 7), or D3 compared to C2v for the corresponding monoadduct, the emission band is blue-shifted to 660-690 nm depending on the solvent used [67,111,112], The fluorescence spectra of o-quinodimethane bis-adducts also strongly depend on the addition pattern. The spectra for three different regioisomers (cis-2, cis-3, e) are all remarkably different from one another, as in the case of the absorption spectra. 

Polysilane-based nanostructured composites were synthesized by the inclusion of poly(di-w-hexylsilane) (Mw = 53,600) into mesoporous, Si-OH-rich silica with a pore size of 2.8 nm.81 Two PL bands are observed for the composite. A narrow band at 371 nm, assigned to a PDHS film on a quartz substrate is blue shifted by 20 nm, a shift attributed to the polymer being incorporated into the pores.82 The size of the monomeric unit of the PDHS is about 1.6 nm, so only one polymer chain can be incorporated into a mesopore with a diameter of 2.8 nm. The narrow PL band at 350 nm is due to the reduction of the intermolecular interactions between polymer chains. This narrow PL band at 350 nm is assigned to the excited state of the linear polymer chain.81 Also, a new broad band of visible fluorescence at 410 nm appeared, which is assigned to localized states induced by conformational changes of the polymer chains caused by its interaction with the silanol (Si-OH) covered pore surface. Visible luminescence in nanosize PDHS is observed only when the polymer was incorporated in hexagonal pores of 2.8 nm and is not seen for the polymer incorporated into cubic pores of 2.8 nm diameter or hexagonal pores of 5.8 nm diameter. 

---