IR Luminescence of Polyfunctional Associates of Indocianine Green and Ag-=SUB=-2-=/SUB=-S Quantum Dots-=SUP=-*-=/SUP=-

In this work, manifestations of IR luminescence sensitization of Indocyanine Green during conjugation with colloidal Ag2S quantum dots with average size of 2.2 and 3.7 nm, passivated with thioglycolic acid molecules (Ag2S/TGA QDs) are studied using absorption and luminescence techniques. The possibility of enhancing luminescence in the dye monomer band (820 nm) under excitation of 660 nm by a factor of 6 in the presence of Ag2S/TGA QDs (2.2 nm) due to a decrease in the dye polymethine chain due movement via coordination interaction with quantum dots was demonstrated. The way to switch-over from the first therapeutic window of biological tissue transparency (NIR-I, 700-950 nm) to the second (NIR-II, 1000-1700 nm), based on sensitization of IR luminescence of Ag2S/TGA QDs with an average size of 3.7 nm in the region of 1040 nm due to of resonance non-radiative transfer of excitation energy from Ag2S/TGA (2.2 nm) QDs at 900 nm to Ag2S/TGA QDs (3.7 nm) via the J-aggregate of ICG dye, which acts as an exciton bridge.

Potential Properties of Plant Sprout Extracts on Amyloidβ

The aim of this study is to examine the amyloidβ(Aβ) inhibition mechanism of plant sprouts’ aqueous extracts (PSAE). In this study, we screened the effects of five plant sprouts’ extracts on Aβ(1–42) structure modification using gel electrophoresis. In PSAE, no band of Aβmonomer was recognized in Japanese butterbur. Similarly, the Aβmonomer band became light in buckwheat, red cabbage, broccoli, and brussels. The neuroprotective effects of PSAE were evaluated by measuring levels of Aβin mixtures (Aβ and PSAE) with AβELISA assay. The treatment with PSAE decreased Aβlevels. The results indicated that the levels of red cabbage, Japanese butterbur, and broccoli were 9.6, 28.0, and 44.0%, respectively. The lowest value was observed with buckwheat. Furthermore, we carried out a Congo Red (CR) and Aβbinding experiment of PSAE to confirm the modification mechanism of PSAE. The correlation coefficient for the absorption spectrum peak of CR was found to be bigger than 0.8 (r=0.882) which proved that the Aβlevels could be attributed to the peak of CR. In conclusion, we demonstrated that treatment with PSAE effectively decreases Aβconcentration. Thus, the mechanism that decreased the Aβlevels may be modification by PSAE.

Solubilization and Photoreaction of Thiazine Dyes in Reversed Micelles

Thiazine dyes were solubilized very slowly in dodecylammonium propionate reversed micellar cyclohexanic solutions containing 0.5 M H2O. Light accelerated highly the solubilization of the dyes. The dye monomer band blue-or red-shifted by the solubilization dependent on the dye species. Thiazine dyes solubilized in the reversed micelles containing 0.1 M H2O exhibited a new absorption band at about 500 nm. The photoreduction of thiazine dyes by allylthiourea was enhanced drastically by solubilizing the dyes in the reversed micellar solutions containing 0.5 M H2O, and the singlet oxygen production was also effectively photosensitized by the solubilized thiazine dyes. The relative quantum yields for the photoreduction of the dyes by allylthiourea and the furan oxidation by singlet oxygen produced by the photosensitization of the dyes were obtained in the reversed micellar solutions. Results obtained were discussed in connection with the solubilization.

Factor Analysis as a Complement to Band Resolution Techniques. III. Self Association in Trichloroacetic Acid

Digitized infrared spectra of nine solutions of trichloroacetic acid in CCl4 have been studied in the carbonyl stretching region. At all concentrations only two bands are visually apparent. However, factor analysis indicates the presence of four absorbing components. The contour resolution technique gives a monomer band at 1786 cm−1, a dimer band at 1749 cm−1, and a third band close to the dimer frequency at approximately 1735 cm−1. Examination of the changes in Cauchy–Gauss shape ratio of the monomer band with increasing concentration indicates the presence of an unresolved component. The band at 1735 cm−1 and the unresolved band near the monomer peak at 1786 cm−1 are assigned to absorption of carbonyl groups in linear polymers of trichloroaceticacid. The monomer–dimer equilibrium constant was calculated from the molar absorption coefficients and absorbances of monomer and dimer bands. The average value over the concentration range 0.305 × 10−3 to 0.1603 M was 287 l/mol at 33.9 ± 0.5 °C.

‘Excimer’ fluorescence - IX. Lifetime studies of pyrene crystals

The increase of the excimer fluorescence lifetime Ƭ D (= 1/ k D ) with increasing purity was used to establish a reproducible criterion of purity for crystalline pyrene. Zone-refining, microsublimation and adsorption chromatography yielded material with similar high values of Ƭ D = 113±2 ns at 293 °K, but recrystallization from solution was ineffective. Single crystals of zone-refined pyrene were grown by sublimation, and Ƭ D and the fluorescence quantum efficiency q D were observed from 100° to 350 °K. Values of k fD = 5·55 × 10 6 s -1 , k 0 iD = 0, and k iD = 4·7 × 10 7 exp [ –0·066 (eV)/ kT ] s -1 are obtained for the rate parameters of fluorescence, temperature-independent intersystem crossing and temperature-dependent intersystem crossing, respectively. Ƭ D for microcrystalline layers ca . 0·5 μ m thick is lower than for single crystals, owing to a crystal-size effect which limits the exciton lifetime. The reduction in Ƭ D is accompanied by the appearance of a surface monomer band in the fluorescence spectrum. The exciton migration process in anthracene and pyrene crystals is discussed. From lifetime data it is concluded that singlet excitons in organic molecular crystals are localized and identical with singlet-excited molecules and that they migrate by a hopping mechanism, rather than through a hypothetical exciton band. The pyrene excimer parameters are similar in the crystal and in solution; it is concluded that the excimer molecular configuration is that of the unexcited crystal dimer but with a reduced spacing between the molecular planes.