[The spectra properties of 2-(2'-hydroxyphenyl)benzothiazole in different solvents].

2-(2 -hydroxyphenyl)benzothiazole (HBT) is a typical compound with excited--state intramolecular proton transfer (ESIPT) effect. The mechanism of the influence of the solvent polarity on the ESIPT effect of HBT was investigated by means of absorption and fluorescence spectra in different polar solvents. The absorption spectra of HBT molecule in all solvents have the similar configuration and are mainly situated in the UV region from 260 to 370 nm. The absorption peaks are located at 287 and 335 nm and have the decline trend with the increase in the solvent polarity. In addition, there is a very weak absorption band at 400 nm and it is attributable to the absorption from the keto form of HBT. Under UV excitation at 335 nm, the fluorescence spectra in all the solvents were obtained. All the fluorescence spectra exhibit dual fluorescence peaks, which are located at 385 and 512 nm respectively. The former is attributed to the emission from the HBT enol forms, named the normal fluorescence, and the latter the emission from the keto tautomer emission, named ESIPT fluorescence. The fluorescence spectra of HBT show that the intensity of the normal fluorescence is obviously increased and the intensity of the ESIPT fluorescence is decreased with enhancing the polarity of the solvents. This indicates that the strong polar solvents are not favorable to the ESIPT of HBT. Because the solvated enols in the polar solvent prevent the ESIPT from happening, the ESIPT efficiency of HBT in cyclohexane is the largest and that of HBT in ethanol is the smallest. The three fluorescence bands of HBT in different polarity solvents were observed with 400 nm excitation. One fluorescence band at ca. 510 nm is referred to as the ESIPT fluorescence. This confirms that the weak absorption at 400 nm results from the keto tautomer and the enol and keto forms can coexist under the normal condition, but the enol form is the absolutely predominant. In addition, the other two unknown fluorescent emission bands appear at 436 and 456 nm respectively. Their possible origin is the emission from the deprotonated anion of HBT keto tautomer.

High photon-to-heat conversion efficiency in the wavelength region of 250-1200 nm based on a thermoelectric Bi2Te3 film structure.

In this work, 4-layered SiO2/Bi2Te3/SiO2/Cu film structures were designed and fabricated and the optical properties investigated in the wavelength region of 250-1200 nm for their promising applications for direct solar-thermal-electric conversion. A typical 4-layered film sample with the structure SiO2 (66.6 nm)/Bi2Te3 (7.0 nm)/SiO2 (67.0 nm)/Cu (>100.0 nm) was deposited on a Si or K9-glass substrate by magnetron sputtering. The experimental results agree well with the simulated ones showing an average optical absorption of 96.5%, except in the shorter wavelength region, 250-500 nm, which demonstrates the superior absorption property of the 4-layered film due to the randomly rough surface of the Cu layer resulting from the higher deposition power. The high reflectance of the film structure in the long wavelength region of 2-20 µm will result in a low thermal emittance, 0.064 at 600 K. The simpler 4-layered structure with the thermoelectric Bi2Te3 used as the absorption layer may provide a straightforward way to obtain solar-thermal-electric conversion more efficiently through future study.

[Study on the fluorescence spectra of 7-hydroxyquinoline in dimethyl sulfoxide solution].

7-hydroxyquinoline (7-HQ) is a kind of organic molecule with excited-state proton transfer (ESPT) effect. 7-HQ in ethanol solution causes ESPT reaction under the excitation of ultraviolet light. The fluorescence spectrum of the sample exhibits two bands. In contrast, 7-HQ in dimethyl sulfoxide (DMS) solution does not cause ESPT reaction. The fluorescence spectrum of the sample exhibits a single band. But after the sample was irradiated with a strong UV light, its fluorescence spectrum also exhibits two bands. This phenomenon is reported for the first time in the present paper, and its cause is investigated through the study on the absorption spectra and fluorescence spectra of 7-HQ in ethanol, dimethyl sulfoxide and N, N-dimethyl formamide solution. The conclusion is that the change in the fluorescence spectrum of 7-HQ in DMS solution is due to the fact that 7-HQ causes ESPT reaction which results from the photodecomposition of DMS and the product of water after the solution was irradiated with strong UV light.