期刊
PHOTOCHEMICAL & PHOTOBIOLOGICAL SCIENCES
卷 9, 期 5, 页码 722-729出版社
SPRINGERNATURE
DOI: 10.1039/b9pp00102f
关键词
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资金
- Ministry of Education, Science & Technology Global Partnership Program [2009-00503]
- National Research Foundation of Korea [과06B1510, 2009-00503] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
The fluorescence emission properties of 2-(2 '-hydroxy-4 '-R-phenyl)benzothiazole (HBT-R) nanoparticles with different substituents (R =-COOH,-H,-CH3,-OH, and-OCH3) were investigated using spectroscopic and theoretical methods. HBT-Rs displayed dual enol and keto (excited-state intramolecular proton transfer (ESIPT)) emissions in nonpolar solvents. The spectral change of their ESIPT emissions was affected differently by the electron donating (or withdrawing) power of the substituents; a bathochromic shift for the electron donating group and a hypsochromic shift in electron withdrawing group. In addition, the changes in energy levels calculated by the ab initio method were consistent with the spectral shifts of HBT-R in solution. We prepared aggregated HBT-R nanoparticles using a simple reprecipitation process in tetrahydrofuran-water solvents. The ESIPT emission of aggregated HBT-R nanoparticles was strongly enhanced (over 45 times) compared to those of monomer HBT-Rs in toluene, as markedly shifted ESIPT emissions are observed at longer wavelength without any quenching by self-absorption. Aggregated HBT-R nanoparticles showed longer lifetimes than those of monomer molecules. The temperature effect on the aqueous dispersion of the aggregated HBT-R nanoparticles was also explored. It shows a fluorescent ratiometric change in a range of temperature from 7 to 65 degrees C. A mechanism of a temperature-dependent equilibrium between the nanoparticles and the solvated enols is proposed for the emission color change.
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