Excited-state intramolecular proton transfer on 2-(2 '-hydroxy-4 '-R-phenyl)benzothiazole nanoparticles and fluorescence wavelength depending on substituent and temperature
- Authors
- Kim, Yong Hee; Roh, Soo-Gyun; Jung, Sang-Don; Chung, Myung-Ae; Kim, Hwan Kyu; Cho, Dae Won
- Issue Date
- 2010
- Publisher
- ROYAL SOC CHEMISTRY
- Citation
- PHOTOCHEMICAL & PHOTOBIOLOGICAL SCIENCES, v.9, no.5, pp.722 - 729
- Indexed
- SCIE
SCOPUS
KCI
OTHER
- Journal Title
- PHOTOCHEMICAL & PHOTOBIOLOGICAL SCIENCES
- Volume
- 9
- Number
- 5
- Start Page
- 722
- End Page
- 729
- URI
- https://scholar.korea.ac.kr/handle/2021.sw.korea/118701
- DOI
- 10.1039/b9pp00102f
- ISSN
- 1474-905X
- Abstract
- 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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Collections - Graduate School > Department of Advanced Materials Chemistry > 1. Journal Articles
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