US EPA

1454464 

Journal Article 

Temperature and viscosity dependence of the nonradiative decay rates of auramine-O and thioflavin-T in glass-forming solvents 

Erez, Y; Amdursky, N; Gepshtein, R; Huppert, D 

2012 

1 

Journal of Physical Chemistry A
ISSN: 1089-5639
EISSN: 1520-5215 

116 

49 

12056-12064 

English 

23176313 

10.1021/jp309471w 

WOS:000312175900008 

Both auramine-O (AuO) and thioflavin-T (ThT) behave as fluorescent molecular rotors, meaning that their (non)radiative properties are markedly affected by the intramolecular rotation of the molecule. In this article, steady-state and time-resolved fluorescence of AuO and ThT were measured in three alcohols, 1-propanol, 1-butanol, and 1-pentanol, over a wide range of temperatures (86-260 K). These solvents are glass-forming liquids, and their viscosity and dielectric relaxation time increase by more than 10 orders of magnitude as the temperature is lowered from room temperature to ~100 K. Accordingly, the fluorescence nonradiative rates constants of AuO and ThT in these solvents decrease by about 3 orders of magnitude at the latter temperature range. We found very good correspondence between the temperature dependence of the nonradiative rate constant, k(nr), of both molecules and the dielectric relaxation rate of the solvents. The k(nr) values of AuO are twice those of ThT along the whole temperature range. The temperature dependence of k(nr) is consistent with the nonradiative model suggested by Glasbeek and co-workers.