Abstract:

The effects of aliphatic alcohol on the twisted intramolecular charge transfer (TICT) of p-N, N-dimethylaminobenzoic acid (DMABOA) in cetyltrimethylammonium bromide (CTMAB) micelle were examined by the TICT-typical dual fluorescence. The introduction of aliphatic alcohol (CnH2n+10H, n=1, 2, 3, 4, 6, 8, 14, 16, 18) to CTMAB micellar solution does not change the positions of the dual fluorescence bands of DMABOA, but results in a decrease in the fluorescence intensities with that of the longer-wavelength TICT band (a band) more repidly, the latter is demonstrated by a linear decrease of the fluorescence intensity ratio of a band to b band (shorter-wavelength normal band) with the concentration of the alcohol added. The logarithm of the absolute value of the linear slope is positively linearly correlated with the carbon number(n) of the alkyl chain in the alcohol molecule when the chain is relatively short (≤8), whereas a negatively linear correlation is observed when the chain length (n=14, 16, 18) is comparable with that of CTMAB. In pure aqueous solution, the intensities and positions of the dual fluorescence bands are not varied by the same concentration of added alcohol. The decrease of the charge density of micellar surface due to the solubilization of alcohol in micelle is considered to be the cause of the alcohol effects on the TICT in charged micelle.

Key words: Twisted intramolecular charge transfer, Dual fluorescence, p-N,N-dimethylaminobenzoic acid, Charge density of micellar surface, Effects of aliphatic alcohol