Department of Spectroscopy, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India.
Photochem Photobiol Sci. 2010 Aug;9(8):1094-100. doi: 10.1039/c0pp00104j. Epub 2010 Jun 5.
This paper reports the changed dynamics of excited state proton transfer (ESPT) photophysics of 4-nitro-1-hydroxy-2-naphthoic acid (NHNA) in ionic and nonionic micelles, as revealed from time-resolved emission spectra (TRES) and time-resolved area normalized emission spectra (TRANES). Both the neutral and anionic bands of NHNA are enhanced and blue-shifted inside the micelles. Quenching of emission by metal Cu(2+) reveals that NHNA does not penetrate into the core of the micelles; rather it binds to the micelle/water interfacial region. The fast decay component is due to decay of normal species and the slow component is assigned to decay of anionic species. In all the micelles the decay time becomes longer by three times compared to that in water. The efficiency of formation of anionic state from the locally excited state gets enhanced in micellar media due to enhanced sojourn in the first excited state in increased viscous medium around NHNA. TRANES data also indicate that of the normal and anionic species in the aqueous phase the anionic species increases in the micelles as the time evolved.
本文报道了 4-硝基-1-羟基-2-萘甲酸（NHNA）在离子和非离子胶束中激发态质子转移（ESPT）光物理性质的变化，这是通过时间分辨发射光谱（TRES）和时间分辨面积归一化发射光谱（TRANES）揭示的。NHNA 的中性和阴离子带都在胶束内得到增强和蓝移。金属 Cu(2+)对发射的猝灭表明 NHNA 不会渗透到胶束的核心，而是结合到胶束/水界面区域。快速衰减分量归因于正常物种的衰减，而慢分量归因于阴离子物种的衰减。与在水中相比，在所有胶束中，衰减时间延长了三倍。由于在 NHNA 周围粘性增加的介质中，第一激发态的停留时间增加，因此在胶束介质中从局部激发态形成阴离子态的效率得到增强。TRANES 数据还表明，在水相中的正常和阴离子物种中，随着时间的推移，阴离子物种在胶束中增加。
