Key Laboratory for Laser Plasmas (Ministry of Education) and Department of Physics, Shanghai Jiao Tong University, Shanghai, 200240, China.
J Phys Chem A. 2011 Apr 7;115(13):2702-7. doi: 10.1021/jp110215g. Epub 2011 Mar 10.
We have measured directly by time-resolved spectroscopy the transient spectra and kinetics of the methylene blue (MB) excited singlet and triplet state as a function of pH from a few picoseconds to several microseconds. The data show that the acidic triplet state (3)MBH(2+) is the protonated analogue of the basic (3)MB(+). It is also shown that the singlet oxygen formation quantum yield is much higher in basic than in acidic media. The transient spectra and their kinetics suggest that because pH exerts a large influence in singlet oxygen and radical formation, it may also be important in bacteria inactivation. Therefore, we performed experiments, which showed that the rate of gram-positive and gram-negative bacteria inactivation at pH 9 is 3-25 times higher than the rate at pH 5.
我们已经通过时间分辨光谱法直接测量了亚甲蓝（MB）激发单线态和三线态的瞬态光谱和动力学，其范围从几皮秒到几微秒，pH 值也在这一范围内。数据表明，酸性三线态（3）MBH（2+）是碱性（3）MB（+）的质子化类似物。研究还表明，在碱性介质中，单线态氧的形成量子产率远高于酸性介质。瞬态光谱及其动力学表明，由于 pH 值对单线态氧和自由基的形成有很大的影响，它在细菌失活中也可能很重要。因此，我们进行了实验，结果表明，在 pH 值为 9 时，革兰氏阳性菌和革兰氏阴性菌的失活速率比在 pH 值为 5 时高 3-25 倍。
