title: A novel "off-on" colorimetric and fluorescent rhodamine-based pH chemosensor for extreme acidity.
abstract: A novel "off-on" colorimetric and fluorescent rhodamine analogue was synthesized and characterized, and used to monitor extreme acidity (below pH 3.5) via the photophysical response to pH. The colorless spirocyclic structure at high pH (pH⩾7.0) opened to the colored and highly fluorescent form at very low pH (pH<3.0). This sensitive pH probe was characterized with short response time, good reversibility and no interaction with interfering metal ions, and the quantitative relationship between the fluorescence intensity and pH value was consistent with the equilibrium equation pH=pKa-log[(Imax-I)/(I-Imin)]. The fluorescent response to strong acidity was further verified by fluorescent imaging of bacteria, Escherichia coli, which contributed to the development of more useful colorimetric and fluorescent sensors based on the rhodamine platform for measuring intracellular pH in extremely acidic conditions.
authors: College of Pharmaceutical Sciences, Southwest University, Chongqing 400715, China.
authors: Jia-Lian
authors: JL
authors: Tan
authors: College of Resources and Environment, Southwest University, Chongqing 400715, China.
authors: Mu-Xue
authors: MX
authors: Zhang
authors: College of Pharmaceutical Sciences, Southwest University, Chongqing 400715, China.
authors: Fang
authors: F
authors: Zhang
authors: College of Pharmaceutical Sciences, Southwest University, Chongqing 400715, China.
authors: Ting-Ting
authors: TT
authors: Yang
authors: College of Pharmaceutical Sciences, Southwest University, Chongqing 400715, China.
authors: Yu
authors: Y
authors: Liu
authors: College of Pharmaceutical Sciences, Southwest University, Chongqing 400715, China. Electronic address: zb63@163.com.
authors: Zhu-Bo
authors: ZB
authors: Li
authors: College of Pharmaceutical Sciences, Southwest University, Chongqing 400715, China. Electronic address: zuohua@swu.edu.cn.
authors: Hua
authors: H
authors: Zuo
mesh_terms: D000143:Acids / Q000737:chemistry; D003124:Colorimetry / Q000379:methods; D004396:Coloring Agents / Q000737:chemistry*; D004926:Escherichia coli / Q000737:chemistry; D005456:Fluorescent Dyes / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D061848:Optical Imaging; D012235:Rhodamines / Q000737:chemistry*; D013050:Spectrometry, Fluorescence / Q000379:methods
chemical_list: D000143:Acids; D004396:Coloring Agents; D005456:Fluorescent Dyes; D012235:Rhodamines
keywords: E. coli; Fluorescence chemosensor; Imaging; Rhodamine analogue; Strong acidity