title: Photophysical properties of rhodamine isomers: a two-photon excited fluorescent sensor for trivalent chromium cation (Cr3+).
abstract: We introduce a new rhodamine-based fluorescent chemosensor, FD8 which exhibits a distinct two-photon excited fluorescence (TPEF) on/off characteristic upon binding Cr(3+) ions. By coordination with metal cation, conformation of FD8 changes from spirocyclic to open-ring, resulting in remarkable enhancement of absorption and fluorescence both in one- and two-photon excitations. As a result, a 29-fold enhancement of two-photon excited fluorescent intensity was observed when 10 eq. Cr(3+) was added to the FD8 solution. The detection limit of Cr(3+) cation concentration down to 1 microM (0.01 eq. of FD8) was achieved under our experimental condition. Besides the excitation within ultraviolet regime by fluorescence resonance energy transfer (FRET) mechanism, the TPEF on/off behavior further extends the excitation to near infrared regime (the biological optimal window of 700-1200 nm), and shows more effective sensitivity. The broad excitation wavelength, on/off fluorescence and high selectivity to Cr(3+) enable FD8 to be a powerful Cr(3+) cation sensor with potential application, especially in biological detection. To the best of our knowledge, this is the first report about two-photon fluorescent sensor for Cr(3+) ions.
authors.affiliation: The State Key Laboratory of Molecular Reaction Dynamics, and Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun North First Street 2, Beijing 100190, PR China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Wan
authors.forename: Qianjin
authors.initials: Q
authors.lastname: Guo
authors.forename: Xuefei
authors.initials: X
authors.lastname: Wang
authors.forename: Andong
authors.initials: A
authors.lastname: Xia