Micelle-Induced Versatile Performance of Amphiphilic Intramolecular Charge-Transfer Fluorescent Molecular Sensors

• Published in: Chemistry : a European journal Vol. 13; no. 26; pp. 7543 - 7552
• Main Authors: Wang, Jiaobing, Qian, Xuhong, Qian, Junhong, Xu, Yufang
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.01.2007; WILEY‐VCH Verlag; Wiley
• Subjects: charge transfer; Chemistry; Chemistry, Multidisciplinary; fluorescence; Fluorescent Dyes - chemistry; Indicators and Reagents; Magnetic Resonance Spectroscopy; mercury; Mercury - chemistry; Micelles; Physical Sciences; Science & Technology; sensors; Sodium Dodecyl Sulfate - chemistry; Solvents; Spectrometry, Fluorescence; Spectrophotometry, Ultraviolet; Surface-Active Agents - chemistry; Temperature; RECOGNITION; mercury; CATION-BINDING; CONJUGATED POLYMER; micelles; charge transfer; MERCURY IONS; HG2; sensors; SPECTROSCOPY; fluorescence; CHEMISTRY; MEDIA; SPECTRA; MODULATION
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.200700435

A series of amphiphilic intramolecular charge‐transfer fluorescent molecular sensors AS1–3, equipped with a rod‐shaped hydrophobic 2‐phenylbenzoxazole fluorophore and a hydrophilic tetraamide Hg2+‐ion receptor, have been prepared. These sensor molecules could be incorporated into the hydrophobic sodium dodecyl sulfate (SDS) micelle, which is confirmed by the clear spectral blue shift and emission enhancement observed at the critical micelle concentration of SDS. Systematic examination of the sensor–Hg2+ complexation, by using both UV/visible and fluorescence spectroscopy, indicates that SDS significantly modulates both the binding event and signal transformation of these sensor molecules. The potential advantages are fourfold: 1) SDS substantially increases the Hg2+‐ion association constant and results in an amplified sensitivity. 2) SDS initiates spectral features which facilitate Hg2+‐ion analysis, for example, in addition to the strengthened fluorescence of the free sensors AS1–3, the original “on–off” response of AS2 toward the Hg2+ ion is transformed into a self‐calibrated two‐wavelength ratiometric signal, while for AS3, Hg2+‐ion complexation in the presence of SDS results in a 180 nm blue shift, which is preferred to the 51 nm spectral shift obtained without SDS. 3) Thermoreversible tuning of the dynamic detection range is realized. 4) Highly specific Hg2+‐ion identification could be achieved by using the SDS‐induced fingerprint emission (358 nm) of the AS2–Hg2+ complex. Altogether, this work demonstrates a convenient and powerful strategy that remarkably elevates the performance of a given fluorescent molecular sensor. It also implies that for a specific utilization, much attention should be paid to the microenvironment in which the sensor resides, as the behavior of the sensor might be different from that in the bulk solution. What a performance! The SDS micelle significantly elevates the performance of amphiphilic intramolecular charge‐transfer fluorescent molecular sensors (see picture). Enhanced sensitivity, desirable spectral changes including “on–off” to ratiometric signal transformation, a thermocontrolled dynamic detection range, and highly specific analyte identification by the fingerprint emission of an analyte–sensor complex have been observed.