Synthesis And Properties Of New Near-infared Fluorescent Chemosensor Based On Tricarboyanine

Now, the design and synthesis of fluorescent chemosensors are attractive forchemists. Because fluorescence measurements are easily and rapidly performed, arehighly selective, and are very sensitive. Chemosensor plays an important role onmedical and chemical aspects.In recent years, near-infrared (NIR) chemosensors are highly desirable. Amongnear-infared dyes, tricarbocyanines with a rigid chlorocyclohexenyl orchlorocyclopentenyl ring in the methine chain can increase the photostability andenhance the fluorescence quantum yield. What’s more, tricarbocyanines normallyabsorbs light with a large extinction coefficient in the near-infrared region (650-900)nm is relatively poorly absorbed by biomolecules, and so it can penetrate more deeplyinto tissues. Long excitation and emission wavelength are very important for reducingscattering and securing low back-ground emissions. However, the excitation andemission wavelengths for most fluorescent dyes are generally in the ultraviolet orvisible region and as a result are vulnerable to interference from backgroundfluorescence. In this thesis, three novel near-infrared fluorescent chemosensors havebeen synthesized to determine Cr3+, Ag+, and Ag+, repectively. The details of thecontents are presented:Firstly, a tricarboyanine derivative is applied as a ratiometric near-infraredchemosensor for detecting trivalent chromium ions (Cr3+) in living cells. Upon theaddition of Cr3+to a solution of the chemosensor, large-scale shifts in the emissionspectrum (from755nm to561nm) are observed. In the newly developed sensingsystem, these well-resolved emission peaks yield a sensing system that covers a linearrange from1.010-7to1.010-5M with a detection limit of2.510-8M. Mostimportant, the proposed chemosensor has been used to detect and quantify Cr3+in thethe running water samples and to image Cr3+in HeLa cells with encouraging results.Secondly, a novel ratiometric and colorimetric fluorescent chemosensor based ontricarboyanine for Ag+has been designed and synthesized. This chemosensor is easierto synthesize, have longer emission wavelength and can exhibit color changes. Underoptimized experimental conditions, the chemosensor exhibits a stable response to Ag+over a concentration range from5.010-7to2.010-5M, with a detection limit to2.010-7M. In addition, the proposed chemosensor has been successfully applied forthe determination of Ag+in real water samples which proves that it has practical value in environment.Finally, we designed and synthesized another ratiometric and colorimetricfluorescent chemosensor based on tricarboyanine for Ag+. This chemosensorinvestigated possesses a high sensitivity and selectivity for Ag+over other metal ionstested. Furthermore, the probes also show fast signal response and good linearity. Thefluorescent spectral results clearly indicate that the chemosensor has remarkableabsorption and emission wavelength shifts.