New Fluorescent Probes Based On Organic Small-molecules And Upconversion Nanoparticles

There were various active species (metal ions, anions and biological molecules)in living systems. They played important roles in the life processes and are of centralimportance for many physiological functions. Since the concentration of smallmolecules in living cells is very low, and the complexity of biological samples, it isnecessary to use a highly selective and highly sensitive method. Based on thechemical and spectral measurement technology, Small molecular fluorescent probesselectively take chemical information of molecular recognition into a fluorescentsignal that is easy to measure. Due to its high sensitivity, high selectivity, spatialresolution for providing in situ and real-time information, the small molecularfluorescent probes is widely used in sensing and bioimaging anions, cations and freeradicals in various samples. Ratiometric fluorescent probes take advantage of the ratioof the intensities of the absorption or the emission at two wavelengths to achievesensing. And provide built-in correction for the environmental effects to improve thesensitivity. However, small-molecule fluorescent probes defects can not be ignored,such as easy photobleaching, background fluorescence interference. Upconversionnanophosphors (UCNPs) as novel probes has been proved to exhibit a largeanti-stokes shift, no autofluorescence from biological samples, a remarkably deeppenetration depth, and no photobleaching, seems to be an ideal candidate for bothsensing and bioimaging.Due to pyrene fluorophores own the characteristics of large conjugated structure,greater rigidity plane and excimer, the pyrenes are commonly used as fluorescentprobes. Rhodamine B and fluorescein both own the advantage of high quantum yields,good light stability, larger rigid planar structure, a spiro ring structure that controlfluorescence, absorption, color changes are also often as a fluorescent probe. In thisthesis, we first study pyrene fluorophores as small molecule probes in biologicalsensing; Against the disadvantage of small-molecule fluorescent probes, we constructa luminescence resonance energy-transfer (LRET). We convert the synthesis ofnanoparticles on different emission wavelengths by varying the rare earth elements,fluorescent probes rhodamine derivative (RhB) and FITC were incorporated into amesoporous silica shell and covalently linked onto the particle surface as energyacceptor. The contents of this thesis are presented as follows: 1. In Chapter2, Based on OCl-can selectively oxidize dibenzoylhydrazine intodibenzoyl diimide, which can further undergo a decomposition in some nucleophilicsolvents water for example. We designed pyrene hydrazine DP as the carrier toachieve the ratiometric detection of hypochlorite (OCl-). In this compound, twopyrene monomers is fixed in a small molecule probe by using a rigid structure ofxanthene to form a pyrene excimer, this kind of pyrene excimer affords a longwavelength, wide shape fluorescence emission from pyrene excimer. The emissiondecrease in495nm and increase in395nm were observed upon adding OCl-, whichdue to the pyrene excimer wasseparated into two pyrene monomers by OCl-. Theproposed chemodosimeter exhibits high selectivity over other common anions, andexcellent ratio-metric detection for OCl-. The linear response range covers aconcentration range of hypochlorite (OCl-) from3.0×10-8to3.0×10-6M and thedetection limit is0.35μM.2. In Chapter3, we introduced upconversion nanophosphors (UCNPs) as probeshas been proved to exhibit a large anti-Stokes shift, no autofluorescence frombiological samples, a remarkably deep penetration depth, and no photobleaching. Wereport a LRET process, a new class of ultraviolet emitting UCNPs, which are coatedwith a layer of SiO2as energy donor. Fluorescent probes rhodamine derivative (RhB)were incorporated into a mesoporous silica shell and covalently linked onto theparticle surface as energy acceptor. In this study, nanoprobes UCNPs@SiO2-RhB wasfabricated as highly sensitive and selective water-soluble probes for UCL monitoringand bioimaging of Hg2+, the detection limit is1.67×10-5M.3. In Chapter4, we expanded the nanoprobes by changing the doping of rareearth elements in the upconversion nanophosphors.The absorption spectra andemission spectra of fluorescein isothiocyanate have some overlap. The as-synthesizedsupramolecular UCNPs@SiO2-FITC complexes show visible emission spectra owingto LRET from nanoparticles to the FITC under near-infrared (NIR) excitation, andexcellent ratio-metric detection for pH.