Synthesis And Application Performances Of Fluorescein-Based Dyes

Fluorescein has excellent optical properties, such as high extinction coefficient, high fluorescence quantum yield in aqueous solution, its excitation and emission wavelength in the visible range and innoxiousness. Since it was first synthesized one hundred years ago, fluorescein has been widely used in the chemical and biological analysis fields. However, some intrinsic properties of fluorescein also limit its further applications in many fields. It's a flexible and effective way to improve the fluorescence properties of dye molecules and application performance by molecular designing to introduce built-in functional groups. In this paper, some derivatives of amino fluorescein were designed and synthesized, to improve its disadvantages, such as low fluorescence quantum yield, poor reactive ability. Moreover, six fluorescein-based dyes were innovatively used in textile dyeing, and the properties of the dyed fabrics were discussed. The details and results of the research are following:Firstly, derivatives of amino fluorescein were prepared through the controllable substitution reaction of the chlorine atoms in cyanuric chloride:[2-(4,6-dichloro-triazinyl)Amino]fluorescein (DTAF) and [2-(2,2,6,6-tetramethylpiperidine-4-amino)-4-(6-dichlorotriazinyl) amino]fluorescein (DTAF-TMP), which contains built-in s-triazine UV absorber and a hindered amine light stabilizer (HALS) fragments. By comparing with amino fluorescein, the built-in groups had little effect on the excitation and emission wavelength, but the fluorescence intensity had greatly increased, as well as the fluorescence quantum yield.Secondly, factors that could affect the fluorescence properties of the fluorescein-based dyes were investigated, such as pH value, metal ions and so on. The results indicated that DTAF and DTAF-TMP were high sensitive to pH value; DTAF-TMP had excellent response to Mg2+. The two fluorescein-based dyes will be as good fluorescent probes in the pH qualitative and quantitative analysis, as well as metal ion detection fields.Finally, the dyeing performances of acidic fluorescein-based dyes (carboxy-fluorescein, chloride substituted fluorescein) and the reactive fluorescein-based dyes (DTAF, DTAF-TMP) on the fabric were discussed. The results indicated that with an increasing dye concentration, the red-shifting of reflectance and fluorescence emission spectra of dyed fabric was found and the maximum reflectivity (Rmax) and the fluorescence intensity (If) of dyed fabric increased initially and decreased afterwards. It showed that both Rmax and If could indicate the high displaying characteristic of the fabric dyed by fluorescent dyes. The lightfastness and anti-ultraviolet performance of dyed cotton fabrics were improved by the dyes with built-in s-triazine UV absorber and a hindered amine light stabilizer fragments.