Preparation of Bridged Thiourea-Based Bis-Tetraphenylethylene Organic Fluorescent Sensor and Application in Detection of Lutein in Water Media

A bridged thiourea-based bis-tetraphenylethylene (Bis-S) organic fluorescent sensor was designed and synthesized with 4-hydroxytetrastyrene and ethyl bromoacetate as starting materials. Bis-S was dissolved in the 95% (volume fraction) tetrahydrofuran solution, and Bis-S solution was prepared. Fluorescence spectrometer was used to measure the fluorescence intensity of the Bis-S system before and after the addition of lutein at excitation wavelength of 360 nm and emission wavelength of 468 nm. It was shown that lutein was added to Bis-S solution or a sensing test paper containing Bis-S, lutein bound to Bis-S at mole ratio of 1∶1, and the bright blue fluorescence of the Bis-S system was quenched due to the encapsulation of lutein by Bis-S cavities. After adding coexisting biomolecules induding guanine, tryptophan, fructose, cytosine, adenine, thymine, vitamin B₁, vitamin B₂, starch, sucrose, glucose, caffeine, and proline to Bis-S solution or a sensing test paper containing Bis-S, there was no significant change in the fluorescence intensity of the Bis-S system. The above-mentioned coexisting biomolecules were added into the Bis-S solution containing lutein, and there was little change in the fluorescence intensity of the system compared to the absence of coexisting biomolecules, indicating that the Bis-S sensor had the good selectivity and anti-interference property for lutein, and had certain application prospects in colorimetric detection of lutein. The fluorescence intensity of Bis-S system decreased with the increase of lutein concentration at the Bis-S concentration of 1.00×10⁻⁵ mol·L⁻¹, giving the detection range within 2.00×10⁻⁵ mol·L⁻¹, and linear quantitative detection range within 0.06 µmol·L⁻¹, with detection limit (2s/k) of 1.21×10⁻⁹ mol·L⁻¹. Test for recovery was made at 4 concentration levels, giving recoveries in the range of 94.0%-101%, and RSDs (n=6) of the determined values ranged from 1.5% to 4.1%.