Synthesis And Properties Of The Conjugated Polymer Fluorescence Sensors

Conjugated polymers(CPs) possess unique photoelectric properties, and its main chains of CPs exhibit the special molecular wire which allows it display amplified fluorescent quenching effect. The conjugated polymer sensors have attracted considerable studied due to it exhibited high selective and high sensitive. On the other hand, 2-thiohydantoin and its derivatives have widely applications in medicine, while using as molecular recognition groups was few reported. In this article, a poly(phenyleneethynylene) derivative containing 2-thiohydantoin groups in the side chain was synthesized as a sensor for anions and metal ions and the biological molecular recognition properties were investigated. A polyfluorene derivative bearing urea moieties in the main chain was synthesized and the properties of p H sensing was studied. The results are summarized as follows:1. A novel poly(phenyleneethynylene) derivative containing 2-thiohydantoin groups [poly(1)] was synthesized, and the recognition abilities for anions and metal ions of poly(1) were investigated. It was found that the addition of F-quenched the fluorescence of poly(1) solution, while the fluorescence of the solution only changed slightly upon adding other anions, indicating the sensing ability of poly(1) towards F-. The addition of Ag+ quenched the fluorescence of thepolymer, whereas the addition of other metal ions resulted in only slight changes on the fluorescence. Compared to the small molecule counterpart, the Stern-Volmer quenching constant of poly(1) caused by F- and Ag+ was 165 and 105 times greater, respectively, and these results indicate the poly(1) displays the amplified quenching effect.2. A new poly(phenyleneethynylene) derivative bearing 2-thiohydantoin moieties [poly(2)] was synthesized. Cuprous ions quenched the fluorescence of the polymer whereas the addition of other metal ions(liked cupric ions) resulted in only little change on the fluorescence. The Stern-Volmer quenching constant of poly(2) caused by Cuprous ions was 6.10×104M-1, which was 94 times greater than that of the small molecule counterpart. When hydrogen peroxide was introduced into the solution containing poly(2) and Cu+, Cu+ was oxidized into Cu2+, leading to the recovery of the fluorescence. The fluorescence of the poly(2)/Cu+ solution could also be recovered by the H2O2 released from glucose oxidation by glucose oxidase(GOD). These results mean that poly(1)/Cu+ platform can be used to detect hydrogen peroxide and glucose.3. A novel fluorescent p H probe [poly(3)] was designed and synthesized via Suzuki coupling reaction. Unlike other reported conjugated polymers, urea moieties, as a recognition groups, were embedded in the main chain of poly(3). In p H value 1 to 10, poly(3) was blue luminescent and the emission spectrum changed slightly. When the p H value increased to 11, the intensity of fluorescence decreased evidently and emission maximum shifted from 438 nm to 514 nm, leading to the visual fluorescent color changed from blue to light green. 1H NMR titration confirmed that the deprotonation process of urea groups is responsible for the fluorescent sensing.