Chemo/Biosensing Based On Novel Composite Systems Of Conjugated Polyelectrolyte And Noble Metal Nanoparticles

Gold and silver nanopartic les have been widely applied in the fields of material, information and life science due to their particular optical, electric and chemical properties. Thus, the preparation and application of gold and silver nanoparticles and their composites have become one of the hot research topics in modern science. In this paper, new composite systems based on conjugated polyelectrolytes(P1, PPESO3 and P2) and noble metal nanoparticles were constructed for the sensing of melamine, biothiols and etimic in with high sensitivity. The main contents of the dissertation are summarized in the following:(1) A new ratiometric nanosensor is developed for selective and ultrasens itive detection of melamine based on conjugated polyelectrolyte(CPE)-stabilized silver nanoparticles(P1-AgNPs) by perfectly combining the advantages of CPE and AgNPs. P1 featuring a π-delocalized backbone bearing pyridinyl groups can act as an excellent dual-emission fluorescenct probe as well as a polymer localizer for AgNPs. In the presence of melamine, the fluorescence intensity at 386 nm increases owing to the turn-on of the fluorescence of P1, whereas FL intensity at 488 nm decreases due to the melamine-induced aggregation and subsequent aggregation-enhanced emission quenching of P1-AgNPs, therefore leading to the ratiometric fluorescent sensing of analyte. Moreover, analyte-induced aggregation of P1-AgNPs also allows the ratiometric colormetric measurement of melamine. Under the optimum conditions, this facile ratiometric nano-sensor favors the fluorescent and colorimetric determination of melamine in liquid milk products with the detection limit as low as 0.1 and 0.45 nM, respectively.(2) Fluorescent conjugated polyelectrolyte PPESO3 was chosen as the protective agent in the synthes is of Au nanocomposite, i.e., PPESO3-AuNPs(~ 5 nm in diameter), us ing Na BH4 as reducing agent. The fluorescence of PPESO3 was quenched by the gold nanopartic les. After the addition of biothiols(Cys、Hcy), the fluorescence of PPESO3 was recovered owing to the strong binding between the mercapto groups of biothiolsand gold nanopartic les. Based on this phenomenon, we built a sensitive method for biothiols detection, which can be convenient and practical for detecting biothiol in HeLa cells.(3)A new nanosensor is developed for ultrasensitive detection of etimic in based on conjugated polyelectrolyte(CPE)-stabilized silver nanoparticles(P2-Ag NPs). Under the optimum conditions, this fac ile nano-sensor favors the fluorescent and colorimetric determination of etimic in with the detection limit as low as 8 nM and 100 nM, respectively.