The Construction And Application Of Sensing Systems Based On Poly(p-phenylene Vinylene)

The living standard of human being improves greatly with the rapid development of the economy,however,the environmental pollution and food safety are still serious threats to human health.Due to their unique molecular wire effects,structural tunability and processability,fluorescent conjugated polymers have attracted considerable attention in the field of sensing.Here,based on poly-(p-phenylenevinylene)(PPV),the most extensively studied conjugated polymer,synthesized via Wessling route,we hope to prepare a variety of fluorescent materials through various methods to detect different analytes,enriching the types of sensing materials and providing more choices for detecting various analytes.System 1: Developing effective methods for detecting illegally added Sudan dyes in food or seasoning is of great significance.Two types of fluorescent solid materials,electrospun fibrous membranes and drop-cast films,were fabricated with PPV as the fluorophore and poly(vinly alcohol)(PVA)as the matrix,respectively.Sudan dyes greatly quenched the fluorescence of the membrane and film,whereas other food colorings or possible food ingredients displayed a much smaller or negligible quenching effect.The sensing mechanism was preliminarily studied,and the selectivity was ascribed to inner-filter effect(IFE).Moreover,the form of materials(membrane or film),the content of PPV,and the cross-linking process did not have much influence on the sensing performance.All the cross-linked materials were found to be stable against water/humidity and displayed good reversibility in sensing and can be reused at least for 10 cycles with negligible influence on the sensing performance.A cross-linked membrane was selected for detecting Sudan dyes in chili powder because folding did not affect the mechanical stability of the membrane.Two different protocols were used to pretreat the chili samples,which allowed the selective detection of Sudan dyes in chili powder.System 2: Aiming to detecting ions in water,the BPEI-PPV particles in colloid solution were prepared by adding the surfactant and branched polyethyleneimine(BPEI)into the precursor of PPV(pre-PPV)solution followed by thermal elimination.The colloid particles solution displayed good fluorescence properties and good stability in buffer solutions with p H 2-10,and significant fluorescence response to Co2+ and Cu2+ in water environment.The complex of Co2+ and Cu2+ with BPEI might result in the decrease of fluorescence intensity.Finally,the BPEI-PPV colloid solution was also demonstrated to be effective in the detection of Cu2+ in four real water samples.System 3: Starting with the elimination effect of BPEI on the precursor of PPV in system 2,the alkaline enviroment for the elimination was studied systematically.At 40 °C,the solution of alkaline substances(NH3,ethylamine,Na OH and BPEI)can promote the elimination of the pre-PPV,and the stronger the alkalinity of solution was,the faster the elimination was.In the solid fibrous membrane containing the precursor of PPV at 105 °C,the introduction of alkaline BPEI could improve the elimination of the precursor of PPV,and a small amount of BPEI could make a greater degree of elimination.The mechanism may be that the OH-or amine group in alkaline environment acting as the catalyst to promote the elimination.