Flourescence-Based Detection of Pesticides via Conjugated Polymer Nanoparticles

The use of synthetic pesticides has played a large role in increasing crop yields throughout the world, but their adverse effects on humans and non-target animals is of major concern due to their toxicity and persistence in the environment. Some of the more persistent examples are organochlorine pesticides, particularly dichlorodiphenyltrichloroethane (DDT) and its metabolites. Reported herein is the development of a detection scheme using organic nanoparticles for the fluorescence detection of a range of pesticides. The nanoparticles were fabricated from a synthetic conjugated fluorescent polymer, and fluorescence experiments were performed using both nanoparticle solutions and polymer thin films. The large extinction coefficients exhibited by conjugated fluorescent polymers (also referred to as conjugated amplifying polymers), such as the one discussed herein, make them useful for chemical detection schemes. In order to maintain this strong fluorescence of the polymer in solution, the polymer must be in an aggregated state, which allows for both intra-polymer and inter-polymer exciton transfer. To achieve this aggregated state in solution, the formation of polymer nanoparticles is used. These nanoparticles allow the polymer to be used for chemical detection of pesticides in solution via fluorescence enhancement. The 2,1,3-benzooxadiazole-alt-fluorene (PFBO) polymer nanoparticles discussed herein were fabricated using the reprecipitation method, which is the formation of spherical particles as a result of the hydrophobic collapse of the polymer in an aqueous solution, and average particle size was confirmed using dynamic light scattering. In solution, a limit of detection of 4.5 ppm was achieved for DDT in the presence of the PFBO nanoparticles