Investigations On Fluorescent Probes Based On Several Fused Ring Compounds And Their Properties

Chemosensors utilizing fluorescence intensity have been developed to be useful tools for sensing various analytes, and fluorescent chemosensors using conjugated polymers are popular due to several important advantages, such as their simplicity of use, signal amplification because of their strong ability to capture light and easy fabrication into devices, thus playing increasingly important role in biological detection. This dissertation focused on five kinds of fused ring aromatic compounds containing fluorine and naphthaline groups as novel fluorescent probes for the sensing to metal ions, pesticides and explosives. The concrete interaction between the conjugated polymers and the analytes were also investigated in detail. Specific studies are as follows:(1) A simple fluorescent probe of (FMOC-Cl) for Fe3+and Cu2+ions over other transition metal ions has been described with a LOD of1.66μM for Fe3+and1.15μM for Cu2+. With the fluorescence characteristic band centered at307and315nm for FMOC-Cl, the introduction of Fe3+or Cu2+ions leads to the fluorescence quenching of FMOC-Cl with different shift and intensities of two fluorescent bands. It allows us to differentiate between Fe3+and Cu2+ion-sensing behavior. The study on fluorescent kinetics confirms that the sensing mechanism is based on the formation of non-fluorescent material, that is, static quenching. Further analyses of bond lengths, Mulliken atomic charges and the frontier orbital compositions for FMOC-Cl and its complexes with Fe3+and Cu2+ions were carried out. The theoretical calculations prove the fluorescence quenching originates from the formation of coordination bonds between the oxygen atom of the carbonyl group of FMOC-Cl and Fe3+and Cu2+ions.(2) Electropolymerized PFMOC-Cl was employed to develop a selective sensor for the determination of Fe3+ions based on the fluorescence quenching of PFMOC-Cl. Its fluorescent intensity exhibited a good linear relationship with the concentration of Fe3+in the wide range of0to350μM with a detection limit of0.67μM. The mechanism of Fe3+-induced fluorescence quenching of PFMOC-C1was confirmed to be static quenching. The determination of Fe3+in real samples was investigated with satisfying results, indicating that the method is reliable. PFMOC-Cl-Fe3+complex can be further employed as fluorescent "turn-on" sensor for the detection of inorganic phosphates rapidly and with very high sensitivity, and the detection limit is4.05μM.(3) Fluorescent spectra indicated that the electrochemically polymerized PDMN was an excellent blue light-emitting material. The insoluble PDMN film deposited on the indium tin oxide glass was used to develop a sensor for the determination of imidacloprid based on the fluorescence quenching of PDMN. The interaction of imidacloprid and PDMN was investigated by electrochemical techniques and infrared spectra. The fluorescent intensity of PDMN has a good linear relationship with the concentration of imidacloprid on the surface of PDMN in the range of4.994X10"*to2.557×102μg/mL with a detection limit of3.093ng/mL. The sensor based on PDMN films showed high recognition ability for imidacloprid and will have more potential applications in the industrial or environmental fields.(4) The application of the electropolymerized P9FM with excellent fluorescent properties as a fluorescent probe for the highly sensitive detection of imidacloprid (IMI) and chlorpyrifos (ANSI) was realized. On binding to the two kinds of pesticides, exceptional fluorescence quenching of P9FM occurred, exhibiting a turn-off fluorescence, and the detection limit of P9FM for the two pesticides are1.98μM and4.30μM, respectively. The working mechanism was also proposed and confirmed by the measurement of lifetime decay curve and other spectral instruments.(5) Fluorescence studies demonstrated that the emission of PFO is sensitive to the presence of some important nitro-containing explosives, in particular,2,4-dinitrophenol (DNP) and2,4,6-trinitrotoluene (TNT). As an example, the detection limits of PFO to DNP and TNT were determined to be0.35μM and1.26μM, respectively. Relevant quenching mechanism is proposed through study on fluorescent kinetics. Based on the discovery, a novel fluorescence probe for the explosives has been developed. The sensitive and selective responses of PFO to the explosives have been tentatively attributed to the adsorptive affinity of PFO to the explosives, and to the higher probability of the electron transfer from electron-rich PFO to the electron-poor nitro-containing explosives. No doubt, present study broadens the family of fluorophores which may be employed for the development of fluorescent sensors.