Preparation And Sensing Performaces Of Nanocomposite Fluorescent Chemosensing Materials

With the rapid development of global economy, our living environment has been severely destroyed. The increase of industrial pollution, not only leads to air quality decline, but also makes sorts of heavy metal pollutants enter into the water through different ways, especially high toxic mercury ion, which resulted in tremendous harm to human life. Therefore, the determination of oxygen and trace mercury ions concentration has important significance in the field of analytical chemistry, biochemistry, medical diagnosis and environmental monitoring. In recent years, chemosensors utilizing fluorescence intensity as their response signal have been developed to be useful tools for sensing various analytes, such as oxygen and mercury ions. Surrounding the design and synthesis of the ?uorescent probes and nanomatrix materials, this dissertation presents a systematic research about the synthesis of the nanocomposite sensing materials by electrospinning or hydrothermal synthesis method. Detailed analyses on the structure, stability, regenerative ability and sensing performances of the final obtained nanocomposite sensing materials are investigated. The major achievement obtained is as follow:（1） A novel Cu（Ⅰ） complex [Cu（POP）phencarz]BF4 was design and synthesized. Then it was incorporated into polystyrene （PS） matrixes and electrospun into composite nanofibrous membranes using the simple electrospinning method. The optical oxygen sensing properties of [Cu（POP）phencarz]BF₄/PS composite nanofibrous membranes were investigated. They showed high sensitivity (I₀/I₁₀₀ = 15.56), good linear Stern-Volmer characteristics （R² = 0.9966） and short response and recovery time （t↓（s） = 7 and t↑（s） = 14）. These results represent the best values reported for oxygen sensors based on Cu（Ⅰ） complexes. The outstanding performances, the simple and versatile preparing method and environmental-friendly and economical attraction endow this kind of composite nanofibrous membrane with the potential for commercial application in oxygen sensors.（2） A novel Eu（Ⅲ） complex of [Eu（TTA）3phencarz] was design and synthesized. Then it was incorporated into polystyrene （PS） matrixes and electrospun into composite nanofibrous membranes using the simple electrospinning method. These materials showed good operational stability, reproducibility and short response and recovery time （t↓（s） = 5 and t↑（s） = 8）. The sensitivity is up to 3.38, which represents the best values reported for oxygen sensors based on Eu（Ⅲ） complexes. The high surface area-to-volume ratio and porous structure of the electrospun nanofibrous membranes are urged to be responsible for the outstanding performances.（3） A novel nanocomposite sensing material was prepared through the functionalization of mesoporous silica （SBA-15） covalently grafted with a pyrene derivative. The obtained material （Py-SBA-15） demonstrates a high selectivity for Hg²⁺ ions in the presence of other metal ions. A good linearity between the fluorescence intensity of Py-SBA-15 and the concentration of Hg²⁺ ions is constructed, and a satisfactory detection limit of 1.7×10^-7 gmL^-1 is obtained. More importantly, Py-SBA-15 shows good regenerative ability. These results indicate that this nanocomposite sensing material could be a promising ?uorescence chemosensor for detecting Hg²⁺ ions.（4） A novel fluorescent chemosensor based on rhodamine derivative has been designed and synthesized for detection of Hg²⁺ ions. Moreover, this‘Off–On’-type fluorescent sensor could successfully mimic a molecular level keypad lock in the presence of Cu²⁺ ions. Only a specific sequence of inputs, i.e. the correct password, results in strong fluorescence emission at 555 nm, which can be used to“open”this molecular keypad lock. Therefore, this molecular keypad lock has the potential for applying in security devices, which would be used to authorize a user, to verify authentication of a product, or to initiate a higher process.（5） A series of novel organic-inorganic hybrid materials with a Eu（Ⅲ） complex covalently bonded into the vinyl modified silica networks have been successfully assembled through a sol-gel process. The luminescence properties of VTES/TEOS composite hybrid materials were systematically studied. The results indicate that the luminescence intensity of VTES/TEOS composite hybrid material by optimizing the molar ratio of VTES to TEOS （VTES:TEOS = 4:6） is enhanced by 3.3 and 2.4 times compared with TEOS-derived hybrid material and pure [（C₂H₅）₄N][Eu（DBM）₄], respectively. In addition, the thermal stability of the emission was also improved considerably.