Solvatochromism Related Luminescence Mechanism Of CPDs And Sensing Applications

Carbon dots(CDs)are a class of carbon-based fluorescent nanomaterials with various oxygen-containing functional groups and/or organic polymers on the surface.Due to their excellent optical properties and biocompatibility,CDs have been widely used in optical devices,sensors,biological imaging and so on.Carbon polymer dots(CPDs)are an emerging class of CDs generally prepared by bottom-up methods.However,the nucleation mechanism and the formation process are different because of the diversity of reaction precursors and the selection of reaction solvents.Therefore,the structure of the CPDs is different,and the luminescence mechanism is still controversial,which limit the development and application of CPDs.Based on these,the main research contents of this thesis are as follows:(1)Novel CPDs were prepared by solvothermal method using small aromatic molecule p-phenylenediamine as carbon source and nitrogen source,and ethanol as reaction solvent.When the CPDs were dispersed in a variety of organic solvents,the solvatochromism was found.Meanwhile,it was found that both general solvent effect and special solvent effect exist in the solvatochromism effect,and the hydrogen bonding between the solute and solvent was the dominant factor.The luminescence mechanism of the CPDs is closely related to the surface groups such as amine groups and amides,and the luminescence mechanism is derived from molecular state related to hydrogen bonding.Finally,the CPDs were successfully used in the detection of trace water in a variety of organic solvents based on polar sensitive property.This work revealed the luminescence mechanism of CPDs with small-molecular aromatic compounds as precursors,and has certain significance for the investigation of the luminescence mechanism of CPDs synthesized by small molecules.(2)We found that Cu(II)ions can chelate with the rich amino and hydroxyl groups on the surface of CPDs to form non-fluorescent complexes,so the fluorescence of CPDs was selectively quenched by Cu(II)ions as a result.Based on this,a sensitive Cu(II)ion fluorescence quantitative detection system was established,and the detection limit was 2.14 ?M,and it was successfully applied to the actual water sample for inspection.At the meantime,when the PPi was added into the system,PPi could bind with part of the Cu(II)ions chelated on the surface of the CPDs to break them off from the surface of CPDs.Due to the stronger binding ability between PPi and Cu(II)ions,resulting in the florescence recovery.Therefore,an off-on system was constructed to detect the concentration of PPi,and detection limit of 1.85 ?M was achieved.It was successfully applied to human urine for examination.This work provides the possibility to detect target molecules in the life body.