Preparation And Application Of Novel Carbon Dots In Visual Detection Of Small Drug Molecules

As one of the emerging nanomaterials in recent years,carbon dots（CDs）have attracted great attention of researchers due to their unique optical,electrical and chemical properties.The carbon sources of CDs are abundant,inexpensive,and the synthesis process is environmentally friendly.More importantly,most of CDs have good water solubility,high biocompatibility,and stable photoluminescence properties,and have been widely used in sensing,bioimaging,drug delivery,and catalysis,among which the most applications of CDs was in sensing.However,most of the research were to use the fluorescent properties of CDs for the detecting various substances as fluorescent probes.These fluorescent probes have high sensitivity and good selectivity,but the visual detection probes have other advantages such as low cost and can be observed with the naked eye.Therefore,it is of great significance to design and synthesize novel CDs as probes that can be used for visual detection.The content monitoring of drugs in the production and use process is important in drug analysis,so the establishment of a rapid detection method for small drug molecules will have important practical application value.Based on this,this dissertation focuses on the design and synthesis of CDs-based visual detection probes,and applied to the analysis and detection of small drug molecules.The main research contents are as follows:1.Dual-emission carbon dots for fluorescence/colorimetric dual-mode detection of levodopaLevodopa（L-Dopa）is a common clinical drug used to treat Parkinson’s disease,and its use in insufficient or excessive doses can cause adverse effects,so it is of great significance for its dose monitoring and control in human body and medicine.This work synthesized a dual-emission carbon dots（NS-CDs）and used it for fluorescence/colorimetric dual-mode detecting L-Dopa.L-Dopa can quench the fluorescence of NS-CDs,while the color of the system also changed from light yellow to yellow-brown.The detection mechanism is mainly internal filtration effect（IFE）and oxidation.The probe is expected to use for the detection and analysis of L-Dopa in human serum and levodopa tablets.2.One-step synthesis of carbon dots for fluorescence-colorimetric detection of Pd²⁺and quininePd²⁺is an important heavy metal ion and its residues in the environment will pose a serious threat to the ecosystem and human health.Quinine（QN）is an antimalarial drug and it is used as a flavoring agent in beverages because of its bitter taste,but excessive intake of QN can cause serious side effects.Therefore,the detection of Pd²⁺and QN is important.This work synthesized a fluorescent/colorimetric dual-mode carbon dots（NRCDs）and used it to visual inspection Pd²⁺and QN.The fluorescence of NRCDs was quenched by Pd²⁺and accompanied the solution color from purple-red to blue-violet,while the fluorescence of NRCDs was restored by QN and the solution color back to purple-red,the coordination and competition between NRCDs and analytes is the main detection mechanism.The probe can be combined with a smartphone,making the detection process more convenient and faster.The probe has some application prospects in the detection and analysis of Pd²⁺in environmental water samples and QN in canned beverages.3.A colorimetric sensing platform based on CDs for amino acid enantiomersChirality is one of the basic characteristics of nature.Although enantiomers have similar physicochemical properties,they often exhibit completely different or even opposite biochemical or pharmacological effects.Therefore,the demand for detection and identification of chiral enantiomers is increasing.This work designed and synthesized a chiral carbon dots（L-TCDs）and used it for the visual detection of amino acid enantiomers.The probe has a good chiral selectivity colorimetric response for the enantiomers of cysteine（Cys）,glutamate（Glu）,valine（Val）and glutamine（Gln）in the presence of H₂O₂.This work also systematically studies the detection mechanism and the chiral recognition is mainly based on the chiral selection of chiral residues on the surface of L-TCDs.To the best of our knowledge,this work is the first time to colorimetric identification of amino acid enantiomers by chiral carbon dots,which provides a new idea for the chirality detection of amino acid enantiomers.