Preparation Of Quinolone-Based Carbon Dots And Analytical Application Of Their Antibacterial And Optical Properties

As a new star of photoluminescence carbon nanomaterials,carbon dots（CDs）have various physical and chemical properties,good water solubility and superior optical properties.Therefore,CDs have good application prospects in the fields of information encryption,phosphorescence sensing and drug delivery.The surface of CDs has abundant functional groups and the ability of photodynamic generation of reactive oxygen species,which makes it unique in antibacterial.CDs with specific structures or characteristics can be tuned and customized by the selection of synthetic precursors and the design of synthetic methods.The strategy of preparing CDs based on small drug molecules as precursors highlights the relationship between chemistry and performance,which is a new research hotspot.Quinolones have good antibacterial and anti-inflammatory effects and excellent optical properties.In this paper,the antibacterial CDs designed and synthesized with small molecules of quinolones as precursors can not only inhibit bacterial DNA synthesis,but also kill bacteria by the release of cytoplasm through electrostatic interaction,which has excellent antibacterial properties.In addition,based on the room temperature phosphorescence（RTP）properties of quinolone CDs,they are embedded in polyvinyl alcohol（PVA）and zinc silicate（Zn₂SiO₄）to achieve multi-functional applications such as antibacterial and advanced information encryption.The main research contents are as follows:1.Preparation of antibacterial and solid room temperature phosphorescent bifunctional quinolone carbon dots.Using Norfloxacin（NOR）as precursor,antibacterial carbon dots（NOR-CDs）with nitrogen heterocyclic structure were synthesized by hydrothermal method.NOR-CDs has the advantages of good water solubility and low cytotoxicity,and its antibacterial activity against E.coli and B.subtilis is superior to NOR.In addition,NOR-CDs has excellent optical properties,with a fluorescence emission peak of 430 nm and a fluorescence lifetime of 5.05 ns.Multiple stimulus response room temperature phosphorescent materials（NOR-CDs@PVA）have been prepared using PVA.At 335 nm,NOR-CDs@PVA shows RTP emission at 440 nm and 610 nm with RTP lifetimes of 7.18 ms and 312.79 ms,respectively.The fluorescence QY and RTP QY of NOR-CDs@PVA are33.98%and 25.62%,respectively.Using NOR-CDs@PVA’s excellent optical properties and humidity sensitive characteristics,it is further applied in anti-counterfeiting and information encryption.2.Preparation of bifunctional quinolone carbon dots with antibacterial and water room temperature phosphorescent.The carbon dots（FLE-CDs）was synthesized by felroxacin（FLE）.The-COOH and C=O functional groups on the surface of FLE were combined with DNA helicase and topoisomerase IV,and the positive charge on the surface of floxacin acted with the negative charge on the bacterial surface,thus achieving the antibacterial effect.In addition,Zn₂SiO₄was selected as the protective substrate to achieve RTP emission in aqueous solution.The covalent bond between FLE-CDs and Zn₂SiO₄not only effectively solidifies the photoluminescent groups of FLE-CDs,but also greatly enhances the rigidity of the system,resulting in the preparation of a room temperature phosphorescent material in water（FLE-CDs@Zn₂SiO₄）.FLE-CDs@Zn₂SiO₄powder has a wide peak centered at 480 nm and an average RTP lifetime of 388.58 ms when excited at 240 nm to 380 nm.After removing the365nm excitation light source,FLE-CDs@Zn₂SiO₄powder showed an ultra-long yellow-green afterglow lasting for 11 s,and FLE-CDs@Zn₂SiO₄solution shows a yellow-green afterglow lasting 5 s.An advanced information encryption strategy is designed based on FLE-CDs@Zn₂SiO₄which has good RTP characteristics in water.3.UV room temperature phosphorescent materials（OFL-CDs@Zn₂SiO₄）were synthesized from Ofloxacin（OFL）with Zn₂SiO₄confinement.A new method for the synthesis of UV room temperature phosphorescent materials was presented.Antibacterial and anti-counterfeiting applications were designed based on the diversity of OFL-CDs properties.At the optimum excitation of 275 nm,OFL-CDs@Zn₂SiO₄solution has an emission wavelength of 375 nm and a phosphorescent lifetime of 1.06 ms.OFL-CDs@Zn₂SiO₄material not only retains the antibacterial properties of quinolone,but also continues to emit light in the ultraviolet region after excitation,it can achieve internal antibacterial and ultraviolet coordination to inactivate Gram-negative bacteria and Gram-positive bacteria,and has particularly obvious antibacterial effect on Gram-negative bacteria.In addition,because OFL-CDs@Zn₂SiO₄emits bright yellow afterglow in aqueous solution,advanced information encryption strategy is designed to enhance the security of information.