Research On The Preparation And Performance Of New Carbon Quantum Dots

Carbon quantum dots(CQDs)is a kind of carbon nanomaterials with microscopic shapes close to quasi-spherical,typically with a size around 10 nm.Compared with other carbon nanomaterials,organic dyes and semiconductor quantum dots,CQDs has several advantages,such as excellent chemical stability,good biocompatibility and superior water solubility.In addition,their properties can be tailored by surface modification and majority of them possess excitation wavelength dependence characteristic.Therefore,more and more attention has been paid to the research of CQDs and applications in the cell imaging,biosensing,drug delivery and photocatalytic continue to increase.The preparation of CQDs continues to improve through the efforts by scientist all over the word.However,there are still some limitations about using carbon sources for preparation of CQDs.The surface functional groups of the obtained CQDs are limited and are not easy to the optimization of fluorescence properties.Moreover,the researchers often introduce passivation agents in the preparation process,which increases the difficulty of subsequent processing of CQDs.Therefore,seeking a high-performance carbon source has attracted a great deal of attention.Adenosine 5'-monophosphate(AMP),an important nucleotide which has good biocompatibility and water solubility,is a good candidate to be the intermediate of the nucleoside acids,food additives and biochemical products.AMP contains carbon,nitrogen and phosphorus which can be used as starting materials for the preparation of CQDs.As a result,this paper mainly focused on the synthesis of miscellaneous CQDs by using AMP without passivating agents and its application in cell multicolor imaging.In order to further adding the function of CQDs,AMP was coordinated with rare earth lanthanum which has good antibacterial properties.Lanthanum doped carbon quantum dots were synthesized by one step hydrothermal method.Finally,PVA/CQDs fluorescence composite films were prepared by adding two kinds of CQDs to polyvinyl alcohol(PVA)and film biocompatibility and bacterial adhesion property were evaluated.The details were summarized as the following:(1)AMP containing heteroatom N and P was used as molecular precursors.The N-P-CQDs were prepared from adenosine 5'-monophosphate(AMP)by one-step hydrothermal method and it demonstrated excellent water solubility and strong fluorescence properties.The structural properties and fluorescence characteristics of N-P-CQDs were characterized by TEM,FA,UV,XRD,FTIR,XPS and EDS.The N-P-CQDs obtained had a median diameter of 3.95nm and fluorescence quantum yield of 26.48%.The fluorescence of N-P-CQDs shows excitation wavelength dependence behavior.The upconversion performance of N-P-CQDs was also studied,which showed that N-P-CQDs emitted 430?517 nm when excited at a long wavelength of 750?950 nm.In different ionic solutions,it was found that 80%of the fluorescence was quenched by Fe3+.The biocompatibility of N-P-CQDs was studied by hemolysis experiment and cytotoxicity experiment.After co-culture with A549 cancer cells,laser scanning confocal microscopy showed that A549 cells emitted blue,green and red fluorescence.Therefore,N-P-CQDs can be used in multi-color cell imaging.(2)The CQDs was combined with rare earth elements to have antibacterial properties.First,AMP and lanthanum chloride(LaC13)were coordinated.Then,the N-P-CQDs@La was prepared by one-step hydrothermal method.The chemical properties and fluorescence characteristics of N-P-CQDs@La were characterized by TEM,FA,UV,XRD,FTIR,XPS,EDS and TGA.The N-P-CQDs@La has an average diameter of 2.55 nm and fluorescence quantum yield of 20.14%.The antimicrobial properties of the N-P-CQDs@La were evaluated by antibacterial kinetics,minimum inhibitory concentration and colony count.Results showed that N-P-CQDs@La had good antibacterial properties and enriched the functions of CQDs.(3)Based on the above work,the application of prepared CQDs as polymer medical dressings was explored.PVA/N-P-CQDs and PVA/N-P-CQDs@La nanocomposite films were prepared by adding N-P-CQDs and N-P-CQDs@La solution into PVA,respectively.PVA/N-P-CQDs and PVA/N-P-CQDs@La nanocomposite films were characterized by FA,TGA,and SCA.Water absorption,fluorescence properties and cytotoxicity of the composite films were evaluated.The release of CQDs in the PBS solution was obtained by in vitro release experiments.Finally,the antibacterial properties of the composite films were researched by bacterial adhesion experiments.