Multi-functional Carbon Dots And Their Composites: Synthesis And Performance Research

In recent years,Carbon dots(CDs),as a new type of luminescent nanomaterials,have drawn increasing attention in various fields owing to their superior optical properties,facile synthesis,low toxicity,diversity of luminous color and good biocompatibility.In virtue of these special advantageous,the CDs have been widely researched for various applications in the field of fluorescent sensors,information storage and anti-counterfeiting,drug delivery,bioimaging,catalysis and cancer therapy.In this dissertation,we prepared different colored fluorescent CDs using hydrothermal or solvothermal method.After the analysis of their luminescent properties microscopic characteristics and stability,they were applied to the detection of copper ions,L-Cysteine and nitrite ions in the environment,biological imaging,information encryption and anti-counterfeiting fields.The main content of our work in the thesis is summarized briefly as follows:Chapter 1:The current research and potential application of carbon dots are briefly reviewed.Firstly,several common preparation methods of CDs are introduced.Secondly,the optical properties of CDs are analyzed,and the potential application of CDs is investigated.Based on the above research content,this paper puts forward the topic selection and subject design.Chapter 2:Recently,fluorescent carbon quantum dots have drawn more and more attention as effective sensors to small ions or biomolecules.Here,we will present a solvothermal method to prepare phosphorus and nitrogen codoped carbon quantum dots(PNCQDs)with green-emitting(quantum yield 18.9%).The as-prepared carbon quantum dots exhibit good photostability,low-toxicity and favorable biocompatibility.In addition,the PNCQDs show a high selectivity detection of NO₂^-with a linear relationship between 10 n M and 90 n M and a detection limit as low as 3.3 n M.Meanwhile,the PNCQDs as fluorescent nanoprobes for detection of nitrite were efficient applied in He La cells imaging and potential applications in biologically related study.Chapter 3:In this work,highly fluorescent CDs(QY=21%)were prepared from 2,3-diamino pyridine as the precursor through a facile solvothermal process.The NCDs showed high stability and a green emission in aqueous,and the optimal emission wavelength of NCDs is 508 nm under the excitation wavelength of 438 nm.Interestingly,the NCDs-based nanoprobe were developed for selective and sensitive fluorescence quenching response to NO₂^-in water,and the quenching mechanism was investigated in the work.Besides,the recovery rates of NO₂^-in the range of 98%?103.5%were found to be acceptable,indicating that the proposed NCDs could be act as potential candidates for determination of nitrite ions in real samples.Meanwhile,the nanoprobe was also successfully employed in visualization biosensing platform for determination of NO₂^-in living cells due to its eminent biocompatibity.Chapter 4:Copper ions(Cu²⁺)and L-Cysteine(L-Cys)in the human body have always plays a critical role in various physiological processes,while abnormal Cu²⁺and L-Cys concentration in the biological system leads to many diseases.In this manuscript,Si-doped carbon dots(Si-CDs)with near-infrared fluorescent were designed for the detection of Cu²⁺and L-Cys through the fluorescent“on-off-on”mode.The carbon dots exhibit not only excellent optical merits including good stability against photobleaching and highly chemical stability,but superior biological potentials.Interestingly,thanks to the abundant amino groups distribute on the surface of Si-CDs,it can be bind to copper ions to form cupric amine complexes and then quench the fluorescence of Si-CDs due to an electron transfer process.In addition,upon addition of L-Cys,the FL intensity of Si-CDs could be effectively recovered accompanying with the complexation between Cu²⁺and function groups in L-Cys,so that leads Cu²⁺to flee from the surface of Si-CDs.Notably,as far as we know,it is the first red-emitting carbon dots for copper ions and L-Cys assays in water samples and human plasma samples.Furthermore,this strategy was successfully applied to the determination of Cu²⁺and L-Cys in living systems,which demonstrating great practicability in biomedical applications.Chapter 5:Carbon dots(CDs)have received much attention in constructing metal-free phosphorescence materials,but it is still a huge challenge to develop a material with long lifetime and phosphorescence emission in aqueous environments.In this work,we design and synthesize a universal approach to produce N-doped carbon dots(N-CDs)with efficient room-temperature phosphorescence(RTP)through simple heating treatment.Then,we prepared a kind of highly efficient N-CDs/MA nanocomposite phosphorescence materials by synthesized through N-CDs mixed with melamine.Excitingly,the characterizations indicate that the nanocomposite materials not only have an ultralong phosphorescence lifetime in the solid state,but also exhibit blue-green RTP in aqueous medium.In addition,based on their unusual RTP features,the obtained RTP materials can be successfully applied in ion determination and shows great potentials in the fields of anti-counterfeiting and information encryption.