Preparation Of N/S-doped Fluorescent Carbon Dots And The Applications In Ion And Drug Sensing

In recent years,the rapid development of nanotechnology has aroused great interest among the biomedicine and analytical researchers.As a new member of the carbon nanomaterials family,carbon dots(CDs)have the advantages of ultra-high biocompatibility,excellent photoluminescence,superior electron transfer ability,low cytotoxicity and multifunctional surface modification,which have shown amazing potential applications in cell/bacterial imaging,biological/chemical sensing,optoelectronic devices,targeted drug delivery,cancer/gene therapy and other biomedicine fields.At present,the preparation of carbon dots still has disadvantages,such as complicated and cumbersome preparation,harsh synthesis conditions and environmental pollution.The use of inexpensive,green and non-toxic reagents or renewable biomass wastes as carbon sources to prepare environmentally friendly CDs has become an inevitable trend of environmental sustainable development.Meanwhile,in order to reduce resource consumption and energy waste,the simultaneous detection of two or more targets by setting different luminous colors or detection mechanisms is the direction of scientific research.In addition,quantum yield is an important indicator for evaluating the fluorescence performance of CDs.Heteroatom doping can change the band gap and energy level of CDs,which can not only effectively improves the fluorescence quantum yield of CDs,but also redshift the emission spectrum of CDs.The optical performance of CDs in the visible light region can be improved which make it have greater biological application prospects.The optical properties of CDs in the visible light region can make it have greater biological application prospects.To solve the above problems,in this thesis,a variety of environmentally friendly functionalized fluorescent CDs were prepared by element doping,and the structure and morphology of CDs were characterized by advanced technical analysis methods.The practical applications of CDs in the field of ion and drug sensing were developed.This dissertation is mainly composed of the following four parts:Chapter 1:The classification,optical properties and sensing mechanism of CDs were described,which focused on the applications of CDs for detailed discussion,including the applications in optical fields such as sensing and information security,the applications in energy fields such as light/electrocatalysts,LEDs,solar cells,supercapacitors and rechargeable batteries,and the research and applications in biomedical fields such as bioimaging,phototherapy,drug/gene transfer and nanomedicine.Chapter 2:A facile,fast,and environmental-friendly route to construct nitrogen doped CDs(NCDs)with green emission was developed using a one-step solvent-free solid phase method with inexpensive tartaric acid as carbon source and urea nitrogen source.Based on the specific affinity between NCDs and Hg²⁺,which caused the aggregation of CDs and quenched the fluorescence.When I^-was added into the NCDs-Hg²⁺system,since the binding constant of Hg I₂was much higher than that of NCDs and Hg²⁺,a method for sensitive detection of I^-with NCDs-Hg²⁺fluorescence-enhanced sensor was studied based on the"turn-off-on"mechanism.The linear range was 0.3-15.0?M with the detection limit of 69.4nM.This method has been successfully used for the quantitative determination of I^-in water and urine samples.Meanwhile,a quenching fluorescence sensor was constructed to determine curcumin based on the internal filtration effect(IFE)and the static quenching,achieving a good linear range of 0.1–20?M with a satisfactory detection limit of 29.8nM,which has been successfully applied to the determination of curcumin in food and environmental water samples with the recovery rate between 95.7-104.8%.In the present work,two sensing mechanisms for the detection of I^-and curcumin were integrated into one NCDs-based chemosensor,which has an extremely high potential for the detection and monitoring of iodine and curcumin in environmental water,biology and food samples.Chapter 3:The nitrogen and sulfur co-doped fluorescent CDs with excellent fluorescence properties were constructed using a solvent-free solid-phase method with cheap tartaric acid as carbon source and thiourea as dopant.High-concentration G-NSCDs and low-concentration B-NSCDs were prepared respectively with the concentration control mechanism,which realizes the highly sensitive and selective sequential detection of rifampicin,morin and Al³⁺.Based on the synergistic effect of light-induced electron transfer and dynamic quenching,the G-NSCDs quenched fluorescence sensor realized the sensitive detection of rifampicin with a linear range of 0.2-20.0?M and a minimum detection limit of 56.6nM.Due to the effective overlap of the B-NSCDs excitation spectrum and the ultraviolet absorption spectrum of Morin,a"turn-off"B-NSCDs fluorescence sensor based on the combined action of the internal filtration effect and static quenching had been constructed to realize the specific identification of Morin.?F and morin concentration(0.2-30.0?M)showed a good linear relationship with the lowest detection limit of 51.2nM.Based on the strong chelation effect of Morin and Al³⁺,a well-selected and highly sensitive Al³⁺fluorescent probe had been constructed using a"turn-off-on"mechanism with B-NSCDs-Morin system.The Al³⁺response range was0.1-2.0?M with the lower detection limit of 45.8nM.In summary,a simple,rapid,selective,and highly sensitive fluorescent method for simultaneous detection of rifampicin,morin and Al³⁺was explored with multi-mode detection mechanism based on the concentration-regulated multi-color fluorescent CDs,which shows excellent application potential in disease diagnosis,water quality detection,and biomedicine fields.Chapter 4:A simple,non-polluting,and one-step solid-phase pyrolysis method to synthesize grape skin CDs(PT-NCDs)emitting green fluorescence with a quantum yield of 15.3%using kitchen waste grape skin as the organic carbon source and urea as dopant.The particle size,structure,element composition and surface functional groups of PT-NCDs had been analyzed deeply with the characterization techniques such as TEM,XRD,XPS,FTIR and PL.Meanwhile,the sensing ability of baicalin was also evaluated.The sensitive detection of baicalin was realized based on the light-induced electron transfer and dynamic quenching mechanism,which is a specific drug for treating liver diseases.A linear relationship between?F and the concentration of baicalin was 0.1-20.0?M with the detection limit of 43.8nM.The fluorescence sensor has been successfully used for the detection of baicalin in biological samples(urine and serum).Compared with the analysis methods in the literature,the constructed fluorescence sensor is convenient and efficient,which has important practical significance in clinical diagnosis and treatment,medical monitoring and environmental analysis.