Preparation Of Fluorescent Nanomaterials And Application For Detection Of Food And Drug

In recent years,food and drug safety have received attention because they are closely related to people's health and life.The illegal use of food additives and improper drug use have caused serious consequences,such as large economic losses,a wide range of impact and serious social harm.Therefore,it is particularly important to detect the contents of food additives and drug ingredients.Fluorescence method has received extensive attention due to some advantages such as quick response,simple operation,low cost,superior performance and high precision.In particular,carbon quantum dots?CQDs?and metal nanoclusters?MNCs?have been widely used in many fields?like biological imaging,sensors,drug delivery and photo-catalysis?,because they have good water solubility,low toxicity,good biocompatibility,easy surface modification and functionalization.In this work,the multi-functional carbon matrix composite nanomaterials were designed by the unique physical and chemical properties of CQDs and MNCs,and a single-emission direct fluorescence quenching,fluorescence“turn-off/on”and dual-emission ratio probes were established for the detection of food pigments,food nutrients and sulfhydryl drug,respectively.Thier detection mechanism was also discussed.The specific work is as follows:?1?Thiamine nitrate?TN?as the only raw material was used to synthesis nitrogen and sulfur doped carbon quantum dots?N,S-CQDs?with a quantum yield of 10.4%through one-pot hydrothermal method,and its morphology and properties were characterized by TEM,XPS,FTIR,fluorescence and UV-vis,respectively.The mechanism of N,S-CQDs fluorescence quenching by VB12/tartrazine was discussed by F?rster resonance energy transfer theory?FRET?.The energy transfer rate constant?K_T?and efficiency?E%?from N,S-CQDs?as donor?to VB12/tartrazine?as receptor?enhance with increasing the concentration of acceptor,and the values of K_T and E%are also varied with the change of excitation wavelength?from 338 nm to 408 nm?.On this basis,the multifunctional fluorescent probe is sensitive and selectively detected with the detection limit?3?/K?of 15.6/18.0 nmol/L.The proposed method was successfully employed to detect VB12/tartrazine in milk and several beverages with a recovery range of 97.5-104.2%/91.0-110.6%.?2?A“turn-off/on”fluorescent probe has been designed to monitor N-acetyl-L-cysteine?NAC?.That is to say,Fe³⁺can effectively quench the fluorescence of N,S-CQDs?turn-off?through screening,while NAC can significantly restore the fluorescence of N,S-CQDs-Fe³⁺system?turn-on?based on REDOX reaction,suggesting that the N,S-CQDs-Fe³⁺system can act as a fluorescent sensor for the detection of NAC with a low limit of detection?65.0 nmol/L?and wide linear ranges of 0.67-25.56 and25.56-193.55?mol/L.In addition,the fluorescence switching cycle characteristics of N,S-CQDs are discussed.?3?Silver nanoclusters?AgNCs?stabilized by BSA were prepared,and the fluorescence of AgNCs was enhanced by aggregation induced emission?AIE?with the addition of trithiocyanuric acid?TA?.AgNCs-TA and N,S-CQDs were mixed in a certain proportion to construct a ratio probe for the detection of2,3-dimercapto-1-propanesulfonate?DMPS?.The fluorescence of N,S-CQDs can be quenched by AgNCs-TA,and the corresponding quenched mechanism can be ascribed to the inner filter effect?IFE?.With the addition of DMPS,the fluorescence intensity of AgNCs-TA at 650 nm decreases due to the breakdown of AgNCs-TA,and the fluorescence of N,S-CQDs at 440 nm recovers.Therefore,the detection method of DMPS has been established through the linear relationship between fluorescence intensity ratio(F₆₅₀/F₄₄₀)and DMPS the concentration of DMPS,and the detection limit is 54.7 nmol/L.