| Carbon dots(CDs)are a kind of zero-dimensional nanomaterials,and have attracted much attention since they were discovered in 2004.Owing to the excellent fluorescence performance,good water-solubility,low toxicity,and good biocompatibility,CDs have found broad applications in multi-fields of chemistry,biology,environment and medicine.Over the years,chemical and natural substances are used as precursor to synthesize CDs,but for the CDs from chemicals,passivation or doping by other specific reagents is necessary to achieve better fluorescence performance.The use of large quantities of chemical reagents pollutes the environment seriously,resulting in the accumulation of pollutants in the organism and damage to human body indirectly.However,the natural source is generally nontoxic and abundant in a variety of elements,and they are used as carbon source to prepare fluorescent CDs via a simple one-step approach.Self-doping may occur during the synthesis process,and the types of functional groups on the surface of CDs are more diversified,thus the selectivity and sensitivity of detection are enhanced.In addition,natural substances are friendly to the environment and fit the essence of green chemistry,and the preparation of CDs from natural garbage is considered as waste recycling.Instrumental analysis is the mainly technique in traditional pharmaceutical analysis,which including high performance liquid chromatography,gas chromatography,liquid chromatography-tandem mass spectrometry,and capillary electrophoresis etc.However,the above methods usually require complicated processes of sample pretreatment or expensive instruments,hence,the fluorescence sensors have developed rapidly in recent years and have been widely used in the field of pharmaceutical analysis on account of the simple mechanism,easy operation and high sensitivity.Two kinds of natural wastes are used as carbon sources to prepare fluorescence CDs through simple and green methods in this thesis.After characterization,the as-prepared CDs are applied to drug detection and cellular labeling successfully.The specific research includes the following three parts:1.An eco-friendly approach which combined pyrolyzation with oxidation was adopted to produce CDs from mango peel without any other treatment.The prepared CDs were 2~6 nm nanoparticles with a high fluorescence quantum yield of 8.5 ± 0.2%.Additionally,the CDs exhibited excellent fluorescent stability towards salt and ultraviolet irradiation,and reversible fluorescence between acid and base conditions.Owing to their low toxicity,good biocompatibility and multicolor fluorescence,CDs were successfully applied to cellular labeling on A549 cells and fluorescent ink for anti-counterfeiting purpose.Fluorescence quenching of CDs took place in the presence of Fe2+;this phenomenon was thus used to quantify Fe2+ in ferrous succinate tablets in the linearity range of 4~16 ?M and the detection limit of 1.2 ?M.2.The green tea leaf residue was used as the carbon source to produce carbon dots(named as T-CDs)by combining pyrolyzation at high temperature and oxidation by concentrated H2SO4.The fluorescence quantum yield up to 14.8% was obtained.The fluorescence of the T-CDs was stable to the environmental p H,ionic strength and ultraviolet radiation,but was sensitive to temperature with switchable intensity between 15 oC and 65 oC.T-CDs penetrated the cells through membrane when they co-incubated with Hep G2 cells.Three colors of fluorescence in cells could be observed under laser confocal fluorescence microscope,indicating the potential application of bioimaging for T-CDs.In addition,the fluorescence of T-CDs was found to be quenched by gefitinib via the inner-filter effect.This phenomenon was used to detect gefitinib in urine samples with good linearity in the range of 0.1~20 ?g/m L with satisfactory accuracy.3.The application of CDs in the field of pharmaceutical analysis in recent years was reviewed and the future development directions were discussed and outlined. |
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