| Carbon Quantum Dots(CQDs)is a class of spherical carbon nanomaterials with the size less than 10 nm.They have been widely used for analysis based on their outstanding properties,including good water solubility,low toxicity,high biocompatibility,easy surface functionalization,high fluorescence intensity and photostability.The raw materials for CQDs synthesis are usually cheap,and various methods can be used for CQDs synthesis.Currently,most CQDs have single-wavelength fluorescence emission signal,which arouses measurement errors from different aspects,including instrumental parameters,microenvironment,photobleaching and so on.Ratiometric fluorescent probes perform quantitative analysis through the ratio of signal changes from at least two emission peaks,which can eliminate measurement errors to obtain more reliable data.However,most CQDs-based ratiometric fluorescent probes need to combine with other organic dyes,semiconductor quantum dots,metal-organic frameworks,and metal nanoclusters,which are difficult and time-consuming.Dual emission carbon quantum dots(DECQDs)can directly construct ratiometric fluorescent probes which can effectively solve these problems.At present,CQDs are mainly used for metal cations analysis.The application for drug analysis has rarely been reported.Herein,the preparation of novel luminescent CQDs,especially DECQDs,and applied them for drug analysis could both improve the method for drug analysis,and further broaden the application area of CQDs.In this thesis,novel CQDs with single or double emission peaks were synthesized by one-step hydrothermal method,and these CQDs were further used as effective sensors for the quantitative determination of small drug molecules.The main works of this thesis are listed here:1.The CB-CQDs with good luminescence performance were synthesized by a simple hydrothermal method using carambola as raw material.Their morphology and properties were characterized by ultraviolet-visible spectroscopy(UV-Vis),infrared spectroscopy(FTIR),transmission electron microscopy(TEM)and fluorescence spectroscopy(FL),respectively.It was found that Ag NPs could significantly quench the fluorescence intensity of CB-CQDs because of the fluorescence resonance energy transfer(FRET)effect.The fluorescence signal"turned off".In the presence of cimetidine(CMT),the fluorescence signal of CB-CQDs was gradually restored and the fluorescence signal"turned on"again,formed an"off-on"CMT sensor.The fluorescence intensity linearly changed with the concentration of CMT.Therefore,a noval CMT sensor was established based on the CB-CQDs-Ag NPs reaction.The basic mechanism was further discussed.Under the optimized conditions,there was a good linear relationship between fluorescence recovery value(?F)and CMT concentration in the range of 9.0×10-8-1.0×10-6mol/L with a correlation coefficient of 0.9986.The detection limit was calculated to be 1.9×10-8 mol/L based on the 3?/k principle.This method was successfully applied to the detection of CMT in real samples with satisfactory results.2.Dual emission carbon quantum dots(m DECQDs)were synthesized by one-step solvothermal treatment of m-aminophenol and citric acid.The morphology,structure,and luminescence properties of m DECQDs were characterized.The results showed that at a single excitation wavelength of 306 nm,m DECQDs exhibited dual-wavelength emission at 340 nm and 420 nm.In the presence of propafenone hydrochloride(PPF),the fluorescence signal at 340 nm was quenched,while the fluorescence intensity at 420 nm was increased.Accordingly,m DECQDs were used as fluorescent probes,and a ratiometric PPF sensor was established.Under the optimal experimental conditions,the concentration of PPF has a good linear relationship with the fluorescence intensity ratio(F420/F340)of m DECQDs in the range of 9.0×10-7-1.0×10-4mol/L,with the correlation coefficient of0.9972.The detection limit of the method was calculated to be 8.8×10-8mol/L.In addition,the proposed ratiometric fluorescent method can be applied to analyze PPF in urine and tablet samples,with satisfactory recoveries.3.The novel dual emission carbon quantum dots(p DECQDs)were synthesized by using p-aminobenzoic acid and o-phenylenediamine as carbon and nitrogen sources.The p DECQDs have good water solubility.The morphology,structure and spectral properties have been characterized.Under the excitation?ex=315 nm,dual emission peaks at?em=347 nm and?em=555 nm were observed.In the presence of KMn O4,the fluorescent signal at 347 nm was gradually quenched,while the signal at 555 nm was kept stable.We interestely found that isonicotinyl hydrazide(INH)can restore the fluorescence signal at347 nm.Accordingly,the signal at 555 nm can be used as a reference signal.Combined with the ratiometric signal and the"off-on"phenomenon,an"off-on"ratiometric p DECQDs-Mn O4-fluorescent probe with specific INH response was designed.There is a good linear relationship between the concentration of INH(8.0×10-7-1.8×10-5 mol/L)and the fluorescence intensity ratio(F347/F555)of the p DECQDs-Mn O4-probe at?em/?em=347nm/555 nm.The detection limit was calculated to be 7.5×10-8 mol/L.The probe was used for the analysis of INH in preparation samples and cell culture media with satisfactory results.4.Dual emission carbon quantum dots(l DECQDs)were synthesized with the one step hydrothermal method by using L-tryptophan and ethylene glycol as raw materials.Under the excitation of 300 nm,the l DECQDs exhibited dual-emission peaks at 357 nm and 445 nm.Experiments found that the ranitidine hydrochloride(RDH)caused the inner filtration effect(IFE)of l DECQDs,resulting the quenching of the two emission peaks of l DECQDs.Therefore,an effective RDH sensor was established based on the quenching signal from single peak and the ratio of the paeks.In the concentration range of 5.0×10-7-8.0×10-5 mol/L,the fluorescence intensity ratio of RDH concentration to l DECQDs(Fs357+Fs445)/(Fb357+Fb445)and the fluorescence quenching at 357 nm and 445 nm The values of Fb357-Fs357and Fb445-Fs445 showed a good linear relationship,and the method detection limits were calculated to be 8.0×10-8 mol/L,1.7×10-7 mol/L and 2.7×10-7 mol/L,respectively.The probe exihibited a variety of determination methods to provide reliability,accuracy and selectivity for the determination of RDH.It has been successfully used to analyze RDH in urine samples with satisfactory results. |
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