Preparation Of Silicon Quantum Dots And Their Applications In Fluorescence Detection Of Dipicolinic Acid And Dopamine

Due to the serious photobleaching and potential biological toxicity,organic dyes and traditional semiconductor nanomaterials have been restricted for the further application in biochemical field.As a new type of fluorescent nanomaterial,silicon quantum dots show excellent optical stability,biocompatibility,water solubility and other characteristics,which have attracted wide attention of researchers.At present,there have already been some mature methods for preparing silicon quantum dots.But considering possible limitations from experimental conditions and the convenience and feasibility in practical applications,the developing of a handy,mild,water-souble and fluorescent tunable preparation method is still very significant.In addition,fluorescence analysis as a common method,plays an essential role in biomedical detection.It is an important respect the author paying attention to that making use of excellent physical and chemical properties of silicon quantum dots and giving full play to these unique advantages in fluorescent detection to realilze the sensitive and accurate analysis for targets.In this thesis,the author studied the preparation and modification of silicon quantum dots,and constructed different fluorescent sensing probes,which were successfully applied to the fluorescent detection of biological molecules such as dipicolinic acid and dopamine.The main research contents are as follows:(1)Lanthanide terbium ion modified fluorescent silicon quantum dots were prepared by a two-step synthesis method and successfully applied to ratiometric fluorescent detection of anthrax spores biomarker(i.e.,2,6-dipicolinic acid).In this system,silicon quantum dots acting as a reference fluorophore,maintain stable fluorescence intensity before and after dipicolinic acid is added.On the other hand,the terbium ions modified in silicon quantum dots regared as a signal fluorophore,after dipicolinic acid is added,it shows strong coordination interaction and emit intense green characteristic fluorescence.In comparision of the system with single fluorescence signal,this sensing system effectively avoids errors caused by environmental and instrument factors,and improves the accuracy of detection for dipicolinic acid.Moreover,the fluorescent probe has good water solubility and the detection process can be carried out in aqueous phase.This method is sensitive and selective.The detection limit of this method is 24 nM.(2)With dopamine as reducing agent and silicon precursors containing differentamino groups as silicon sources,the author synthesized silicon quantum dots in aqueous phase at room temperature and discussed the properties of the products.The method is simple,economical,operated at room temperature,without strict experimental conditions and consistent with the requirements of green chemistry.It provides a new direction and idea for the simple synthesis methods of silicon quantum dots.Furthermore,based on the synthesized process,we have developed a new,simple and sensitive method for direct detection of dopamine.In the system,a small amount of(3-aminopropyl)trimethoxysilane acted as a response substrate,reacts with different concentrations of dopamine and directly generates fluorescence signals.Meanwhile,the addition of horseradish peroxidase can improve the intensity of fluorescence signals generated during this process.Therefore,we realized the selective,rapid and effective fluorescent detection for dopamine.The detection limit of this method is 2.9 nM.