Preparation,Property And Application Of Functionalized Sulfur Quantum Dots

In recent years,with the continuous development of quantum dot(QDs)nanomaterials,a series of potential problems existing in traditional heavy metal QDs nanomaterials have been gradually exposed to the vision of researchers.Therefore,it is necessary to develop the application of pure elemental QDs nanomaterials.Sulfur quantum dots(SQDs),as the representative of the emerging pure element QDs,have the advantages of long fluorescence life and good biocompatibility,resulting in many potential applications.Based on SQDs and functionalized SQDs nanomaterials,sensors with superior performance were fabricated and applied for the detection of environmental pollutants.The research contents are as follows:Chapter 1:This chapter gives a brief overview of QDs nanomaterials,especially pure element QDs nanomaterials,and summarizes the performance and application of SQDs nanomaterials.Chapter 2:Bacteria exist in all aspects of human life,affecting human activities and life health.An electrochemiluminescence(ECL)performance of SQDs was investigated,and an ECL sensor was constructed using?-nicotinamide adenine dinucleotide(NADH)as an important parameter to detect the total bacterial count in the environment.The linear relationship I₀-I=16524+1103.1logc _NADH(R~2=0.9961)was obtained in the range from 1 p M to 10?M with the limit of detection(LOD)of 1 p M.According to the positive correlation between the content of NADH after cell lysis and the total bacteria count,NADH can be used as an important parameter to combine the ECL strength of SQDs with the total bacteria count.When the total bacteria count was 10~3-10~7 CFU m L^-1,the linear relationship between ECL intensity and the total bacteria count was I₀-I=1138.4 logc _E.Coli-439.96(R~2=0.9927)with LOD of 10~3 CFU m L^-1.The accurate detection of the total bacteria counts in the real samples also verified the good ECL performance of SQDs.This sensor provides a powerful tool for the development of ECL emitters and opens a broad prospect to develop new ECL systems for environmental monitoring.Chapter 3:Hydrazine(N₂H₄)is highly toxic and could cause serious damage to the lungs,kidneys,liver,and central nervous system in humans when exposed to it.An"Off-On"type fluorescence sensor based on adsorption of SQDs by Manganese dioxide nanosheets(Mn O₂ NS)was developed to detect N₂H₄ in the environment.When SQDs was adsorbed by Mn O₂ NS,the fluorescence intensity was quenched,and the sensor was in the state of"Off";In the presence of N₂H₄,the sensor was in the state of"On"with the recovery of the fluorescence intensity.The recovery of fluorescence intensity showed a good linear relationship with the concentration of N₂H₄in the range of 0.1?M-10 m M.The linear equation was I=1010.4 logc(N₂H₄)+8116.2(R~2=0.9972)with LOD of 0.072?M.The recoveries of the fluorescence sensor to detect N₂H₄ in the environment real samples were 90.2%?107.3%and 92.5%-109.1%,respectively.The fluorescence sensor has high sensitivity and good selectivity and provides a new idea for the detection of N₂H₄.Chapter 4:Mercury ion(Hg²⁺),as one of the most toxic heavy metal ions,has seriously harmed human life and health.A kind of functionalized SQDs was developed and successfully combined with aptamer.Based on this,a fluorescence aptasensor was fabricated to ultra-sensitively detect Hg²⁺Through the strong combination of S_x^2-and Hg²⁺and the sensitive recognition of Hg²⁺by T-Hg²⁺-T structure,the sensor realizes the ultra-sensitive detection of Hg²⁺in the range of 1 f M-0.1?M with LOD of 0.78 f M.The sensor has good selectivity and high sensitivity,and portable test papers for Hg²⁺detection has been successfully prepared based on this sensing strategy.The portable test paper has been further applied to the detection of Hg²⁺in real environmental water samples with satisfactory results.The development of this sensor not only successfully solves the problem of poor selectivity of SQDs for heavy metal elements,but also greatly expands the application of SQDs,and provides a new method for the detection of Hg²⁺in the environment.