Sensing Of Melamine And Ag~+ In The Environme Nt By Phosphorescent Quantum Dots Based On DNA Functionalization

Eco-environment assessment is a premise to prevent the environmental pollution,food safety and other issues,while the primary task of accurate eco-environmental assessment is to develop new environmental pollutant detection technologies.As a sensor combining nanotechnology and biotechnology,nanobiosensor synthesized on the basis of bio-molecules has the advantages of large surface area,good selectivity,high sensitivity,etc.In this research,two kinds of single-stranded DNA(ss DNA)rich in thymine T and cytosine C were selected as templates,and a single-stranded DNA functionalized Mn-doped Zn S(Mn-Zn S)was directly synthesized by aqueous phase synthesis phosphorescent(RTP)quantum dots(QDs)(PQDs)and developed RTP sensor with simple structure,low environmental toxicity,high specificity and good biocompatibility.Due to the RTP characteristics of such sensor,the interference of background fluorescence can be avoided.It is simple,convenient and fast,and is very suitable for the detection of target molecules in complex environmental samples.According to the principle that the combination of PQDs with melamine or Ag~+will lead to RTP quenching of PQDs,the sensitive detection of melamine and Ag+was realized,and the reaction mechanism and application performance analysis in environmental water samples were discussed.The main research contents and conclusions are as follows:(1)Using ss DNA rich in thymine T and thioguanine G taken as the template,a new-type nanocomposite material(T-ss DNA-PQDs)synthesized from low-toxicity T-ss DNA functionalized Mn-Zn S PQDs was prepared by optimizing synthesis conditions,and these T-ss DNA-PQDs could emit orange RTP signals at 590 nm.As these T-ss DNA-PQDs are rich in T sequences and T sequences can bond with melamine through the hydrogen-bond interaction,T-ss DNA-PQDs experience aggregation,thus causing phosphorescent exciton energy transfer(PEET)between T-ss DNA-PQDs of different particle sizes and their RTP quenching.Based on this principle,an RTP detection method of melamine was established.Linearity range and detection limit of the detection method are 0.005-6 m M and 0.0016 m M respectively.This sensor is very suitable for the detection of melamine in environmental water samples and milk.(2)A green low-toxicity Mn-Zn S room-temperature phosphorescent PQDs nanocomposites(C-ss DNA-PQDs)under the optimal conditions by using ss DNA(PS-C-ss DNA)rich of cytosine C and Thioguanine G(PS)as the template.Given the existence of Ag~+,C-ss DNA-PQDs interacts with Ag~+,forming Ag-N bonds and further producing C-Ag~+-C conjugates.As a result,C-ss DNA-PQDs cluster and induce PEET,thus resulting in quenching of room-temperature phosphorescent of C-ss DNA-PQDs.Based on this principle,an Ag~+RTP detection method was established.The linear range of the method was 0.01-1μM and 1-10μM,respectively,and the detection limit((3σ))was 0.0031μM.This sensor is suitable for the detection of Ag~+in environmental water samples.