The Construction And Application Of Off-on Fluorescence Sensing System Of Cysteamine Functionalized CdTe Quantum Dots

Quantum dots?QDs?is a kind of zero-dimensional semiconductor nanocrystals composed of II-VI and III-V elements,which has different fluorescence characteristics compared with different fluorescent dyes.Based on fluorescence sensing analysis of QDs has been the focus for researching.Off-on fluorescence sensing is an analytical method established by the specific molecular recognition between the target molecule and the fluorescent quencher.The detection of the target has a high degree of selectivity and sensitivity,and is the main design strategy for the construction of highly sensitive and highly selective fluorescence sensors.The functionalized groups on the surface of quantum dots are important factors that affect the performance of quantum dots.Cysteamine?CA?is a mercapto amine compounds,the mercapto group can coordinate with the central metal atoms of the quantum dots,and the amino groups give the quantum dots the better water solubility,surface positron and other more molecular functions.In this paper,CA-CdTeQDs were prepared by using cysteamine?CA?as modifier and stabilizer and synthesized by hydrothermal method,and three kinds of off-on fluorescence sensors were constructed.The practical application of the proposed fluorescence sensor is discussed through the detection of the actual sample.The results provide a reference and basis for the construction of high sensitivity and high selectivity by fluorescence sensor.The specific content are as follows:?1?Determination of glutathione?GSH?by off-on fluorescence sensor based on CA-CdTeQDs-Au NPs.Cysteamine?CA?was used as stabilizer and modifier,tellurium powder was Te source and Cd Cl2 was Cd source for the synthesis of CACdTeQDs.Sodium citrate was used as stabilizer and reducing agent to synthesize negatively charged gold nanoparticles?Au NPs?.Due to the large overlap between the UV-vis absorption spectra of Au NPs and the fluorescence spectra of CA-CdTeQDs,the internal filtering effect took up and CA-CdTeQDs fluorescence quenched.Au NPs and GSH strong coordination effect made the Au NPs released from quantum dots,so GSH can cause the agglomeration of Au NPs.The positive conductance of GSH under the detection conditions made the negative Au NPs agglomerated,UV-vis absorption spectra of Au NPs appeared redshift,so the IFT process blocked and the fluorescence of CA-CdTeQDs recovered.Based on this mechanism,a off-on fluorescence sensor for detecting glutathione is constructed.Under the optimal experimental conditions,the fluorescence recovery of CA-CdTeQDs was linear with the concentration of GSH at 6.7-4.0×104 nmol/L and the detection limit was 3.3 nmol/L.Compared with the reported methods,this method has higher sensitivity and selectivity,and 10 times of the cysteine and homocysteine has no interfere with the determination,so it could be used for the detection of GSH in serum and biological field.It provides a methodological basis and reference on the high sensitivity and high selection for the detection of GSH.?2?Determination of homocysteine?Hcy?based on CA-CdTeQDs-Cu²⁺ off-on fluorescence sensor.The surface state of CA-CdTeQDs changed due to the interaction with Cu²⁺,and fluorescence quenched of CA-CdTeQDs.As Cu²⁺ has a strong coordination effect on homocysteine,and competed with CA-CdTeQDs,so the interaction between Cu²⁺ and CA-CdTeQDs were relieved and the fluorescence of CACdTeQDs recovered.Based on the above principles,a off-on fluorescence sensor for detecting homocysteine is constructed.Under the optimal experimental conditions,the fluorescence recovered degree of the whole system was linear with the concentration of homocysteine in the range of 0.05-10 ?mol/L,and the detection limit was 10 nmol/L.Compared the determination methods,this method has better selectivity and sensitivity,and better solved the interference of structural analogues about two coexistence of GSH and cysteine in the samples,so it can be used for selective biological detection in blood homocysteine.?3?Determination of L-ascorbic acid?AA?based on CA-CdTeQDs-PSS-methyl violet(Mv²⁺)off-on fluorescence sensor.The anionic polymer sodium polystyrene sulfonate?PSS?was used as a bridge for positively charged electron donor of CA-CdTeQDs and positively charged electron acceptor of methyl viologen(Mv²⁺)under the action of the electron transfer,so the fluorescence of CA-CdTeQDs quenched.AA has a strong reduced ability which can reduce Mv²⁺ to Mv+,so the electron transfer between CA-CdTeQDs and Mv+ were relieved and fluorescence of CA-CdTeQDs recovered.Based on the above principles and builded the way to detect of L-ascorbic acid by off-on fluorescence sensor system.Under the optimum experimental conditions,the concentration of L-ascorbic acid was 0.8-20 ?mol/L,which was proportional to the recovery of the whole system.The detection limit was 50 nmol/L.Compared with the reported method,the experiment not only has high detection sensitivity,but also has good selectivity,and 10 times of GSH,Hcy and cysteine were not interfered with the assay,so it could be applied to the detection of AA in serum and cells.