Research On Design And Response Mechanism Of Fluorescence Sensor Based On Small Molecule Detection

With the rapid development of science and technology,using modern analytical techniques to achieve small-scale detection of small molecules was particularly important.Fluorescence sensing with unique fluorescence properties was currently a very important modern analytical technology,which has filled many gaps in environmental,chemical,energy,food,and biological applications.Among them,carbon dots（CDs）and quantum dots（QDs）were the typical common materials.Based on it,this thesis used CDs and QDs to construct fluorescent sensors that achieve trace detection of small molecules and explore the response mechanisms,respectively.The main contents of this thesia included:1.The nitrogen-sulfur co-doped CDs were synthesized using scallion leaves and did not surface passivating agents.The characterization of CDs disserved that the N and S elements were existence and uniform distribution.The particle size was mainly distributed at 3.5±0.7 nm and surface contained a large number of hydrophilic groups.Compared with the detection of various amino acids and cations,the fluorescence sensor has a good selective response to hemin.In the concentration of Hemin from 0.5to 10.0μM,there were a good linear relationship with the fluorescence quenching.The detection limit was 0.1μM,which indicated that the fluorescence sensor was a high sensitivity to Hemin.The mechanism of fluorescence quenching was explored by spectrometry and electrochemical systems.The experimental results showed that the mechanism were IFE and PET,meanwhile IFE was the main quenching factor.The calculation results of Gaussian software theory also further verified the fluorescence quenching mechanism.Finally,the practical application of human serum samples has further verified,there were great application value in clinical blood testing.2.Molecularly imprinted was synthesized in Tris-HCl buffer by using water-soluble CdS QDs as core,17β-estradiol（E₂）as template molecule and dopamine as polymerized monomer.At the same time,the polymerization time and dopamine monomer of MIP were fully optimized.Compared with non-molecular imprinting（NIP）,the MIP exhibits distinct specificity to E₂ under the optimal conditions.Within the concentration range of E₂ from 5 to 50 nM,the experimental results show the excellent linear relationship and the fluorescence enhancement.the detection limit was1.2 nM.By comparing the imprinting factors and selectivity coefficients of E₂,estrone（E₁）and ethynyl estradiol（EE₂）,the MIP has obvious selectivity for E₂.Calculating the binding constants at different temperatures and thermodynamic parameters,it showed that the interactions between the MIP and E₂ were mainly ascribed to hydrogen bonding andπ-πconjugatione.The interactions lead to increase the radiative transition coefficient which increase the fluorescence intensity.Finally,the practical application of milk samples has further verified,which has a certain practical application prospect.