| Heterocyclic Schiff bases have more excellent chemical properties than other Schiff bases, such as fluorescence properties, electrochemical catalytic properties.In this paper, three 4-amino-antipyrine heterocyclic Schiff base were synthesized by 4-amino-antipyrine and isovanillin, 2- naphthalene formaldehyde,2,5-dihydroxyben--zaldehyde. Three carbaldehyde heterocyclic Schiff base were synthesized by thioph--ene-2-carboxaldehyde and o-aminothiophenol, L-cysteine, thiosemicarbazide. The structures and properties of six novel heterocyclic Schiff base were characterized by Infrared spectroscopy, ultraviolet-visible spectrum,fluorescence spectra, X-ray single crystal diffraction, thermogravimetric analysis and nuclear magnetic resonance Hydro--gen spectrum analysis(HNMR).The new fluorescent probe 4-amino-antipyrine shrink 2,5dihydroxybenzaldehyde Schiff base with Cd Te quantum dot binding ligands was obtained. Fluorescence analy--sis method was used to detect the strong binding capacity which make the lead ions with Schiff base away from the quantum dot surface, closed the way fluorescence resonance energy transfer, fluorescence quantum dots restored. It showed a good linear relationship between lead ion concentration and the fluorescence intensity in the range of 0.01 to 100 μmol/L and 100 to 10000μmol/L. Thus the new type of quantum dot fluorescent switch was constructed, and a new method to detect lead ions was establi--shed.This method was used for the determination of lead ions in water samples; the relative standard deviation was less than 4.1%, and the rate of recovery was 96.7 to 102%.The Schiff base- quantum dot composites material was prepared by Thiophene--2-carboxyl containing formaldehyde condensation L- cysteine Schiff base and β-mercaptoethylamine(CA) stabilized Cd Te quantum dots through covalent binding between the amino and carboxyl groups. The responses mechanism of Schiff bases modified the two different particle quantum dots were studied by fluore scence analysis, the concentration of superoxide anion radicals showed a linear relationship in 0-1.0× 10-5mol/L, the linear equation was respectively: y=56.27C(10-4mol·L-1)+ 5588.28(R=0.9934),y = 358.03 C(10-4 mol·L-1)+ 4979.1(R=0.9820), and the relative standard deviation(RSD) was 0.156% and 0.109% respectively, the detection limit were 1.8× 10-6mol/L and 4.6×10-6mo /L.The L- cysteine, gold nanoparticles, L-cysteine, cysteamine modified Cd Te quantum dots and thiophene-2-carboxaldehyde Shrink L-cysteine Schiff base nickel complexes(L5-Ni)followed modified on bare gold electrode surface by selfassembly method, The cyclic voltammetry method and electrochemical impedance spectroscopy method were used to characterize the prepared modified electrode, a new method for the rapid determination of the content of lemon was established. lemon concentration was ranged from 0 to 2.5mg/L. It showed a good linear relationship between the anodic peak current and lemon concentration, and the linear equation was I=(-1.88× 10-4)C-4.36×10-5, the correlation coefficient r = 0.995, the detection limit was 0.37 mg/L. This method was used to analyze the content of lemon drinks, and the relative standard deviation(RSD) was 2.15% to 3.23%, and the rate of recovery was ranged from 97.33 % to104.02%.Density functional theory(DFT) method in quantum chemistry was used to perform geometry optimization of the self-six novel Schiff base compounds, and then a single excitation configuration interaction(CIS) and time-dependent density func--tional theory(TD-DFT) method were used to perform further optimization according to the calculation results above. The error between calculated spectrum and actual test spectrum was compared, and the fluorescent light-emitting mechanism of the six New Schiff base compounds was discussed, it provide an important theoretical basis for the future design of Schiff base molecule. |
PDF Full Text Request