Studies On Rapid And Visual Recognization Of Fluoroquinolone Residues Based On Spherical Gold Nanoparticles

Objective:By synthesis of different sizes of gold nanoparticles(AuNPs)and regulation of the existing formation of fluoroquinolone(FQs),the reaction and interaction mechanisms between spherical AuNPs and eight kinds of FQs were studied in detail.As a result,a visual,simple and rapid detection system of FQs residues was successfully set up.Method:Firstly,the synthesis conditions of spherical AuNPs were optimized in order to attain spherical AuNPs with uniformity,good dispersibility and delicate reproducibility.Secondly,buffer solutions with different p H value were considered for changing the existing formation of FQs.Then the concentration of HAc-Na Ac buffer and the ratio of the volume of reaction components were investigated,respectively.Furthermore,with the help of sensitive promoter NaHCO₃,the optimal conditions of quickly visualization of FQs were proposed based on the negative AuNPs.Moreover,the analytical performance of eight kinds of FQs and anti-interference ability were investigated under the optimal conditions.Additionally,the recognization mechanisms spherical AuNPs and FQs were studied by using UV-Vis absorption,transmission electron microscope(TEM)and Zeta potential analysis characterization methods.Results:The best experimental conditions for quickly identifying FQs by spherical AuNPs are as followed:particle size with 15nm,p H 5.0 and 0.10mol.L^-1NaHCO₃as well as the best volume ratio of NaHCO₃:AuNPs:FQs 2:5:4.Under the optimal conditions,the detection limit for pefloxacin and norfloxacin is 1×10^-7mol.L^-1,as for enoxacin,ofloxacin and levofloxacin 2×10^-7mol.L^-1and ciprofloxacin,fleroxacin and lomefloxacin is 2×10^-6mol.L^-1.The results of Zeta potential analysis indicated that the addition of NaHCO₃can change the charge on the surface of AuNPs,while the results of TEM showed that the positive charge of FQs let AuNPs connect like a chain,which result in the color of AuNPs shifting from wine red to blue.Conclusion:The addition of NaHCO₃could significantly improve the sensitivity of reaction between AuNPs and FQs,and sodium bicarbonate take the place of citric absorbing on the surface of AuNPs by ligand exchange.The positive charge of FQs is helpful for the recognization of spherical AuNPs.The positively charged FQs reach the surface of AuNPs by electrostatic effect,decreasing the repulsion of AuNPs.In addition,the hydrophobic-hydrophobic interaction of quinolone ring between molecules of FQs triggers a chain type combination and aggregation among AuNPs.