A Molecularly Imprinted Photoelectrochemical Sensor Based On NH₂-MIL-125(Ti)/TiO₂ For The Sensitive And Selective Determination Of Oxtetracycline

Oxytetracycline(OTC)is one of the tetracycline antibiotics.OTC is widely used in animal husbandry and aquaculture due to its low price,high efficiency and superior antibacterial properties.The unreasonable use of OTC will affect the safety of the ecological environment and human health.At present,common analytical methods widely applied for OTC detection are high performance liquid chromatography(HPLC),liquid chromatography-tandem mass spectroscopy(LC-MS/MS)and immunoassay method.However,these methods based on chromatography technique often need expensive instruments,complex sample treatment and experienced operators.The immunoassay method is fast and suitable for on-site testing,but the reproducibility is poor.Therefore,it is urgent to develop a simple,sensitive and reliable rapid detection method for OTC.Compared with traditional detection methods,molecularly imprinted photoelectrochemical(MIP-PEC)sensing detection methods is more suitable for rapid and sensitive detection of OTC residues due to the advantages of high sensitivity,fast analysis speed,low cost,and easy miniaturization of equipment.In this work,a MIP-PEC sensor based on a novel PEC composite of metal-organic frameworks(MOFs)and TiO₂(NH₂-MIL-125(Ti)-TiO₂)was established for the ultrasensitive and selective detection of OTC.This is the first attempt of applying MOFs in the construction of MIP-PEC sensor.The specific content is as following:The NH₂-MIL-125(Ti)-TiO₂ was synthesized by a simple one-step solvothermal method and modified onto the surface of indium tin oxide(ITO)electrode to form the NH₂-MIL-125(Ti)-TiO₂/ITO electrode.Subsequently,the functional monomer o-PD and OTC are polymerized on the surface of the NH₂-MIL-125(Ti)-TiO₂/ITO electrode by electropolymerization to form the imprinted electrode.The construction of the molecularly imprinted photoelectrochemical sensing interface was completed after eluting OTC with 5%HNO₃.The morphology,structure and optical properties of the prepared composite materials were discussed and studied by scanning electron microscopy(SEM),X-ray diffraction(XRD),ultraviolet visible diffuse reflectance spectra(UV-vis DRS),fluorescence(FL)spectra and other methods.The electrochemical performance of the prepared MIP-PEC sensing platform was investigated using fourier transform infrared(FT-IR)spectra,cyclic voltammetry(CV)and electrochemical impedance spectra(EIS)methods.The mechanism of photocurrent generation and OTC target recognition were further explored.The conditions affecting the detection performance of the MIP-PEC sensor were optimized,including the elution time of the target,the incubation time,the p H of the buffer solution and incubation temperature.Under optimal conditions,the performance of the constructed MIP-PEC sensor was evaluated,including the establishment of the sensor standard curve,the selectivity,anti-interference ability,reproducibility and stability of the sensor.Experimental results showed that the photocurrent response was reduced after incubation of OTC because the specific binding of OTC to the imprinted cavities blocked the electron transfer of the electrode and the MIP-PEC sensor exhibited a wide detection range from 0.1 n M to 10?M with a low limit of detection(LOD)of 60 p M,as well as certain selectivity,reproducibility,stability and good applicability in real samples.