MOF Based High-performance Photoelectrochemical Sensor For Efficient Phenylarsonic Acid Compounds Detection

Phenylarsonic acid compounds,such as p-arsanilic acid?p-ASA?and roxarsone?ROX?,are widely used as the animal feed additives.However,after excretion in manure,the water-soluble organoarsenic compounds would be degraded into high-toxic inorganic arsenic species in complex environment.Thus,knowing the exact distribution and concentration of organoarsenic compounds becomes increasingly essential for environmental risk assessment and pollution treatment.Photoelectrochemical?PEC?sensor has been widely applied in environmental monitoring for its high sensitivity,excellent selectivity and low cost.Generally,the electrode material is a key component of a PEC sensor.Developing electrode materials with excellent photoelectric activity and strong binding characteristics can avoid bio-recognizers modification,simplify PEC sensor construction and improve environmental stability.Herein,two zirconium-porphyrinic metal-organic frameworks?PCN-222&PCN-224?and PCN-224/rGO&PCN-222/MXene were prepared and used to fabricate PEC sensors with intrinsic recognition ability for efficient p-ASA and ROX detection.The main research contents are as follows:?1?The isostructural MOFs?PCN-222&PCN-224?with different unsaturated coordination numbers of metal centers were used as the photoelectric materials to develop PEC sensors for p-ASA detection.First,spectroscopic characterization indicated that both PCN-222 and PCN-224 could be excited in visible light?420 nm?,and two MOFs had a wide visible light absorption range,which will facilitate photoelectric conversion.Furthermore,PCN-222 and PCN-224 can chemoselectively capture p-ASA.Thus two MOFs have photoelectric activity and binding ability for p-ASA.Both PCN-222 and PCN-224 electrodes had excellent photocurrent response to p-ASA.To be specific,under the optimized conditions,PCN-222 and PCN-224 based sensors respectively had wide detection ranges?10?g/L-50 mg/L,1?g/L-50 mg/L?consisting of three consecutive linear ranges for p-ASA,and the detection limits were 5.87?g/L?PCN-222?and0.61?g/L?PCN-224?.Comparing the detection results of two sensors,PCN-222 electrode had stronger capture ability for high concentration p-ASA,which showed higher sensitivity in high concentration.While PCN-224 electrode had stronger binding ability for low concentration p-ASA,which was more suitable for detecting low concentration p-ASA.That may be attributed to the different metal coordination states of PCN-222 and PCN-224 and distinct binding mechanisms at high and low concentrations.?2?PCN-224/rGO nanocomposite was used as the photoelectric material to fabricate a PEC sensor for p-ASA detection.Highly conductive rGO can improve the photoelectric conversion efficiency,obtaining significantly enhanced photocurrent signal.The analytical performance of the developed PEC sensor was measured under the optimized conditions.The constructed sensor had two consecutive linear ranges?10 ng/L-100?g/L and 100?g/L-10 mg/L?for p-ASA detection,and the detection limit was 5.47 ng/L.Furthermore,the PEC sensor had excellent detection behavior for p-ASA in simulated natural water and swine manure lixivium.The analysis of XPS results and principle of semiconductor electrochemistry demonstrated PCN-224/rGO electrode had strong affinity to p-ASA through Zr-O-As coordination and?-?stacking,and p-ASA as the adsorbate tuned the band position of the PCN-224/rGO electrode,causing a shorter distance of the depletion layer as well as weaker intensity of the electric field.Thus,there were more electrons passing over the potential barrier to reduce O₂ which generated increased photocurrent.?3?PCN-222/MXene composite was used as the photoelectric material to develop a PEC sensor for ROX detection.PCN-222 hollow nanotubes were synthesized via a competitive coordination procedure.The introduction of MXene not only increased the photocurrent of PCN-222,but also enhanced the binding ability for ROX through destroying the structure of PCN-222 and exposing more binding sites.The developed PEC sensor achieved good detection performance for ROX.The linear monitoring ranges consisted of 100-5000?g/L and 5-50 mg/L,and the detection limit was 11.47?g/L.