Preparation Of Er-MOFs With Different Morphologies And Their Application In Electrochemical Sensing

Metal-organic frameworks(MOFs),a new class of porous coordination polymers emerging at the end of the 20 th century,in the past two decades,researches on the synthesis,structure,properties and applications of MOFs have been deeply developed.However,there are relatively few reports of MOFs in the field of electrochemical sensing,especially lanthanide metal-organic frameworks.Therefore,this article focuses on the preparation,electrochemical performance regulation and sensing applications of Er-MOFs:(1)Two kinds of MOFs were prepared by using Eu and Er as metal centers,1,3,5-benzenetricarboxylic acid as ligand,reacting at 130°C for 12 h in DMF.FTIR,XRD,XPS and SEM confirmed the formation of Eu-BTC and Er-BTC,and their morphology was straw-sheaf-shaped.CV and EIS were used to study their electrochemical performance,the results showed that Er-BTC can provide larger electrochemical response area and stronger electron transport capability.Further research found that Er-BTC exhibited stronger adsorption and enrichment abilities for sunset yellow,which led to the oxidation signal of it significantly increased.Based on the excellent interface enhancement effect of Er-BTC,a highly sensitive electrochemical sensing platform was constructed to detect sunset yellow,with a linear range of 0.2-100 nM and a detection limit of 0.05 nM.The method was applied to the determination of drink samples,and the relative error was less than 4% compared with HPLC.(2)Three Er-MOFs materials were synthesized by controlling the amount of ammonium acetate at room temperature under stirring,which is simple,energy-saving and efficient.FTIR,XRD,XPS and SEM proved that the synthesized materials were Er-BTC with different morphology(rod-shaped,chips-shaped and particles,respectively).CV,EIS and RDE were used to characterize the electrochemical properties of them,it was found that morphology has a great impact on their electrochemical sensing activity,and particle-shaped Er-BTC-3 showed larger sensing surface area and faster electron exchange rate,and its performance was better than that prepared by solvothermal method in the previous chapter.In addition,we also found that the three materials have different sensitizing effects on the electrochemical oxidation of allura red and rhodamine B,and Er-BTC-3 showed higher interface enrichment ability and stronger signal amplification effect.Using Er-BTC-3 as the sensing material,an electrochemical system for simultaneous determination of allura red and rhodamine B was set up with detection limits of 0.30 nM and 0.56 nM,respectively.It was used for the determination of drink samples and the results were consistent with HPLC.A further explore about the electrochemical sensing application of Er-BTC-3 was made,and it was found that it showed a strong signal enhancement effect on two flavonoids of quercetin and luteolin.Based on this,an electrochemical method for the simultaneous determination of the two was established,with detection limits of 0.22 nM and 0.14 nM,respectively.It was used for the determination of tea samples,and the results were agree with HPLC.