Electrochemical Analysis Properties Of Electrospun PAN/PEI Composite Nanofiber Membranes

Polyethylene imine(PEI)is a water-soluble polymer with weak chemical toxicity.The primary,secondary,tertiary amine base on the PEI molecule make it alkaline and cationic active.It is easy to react with electrophilic reagents and can be modified by amine reaction.It has good affinity and absorbability to anionic substances.At the same time,a large number of amino on PEI have certain coordination ability for metal ions,therefore,it has very extensive application in analytical chemistry.However,because PEI has free molecular form and is easily soluble in water,it is necessary to immobilize PEI on the main material.The methods of adsorption,covalent,encapsulation and cross-linking aggregation are commonly used to immobilize PEI.However,the above methods of immobilization of PEI often consume the active functional group amino on PEI.So the loading efficiency and the desired performance of PEI is difficult to ensure.Therefore,it is still a challenge to immobilize PEI without weakening its original advantages.Electrospinning is one of the most effective methods to produce nano fibers.Because of its advantages such as simple device,low cost,simple operation and controllable process,Electrospinning has attracted widespread attention.Nanofiber films prepared by electrospinning technology have large specific surface area and length-diameter ratio,and many spinnable materials.It also can be functionalized easily.Based on this,we used electrospinning technology to immobilize PEI onto the nanofiber membrane.This immobilization method not only does not consume the active functional group amino of PEI,but also realizes the orientation of three amino groups.Based on the excellent properties of PEI and the characteristics of electrospun nanofiber membrane,it was applied to electrochemistry and electrochemiluminescence sensing,respectively.Specific research contents are as follows:1.Preparation of PAN/PEI nanofiber membrane modified electrode and its high sensitive and selective electrochemical detection of Hg(?)in tap water.Firstly,the amino-rich PAN/PEI nanofiber films were prepared in situ on the surface of glassy carbon electrode by the electrospinning technology.A large number of amino functional groups in electrospun PAN/PEI nanofibers can react with mercury ions and chloride ions in solution to generate electroactive mercury aminechloride on the surface of the electrode.Based on the electrochemical behavior of mercury aminochloride,a new method for the determination of Hg(?)was developed.The large specific surface area and porosity of the nanofibers as well as the coordination ability of a large number of amino groups on the fiber surface can realize the effective enrichment of Hg(?),which improves the sensitivity of the determination.The selectivity of the determination was improved by controlling the enrichment potential and based on the specific chemical reaction of mercury ions with amino and chloride ions to form mercury aminechloride.The linear range of Hg(?)detected by the proposed sensor is 1.0×10-11 mol/L?9.0×10-10 mol/L,and the detection limit is 3.3 pM.2.Electrochemiluminescence behaviors of Ru(bpy)32+ on PAN/PEI nanofiber membrane modified electrode and its application in formaldehyde sensing.Because amino-rich PEI can enhance the electrochemiluminescence(ECL)of Ru(bpy)32+,it is often used as a co-reactant in Ru(bpy)32+ECL system.In this work,we prepared PAN/PEI nanofiber films on the surface of glassy carbon electrode using PEI and PAN as raw materials by electrospinning technology.The co-reactive reagent(PEI)was directly spun into fibers and assembled on the surface of the electrode,which not only reduced the consumption of co-reactant,but also realized the ECL signal amplification.The experimental results showed that the ECL of Ru(bpy)32+obtained on the PAN/PEI nanofiber film modified electrode is increased by 20 times compared with that obtained at the bare glass carbon electrode.In addition,the amino group on PEI molecule can react with formaldehyde by nucleophilic addition reaction,which reduces the amino group in PEI molecule and reduces the sensitization effect of PEI as co-reactant on the ECL reaction of Ru(bpy)32+system.Based on the inhibition of formaldehyde on the ECL reaction of Ru(bpy)32+sensitized by PEI,the detection of formaldehyde by Ru(bpy)32+ECL was realized.The inhibition ECL signal on the Ru(bpy)32+-PEI system was linear with the concentration of formaldehyde in range of 3.6×10-9 mol/L?4.0×10-8 mol/L,and the detection limit is 1.2 nM.