| The harm of carcinogenic aromatic amine compounds to the environment and human health hazard is pretty large.Therefore,it is very important to finding a simple,fast and accurate method for the detection of carcinogenic aromatic amine becomes quite important.Molecularly imprinted polymers have excellent specific recognition and selectivity.And we also know that graphene is a new type of2-dimensional nanomaterials with high conductivity and specific surface area.The zero current potential method is based on the conventional three electrode system,which is connected with the working electrode and the auxiliary electrode port by the potential sensing technology.The core of pencil is made by graphite and clay with a specific ratio through extrusion and bonding process,which has high conductivity.The pencil core electrode can be used as a kind of inert electrode,and its electrochemical performance is similar to that of glass carbon and carbon paste electrode,however it is cheaper,and more stable.And its potential window is also wide,one more advantage is its easy-modification property.In this paper,using electrochemical polymerization method,we constructed four types of novel molecularly imprinted polymer film sensors by using 2,4,6-trimethylaniline,5-nitro-o-toluidine,2,6-dimethylaniline and2,4-diaminotoluene at the surface of graphene modified pencil electrode,respectively.The work is summarized as following:1.The 2,4,6-Trimethylaniline-MIP was prepared by acrylicacidand2,4,6-trimethylaniline using electrochemical polymerization method.Using zero current potentiometry,the preparation conditions?such as concentration ratio?washing time?scan potential?scan cycles?were optimized.By measuring the change of zero current potential before and after imprinting,the 2,4,6-trimethylaniline-MIP and its structure were calculated.The calculated results show that the2,4,6-trimethylaniline-MIP has good recognition and selectivity.Under zero current potential,the Gibbs free energy,enthalpy change and entropy change of2,4,6-Trimethylaniline-MIP when imprinting 2,4,6-Trimethylaniline under different temperatures?328K,333K,298K?were recorded and calculated.The results show that the binding reaction is a spontaneous,disordered and endothermic process.In addition,the binding reaction was demonstrated to be first order kinetic equation.The calculated polymer imprinting factor is 2.0,and the selectivity factor of o-toluidine,4-chloroaniline,p-aminoazobenzene,2,4-dimethylaniline and 2,4-diaminotoluene,2,6-dimethylaniline and 5-nitro-o-toluidine is 1.5,1.7,1.8,1.6,1.3,1.7,1.6,separately,which implies that the ability of the imprinted polymer to recognize2,4,6-trimethylaniline is way high than that of non-imprinted polymer.It also demonstrated that the imprinted polymer can be applied to distinguish2,4,6-trimethylaniline and the materials with similar structure with it.Directly with molecularlyimprintedpolymermodifiedpencilleadelectrodefor2,4,6-trimethylaniline zero flow potential response of linear range(5.0×10-8–1.0×10-5mol·L-1)and the detection limit(8.1×10-99 mol·L-1)compared to the molecularly imprinted polymers?MIPS?pencil lead graphene modified electrode for2,4,6-trimethylaniline zero flow potential response of linear range wider(1.0×10-8–5.0×10-55 mol·L-1),a lower detection limit(1.6×10-99 mol·L-1).When using it in the detection of wastewater samples,the range of the recovery is 91.4-97.3%,which is consistent with traditional chromatography method.2.At the surface of graphene modified pencil lead electrode?G-PEC?,through direct electrical aggregating functional monomers?acrylic acid?and the template molecules?5-nitro-o-toluidine?to prepare 5-nitro-o-toluidine molecularly imprinted polymer.Using zero current potentiometry,the conditions of electrical aggregation were optimized.By comparing the zero flow potential change before and after imprinting of the 5-nitro-o-toluidine-MIP,the imprinting capacities of the5-nitro-o-toluidine and other materials of similar structure with 5-nitro-o-toluidine were calculated.The experiments demonstrated that the ability of specific recognition andselectivityof5-nitro-o-toluidinemolecularlyimprintedpolymerto5-nitro-o-toluidine are much better than that to other materials.Under the zero flow potential system,the imprinting factor of 5-nitro-o-toluidine is 9.4,and the selectivity factor of o-toluidine,4-chloroaniline,p-aminoazobenzene,2,4-dimethylaniline,2,4-diaminotoluene and the choice of 2,6-dimethylaniline is 2.1,3.1,3.4,3.1,3.0,4.2,respectively.It also demonstrated that the performance of recognizing 5-nitro o-toluidine of the molecularly imprinted polymers?MIPS?is much better than non-imprinted membrane,and this implies that it can differentiate 5-nitro o-toluidine and other materials with similar structure.At the surface of graphene modified pencil lead electrode,we examined thermodynamic parameters of 5-nitro-o-toluidine in the process of imprinting,and the calculated imprinting binding reaction constant is2.0×108 L·mol-1,Gibbs free energy is 47.4 KJ·mol-1.Compared with the zero flow potential response linear range(5.0×10-8–1.0×10-55 mol·L-1)and the detection limit(8.1×10-99 mol·L-1)of the imprinted polymers?MIPS?pencil lead and electrodes to5-nitro-o-toluidine,the zero flow potential response(5.0×10-9–5.0×10-55 mol·L-1)of5-nitro-o-toluidine molecularly imprinted polymers?MIPS?to 5-nitro-o-toluidine is much wider at the surface of graphene pencil lead electrode,also the detection limit(7.7×10-1010 mol·L-1)becomes lower.When using this method to test wastewater sample,the recovery range is 90.5-100.7%,which is consistent with chromatography.3.At the surface of graphene modified pencil lead electrode,through direct electrical aggregation function monomer?acrylamide?and the template molecules?2,6-dimethylaniline?preparation of 2,6-dimethylaniline molecularly imprinted polymer.Under the condition of zero streaming potential technology,the polymerization conditions are optimized.By using 2,6-dimethylaniline molecularly imprinted polymer in imprinting testing before and after the change of the zero flow potential,calculated from 2,6-dimethylaniline and some of its structure of similar material in the2,6-dimethylaniline molecular imprinting polymer imprinted capacity were 1.1,0.18,0.06,0.12,0.057,0.23,0.18,0.057,and showed the MIP to 2,6-dimethylaniline specific recognition and good selectivity,and other substances do not interfere with the template molecule with the molecularly imprinted polymer imprinted loci combination.Calculated under the zero flow potential system,the imprinting factor is2.9,of o-toluidine,4-chloroaniline,p-aminoazobenzene,2,4-dimethylaniline,2,4-aminotoluene and 2,4,6-Trimethylaniline choice factors were 1.4,1.3,1.3,1.2,1.2,1.2,molecularly imprinted polymers?MIPS?recognize that the performance of 2,6-dimethylaniline in far greater than the molecularly imprinted membrane,and can better will be 2,6-dimethylaniline differentiated by the material and its structure is similar.In graphene modified pencil lead electrode surface looked at 2,6-dimethylaniline,molecularly imprinted polymer imprinted in combination with the thermodynamic mechanism of 2,6-dimethylaniline,calculated imprinting binding constant 1.4×109 L·mol-1,Gibbs free for 52.3 KJ mol-1.Due to high conductivity and high specific surface area of graphene and graphene modified 2,6-dimethylaniline molecularly imprinted pencil lead electrode of 2,6-dimethylaniline zero flow potential response of linear range(5.0×10-8–1.0×10-44 mol·L-1)than that of 2,6-dimethylaniline,molecularly imprinted polymer pencil lead electrode of 2,6-dimethylaniline zero flow potential response of linear range(5.0×10-7–5.0×10-55 mol·L-1)wide,detection limit(5.0×10-7–5.0×10-55 mol·L-1)than the(9.2×10-88 mol·L-1)low.Test wastewater samples using this method,the scope of its detection rate of 89.5-97.3%,in line with chromatography.4.At the surface of graphene modified pencil lead electrode,through direct electrical aggregation function monomers?acrylic acid?and the template molecules?2,4-Diaminotoluene?preparation of 2,4-diaminotoluene molecularly imprinted polymer.Under the condition of zero streaming potential technology,the polymerization conditions are optimized.With 2,4-diaminotoluene-MIP in imprinting testing before and after the change of the zero flow potential,calculate the amino toluene 2,4-diaminotoluene and some of its structure is similar in 2,4-diaminotoluene molecular imprinting polymer imprinted capacity,the experiment showed that2,4-diaminotoluene toluene molecularly imprinted polymer of amino toluene2,4-diaminotoluene specific recognition and good selectivity,and other substances do not interfere with the template molecule with the molecularly imprinted polymer imprinted loci combination.2,4-diaminotoluene concentration in 1.0×10-5-8.0×10-8mol·L-11 within the scope of the molecularly imprinted polymer of zero flow potential EZCP concentration logarithm with log[c]show good linear relationship.Test wastewater samples using this method,the scope of its detection rate of 84.0-99.1%,in line with chromatography. |
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