Design Of The Surface Of Carbon Material Based Electrode And Its Application To Simultaneous Detection Of Purine Compounds

Purine and their derivatives including xanthine?XA?,hypoxanthine?HX?and uric acid?UA?are the essential components of the DNA,which is playing an important role in energy supply and metabolism regulation of organisms.It has been reported that excessive accumulation of these metabolities in the body would cause some serious diseases such as gout,hyperuricemia,high blood pressure,cerebral infarction and diabetes.Hence,it is very important to monitor UA,XA and HX in human body will have great significance in the precaution and prevention of relating diseases.Electrochemical methods have some advantages such as high sensitivity,easy miniaturization and other characteristics of achieving real-time and dynamic clinical detection in the research of physiological and pathological.Designing the excellent surface structure of electrode in electrochemical analisis plays an important role in analyzing.A series of functional materials with different properties were designed and synthesized modifying the electrode surface,so as to form a functional interface with good catalytic performance,strong stability and high sensitivity,which can provide a solution for obstaining good sensitivity,selectivity,reproducibility,stability and other analytical properties.Therefore,we have synthesized two compounds of amine-functionalized metal-organic-framework?NH₂-MIL-101?Fe??and graphene?GO?,hydroxyl-functionalized metal-organic-framework?OH-MIL-101?Fe??and graphene?GO?complexes.The namoposites were prepared by ultrasonic method with mild conditions and friendly environment,which has the advantages of good reproducibility and easy operation.We have found that Fe-O coordination bond was formed between Fe on NH₂-MIL-101?Fe?and carboxyl oxygen on GO,and the coordination bond still existed after electrochemical reduction.Meanwhile,carboxyl oxygen on the glass carbon electrode also forms the Fe-O coordination with the Fe in NH₂-MIL-101?Fe?.This finding has not been reported in other report.The modified electrodesNH₂-MIL-101?Fe?-GO have the high sensitivity and ultra-stability detecting the UA,XA and HX in human uric and serum.In particular,the electrode was continuously measured 120 times without sigal attenuation.Obviously,the formation of Fe-O coordination covalent bond is an important reason for the high stability.In view of the simple preparation method of NH₂-MIL-101?Fe?-GO modified electrode and its super stability performance,the modified electrode is expected to have a broad application prospect in electrocatalysis,electrochemical sensing and other aspects.The work in this paper can be summed up in two aspect as follows:First,highly stable electrochemical analysis at graphene oxide covalently functionalized by a metal-orgaic framework.A new method to detect the purine by design the metal organic frameworks NH₂-MIL-101?Fe?and graphene nanocomposite.Here we report a covalent functionalization of graphene?GO?by prepared NH₂-MIL-101?Fe?MOFs through simple ultrasonication method of the two materials in aqueous solution.The shape and structure of the obtained NH₂-MIL-101?Fe?nanocomposites were characterized via scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,UV-vis,Fourier-transform infrared?FT-IR?,X-ray diffraction?XRD?,X-ray photoelectron spectroscopy?XPS?and Raman spectra.And the covalent bonding Fe-O in the NH₂-MIL-101?Fe?-GO?name as the nanohybrid hereinafter?is evidented,which still remains after electrochemical reduction.The electrodechemically reduced nanohybrid demonstrates an excellent performance in simultaneous electrochemical detection of three purine metabolic products?UA,XA and HX?.Under the optimum conditions,the oxidation peak currents of UA,XA and HX were linearly correlated to their concentrations in the range of 0.01-1.0?mol/L,0.005-2.0?mol/L,0.05-3.0?mol/L,respectively.The detection limits for UA,XA and HX were estimated to be as low as0.008?mol/L,0.004?mol/L,0.030?mol/L?S/N=3?.Moreover,this proposed electrode has the highly stable for multipling 120 times.The covalent bonding plays a key role in the stability of the electrode and also provides a new way to monitoring the UA,XA and HX in vivo.Second,rational design of metal organic framework nanocomposite based functionalized interface for simultaneous electrochemical determination of purine metabolites.We made a comparison in different groups of R-MIL-101?Fe?-GO?R=-OH,-H and-NO₂?nanocomposites to detect the purine according to the cooperative catalysis.Nano-composites were prepared by ultrasonic mixing method and characterized by X-ray diffraction?XRD?,Fourier transform infrared?FT-IR?and UV-vis spectroscopic methods.By casting the surface of glassy carbon electrode?GCE?with the composite and electrochemical reduction of the modified electrode,R-MOFs-ERGO/GCE was obtained.The results shows OH-MIL-101?Fe?-ERGO has the best response to UA,XA and HX in the different modified electrodes.The MOFs with–NO₂ group has the worst response to the purine.This indicates the Lewis acid metal centres and base sites in R-MIL-101?Fe?with different donating groups has the big influence in detecting the purine.And the lone pair electrons on the oxygen atom and the electrons on the benzene ring are connected together through the p-?bond in the group–OH.Under the optimum conditions,the oxidation peak currents of UA,XA and HX were linearly correlated to their concentrations in the ranges of 0.20-1150?mol/L,0.15-800?mol/L,and 0.40-600?mol/L,respectively.The detection limits for UA,XA and HX were0.12,0.10 and 0.20?mol/L?S/N=3?,respectively.The recoveries of UA,XA and HX in real serum and uric samples were between 99.5%and 105.8%.The proposed electrode was expected to provide a simple and easy detection method for the physiological and pathological study of purine metabolism.This work is beneficial to find the best materials with different groups to detect the purine,and is expected to provide a simple method for the research of purine in human body.