Non-Enzyme Glucose Sensors Based On Transition Metal Compound Nanomaterials

Diabetes are chronic,endocrine and metabolic diseases caused by insulin secretion defects or their biological effects.With the improvement of human economy and living standards,people's nutrition and lifestyle have changed.Diabetes patients?mainly type II diabetes?showed a significant increase in the number of people.The occurrence of diabetes is the result of genetic factors and environmental factors.Activity reduce,obesity,dietary changes,pregnancy and psychological stress are the leading environmental factors leading to the occurrence of diabetes.Diabetes and its associated complications,such as coronary heart disease,stroke,hypertension,diabetic nephropathy,blindness and amputation,have become public health problems that poses serious harm to human health and life.At present,the clinical treatment of diabetes is mainly on patients with strict monitoring of blood sugar to ensure that blood glucose concentration in a safe range.This is very important for disease control and prevention of serious complications.Objective:Diabetes is a chronic endocrine and metabolic disease caused by the defective insulin secretion or the obstructed biological effects of insulin.At present,diabetes can not be completely cured.The main clinical treatment method now,is the strict monitoring and control of diabetic patients'blood glucose concentrations to ensure a safe level.Blood glucose detection is important to diabetes'clinical diagnosis and patients'personal care.Therefore,developing fast,sensitive,cheap and commercialized glucose detection devices becomes an urgent demand.In this work,two transition metal compounds were synthesized using cheap,accessible raw materials and simple methods.The catalysts were directly decorated on the surface of glassy carbon electrodes.Thus,two kinds of non-enzyme glucose electrochemical sensors were fabricated.Methods:First of all,the preparation methods of nano-catalytic materials and electrochemical sensors are as follows.In the first chapter,CuCo₂S₄ nano-flowers were synthesized from copper chloride,cobalt chloride and thiourea by using solvothermal method.The products were dissolved in 0.5%Nafion aqueous solution and sonicated for 30 minutes to get a homogeneous solution.Then,the above solution was dropped on a glassy carbon electrode?GCE?,thus the glucose sensor,CuCo₂S₄/GCE,was prepared.In the second chapter,the preparation process of NiMoO₄ nanorods?NiMoO₄ NRs?included 3 steps.Firstly,glucose was used as raw material to synthesis nano-carbon balls via hydro-thermal method.Secondly,the aqueous solution containing nano-carbon balls,nickel nitrate and sodium molybdate was poured into a reactor to generate bimetallic hydroxide.Thirdly,the precursor material,bimetallic hydroxide,was annealed in the air at 400oC for 1 hour.Consequently,NiMoO₄ nanorods with a length from several hundred nanometers to3⁴?m and a diameter from 100 to 200 nmwere obtained.Finally,the glucose sensor,NiMoO₄ NRs/GCE was prepared by decorating the mixed solution of NiMoO₄NRs and Nafion on a glassy carbon electrode.In addition,the characterizations of the as-prepared catalytic materials were performed by SEM?scanning electron microscopy?,XRD?X-ray diffractometer?and XPS?X-ray photoelectron spectroscopy?.The sensors'performances were investigated by cyclic voltammetry?CV?and chronoamperometry?i-t?methods.Results:Thesuccessful preparation of CuCo₂S₄ nano-flowers and NiMoO4nanorods is confirmed by SEM,XRD and XPS patterns.CV and i-t curves show that the two as-prepared nano-materials have good catalytic activity for the oxidation of glucose.The optimal experimental conditions of working potential and nanomaterial loading were selected for glucose detection by chronoamperometry.CuCo₂S₄/GCE has a linear range from 0.5?M to 2.5 mM,with a low detection limit of 0.1?M?S/N=3?and a high sensitivity of 3858?A?mM^-1?cm^-2.Moreover,NiMoO₄ NRs/GCE has a wider linear range,whichis divided into two parts:from 0.2?M to 2.633 mM and from 2.633 mM to 10.133 mM.The sensor's sensitivities for the two linear ranges are469.3?A?mM^-1?cm^-2 and 277.6?A?mM^-1?cm^-2,respectively.Furthermore,NiMoO₄NRs/GCE has a lower detection limit of 0.02?M?S/N=3?.Conclusions:In this work,weconstructedtwo glucose sensors,CuCo₂S₄/GCE and NiMoO₄ NRs/GCE.Theyhad good sensing performancefor glucose detection,including good catalytic activity,selectivity,repeatability and stability,etc.Apart from this,they showed excellent performancein glucose detection in actual blood samples.In contrast to other enzyme-free glucose sensors reported,CuCo₂S₄/GCE has a relatively high sensitivity and low detection limit.Moreover,NiMoO₄ NRs/GCE has a lower detection limit and a wider linear range.The spike recovery experiments of blood samples showa high recovery rate,indicating that the two enzyme-free glucose electrochemical sensors can be applied to the actual detection of blood glucose.