Cathodized gold nanoparticle graphite pencil electrode and method for glucose detection

Abstract

The cathodized gold nanoparticle graphite pencil electrode is a sensitive enzymeless electrochemical glucose sensor based on the cathodization of AuNP-GPE. Cyclic voltammetry shows that advantageously, the cathodized AuNP-GPE is able to oxidize glucose partially at low potential (around −0.27 V). Fructose and sucrose cannot be oxidized at <0.1 V, thus the glucose oxidation peak at around −0.27 V is suitable enough for selective detection of glucose in the presence of fructose and sucrose. However, the glucose oxidation peak current at around −0.27 V is much lower which should be enhanced to obtain low detection limit. The AuNP-GPE cathodization increases the oxidation peak current of glucose at around −0.27 V. The dynamic range of the sensor is in the range between 0.05 to 5.0 mM of glucose with good linearity (R 2 =0.999). Almost no interference effect was observed for sensing of glucose in the presence of fructose, sucrose and NaCl.

We claim: 
     
         1 . A cathodized gold nanoparticle graphite pencil electrode, comprising:
 a graphite electrode; and   gold nanoparticles chemically disposed on a said graphite electrode to form a gold nanoparticle modified graphite pencil electrode (AuNP-GPE), said AuNP-GPE being subjected to a negative voltage to cathodize said AuNP-GPE before use of said AuNP-GPE as a voltammetric sensor in a glucose analyte solution.   
     
     
         2 . The cathodized gold nanoparticle graphite pencil electrode according to  claim 1 , wherein said AuNP-GPE is sensitive to the oxidation of glucose around approximately −0.27 volts. 
     
     
         3 . The cathodized gold nanoparticle graphite pencil electrode according to  claim 1 , wherein said AuNP-GPE is cathodized by applying −1.0 volts to said AuNP-GPE for approximately 30 seconds. 
     
     
         4 . The cathodized gold nanoparticle graphite pencil electrode according to  claim 3 , wherein said AuNP-GPE is sensitive to the oxidation of glucose around approximately −0.27 volts. 
     
     
         5 . A method for forming a cathodized gold nanoparticle graphite electrode, comprising the steps of:
 placing a solid graphite member into a tube filled with a prepared solution of L-ascorbic acid (AA) and Gold(III) chloride;   placing the filled tube and solid graphite member combination into a water bath preheated to approximately 75° centigrade (C);   retaining said filled tube and solid graphite member combination in said water bath for approximately 15 minutes to form a gold nanoparticle graphite electrode (AuNP-GPE);   removing said solid graphite member from said tube, said solid graphite member being transformed into said AuNP-GPE;   washing said AuNP-GPE in deionized water;   drying said AuNP-GPE at approximately 60° C. for approximately 5 minutes prior to use; and   cathodizing said AuNP-GPE by placing said AuNP-GPE in a basic solution and applying −1.0 volts to said AuNP-GPE for approximately 30 seconds.   
     
     
         6 . The method for forming a cathodized gold nanoparticle graphite electrode according to  claim 5 , wherein said basic solution is a glucose analyte solution. 
     
     
         7 . The method for forming a cathodized gold nanoparticle graphite electrode according to  claim 5 , wherein said basic solution consists essentially of NaOH. 
     
     
         8 . The method for forming a cathodized gold nanoparticle graphite electrode according to  claim 5 , wherein said basic solution includes NaOH and glucose. 
     
     
         9 . The method for forming a cathodized gold nanoparticle graphite electrode according to  claim 5 , wherein said basic solution consists essentially of a 0.1 molar (M) NaOH including glucose. 
     
     
         10 . The method for forming a cathodized gold nanoparticle graphite electrode according to  claim 5 , further comprising the step of:
 preparing said AA and Gold (III) chloride solution in equal volumes, approximately 1.5 milliliters (ml) of each aqueous solutions of approximately 1.65 millimolar (mM) AA and 1.0 mM Gold(III) chloride, wherein said tube is approximately 3.0 ml in volume.   
     
     
         11 . The method for forming a cathodized gold nanoparticle graphite electrode according to  claim 5 , wherein said solid graphite member is a mechanical pencil lead. 
     
     
         12 . The method for forming a cathodized gold nanoparticle graphite electrode according to  claim 11 , wherein said mechanical pencil lead is a hi-polymer graphite pencil HB grade lead. 
     
     
         13 . The method for forming a cathodized gold nanoparticle graphite electrode according to  claim 11 , further comprising the step of:
 fixing an electrically conductive holder of said mechanical pencil lead vertically with 15 millimeters (mm) of said mechanical pencil lead extruded outside said electrically conductive holder and 10 mm of said mechanical pencil lead immersed in a glucose analyte solution as said basic solution, maintaining a geometric electrode area of approximately 15.90 mm 2 .   
     
     
         14 . The method for forming a cathodized gold nanoparticle graphite electrode according to  claim 5 , wherein placement of said solid graphite member into the tube of AA and Gold(III) chloride chemically deposits gold nanoparticles in the range of 20-85 nanometers (nm) on said solid graphite member. 
     
     
         15 . A method for detecting glucose, comprising the steps of:
 placing a cathodized gold nanoparticle graphite electrode (AuNP-GPE) in a glucose analyte solution; and   performing cyclic voltammetry on the glucose analyte solution using the cathodized AuNP-GPE to detect the glucose.   
     
     
         16 . The method for detecting glucose according to  claim 15 , further comprising the step of:
 using said cathodized AuNP-GPE to record cyclic voltammetry in the glucose analyte solution.   
     
     
         17 . The method for detecting glucose according to  claim 15 , further comprising the step of:
 bubbling argon gas in the glucose analyte solution to remove oxygen from the glucose analyte solution.   
     
     
         18 . The method for detecting glucose according to  claim 17 , wherein the argon gas is bubbled in the glucose analyte solution for approximately 30 minutes to remove oxygen from the glucose analyte solution.