Syntheses Of Nanocomposites And Their Applications In Electrochemical Biosensing

Objective:1.The nano-scale GNPs-Hap composite material was synthesized for the first time with the precipitation method. Due to the particular multi-absorbing sites and well electric power, the nanocomposite material can be used as a novel favorite promoter for the direct electrochemistry of hemoglobin.2.To study the effects of the volume ratio of Hap suspension to GNPs solution on electron transfer speed, and observe the morphology of GNPs-Hap complex material on copper net by SEM.3.To study the influence of solution pH and different scan rates on peak currents and potentials of Hb/GNPs-Hap/GCE.4. To investigate the electrochemical behavior of Hb/GNPs-Hap/GCE, and explor the catalysis ability of Hb/GNPs-Hap/GCE on hydrogen peroxide. Methods:1.An aqueous solution of H₃PO₄ was added dropwise to stirred vigorously aqueous solution of Ca(OH)₂ at 60℃, and the pH of the resulting suspension was adjusted to pH 7.0. After aging, washing, filtration and centrifugation, the HAP nanotubes could be formed at 100℃in vacuum. Adding Na3-citrate solution to a boiling solution of 0.01 % HAuCl₄ and maintaining the mixture at the boiling point for 15min and stirred. Finally, mix a suspension of Hap nanotubes and the prepared Au colloid solution with sonication for 10 min.2. To study the UV-Vis spectra of Hb/GNPS-Hap,Hb and GNPs-Hap dispersing in water by UV-Vsi-3600-Nir spectrophotometer. And to obtain the cyclic voltammograms of Hb/GNPs-Hap,Hb/Hap,Hb/GNPs,GNPs-Hap in 0.1 mol/L pH 7.0 PBS at 100 mV/s.3. To investigate the effect of solution pH on the direct electrochemistry of the immobilized Hb. And in the optimized pH, to observe the relationship of scan rate and peak current.4.The Cyclic voltammograms of Hb/GNPs-Hap/GCE in 0.1 mol/L pH 7.0 PBS containing different H₂O₂ concentration and typical current-time response curve of the biosensor upon successive additions of different amounts of H2O2 into 0.1 mol/L pH 7.0 PBS at applied potential of–372 mV. Results:1. Considering the stable film of GNPs-Hap nanocomposite with high carrying capacity, the volume ratio of 1:1 was used for the preparation of GNPs-Hap nanocomposite in whole experiment. The morphology of GNPs-Hap nanocomposite film which was also characterized by SEM, GNPs can strongly adsorb on the surface of Hap to form a uniform,porous structure. The configuration increased the carrying capacity of Hemoglobine.2.From the UV-Vis spectra of Hb/GNPS-Hap,Hb and GNPs-Hap in water,it can be seen that both films containing Hb displayed a maximum absorption at 405.78 nm. The phenomenon showed the Hb had mixed in the nancomposite film retained its natural secondary structure. So, GNPs-Hap nanocomposite film provided a good matrix for Hb immobilization and kept the good biocompatibility. From the cyclic voltammograms of Hb/GNPs-Hap,Hb/Hap,Hb/GNPs,GNPs-Hap , it can be seen that the GNPs-Hap nanocomposite coating showed a synergistic effect between GNPs and Hap nanotubes for accelerating the surface electron transfer of Hb.3.The cyclic voltammeter peak currents and peak potentials of hemoglobin was changed reversible along with different pH and the plot of formal potential versus pH showed a slope of–51 mV pH-1. It was proved that electrode reaction was one-electron coupled one-proton reaction process. And with an increasing scan rate ranging from 10 to 1000 mV/s, the reduction and oxidation peak currents increased linearly, indicated that the redox process was typical surface-controlled process.4. In the optimal experiment condition, a new biosensor Hb/GNPs-Hap/GCE for hydrogen peroxide with a linear range from 0.5 to 25μM and a limit of detection of 0.2μM. The hydrogen peroxide biosensor possessed favorable repeatability and stability.Conclusion:1 . Hap nanotubes with good biocompatibility and particular multi-adsorbing sites, mixed with GNPs specifically proportion. The new nanocomposite of GNPs-Hap was synthesized, had got characteristic of uniform,porous external frame and owned the property of high surface area and satisfactory biocompatibility. These characters kept native configuration of Hb, but also greatly accelerated the direct electron transfer.2. Owing to the good biocompatibility of the nanocomposite, the as-prepared Hb/GNPs-Hap/GCE displays high electrocatalytic performance toward reduction of H₂O₂ with fast response and the biosensor shows good stability and acceptable repeatability.