Single Walled Carbon Nanotube Sandwiched Ni-Ag Hybrid Nanoparticle Layers for the Extraordinary Electrocatalysis toward Glucose Oxidation

Single walled carbon nanotube (SWCNT) sandwiched Ni-Ag hybrid nanoparticle layers were developed as electrocatalyst for glucose (Glu) oxidation. By mixing the carboxylated SWCNTs and Ni/Ag ions, Ni/Ag ions were easily adsorbed on both sides of SWCNTs in good order due to the electrostatic interaction between them, forming the Ni/Ag ion doubly adsorbed SWCNTs. Once the electrode modified with Ni/Ag ion doubly adsorbed SWCNTs was immersed in Ni-Ag solution, the Ni/Ag ion doubly adsorbed SWCNTs were immediately surrounded by a large amount of Ni/Ag ions. As the electrodeposition started, the Ni/Ag ions pre-adsorbed on the walls of SWCNTs were first reduced to very small particles as seeds to induce the further growth of Ni-Ag nanoparticles (NPs) on SWCNTs (seed-induced effect), forming the SWCNTs sandwiched Ni-Ag hybrid nanoparticle layers. Compared with the electrodeposition of Ni-Ag on bare GCE, the proposed Ni-Ag/SWCNTs composite was greatly improved in many properties like the particle size of Ni-Ag NPs, the hydrophilicity, the electron transfer ability and the electrocatalytic activity. For Glu electro-oxidation, Ni-Ag/SWCNTs/GCE demonstrated extraordinary electrocatalytic performance where the good linear current responses were obtained in two Glu concentration ranges of 0-2.5 mM and 0-350 mu M with correlation coefficients (R-2) of 0.9935 and 0.9985. A high sensitivity of 2946 mu A mM(-1) cm(-2) was achieved with the proposed Ni-Ag/SWCNTs based sensor. More importantly, three excellent linear relations were also achieved in the ranges of 0-11 mu M, 10-90 mu M and 170-350 mu M with R-2 as high as 0.9999 and the detection limits of 0.094, 0.076 and 0.062 mu M, respectively. The new method was successfully applied to Glu detection in blood samples with preferable accuracy and precision. (C) 2015 Elsevier Ltd. All rights reserved.