Direct Electrochemistry and Electrocatalysis of Hemoglobin on Aligned Carbon Nanotubes Based Electrodes Modified with Au Nanoparticles and SiO₂ Gel

Abstract

Here we report on the preparation and characterization of new electrodes based on aligned carbon nanotubes (ACNTs) for hemoglobin (Hb) electrochemistry and electrocatalysis. The ACNTs are obtained by a thermal chemical vapor deposition method under normal pressure. Then the electrodes are elaborated by first sputtering a thin Au film (thickness of 200 nm) onto the top of the ACNTs, and then removing the Au layer/ACNTs from the quartz substrate with the aide of hydrofluoric acid (HF) treatment. Field emission scanning electron microscopy (FESEM) demonstrates that after nitric acid (HNO 3 ) treatment, the nanotubes of the removed Au layer are totally tipopened, purified and organized in a perfect vertically aligned architecture. The final ACNTs electrode is obtained by attaching the Au layer of ACNTs onto a glassy carbon electrode. Then the electrode was modified to act as a matrix for hemoglobin (Hb) immobilization and as an electrode for Hb electroanalysis by the assistance of Au nanoparticles (AuNPs) and SiO 2 gel. Due to the individual specific effects of AuNPs, SiO 2 gel and ACNTs, the resulting SiO 2 /Hb-AuNPs/ACNTs electrode showed good direct electrochemistry of Hb with an apparent MichaelisÀ Menten constant of 0.44 mM. The electrode showed an excellent electrocatalytic activity towards H 2 O 2 , possessing a linear range from 40 mM to 4 mM and the detection limit was 22 mM based on a signal to noise ratio of 3.

Direct Electrochemistry of Horseradish Peroxidase on NiO Nanoflower Modified Electrode and Its Electrocatalytic Activity

“…The ks value of 2.97 s -1 was much larger than that of 0.97 s -1 at Nafion/Hb-GR-MWCNT/CILE, [26] 1.14 s -1 at Hb/Chit-IL-Fc/Gr/GCE, [27] 1.17 s -1 at Hb immobilized on SiO2/AuNPs/ACNTs. [28] This ks value indicated that the presence of NiO nanoflower could form a suitable microenvironment that benefit the electron transfer of HRP with electrode. The effect of buffer pH on electrochemical responses of CTS/NiO-HRP/CILE was further investigated in the pH range from 3.0 to 8.0 with the results shown in Figure 5D.…”

Direct electrochemistry and electrocatalysis of hemoglobin on three-dimensional graphene modified carbon ionic liquid electrode

“…[44], which indicated that 3D-GR/CILE could provide a specific microenvironment that was suitable for the fast electron transfer of Hb. By the integration of cyclic voltammetric reduction peaks, the surface concentration ( *) of electroactive Hb on the electrode can be calculated from the equation: Q = nFA * [40], where Q is charge passing through the electrode with full reduction of electroactive Hb, n is the number of electron transferred, F is the Faraday's constant, A is the effective area of electrode.…”

Preparation and electroanalytical applications of vertically aligned carbon nanotubes

“…Another biosensor to determine H 2 O 2 using VACNT, AuNPs, SiO 2 gel and hemoglobin (Hb) (SiO 2 /Hb-AuNPs/VACNT electrode), was proposed by Yang et al 100 The use of AuNPs provided better direct electrochemistry and electrocatalysis of Hb, since the voltammetric response of the Hb's heme Fe(III)/Fe(II) showed a well-defined pair of peaks and higher magnitude of peak currents. Moreover, the use of the SiO 2 gel coating was found to be important to maintain the Hb-AuNP complex immobilised on the VACNT surface.…”