Synthesis and electrochemical properties of single-walled carbon nanotube–gold nanoparticle composites

We report a facile and environmentally friendly, one-step procedure that allows the aqueous synthesis of a nanocomposite composed of single-walled carbon nanotubes (SWNTs) and gold nanoparticles. In this procedure, chitosan (a nontoxic natural polysaccharide) served as a polymer for wrapping SWNTs, allowing dispersion of SWNTs in aqueous solution, and also functions both as a reducing agent for gold cations and a stabilizing agent for the resulting gold nanoparticles (GNPs). The synthesized GNPs are shown by TEM to coat the side walls of the carbon nanotubes (CNTs). We report UV–vis, Raman, and electrochemical measurements that provide information concerning properties of the resulting nanocomposite. A discussion is provided regarding the use of a film composed of the nanocomposite on a gold electrode to promote the direct electron transfer of immobilized microperoxidase-11 (MP-11). Additionally, our studies indicate that the immobilized MP-11 retains its bioelectrocatalytic activity for the reduction of oxygen.