Synthesis of Au-MWCNT-Graphene hybrid composite for the rapid detection of H2O2 and glucose

We report the fabrication of a novel amperometric biosensor based on narrow sized Au nanoparticles (similar to 4 nm) decorated multiwalled carbon nanotube-solar exfoliated graphene (MWCNTs-sG) hybrid composite as an enzyme immobilizer and sensing matrix for hydrogen peroxide (H2O2) and glucose. Au nanoparticles decorated MWCNTs-sG hybrid composite was synthesized by a green technique using focused solar radiation and was then characterized. The fabricated biosensor displays good catalytic response toward H2O2 redox reaction with wide linearity ranging from 1 mM to 62 mM and with fast amperometric response at a response time of <1 s. The limit of detection is calculated to be 13 mu M (S/N 3). When employed for enzymatic glucose detection, the sensor shows excellent fast response with a response time of similar to 0.1 s toward glucose over a concentration range from 50 mu M to 20 mM with a detection limit of 2.48 mu M. Using Michaelis-Menton enzyme kinetics, the apparent Michaelis-Menton constant (K-m) is estimated to be 1.07 mM which depicts high affinity of the enzyme biosensor toward substrate. This is because of the synergistic combination of small sized Au nanoparticles on graphene layers in the presence of MWCNTs as conducting spacer which in turn enhances the electrochemically active surface area. This favors better enzyme immobilization on the hybrid material and promotes direct electron transfer mechanism. In addition, the biosensor shows satisfactory selectivity over coexisting interference species, such as UA, AA, DA, and good reproducibility. On the basis of easy large-scale green synthesis technique of the sensor material, its ultrafast response, wide range of linearity and low detection limit, the present biosensor promises potential applications in electrochemical biosensing.