Glucose biosensor based on multiwalled carbon nanotubes grown directly on Si

An amperometric biosensor based on covalent immobilization of glucose oxidase (GOx) on multiwalled carbon nanotubes (MWCNTs) with potassium ferricyanide as the redox mediator was developed. The MWCNTs were grown directly on a layered structure of Co/Ti/Cr on a SiO2/Si substrate by microwave-heated chemical vapor deposition. The mediator helps to shuttle the electrons between the immobilized GOx and the MWCNT electrode, therefore operating at a potential of 0.25 V vs. the saturated calomel electrode. This potential precludes the interfering compounds from oxidization. The sensitivity of biosensors to glucose was found to depend on the acid pretreatment and GOx reaction times. The steady-state response of the optimized biosensor exhibits a sensitivity of 20.6 μA mM−1 cm−2, a linear range of up to 8 mM, and a response time of <5 s.