Graphene nanoplatelet/graphitized nanodiamond-based nanocomposite for mediator-free electrochemical sensing of urea

Urea is well-known to offer tremendous scope for sensing/diagnosing such as adulteration in dairy products or diseases in human body. This study was organized to describe and validate a new mediator-free, unsophisticated, and direct current voltage (IV)-based sensor for facile detection of urea using nanocomposites made of urease-immobilized graphene nanoplatelets and graphitized nanodiamonds. This nanocomposite displayed sensitive and direct signal in the form of current at 0 V without the need of any complex chemical reaction. This platform was highly sensitive (limit of detection of 5 μg/mL) far superior to the comparable systems introduced recently. The incorporation of graphitized nanodiamonds within the graphene nanoplatelets layers helped improve the sensitivity by a factor of three (up to 806.3 µA (mg mL^-1)^-1 cm^-2) with 20 s response time. As such, the use of this nanocomposite was helpful in improving sensing performances with enhanced enzyme loading capacity.