Nickel nanoparticle-chitosan-reduced graphene oxide-modified screen-printed electrodes for enzyme-free glucose sensing in portable microfluidic devices.

A facile one-step strategy is reported to synthesize nanocomposites of chitosan-reduced graphene oxide-nickel nanoparticles (CS-RGO-NiNPs) onto a screen-printed electrode (SPE). The synthesis is initiated by electrostatic and hydrophobic interactions and formation of self-assembled nanocomposite precursors of negatively charged graphene oxide (GO) and positively charged CS and nickel cations (Ni(2+)). The intrinsic mechanism of co-depositions from the nanocomposite precursor solution under cathodic potentials is based on simultaneous depositions of CS at high localized pH and in situ reduced hydrophobic RGO from GO as well as cathodically reduced metal precursors into nanoparticles. There is no need for any pre- or post-reduction of GO due to the in situ electrochemical reduction and the removal of oxygenated functionalities, which lead to an increase in hydrophobicity of RGO and successive deposition on the electrode surface. The as-prepared CS-RGO-NiNPs-modified SPE sensor exhibited outstanding performance for enzymeless glucose (Glc) sensing in alkaline media with high sensitivity (318.4µAmM(-1)cm(-2)), wide linear range (up to 9mM), low detection limit (4.1µM), acceptable selectivity against common interferents in physiological fluids, and excellent stability. A microfluidic device was fabricated incorporating the SPE sensor for real-time Glc detection in human urine samples; the results obtained were comparable to those obtained using a high-performance liquid chromatography (HPLC) coupled with an electrochemical detector. The excellent sensing performance, operational characteristics, ease of fabrication, and low cost bode well for this electrochemical microfluidic device to be developed as a point-of-care healthcare monitoring unit.