A highly sensitive and selective biosensor based on nitrogen-doped graphene for non-enzymatic detection of uric acid and dopamine at biological pH value

Few layered graphene nanosheets were successfully doped with nitrogen through microwave irradiation and thoroughly characterized by using electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. The electrochemical efficiency of N-doped graphene toward enzyme-free detection of uric acid (UA) and dopamine (DA) at neutral pH (7.4) was studied by chronoamperometry and cyclic voltammetry measurements. At working potential of +0.3 V (vs. Ag/AgCl), N-doped graphene electrode revealed ultra-high sensitivity of 2.06 mA mM−1 cm−2 and low limit of detection (LOD) of 0.13 μM within a concentration range of 0 to 0.6 mM for UA detection. Also, at very higher potential of +1.8 V (vs. Ag/AgCl), N-doped graphene sensor exhibited a highly selective response toward DA with very low LOD of 4.5 nM and high sensitivity of 7.63 mA mM−1 cm−2 in a broad linear concentration range from 0.1 to 100 μM. Furthermore, the performance of UA and DA sensors in the real blood sample was satisfactory.