Nitrogen-Doped Graphene Quantum Dots Incorporated into MOF-Derived NiCo Layered Double Hydroxides for Nonenzymatic Lactate Detection in Noninvasive Biosensors

Rapid interest in identifying specific biomarkers has been sparked by the development of wearable electrochemical sensors for physiological and biological monitoring via noninvasive measurement. During anaerobic metabolic circumstances, monitoring the lactate content become critical for noninvasive diagnostic of hypoxia. To improve the sensitivity of wearable sweat biosensors for detecting lactate concentrations, in this study, metal–organic framework (MOF)-derived NiCo-based layered double hydroxides (m-NiCo LDHs) with N-doped graphene quantum dots (NGQDs) decoration are designed. According to the X-ray absorption spectroscopy (XAS) analysis, the incorporation of NGQDs will alter the local electronic structure of transition metals in m-NiCo LDHs, thereby reducing the charge transfer resistance and accelerating the electron transfer kinetics during electrochemical reactions of lactate detection. After understanding the role of NGQDs in the matrix of m-NiCo LDHs, as-designed NGQD/m-NiCo LDH-based electrochemical biosensors for lactate detection displayed superior sensitivity of 62.63 ± 1.50 μA mM–1 cm–2 under an applied potential of 0.60 V (vs Ag/AgCl/3 M KCl) with the lactate concentration range of 0 to 15 mM in alkaline condition, compared to pristine NiCo LDH (16.77 ± 1.70 μA mM–1 cm–2)- and m-NiCo LDH (45.45 ± 4.39 μA mM–1 cm–2)-based ones. This research provides a potential electrocatalyst of GQD-modified MOF-derived LDHs for using enzyme-free electrochemical lactate sensors with reliable and stable performance in order to implement noninvasive human perspiration monitoring on wearable bioelectronics.