Designing ZIF-67 derived NiCo layered double hydroxides with 3D hierarchical structure for Enzyme-free electrochemical lactate monitoring in human sweat

Emerging wearable devices with non-invasively biosensing technics have drawn considerable attention to continuously monitor several metabolites in body fluids, such as a tear, saliva, and sweat, to diagnose human health conditions. To further boost up the reproducibility and reliability of wearable biosensors to detect lactate concentration levels from human sweat, in this study, ZIF-67 derived NiCo LDH was synthesized as the electrocatalyst for non-enzymatic lactate detection. Co-based ZIF-67 served as self-sacrificial templates to fabricate hierarchically structural NiCo LDH with uniform porosity and high electrochemically active surface area to achieve outstanding electrocatalytic performance for lactate sensing. After optimizing the particle size of ZIF-67 and transformation times, ZIF-67 derived NiCo LDH reached the ultrahigh sensitivity of 83.98 μA mM−1 cm−2 at an applied potential of 0.55 V (vs. Ag/AgCl KCl sat’d) in the concentration range from 2 to 26 mM. Moreover, the lactate concentration difference in the human sweat can be verified under different exercise conditions, namely anaerobic exercise and aerobic exercise, using ZIF-67 derived NiCo LDH modified electrode. Overall, this research provides a potential electrocatalyst for utilizing enzyme-free electrochemical lactate sensors with reliable and stable performance to introduce non-invasive human sweat monitoring on wearable bioelectronics.