Smartphone light-driven zinc porphyrinic MOF nanosheets-based enzyme-free wearable photoelectrochemical sensor for continuous sweat vitamin C detection

Maintaining normal vitamin C levels is essential for the proper functioning of the body's immune system. The development of real-time non-invasive wearable sensors for monitoring sweat vitamin C holds important promise in guiding personalized health management. Here, we present a smartphone light-driven enzyme-free wearable photoelectrochemical (PEC) sensor based on two-dimensional zinc porphyrinic MOF nanosheets/multi-walled carbon nanotubes (2D-TCPP(Zn)/MCNTs) for the precise monitoring of sweat vitamin C. 2D-TCPP(Zn) nanosheets are prepared with the modulation of the pillared 4,4′-biphenyldicarboxylic acid (BPDC) molecules to form the final square-like structure. After the introduction of MCNTs, the developed 2D-TCPP(Zn)/MCNTs modified screen printing paper electrode exhibits an enhanced cathodic photocurrent response to vitamin C driven by smartphone light due to the effective charge separation with electron injection from 2D-TCPP(Zn) to MCNTs. A low limit of detection (LOD) of 3.61 μM and a wide detection range of 10–1100 μM for vitamin C are achieved. Also, the proposed electrode possesses high selectivity, satisfactory PEC stability and long-time storage stability. Moreover, a novel flexible PEC sensing patch was designed for the effective collection and continuous monitoring of sweat. The smartphone light-driven enzyme-free wearable PEC sensor detects the vitamin C concentration in real sweat with good accuracy, which can help to ensure proper nutritional balance.