A rime ice-inspired bismuth-based flexible sensor for zinc ion detection in human perspiration

A nature-inspired special structure of bismuth is newly presented as Zn ion sensing layer for high-performance electrochemical heavy metal detection sensor applications. The rime ice-like bismuth (RIBi) has been synthesized using an easy ex situ electrodeposition method on the surface of a flexible graphene-based electrode. The flexible graphene-based electrode was fabricated via simple laser-writing and substrate-transfer techniques. The Zn ion sensing performance of the proposed heavy metal sensor was evaluated by square wave anodic stripping voltammetry after investigating the effects of several parameters, such as preconcentration potential, preconcentration time, and pH of acetate buffer. The proposed RIBi-based heavy metal sensor demonstrated a good linear relationship between concentration and current in the range 100-1600 ppb Zn ions with an acceptable sensitivity of 106 nA/ppb·cm². The result met the requirements in terms of common human perspiration levels (the average Zn ion concentration in perspiration is 800 ppb). In addition, the heavy metal sensor response to Zn ions was successfully performed in human perspiration samples as well, and the results were consistent with those measured by atomic absorption spectroscopy. Besides, the fabricated Zn ion sensor exhibited excellent selectivity, repeatability, and flexibility. Finally, a PANI-LIG-based pH sensor (measurement range: pH 4-7) was also integrated with the Zn ion sensor to form a single chip hybrid sensor. These results may provide a great possibility for the use of the proposed flexible sensor to realize wearable perspiration-based healthcare systems. Graphical abstract.