A Flexible Electrochemical Biosensor Based on NdNiO₃ Nanotubes for Ascorbic Acid Detection

Flexible and wearable electrochemical biosensors are considered a non-invasive tool for monitoring biological substances, thus attracting attention due to the simple assembly, fast response, ultra-sensitivity, and low cost. Among the substances detected by electrochemical methods, ascorbic acid (AA) stands out, as its presence in the body promotes adequate physiological functions of the immune, central nervous, and circulatory systems, thus preventing and treating various diseases. Herein, this work focuses on the use of nanostructured NdNiO3 compounds in an alternative flexible biosensor for AA detection by electrochemical sensing. Here, 1D nanostructures of NdNiO3 were obtained by wet pore filling of a mesoporous aluminum oxide template. To the best of our knowledge, no electrochemical biosensors using NdNiO3 nanotubes supported onto GO flexible electrodes have been reported for AA or other bioanalyte detection. Next, an electrochemical biosensor for AA was built using a laser-induced graphene (GO) electrode and two different NdNiO3 (NNO) nanotubes, one with an external diameter of 20 nm (NNO20) and the other with 100 nm (NNO100). The size effect and Ni3+/Ni2+ ratio influence on the sensing properties can be verified through electrochemical characterization. The GO/NNO20 and GO/NNO100 biosensors presented a detection range of 30 to 1100 μmol L–1, but the minimum detectable limit (3.8 μmol L–1) and sensitivity (0.031 μA μM–1 cm–2) are significantly better for the GO/NNO100 device. These outstanding results make both devices competitive with other AA devices listed in the literature. We also simulated the biosensors’ real application and verified that these biosensors could detect AA in synthetic sweat and under application of mechanical deformations. Thus, the GO/NNO biosensors showed a promising alternative to the development of real-time monitoring, POC devices, and flexible wearable electrochemical devices to use in AA detection. Future works should address the potential to detect other bioanalytes.