Non-enzymatic electrochemical detection of hemoglobin via analyte-triggered in situ phase transformation of β-Ni(OH)2 nanosheets

Abstract

Haemoglobin (Hb) is the principal diagnostic biomarker for anemia, which affects over one billion people globally and poses a critical public health burden in low- and middle-income countries. Rapid, and affordable methods for Hb quantification are urgently needed for point-of-care (POC) deployment in resource-limited settings. Here, we report a mediator-free, non-enzymatic electrochemical sensor for Hb based on surfactant-free β-Ni(OH)₂ nanosheets synthesised by a simple hydrothermal route. The hexagonal β-Ni(OH)₂ exhibits a surface enriched with positively charged sodium ions, which promotes electrostatic attraction of negatively charged Hb and triggers the in situ generation of an α-Ni(OH)₂ layer on its surface. The resulting dynamic interplay between α- and β-Ni(OH)₂ confers enzyme-like electrocatalytic properties upon the β-Ni(OH)₂ electrode. The proposed sensor operates over a linear detection range of 0.001–0.7 µM, with a limit of detection (LOD) of 100 nM and a response time of approximately 0.1 s. The sensor was validated against clinical reference values using real human blood from healthy and diabetic volunteers, confirming its potential for Hb monitoring.