Preparation of ultra-sensitive UV device for nanomolar-level hydrocortisone detection

The detection of hydrocortisone (cortisol, HC) at physiological concentrations ranging from nanomolar to picomolar levels presents significant technical challenges. Although UV spectroscopy offers rapid and economic analysis, existing detectors lack the necessary sensitivity and exhibit excessive noise for reliable low-concentration measurements. This study introduces an advanced UV photodetector employing a novel vertical architecture of ITO/TiO 2 /Bi 2 O 3 /NiO/AgNWs, enhanced with a pyrolytic hafnium acetylacetonate protective (PHAA) layer. The developed device demonstrates exceptional performance metrics including a detectivity surpassing 1.1×10 11 Jones, an ultralow detection threshold below 1 nW cm −2 , and rapid response times between 9–12 ms. Remarkably, the unencapsulated device maintains outstanding stability with less than 2% performance variation after three months of ambient exposure. Building on this platform, we created an integrated HC detection system that overcomes baseline drift issues through innovative pulse signal design. The system achieves detection limits of 8–16 nmol/L across a broad concentration range, while demonstrating excellent specificity against common interferents (urea, sodium chloride, and other electrolytes) and robust ambient light immunity. These combined advancements establish our photodetector as a transformative solution for next-generation medical HC monitoring systems.