An Ultrasensitive SPR biosensor for RNA detection based on robust GeP₅ nanosheets

Ultrasensitive and rapid detection of biomarkers is among the upmost priorities in promoting healthcare advancements. Improved sensitivity of photonic sensors based on two-dimensional (2D) materials have brought exciting prospects for achieving real-time and label-free biosensing at dilute target concentrations. Here, we report a high-sensitivity surface plasmon resonance (SPR) RNA sensor using metallic 2D GeP₅ nanosheets as the sensing material. Theoretical evaluations revealed that the presence of GeP₅ nanosheets can greatly enhance the plasmonic electric field of the Au film thereby boosting sensing sensitivity, and that optimal sensitivity (146° RIU^-1) can be achieved with 3-nm-thick GeP₅. By functionalizing GeP₅ nanosheets with specific cDNA probes, detection of SARS-CoV-2 RNA sequences were achieved using the GeP₅-based SPR sensor, with high sensitivity down to a detection limit of 10 aM and excellent selectivity. This work demonstrates the immense potential of GeP₅-based SPR sensors for advanced biosensing applications and paves the way for utilizing GeP₅ nanosheets in novel sensor devices.