Plasmonic-enhanced lanthanide nanotransducers for mid-infrared detection

Advanced mid-infrared (MIR) detection underpins a wide range of applications from chemical sensing to thermal imaging. Conventional MIR photodetectors rely on narrow-bandgap semiconductors that typically require cryogenic cooling, whereas uncooled alternatives suffer from inherently low detectivity. An emerging strategy addresses this trade-off by converting MIR photons into near-infrared or visible (NIR/VIS) emission using lanthanide-based nanotransducers, enabling room-temperature operation. However, practical implementation is hindered by pronounced nonradiative quenching, which limits conversion efficiency and suppresses MIR-induced ratiometric luminescence. Here, we report a plasmonic-enhanced, self-assembled MIR detection platform based on Nd³⁺/Yb³⁺ co-doped NaYF₄ nanoparticles coupled to gold nanospheres. This platform transduces MIR signals into NIR emission detectable by low-cost silicon photodetectors, achieving a room-temperature specific detectivity of 2×10⁹ Jones at 8 μm. Localized surface plasmon resonances generate strongly confined electromagnetic fields that concurrently amplify excitation and emission, delivering a seven-fold boost in specific detectivity relative to pristine nanoparticles. Combining scalable fabrication with silicon-readout compatibility, this plasmonic-assisted approach paves the way for high-performance MIR sensing, imaging, and spectroscopy.