High-brightness transition metal-sensitized lanthanide near-infrared luminescent nanoparticles

The demand for near-infrared (700–1,700 nm) materials in optical communications, laser sources and biological imaging applications has led to extensive research on lanthanide-doped nanoparticles, owing to their nanostructure modulation and interface property tunability. However, the low molar extinction coefficient of conventional lanthanide sensitizers limits the brightness of lanthanide near-infrared nanoparticles for applications in low-power excitation scenarios. Here we introduce Na₃CrF₆, a new crystalline nanoparticle that serves as both sensitizer and host for high-brightness near-infrared emission from lanthanide activators (Er³⁺, Tm³⁺, Yb³⁺ or Nd³⁺). We demonstrate an increase in brightness of up to 370 times compared with the most intense conventional lanthanide-sensitized nanoparticles. This discovery is also validated for other lanthanide-doped nanoparticles sensitized with low-cost transition metals (Mn²⁺ or Ni²⁺). Our transition metal-based nanoparticles represent a powerful toolbox to enable high signal-to-noise-ratio labelling and imaging with low-power excitation sources such as white light-emitting diode or persistent luminescence materials. This work paves the way for next-generation high-brightness near-infrared luminescence systems, suited for a wide range of low-illumination excitation applications.