Boosting near-infrared-triggered photon upconversion in optical nanomaterials via lanthanide-doped nanoparticle sensitization†

A broad spectrum of optical nanomaterials, including organic molecules, quantum dots, and metallic nanoparticles, has attracted great attention in fields such as biological imaging, data storage, solid-state lasers and solar energy conversion owing to their nonlinear optical properties facilitated by the two-photon absorption process. However, their nonlinear optical properties, particularly photon upconversion triggered using near-infrared light, are constrained by a limited multiphoton absorption cross-section, requiring a costly pulsed laser with high-density excitation. Herein, we present a straightforward and versatile strategy to enhance upconversion luminescence in various optical nanomaterials via sensitization with lanthanide-doped nanoparticles. This approach not only broadens the near-infrared responsivity of these luminescent nanomaterials but also introduces novel emission profiles to lanthanide-doped nanoparticles, enabling multidimensional tunability in terms of wavelength, lifetime, and polarization under low-density excitation. Concentration-dependent photoluminescence spectra and decay curves reveal a radiative energy transfer upconversion mechanism. These findings provide a general strategy for controlling photon upconversion in a wide range of luminescent nanomaterials, paving the way for innovative and versatile applications in diverse fields.