Broadband SWIR emission through Cr3+-Ni2+ energy transfer in YAGG fluorescent ceramics for bioimaging applications

Abstract

Short-wave infrared (SWIR) light in the 1000–1700 nm range has high penetration capability through biological tissues and is non-destructive, making it widely used in biomedical applications and near-infrared imaging. Currently, the development of SWIR light sources is urgently needed. This paper discusses the luminescent properties of the near-infrared emitting transition metal ions Cr3+ and Ni2+. By using the traditional high-temperature solid-state method, we successfully synthesized YAGG:3.5 %Cr3+-0.5 %Ni2+ (YAGG:Cr-Ni) garnet-based phosphor ceramic in one step. The phosphor ceramic emits ultra-broadband NIR-I (600–900 nm, FWHM=131 nm) and SWIR (1100–1700 nm, FWHM=377 nm) light when excited by a 450 nm commercial blue LED. Position analysis combined with density functional theory (DFT) simulation confirmed the effective substitution of luminescent center ions for the [Al/GaO6] sites. Spectral and lifetime analyses further verified the energy transfer process between Cr3+ and Ni2+ is dipole-quadrupole interaction. Additionally, this phosphor ceramic has a high thermal conductivity of 8.018 W·m⁻¹·K⁻¹ at room temperature. Finally, SWIR pc-LED devices were fabricated by packaging the phosphor ceramic with a 450 nm commercial blue LED, achieving skeletal and venous imaging of biological tissues up to 20 mm thick, providing a new approach for the development of SWIR devices.