Long-Wavelength Near-Infrared Divalent Nickel-Activated Double-Perovskite Ba2MgWO6 Phosphor as Imaging for Human Fingers

Transmission near-infrared (NIR) imaging technology has great potential for biomedical imaging because of its lower water absorption coefficient and highly reduced photon scattering effect in biological tissues compared to visible light. The extent of biological tissue photon scattering is inversely proportional to wavelength; therefore, in principle, imaging with long-wavelength NIR helps improve the resolution of the optical image, but deep tissue high-resolution luminescence imaging is still very challenging technically. Here, we report the discovery of a Ba2MgWO6:Ni2+ double perovskite phosphor that emits broadband long-wavelength NIR (1200-2000 nm) under 365 nm near-ultraviolet (UV) excitation, with a full width at half-maximum of 255 nm. The luminescence quantum efficiency of the phosphor with optimized composition reached 16.67%. The analysis of the crystal structure of Ba2MgWO6:Ni2+ suggests that Ni2+ ions preferentially occupy the W6+ site in octahedrons with a weak crystal field, which leads to a large Stokes shift. An as-prepared long-wavelength NIR pc-LED device was built by packaging an optimized phosphor with a low-power near-UV-LED chip, which was tested to generate clear imaging of venous vessels in human fingers. These unique properties of the Ba2MgWO6:Ni2+ double perovskite phosphor makes it a promising application in the field of imaging sources for body tissue..