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

Transmissionnear-infrared (NIR) imaging technology has great potentialfor biomedical imaging because of its lower water absorption coefficientand highly reduced photon scattering effect in biological tissuescompared to visible light. The extent of biological tissue photonscattering is inversely proportional to wavelength; therefore, inprinciple, imaging with long-wavelength NIR helps improve the resolutionof the optical image, but deep tissue high-resolution luminescenceimaging is still very challenging technically. Here, we report thediscovery of a Ba2MgWO6:Ni2+ doubleperovskite phosphor that emits broadband long-wavelength NIR (1200-2000nm) under 365 nm near-ultraviolet (UV) excitation, with a full widthat half-maximum of 255 nm. The luminescence quantum efficiency ofthe phosphor with optimized composition reached 16.67%. The analysisof the crystal structure of Ba2MgWO6:Ni2+ suggests that Ni2+ ions preferentially occupythe W6+ site in octahedrons with a weak crystal field,which leads to a large Stokes shift. An as-prepared long-wavelengthNIR pc-LED device was built by packaging an optimized phosphor witha low-power near-UV-LED chip, which was tested to generate clear imagingof venous vessels in human fingers. These unique properties of theBa(2)MgWO(6):Ni2+ double perovskite phosphormakes it a promising application in the field of imaging sources forbody tissue..