X-ray-activated near-infrared luminescent nanoparticles are considered as new alternative optical probes due to being free of autofluorescence, while both their excitation and emission possess a high penetration efficacy in vivo . Herein, we report silicon carbide quantum dot sensitization of trivalent chromium-doped zinc gallate nanoparticles with enhanced near-infrared emission upon X-ray and UV–vis light excitation. We have found that a ZnGa 2 O 4 shell is formed around the SiC nanoparticles during seeded hydrothermal growth, and SiC increases the emission efficiency up to 1 order of magnitude due to band alignment that channels the excited electrons to the chromium ion.

Chromium-doped spinel crystals show long-lasting emissions in the near-infrared wavelength region. The emission can be activated by X-ray or ultraviolet–visible (UV–visible) light. Such properties make this material a promising candidate for background-free deep-tissue bioimaging, photodynamic or photon-induced therapy, and other applications. Here, we apply hydrothermal synthesis for the preparation of Cr-doped zinc gallate (ZnGa2O4) nanoparticles of small sizes with around 10 nm in diameter, which has the potential to be intravenously introduced to patients. We find that annealing of the as-prepared nanoparticles at 800 °C yields an order of magnitude increase in the emission intensity in the near-infrared wavelength region upon X-ray exposure with favorable long-lasting photoluminescence, which may be directly employed for deep-tissue cancer treatments when combined with IR700-mAb conjugate drug agents. We discuss the effect of annealing on the structural changes and the evolution of Cr defects of 10 nm Cr-doped zinc gallate nanoparticles by imaging techniques and monitoring their magneto-optical signals.