Molten Salt Synthesis of Persistent Luminescent/Magnetic Cr³⁺-Doped Zinc Gallogermanate Particles

Near-infrared persistent luminescent particles are appealing materials for a diverse range of optoelectronic and biomedical applications. Thermal treatment at high temperature (e.g., solid-state annealing process) has been shown to enhance the luminescence intensity of these particles, while it remains a challenge to manipulate the morphology and solution dispersibility. Herein, molten salt in situ synthesis of Cr3+-doped zinc gallogermanate (ZGGO) with well-defined morphology and solution dispersibility is developed in combination with citric acid. In the absence of the physical grinding treatment (e.g., mechanically milling), the resulting ZGGO particles are not only readily dispersible in the aqueous solution but also exhibit enhanced persistent luminescence. The synergetic effects of salt and citric acid on the particle formation process as well as the optical properties are elucidated. Interestingly, these particles also exhibit enhanced ferromagnetism properties, showing promise for multiple optical/magnetic applications. The molten salt synthesis approach demonstrated in this work offers an alternative pathway for producing persistent luminescent particles, and the method may help to improve the synthesis of other complex metal oxide particles.