VIS-to-UVC upconversion of Pr³⁺-doped fluoride nano- and microcrystals for inactivation of human viruses

In a view of viral infections emerging and re-emerging worldwide, a development of unconventional virus disinfection methods is of great importance. Light in the deep ultraviolet range (UVC) is widely used for germs disinfection, which is mostly associated with a photoinduced damage of nucleic acids. Praseodymium(III)-doped silicate materials emitting upconversion (UC) luminescence in UVC range under visible (VIS) excitation have been recently reported, revealing antiviral and antibacterial activities. In this work, we report synthesis of a series of Pr³⁺-doped fluoride (NaYF₄ and LiYF₄) nanoparticles (NPs) and microcrystals (MCs) using wet chemistry techniques. The synthesized NPs and MCs are different in size, internal structure, doping composition and manifest UC photoluminescence (PL) in UVC range (at ~ 255–275 nm) under VIS excitation. Based on the results of PL spectroscopy and the essay on UVC UC PL-induced DNA degradation, the most promising LiYF₄ and NaYF₄ NPs and MCs were selected and their antiviral efficacy was evaluated toward two types of human viruses: (I) the enveloped virus—herpes simplex virus, HSV-1, and (II) the naked virus—adenovirus type 5, HAdV-C5. The experiments on photoactivated disinfection revealed a great potential of Pr³⁺-doped fluoride NPs and MCs for inactivation of human viruses. Under laser exposure, all tested materials showed a high virucidal efficacy, especially against HAdV-C5 adenovirus: the adenovirus inactivation capacity by the NPs and MCs was shown to be up to ≥ 99.99%. The presented proof-of-concept studies open new perspectives for nano- and micro-sized fluoride materials, paving the way to the design and development of light-activated self-disinfecting surfaces and fabrics with sterilizing properties.