Janus-Faced Redox Activity of LnVO₄:Eu³⁺ (Ln = Gd, Y, and La) Nanoparticles

We report Janus-faced redox activity (pro- and anti-oxidant action) of LnVO 4:Eu 3+ (GdYVO 4:Eu 3+, GdVO 4:Eu 3+, and LaVO 4:Eu 3+ ) nanoparticles (NPs), which was revealed at different external conditions. Redox properties of LnVO 4:Eu 3+ NPs have been studied in water solutions and lipid suspensions, which mimic a biological environment, at UV and X-ray irradiation and during storage at high temperatures (lipid autoxidation conditions). It was shown that under UV irradiation, NPs increase sufficiently the reactive oxygen species (ROS) amount in the water solutions and lipid suspensions because of NP photocatalytic properties. Energies of valence band ( E v ) and conduction band ( E c ) edges for LnVO 4:Eu 3+ NPs were calculated using Portier’s empirical equations. Analysis of E v and E c values and redox potential for H 2 O/ • OH and O 2 /O 2 •– reactions indicates that the generation of these ROS is thermodynamically favorable. For the first time, the ROS scavenging ability of LnVO 4:Eu 3+ NPs at X-ray irradiation and at high temperature storage has been observed. The mechanism of ROS scavenging has been discussed. Our finding is a step to get a deeper understanding of the mechanism of NP redox activity for taking greater advantage of this type of nanomaterials with a Janus-faced action for diverse therapeutic applications.