Impact of Eu3+ Ions on Pro-oxidant Activity of ReVO4:Eu3+ Nanocrystals

In the present paper, we analyze the impact of doping of GdYVO4 and LaVO4 nanoparticles (NPs) with Eu3+ ions on their redox properties, in particular, dark reactive oxygen species (ROS) generation ability. Using an optical spectroscopy technique, absorption and fluorescence spectra of GdYVO4:Eu(3+ )and LaVO4:Eu3+ nanoparticles before and after UV-light pretreatment were analyzed. Using fluorescence probe molecules specific for superoxide anion (O-2(center dot-)) and hydroxyl radicals (center dot OH), as well as a nonspecific ROS sensor, the efficiency of the dark ROS generation for GdYVO4:Eu3+ and LaVO4:Eu3+ NPs were studied and compared with those for pure GdYVO4 and LaVO4 NPs. It was revealed that in small GdYVO4:Eu3+ (d = 2 nm) NPs, UV-light pretreatment causes Eu(3+ )reduction to Eu2+. Electrons stored in Eu2+ participate in electron transfer reactions with oxygen molecules producing O-2(center dot-) and other ROS that enhances the total efficiency of the dark ROS generation as compared to pure GdYVO4 NPs. For larger LaVO4:Eu3+ NPs (10 X 80 nm), the process of Eu3+ reduction is not effective due to Eu3+ location far from the surface of LaVO4:Eu3+ NPs that requires more energy to create oxygen vacancy V-o for reduced Eu2+ ion stabilization.

Automated summary

This paper analyzes the impact of doping of GdYVO4 and LaVO4 nanoparticles with Eu3+ ions on their dark reactive oxygen species (ROS) generation efficiency. It was found that UV light pretreatment can enhance the dark ROS generation efficiency in small GdYVO4:Eu3+ nanoparticles through Eu3+ reduction to Eu2+. However, in larger LaVO4:Eu3+ nanoparticles, the process of Eu3+ reduction is not as effective due to the energy required to stabilize the reduced Eu2+ ion.