Nanomaterials, which promote the generation of reactive oxygen species (ROS) and precipitate the onset of oxidative stress responsible for the development of a variety of adverse conditions, have a great prospect for various nanomedicine applications. In this paper, for the first time, we report the pro-oxidant activity of GdYVO 4 :Eu 3+ and GdVO 4 :Eu 3+ nanoparticles (NPs) in water solutions without any external stimuli (in the darkness). This dark pro-oxidant activity is shown to be associated with superoxide (O 2•− ) and hydroxyl radical ( • OH) generation and is dependent on the size of NPs and, consequently, the concentration of surface defects, such as oxygen vacancies V O . For small 2 nm GdYVO 4 :Eu 3+ NPs, strong O 2•− and • OH radical production has been revealed, whereas for larger GdVO 4 :Eu 3+ NPs, low level of O 2•− and negligible level of • OH radical production have been detected during the sample storage in the darkness. The possible mechanisms of the dark ROS generation in ReVO 4 :Eu 3+ NPs are considered.

It this letter, we report the study of free radicals and reactive oxygen species (ROS) generation in water solutions containing gadolinium orthovanadate GdVO4:Eu3+ nanoparticles (VNPs) and their complexes with methylene blue (MB) photosensitizer. The catalytic activity was studied under UV-Vis and X-ray irradiation by three methods (conjugated dienes test, OH· radical, and singlet oxygen detection). It has been shown that the VNPs–MB complexes reveal high efficiency of ROS generation under UV-Vis irradiation associated with both high efficiency of OH· radicals generation by VNPs and singlet oxygen generation by MB due to nonradiative excitation energy transfer from VNPs to MB molecules. Contrary to that under X-ray irradiation, the strong OH. radicals scavenging by VNPs has been observed.Electronic supplementary materialThe online version of this article (10.1186/s11671-018-2514-5) contains supplementary material, which is available to authorized users.

Oxidative stress caused by an overproduction of reactive oxygen species (ROS) is the key factor in developing a variety of pathological conditions. Recently various nanomaterials have attracted growing interest as nanoantioxidants with ROS-regulating ability. Here, for the first time, we report on high antioxidant behavior (enzyme-like activity) of GdYVO4:Eu3+ nanoparticles (GdYVO NPs) revealed by spectroscopic methods both in cell-free and biological milieu using various ROS sensors. It was revealed that GdYVO NPs (d = 2 nm) effectively scavenge hydroxyl radicals · O H , superoxide anions O 2 · − , hydrogen peroxide H 2 O 2 , peroxyl radicals R O O · , and remarkably reduce the lipopolysaccharide-induced ROS generation in rat leukocytes. The antioxidant activity of GdYVO NPs is ascribed to high amount of V4+ and V3+ ions in the structure of the NPs and the reversible switching V 3 + ↔ V 4 + and V 4 + ↔ V 5 + vanadium oxidation states.