Malyukin Yuri, Klochkov Vladimir, Maksimchuk Pavel, Seminko Vladyslav, Spivak Nikolai
Institute for Scintillation Materials, National Academy of Sciences of Ukraine, 60 Nauky Ave, Kharkiv, 61001, Ukraine.
Zabolotny Institute of Microbiology and Virology, National Academy of Sciences of Ukraine, 154 Akademika Zabolotnogo St, Kyiv, 03680, Ukraine.
Nanoscale Res Lett. 2017 Oct 13;12(1):566. doi: 10.1186/s11671-017-2339-7.
The redox performance of CeO nanocrystals (nanoceria) is always accompanied by the switching of cerium oxidation state between Ce and Ce. We monitored Ce → Ce oxidation of nanoceria stimulated by oxidant in aqueous colloidal solutions controlling the luminescence of Ce ions located at different distances from nanoceria surface. The observed Ce luminescence changes indicate that Ce → Ce reaction develops inside nanoceria being triggered by the diffusing oxygen originated from the water splitting on oxidized nanoceria surface. We present the first observation of the pronounced oscillations of Ce luminescence intensity arising from Ce ↔ Ce reversible switching. This threshold effect is to be driven by uptaking and releasing oxygen by nanoceria, when the concentration of oxygen vacancies in nanoceria lattice, oxidant concentration in colloidal solution, and temperature reach certain critical values. So, the ability of nanoceria to uptake and release oxygen depending on the environmental redox conditions really makes it the self-sufficient eternal antioxidant.
CeO纳米晶体（纳米氧化铈）的氧化还原性能总是伴随着铈的氧化态在Ce³⁺和Ce⁴⁺之间切换。我们在水胶体溶液中监测了由氧化剂刺激的纳米氧化铈的Ce³⁺→Ce⁴⁺氧化过程，控制位于距纳米氧化铈表面不同距离处的Ce³⁺离子的发光。观察到的Ce³⁺发光变化表明，Ce³⁺→Ce⁴⁺反应在纳米氧化铈内部发生，由源自氧化纳米氧化铈表面水分解的扩散氧引发。我们首次观察到由Ce³⁺↔Ce⁴⁺可逆切换引起的Ce³⁺发光强度的明显振荡。当纳米氧化铈晶格中的氧空位浓度、胶体溶液中的氧化剂浓度和温度达到某些临界值时，这种阈值效应由纳米氧化铈吸收和释放氧驱动。因此，纳米氧化铈根据环境氧化还原条件吸收和释放氧的能力确实使其成为自给自足的永恒抗氧化剂。
