Tokyo University of Science

About: Tokyo University of Science is a education organization based out in Tokyo, Japan. It is known for research contribution in the topics: Thin film & Enantioselective synthesis. The organization has 15800 authors who have published 24147 publications receiving 438081 citations. The organization is also known as: Tōkyō Rika Daigaku & Science University of Tokyo.

Ratiometric near-infrared fluorescence nanothermometry in the OTN-NIR (NIR II/III) biological window based on rare-earth doped β-NaYF4 nanoparticles

Abstract: A novel nanothermometer based on over-1000 nm (OTN) near-infrared (NIR) emission of rare-earth doped ceramic nanophosphors (RED-CNPs) was developed for temperature measurement in deep tissue. Hexagonal-phase β-NaYF4 nanoparticles co-doped with Yb3+, Ho3+, and Er3+ (NaYF4:Yb3+,Ho3+,Er3+ NPs) were synthesized and used as a nanothermometer. The NaYF4:Yb3+,Ho3+,Er3+ NPs displayed two OTN-NIR emission peaks in the second (NIR-II) (at 1150 nm of Ho3+) and third (NIR-III) (at 1550 nm of Er3+) biological window regions under NIR (980 nm) excitation in the first (NIR-I) biological window region. Oleic acid (OA) capped NaYF4:Yb3+,Ho3+,Er3+ NPs were dispersed in non-polar media, i.e., cyclohexane, and showed a temperature-dependent intensity ratio of the emission peaks of Ho3+ and Er3+ (IHo/IEr). The temperature-dependent IHo/IEr of the OA-NaYF4:Yb3+,Ho3+,Er3+ NPs was also evident through imitation tissue. The surfaces of the NaYF4:Yb3+,Ho3+,Er3+ NPs were modified with a poly(ethylene glycol) (PEG)-based block copolymer. The PEGylated NaYF4:Yb3+,Ho3+,Er3+ NPs were dispersed in water and emitted strong NIR-II and III emissions under NIR-I excitation. The PEGylated NaYF4:Yb3+,Ho3+,Er3+ NPs were injected into mice via the tail vein, and the OTN-NIR emissions of the PEGylated NaYF4:Yb3+,Ho3+,Er3+ NPs from the mouse blood vessels were clearly observed using an OTN-NIR fluorescence in vivo imaging system. In a polar media, water, the IHo/IEr of PEGylated NaYF4:Yb3+,Ho3+,Er3+ NPs was inversely related to the temperature. In both non-polar and polar media, the IHo/IEr values of the NaYF4:Yb3+,Ho3+,Er3+ NPs were almost linearly dependent on the temperature. The obtained NaYF4:Yb3+,Ho3+,Er3+ NPs are promising as a novel fluorescent nanothermometer for deep tissue.

Polarization anisotropy of X-ray atomic factors and `forbidden' resonant reflections

Abstract: Symmetry and physical aspects of `forbidden' reflections excited by a local polarization anisotropy of the X-ray susceptibility are surveyed. Such reflections are observed near absorption edges where the anisotropy is caused by distortions of the atomic electronic states owing to interaction with neighbouring atoms. As a consequence, they allow for extracting nontrivial information about the resonant atom's local environment and their physical conditions. The unusual polarization properties of the considered reflections are helpful to distinguish them from other types of `forbidden' reflections. When such reflections are excited, it is, for example, possible to determine not only the intrinsic anisotropy of an atomic form factor but also additional anisotropy induced by thermal motion, point defects and/or incommensurate modulations. Even the local `chirality' of atoms in centrosymmetric crystals is accessible. Unsolved key problems and possible future developments are addressed.