Valleytronics is a promising paradigm to explore the emergent degree of freedom for charge carriers on the energy band edges. Using ab initio calculations, we reveal that the honeycomb boron nitride (h-BN) monolayer shows a pair of inequivalent valleys in the vicinities of the vertices of hexagonal Brillouin zone even without the protection of the C symmetry. The inequivalent valleys give rise to a 2-fold degree of freedom named the valley pseudospin. The valley pseudospin with a tunable bandgap from deep ultraviolet to far-infrared spectra can be obtained by doping h-BN monolayer with carbon atoms. For a low-concentration carbon periodically doped h-BN monolayer, the subbands with constant valley Hall conductance are predicted due to the interaction between the artificial superlattice and valleys. In addition, the valley pseudospin can be manipulated by visible light for high-concentration carbon doped h-BN monolayer. In agreement with our calculations, the circularly polarized photoluminescence spectra of the BNC sample show a maximum valley-contrasting circular polarization of 40% and 70% at room temperature and 77 K, respectively. Our work demonstrates a class of valleytronic materials with a controllable bandgap.

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Using x-ray diffraction, powder neutron diffraction, high-field magnetization measurement and thermomagnetic analysis, we have studied the structural and magnetic properties of alloys ( R = Sm or Y) made by arc melting, in which the carbon was added using Fe - C alloy. Both samples are found to be nearly single phase with -type structure and with a small amount of -Fe phase (less than 4 wt%). The neutron diffraction of the Y-containing compound indicates that the real composition of the main phase is , and that the carbon atoms occupy not only the interstitial 2b site but also the substitutional 8i site. The Fe moments of the 8i site as well as the 8j site are found to be reduced in the compound compared with its carbon-free counterpart. The decrease in the Fe moment at the 8j site is due to the surrounding interstitial carbon atoms, while the decrease in the Fe moment at the 8i site is ascribed to the surrounding substitutional carbon atoms as nearest neighbours. The high-field magnetization measurements indicate that the anistropy field of and are slightly higher than those of and , respectively. In , the magnetization curve in the hard direction at 4.2 K shows a first-order-magnetization-process (FOMP)-like or quasi-FOMP-like transition.

sym-Dibenzo-16-crown-5-oxyacetic acid and its analogues are selective for the extraction of Y3+ over Sr2+ from aqueous solutions into chloroform. The selectivity and the pH range of extraction are influenced by the structure of the ligand. The size of the macrocyclic cavity, the tether length of the lariat, the attachment of alkyl functional groups to the lariat, and the identity of the ionizable group can affect selectivity and extraction efficiency. When the carboxylic acid at the terminal end of the lariat is replaced by a hydroxamic acid, the selectivity for Y3+ over Sr2+ is significantly increased. Using these ionizable crown ethers as extractants, 90Y fractions of greater than 99.9% purity can be obtained in a single solvent extraction step from solutions of 90Sr.

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