Aseries of assembled Pt II complexes comprising Nheterocyclic carbene and cyanide ligands was constructed using different substituent groups,[ Pt(CN) 2 (R-impy)] (R-impyH + = 1-alkyl-3-(2-pyridyl)-1H-imidazolium, R = Me (Pt-Me), Et (Pt-Et), i Pr (Pt-i Pr), and t Bu (Pt-t Bu)). All the complexes exhibited highly efficient photoluminescence with an emission quantum yield of 0.51-0.81 in the solid state at room temperature,originating from the triplet metal-metal-toligand charge transfer (3 MMLCT) state.Their emission colors cover the entire visible region from red for Pt-Me to blue for Pt-t Bu.I mportantly, Pt-t Bu is the first example that exhibits blue 3 MMLCT emission. The 3 MMLCT emission was proved and characterized based on the temperature dependences of the crystal structures and emission properties.T he wide-range color tuning of luminescence using the 3 MMLCT emission presents an ew strategy of superfine control of the emission color.

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An exclusive advantage of semiconductor spintronics is its potential for optospintronics that will allow integration of spin-based information processing/storage with photon-based information transfer/communications. Unfortunately, progresses have so far been severely hampered by the failure to generate nearly fully spin-polarized charge carriers in semiconductors at room temperature. Here, we demonstrate successful generation of conduction electron spin polarization exceeding 90% at room temperature without a magnetic field in a non-magnetic all-semiconductor nanostructure, which remains high even up to 110°C. This is accomplished by remote spin filtering of InAs quantum-dot electrons via an adjacent tunneling-coupled GaNAs spin filter. We further show that the quantum-dot electron spin can be remotely manipulated by spin control in the adjacent spin filter, paving the way for remote spin encoding and writing of quantum memory as well as for remote spin control of spin-photon interfaces. This work demonstrates the feasibility to implement opto-spintronic functionality in common semiconductor nanostructures.

Electric field control of spin polarity in spin injection into InGaAs quantum dots (QDs) from a tunnel-coupled quantum well (QW) was studied. The degree of freedom of the spin state in high-density QDs will play an important role in semiconductor spintronics such as a spin-functional optical device, where it is crucial to establish spin injection and manipulation by electric fields. To solve this subject in a layered device structure, electric field effects on spin injection from a 2-dimensional QW into 0-dimensional QDs were studied. Spin-polarized electrons were photo-excited in a QW and then injected into QDs via spin-conserving tunneling. After the injection, parallel spin states to the initial spin direction in the spin reservoir of QW were observed in QDs as a result of efficient spin injection, by circularly polarized photoluminescence indicating spin states in the QDs. Moreover, reversal of spin polarity was clearly observed at QD ground states, depending on the electric fields applied along the QD-QW growth direction. The tunneling rate of an electron is different from that of a hole and largely depends on the electric field, owing to electric field induced modifications of the coupled QD-QW potential. This results in negative trions in the QDs with anti-parallel spins to the initial ones in the QW, which is evidently supported by a significant effect of p-doping. The polarization degrees of both spin polarities can be optimized by excitation-spin density, in addition to the electric field strength.

We report on changes of surface structures induced by hydrogen adsorption on a Jahn-Teller distorted magnetite (Fe3O4)(001) surface and priorities of hydrogen-adsorbed sites by means of in-situ scanning tunneling microscopy. The experiments have revealed that surface Fe cations relax toward the bulk-terminated positions by OH species formed between adsorbed-hydrogen and surface ON anion (The labeled "N"in ON denotes that the O-O distance in the surface is compressed compared with bulk). Moreover, two types of surface ON sites were found to be almost equivalent for hydrogen adsorption.