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Hydrogen boride (HB), a freestanding 2D hydrogenated‐borophene (borophane) polymorph, is synthesized via ion exchange. HB sheets with a B/H atomic ratio of 1.0 are confirmed to contain three‐center–two‐electron B–H–B bonds and two‐center–two‐electron terminal B–H bonds. The optical properties of HB sheets are expected to be tunable by changing the BHB/BH bond ratio, which alters the electronic structure of HB sheets; however, this is not yet achieved. This study demonstrates that controlling the BHB/BH bond ratio in the HB sheets is possible without altering the hydrogen content by adjusting the volume of ion‐exchange resin during synthesis, thus enabling the tuning of the photoinduced H2 release under UV irradiation. Furthermore, the fluorescence intensity correlates with the absorbance ratio of the BHB and BH vibrational modes. Increasing the BHB/BH bond ratio enhances the luminescence intensity, whereas reducing it enhances the photoinduced H2 release rate under UV irradiation. The ability to control the BHB/BH bond ratio of HB sheets provides new avenues for optimizing their properties for various applications, including hydrogen storage and photocatalysis. [ABSTRACT FROM AUTHOR]

We have extensively searched for a cyclic hydrogenated boron molecule that has a three-center two-electron bond at the center. Using first-principles calculations, we discovered a stable molecule of 2:4:6:8:-2H-1,5:1,5-μH-B8H10 and propose its existence. This molecule can be regarded as a building block for sheets of topological hydrogen boride (borophane), which was recently theoretically proposed and experimentally discovered. The electronic structure of the cyclic hydrogenated boron molecule is discussed in comparison with that of cyclic hydrogenated carbon molecules. [ABSTRACT FROM AUTHOR]

The search for free-standing 2D materials has been one of the most important subjects in the field of studies on 2D materials and their applications. Recently, a free-standing monolayer of hydrogenated boron (HB) sheet has been synthesized by hydrogenation of borophene. The HB sheet is also called borophane, and its application is actively studied in many aspects. Here, we review recent studies on the electronic structures of polymorphic sheets of borophane. A hydrogenated boron sheet with a hexagonal boron frame was shown to have a semimetallic electronic structure by experimental and theoretical analyses. A tight-binding model that reproduces the electronic structure was given and it allows easy estimation of the properties of the material. Hydrogenated boron sheets with more complicated nonsymmorphic boron frames were also analyzed. Using the symmetry restrictions from the nonsymmorphic symmetry and the filling factor of hydrogenated boron sheets, the existence of a Dirac nodal line was suggested. These studies provide basic insights for research on and device applications of hydrogenated boron sheets. [ABSTRACT FROM AUTHOR]

A metallic band having the d z 2 -symmetry was evidenced at the interface between a Cs film and the SrTiO 3 (001) substrate. The symmetry assignment was carried out with the dipole-transition selection rule, probed by polarization-dependent photoemission spectroscopy. The e g -derived state of the SrTiO 3 (001) crystal is likely to be a bonding state composed of Cs s -orbital and Ti d -orbital with the e g symmetry, as predicted theoretically. [ABSTRACT FROM AUTHOR]

Time-resolved soft X-ray photoelectron spectroscopy is utilized to determine an energy level alignment and the photoexcited carrier dynamics at a C 60 /TiO 2 (110) interface. The interface electronic structure is characterized by a type II junction, which favors an injection of photoexcited electrons from C 60 to TiO 2 . Ultraviolet (UV) laser pulse irradiation induces transient shifts of both C 1s and Ti 2p core levels towards the higher binding energies. These energy shifts are caused by a laser-induced charge transfer between the C 60 layer and the TiO 2 (110) surface. Upon UV absorption, valence electrons of C 60 are promoted to unoccupied levels, followed by a resonant transfer to TiO 2 , leaving C 60 in a cationized state. On the TiO 2 (110) side, the electrons are injected into the conduction band to raise the carrier density so that downward bending of the TiO 2 band is induced. The UV-excited states of C 60 and TiO 2 have sufficiently longer lifetime than the lifetime of the electron–hole pairs in solid C 60 . The C 60 /TiO 2 (110) interface is, thus, proved to be efficient for separating the electron–hole pairs generated within the C 60 layer. [ABSTRACT FROM AUTHOR]