Conduction Band and Defect Engineering for the Prominent Visible-Light Responsive Photocatalysts.

Controlling trap depth is crucial to improve photocatalytic activity, but designing such crystal structures has been challenging. In this study, we discovered that in 2D materials like BiOCl and Bi4NbO8Cl, composed of interleaved [Bi2O2]2+ and Cl- slabs, the trap depth can be controlled by manipulating the slab stacking structure. In BiOCl, oxygen vacancies (VO) create deep electron traps, while chlorine vacancies (VCl) produce shallow traps.

Observation of THz surface waves escaping from metal gratings through a dielectric substrate.

Extensive research has been conducted on generating THz waves using Smith-Purcell radiation, yet a portion of the electron bunch's interaction energy with the gratings is confined to the metal gratings' surface, leading to a low THz radiation power. This paper experimentally demonstrates that metal gratings with a dielectric substrate can emit the resonant modes in surface waves when excited by relativistic femtosecond electron bunches. The observed spectra of the resonant THz waves align well with the theoretical estimations derived from the configuration's dispersion relation and 3D simulations.

Complex anisotropy ratio of third harmonic generation in a semiconductor using a terahertz free electron laser.

The nonlinear susceptibility in the terahertz region is expected to have a non-negligible imaginary part originating from the momentum-dependent scattering time of free carriers, but it has been scarcely reported. By utilizing an intense 4 THz beam from a terahertz free electron laser, we investigated the azimuth angle dependence of the third harmonic generation (THG) from semiconductors. The observed angular anisotropy of THG revealed the contribution of the imaginary part of the nonlinear susceptibility originating from the momentum-scattering time relation in addition to its real part originating from the band nonparabolicity.

Boosting charge separation in organic photovoltaics: unveiling dipole moment variations in excited non-fullerene acceptor layers.

The power conversion efficiency (PCE) of organic photovoltaics (OPVs) has reached more than 19% due to the rapid development of non-fullerene acceptors (NFAs). To compete with the PCEs (26%) of commercialized silicon-based inorganic photovoltaics, the drawback of OPVs should be minimized. This drawback is the intrinsic large loss of open-circuit voltage; however, a general approach to this issue remains elusive.

Near-infrared imaging via upconversion in Er:CaF crystal with dual wavelength excitation.

We propose a system for imaging 1510 nm near-infrared (NIR) wavelength via upconversion (UC) luminescence in an Er-doped CaF crystal. Er ions are excited from the ground to the excited state levels by an 800-nm pre-excitation wavelength, followed by the promotion of these ions to a higher energy level by the NIR excitation wavelength. Relaxation of these excited ions gives rise to 540 nm UC luminescence in the visible region, enabling the detection of the 1510 nm NIR wavelength.

Design and fabrication of a microcoil metamaterial absorber for the sub-terahertz region.

The development of electromagnetic wave absorbers operating in the sub-terahertz (sub-THz) region is necessary in 6G communications. We designed and fabricated a sub-THz metamaterial absorber based on metal microcoils embedded and periodically arranged in a dielectric substrate. The microcoil parameters were optimized by calculating the electromagnetic response of the metamaterial using finite element analysis.

Photocatalytic Hydrogen Evolution Activity of Nitrogen/Fluorine-Codoped Rutile TiO.

The development of a photocatalyst capable of evolving H from water under visible light is important. Here, the photocatalytic activity of N/F-codoped rutile TiO (TiO:N,F) for H evolution was examined with respect to metal cocatalyst loading and irradiation conditions. Among the metal species examined, Pd was the best-performing cocatalyst for TiO:N,F under UV-vis irradiation (λ > 350 nm), producing H from an aqueous methanol solution.

An emissive charge-transfer excited-state at the well-defined hetero-nanostructure interface of an organic conjugated molecule and two-dimensional inorganic nanosheet.

Precise engineering of excited-state interactions between an organic conjugated molecule and a two-dimensional semiconducting inorganic nanosheet, specifically the manipulation of charge-transfer excited (CTE) states, still remains a challenge for state-of-the-art photochemistry. Herein, we report a long-lived, highly emissive CTE state at structurally well-defined hetero-nanostructure interfaces of photoactive pyrene and two-dimensional MoS nanosheets an -benzylsuccinimide bridge (Py-Bn-MoS). Spectroscopic measurements reveal that no charge-transfer state is formed in the ground state, but the locally-excited (LE) state of pyrene in Py-Bn-MoS efficiently generates an unusual emissive CTE state.

Surface-Specific Modification of Graphitic Carbon Nitride by Plasma for Enhanced Durability and Selectivity of Photocatalytic CO Reduction with a Supramolecular Photocatalyst.

Photocatalytic CO reduction is in high demand for sustainable energy management. Hybrid photocatalysts combining semiconductors with supramolecular photocatalysts represent a powerful strategy for constructing visible-light-driven CO reduction systems with strong oxidation power. Here, we demonstrate the novel effects of plasma surface modification of graphitic carbon nitride (CN), which is an organic semiconductor, to achieve better affinity and electron transfer at the interface of a hybrid photocatalyst consisting of CN and a Ru(II)-Ru(II) binuclear complex ().

A general interfacial-energetics-tuning strategy for enhanced artificial photosynthesis.

The demands for cost-effective solar fuels have triggered extensive research in artificial photosynthesis, yet the efforts in designing high-performance particulate photocatalysts are largely impeded by inefficient charge separation. Because charge separation in a particulate photocatalyst is driven by asymmetric interfacial energetics between its reduction and oxidation sites, enhancing this process demands nanoscale tuning of interfacial energetics on the prerequisite of not impairing the kinetics and selectivity for surface reactions. In this study, we realize this target with a general strategy involving the application of a core/shell type cocatalyst that is demonstrated on various photocatalytic systems.

Improvement of Visible-Light H Evolution Activity of Pb Ti O F Photocatalyst by Coloading of Rh and Pd Cocatalysts.

Pb Ti O F modified with various metal cocatalysts was studied as a photocatalyst for visible-light H evolution. Although unmodified Pb Ti O F showed negligible activity, modification of its surface with Rh led to the best observed promotional effect among the Pb Ti O F samples modified with a single metal cocatalyst. The H evolution activity was further enhanced by coloading with Pd; the Rh-Pd/Pb Ti O F photocatalyst showed 3.

Manipulation of charge carrier flow in BiNbOCl nanoplate photocatalyst with metal loading.

Separation of photoexcited charge carriers in semiconductors is important for efficient solar energy conversion and yet the control strategies and underlying mechanisms are not fully established. Although layered compounds have been widely studied as photocatalysts, spatial separation between oxidation and reduction reaction sites is a challenging issue due to the parallel flow of photoexcited carriers along the layers. Here we demonstrate orthogonal carrier flow in layered BiNbOCl by depositing a Rh cocatalyst at the edges of nanoplates, resulting in spatial charge separation and significant enhancement of the photocatalytic activity.

Identification of a Self-Photosensitizing Hydrogen Atom Transfer Organocatalyst System.

We developed organocatalyst systems to promote the cleavage of stable C-H bonds, such as formyl, α-hydroxy, and benzylic C-H bonds, through a hydrogen atom transfer (HAT) process without the use of exogenous photosensitizers. An electronically tuned thiophosphoric acid, 7,7'-OMe-TPA, was assembled with substrate or co-catalyst -heteroaromatics through hydrogen bonding and π-π interactions to form electron donor-acceptor (EDA) complexes. Photoirradiation of the EDA complex induced stepwise, sequential single-electron transfer (SET) processes to generate a HAT-active thiyl radical.

Overall photosynthesis of HO by an inorganic semiconductor.

Artificial photosynthesis of HO using earth-abundant water and oxygen is a promising approach to achieve scalable and cost-effective solar fuel production. Recent studies on this topic have made significant progress, yet are mainly focused on using  organic polymers. This set of photocatalysts is susceptible to potent oxidants (e.

Surface Modifications of (ZnSe)(CuGaSe) to Promote Photocatalytic Z-Scheme Overall Water Splitting.

Charge separation is crucial for an efficient artificial photosynthetic process, especially for narrow-bandgap metal sulfides/selenides. The present study demonstrates the application of a pn junction to particulate metal selenides to enhance photocatalytic Z-scheme overall water splitting (OWS). The constructed pn junction of CdS-(ZnSe)(CuGaSe) significantly boosted charge separation.

Magnetic-Pole Flip by Millimeter Wave.

In the era of Big Data and the Internet of Things, data archiving is a key technology. From this viewpoint, magnetic recordings are drawing attention because they guarantee long-term data storage. To archive an enormous amount of data, further increase of the recording density is necessary.

Synthesis of Three-Layer Perovskite Oxynitride KCaTaON·2HO and Photocatalytic Activity for H Evolution under Visible Light.

Substitution of oxide anions (O) in a metal oxide for nitrogen (N) results in reduction of the band gap, which is attractive in heterogeneous photocatalysis; however, only a handful of two-dimensional layered perovskite oxynitrides have been reported, and thus, the structural effects of layered oxynitrides on photocatalytic activity have not been sufficiently examined. This study reports the synthesis of a Ruddlesden-Popper phase three-layer oxynitride perovskite of KCaTaON·2HO, and the photocatalytic activity is compared with an analogous two-layer perovskite, KLaTaON·1.6HO.

Enhancement of photoelectrochemical activity of TiO electrode by particulate/dense double-layer formation.

Photoelectrochemical water splitting has attracted significant attention as an environment-friendly method to generate H and O. Electrodes composed of powders exhibit a large surface area and are favorable for surface reactions; however, their high resistance prevents charge transportation. In contrast, photoelectrodes composed of a dense film exhibit high conductivity; however, they constitute a small surface area.

Reconfiguration of magnetic domain structures of ErFeO by intense terahertz free electron laser pulses.

Understanding the interaction between intense terahertz (THz) electromagnetic fields and spin systems has been gaining importance in modern spintronics research as a unique pathway to realize ultrafast macroscopic magnetization control. In this work, we used intense THz pulses with pulse energies in the order of 10 mJ/pulse generated from the terahertz free electron laser (THz-FEL) to irradiate the ferromagnetic domains of ErFeO single crystal. It was found that the domain shape can be locally reconfigured by irradiating the THz - FEL pulses near the domain boundary.

Solar-Driven Photoelectrochemical Water Oxidation over an n-Type Lead-Titanium Oxyfluoride Anode.

Mixed-anion compounds (e.g., oxynitrides and oxysulfides) are potential candidates as photoanodes for visible-light water oxidation, but most of them suffer from oxidative degradation by photogenerated holes, leading to low stability.

Terahertz generation measurements of multilayered GeTe-SbTe phase change materials.

Multilayered structures of GeTe and SbTe phase change material, also referred to as interfacial phase change memory (iPCM), provide superior performance for nonvolatile electrical memory technology in which the atomically controlled structure plays an important role in memory operation. Here, we report on terahertz (THz) wave generation measurements. Three- and 20-layer iPCM samples were irradiated with a femtosecond laser, and the generated THz radiation was observed.

Terahertz emission from gold nanorods irradiated by ultrashort laser pulses of different wavelengths.

Electron photoemission and ponderomotive acceleration by surface enhanced optical fields is considered as a plausible mechanism of terahertz radiation from metallic nanostructures under ultrafast laser excitation. To verify this mechanism, we studied experimentally terahertz emission from an array of gold nanorods illuminated by intense (~10-100 GW/cm) femtosecond pulses of different central wavelengths (600, 720, 800, and 1500 nm). We found for the first time that the order of the dependence of the terahertz fluence on the laser intensity is, unexpectedly, almost the same (~4.