Manganese oxide nanocluster catalysts are known to be active in the oxidative dehydrogenation of alcohols, but their catalytic performance depends on the support. In this study, we selected three kinds of supports―Mg(OH)₂, Al₂O₃, and SiO₂―to prepare Mn oxide nanocluster catalysts. Among them, MnO_x/Mg(OH)₂ catalyst showed the highest yield and has higher Mn oxidation states revealed by Mn K-edge X-ray absorption near edge structure (XANES) and Mn 2p X-ray photoelectron spectroscopy (XPS) analyses. The pretreatment with CO₂ before reaction significantly lowered the catalysis, suggesting that the basic sites on the support help promote the reaction. Transmission electron microscopy (TEM) analysis showed similar nanocluster sizes across all supports, indicating that activity is governed more by the oxidation state of Mn species and the basicity of the support rather than particle size. Both the Mn oxidation state and support basicity are essential for enhancing catalytic performance in alcohol oxidation.

We investigated the atomic sites occupancy for the Si dopants in Si-doped κ-Ga₂O₃(001) using photoelectron holography (PEH). From PEH, we found that three types of inequivalent Si substitutional sites (Si_Ga) were formed. The ratios for the tetrahedral, pentahedral, and octahedral Si_Ga sites were estimated to be 51%, 35%, and 14%, respectively. Higher (lower) ratios for the three inequivalent Si_Ga sites may come from lower (higher) formation energy. The tetrahedral (octahedral) Si_Ga site has the highest (lowest) ratio of the three Si_Ga sites since it has the lowest (highest) formation energy. We suggest that the tetrahedral Si_Ga site is due to the active dopant site, whereas the pentahedral and octahedral Si_Ga sites can be attributed to the inactive dopant sites for the Si-doped κ-Ga₂O₃(001).

We report the reversible tunneling conductivity switching induced by external electric field (EEF) for a proton (H^＋) donor/acceptor bilayer film on Au(111) substrates under ambient conditions at room temperature.¹⁾ The hetero-bilayer film was self-assembled through two-step immersion : the H^＋-donor, the electron-H^＋-correlated molecule (catechol-fused bis(propylthio)tetrathiafulvalene), was hydrogen-bonded to the H^＋-accepting imidazole-terminated undecanethiolate self-assembled monolayer (SAM) on Au(111). The bilayer film topographies, molecular adsorption states, and physical properties were characterized using several spectroscopic and microscopic methods. In particular, scanning tunneling microscopy and spectroscopy measurements revealed reversible changes in the tunneling conductivity of the bilayer film depending on EEF stimulation. This was attributed to reversible EEF-induced H^＋-transfer in the bilayer, based on theoretical model calculation and H/D isotope examination. Notably, the reversible response exhibited hysteresis, indicating that the bilayer film could function as a molecular memory driven by the H^＋-switch.

This article reports the development of Imaging-type Spin-Resolved PhotoEmission Microscopy (iSPEM), an instrument enabling spin-resolved photoelectron imaging in both real and momentum spaces. The system combines a photoelectron emission microscopy (PEEM)-based electron lens with an imaging double-energy analyzer, enabling rapid switching between real- and momentum-space modes with energy-resolved imaging. By incorporating a multichannel spin detector, iSPEM achieves significantly higher efficiency in spin-polarization measurements than conventional spin-resolved photoemission spectroscopy. A delay-line detector for time-of-flight analysis further enables efficient acquisition of multidimensional datasets. The instrument allows visualization of electronic states in submicrometer-scale and inhomogeneous samples, including polycrystals and magnetic domain structures. Representative demonstrations highlight its potential for studying quantum, magnetic, and low-dimensional materials, as well as spin-based devices.

The surface chemistry of formic acid and the CO₂ hydrogenation process on the Pd/Cu(111) single atom alloy surface was investigated using synchrotron-radiation X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations. High-resolution XPS revealed that the decomposition process of formic acid on Pd/Cu(111) is almost identical to that on Cu(111). Density functional theory calculations showed that the indirect charge transfer from Pd to monodentate formate species through the Cu substrate, which causes the considerable chemical shift in Pd 3d_5/2. In addition, it was found that formate species are preferably adsorbed on the Cu site rather than the Pd site, implying the advantage of Pd/Cu(111) in methanol synthesis. Ambient pressure XPS (AP-XPS) demonstrated that hydrogen spillover drives CO₂ hydrogenation into formate and methoxy species even at room temperature. Semi-quantitative analysis of AP-XPS spectra proposed that carbonate acts as a reactive intermediate in methanol synthesis.

We elucidate the origin of visible-light inactivity in a Rh,Sb co-doped SrTiO₃ photocatalyst loaded with Rh/Cr₂O₃ and CoOOH cocatalysts. Although the photocatalyst absorbs both UV and visible light, water splitting occurs only under UV-light irradiation. Operando soft X-ray absorption spectroscopy reveals the valence state of the CoOOH cocatalyst surface, which serves as the oxygen evolution reaction (OER) site. Under UV-light irradiation, oxidation of the CoOOH surface is observed, indicating transfer of photoinduced holes and promotion of the OER. In contrast, visible-light irradiation induces reduction of the CoOOH surface, demonstrating preferential electron transfer and suppression of the OER. Further analyses indicate that this excitation-wavelength-dependent reversal in carrier transfer originates from localization of photoinduced holes at Rh dopant sites under visible-light excitation. These results establish that excitation-wavelength-dependent carrier dynamics critically govern photocatalytic performance and underscore the necessity of rational dopant selection and band engineering for efficient visible-light-driven water splitting.

Atomic force microscopy (AFM) with CO-functionalized tips has revolutionized the visualization of molecular structures, yet it remains limited by slow scan speeds and a reliance on constant-height operation. In this article, we demonstrate a significant advancement by operating a silicon cantilever in its second resonance mode, leveraging its high f₀/k ratio (where f₀ and k denote the resonance frequency and spring constant, respectively) to enhance force sensitivity. This platform achieves robust chemical-structure imaging at speeds up to 200 nm/s―over 60 times faster than previous reports. Additionally, by utilizing large oscillation amplitudes to maintain monotonic frequency-shift feedback, we successfully resolve molecular bonds directly in topographic mode. These breakthroughs expand the frontiers of AFM, enabling the structural analysis of complex 3D molecules and the real-time tracking of dynamic on-surface reactions.

In this part 4, plasma-enhanced chemical vapor deposition (PECVD) methods, which are film deposition methods via excited states of species in a plasma, are explained. Unlike thermal CVD methods, PECVD methods are film deposition technologies that use excited states. As a result, it is possible to deposit films without being affected by the activation energy (activation enthalpy ΔH) that is a limitation of thermal CVD methods. PECVD has the following features : (1) It is possible to produce metastable films such as diamond. (2) It is possible to achieve high-speed film deposition at low temperatures.

PECVD methods are classified into capacitively coupled and inductively coupled types. Capacitively coupled types are the basic type of PECVD method because they can create uniform plasma. On the other hand, inductively coupled types can generate a lot of molecular dissociation species due to the high-density plasma. This allows for film deposition that makes effective use of activated species.

Plasma generation uses commercial frequency radio waves (13.56 MHz). This requires high-frequency technology such as impedance matching.