Anisotropic growth of Au-Ag heteronanostructures through plasmon-induced reduction.

Plasmonic heteronanostructures are promising building blocks for photofunctional materials and devices including photocatalysts, optical materials, and optoelectronic devices. In the present work, we fabricated Au-Ag bimetallic heteronanostructures based on site-selective and anisotropic Ag deposition and growth on Au nanocubes. Plasmonic Au nanocubes were adsorbed onto a glass plate, and the distal mode or proximal-distal mode of the nanocubes was selectively excited in the presence of Ag+ and citrate ions. Polycrystalline Ag was deposited around the top of the Au nanocubes by the distal mode excitation, and single crystalline Ag was grown laterally from the Au nanocubes by the proximal-distal mode excitation. The present method would be applied to the fabrication of various plasmonic nanostructures composed of two or more heterodomains.

Hydrogen evolution from water based on plasmon-induced charge separation at a TiO2/Au/NiO/Pt system.

Metal-semiconductor plasmonic nanostructures are capable of converting light energy through plasmon-induced charge separation (PICS), providing fruitful new strategies to utilize solar energy in various fields, including photocatalysis. Here, we enhance the PICS efficiencies for hydrogen evolution from water at a Pt cathode coupled with a TiO2/Au photoanode by coating the TiO2/Au with a p-type NiO layer on which a Pt co-catalyst is deposited. PICS occurs at the Au-TiO2 interface under visible light. The electrons injected from the Au nanoparticles into TiO2 are transported to the Pt cathode and cause hydrogen evolution from water, the action spectrum of which matches the plasmonic extinction spectrum of the Au nanoparticles. The NiO layer extracts the separated positive charges from the Au nanoparticles, accumulates the charges and drives methanol oxidation at the Pt co-catalyst on NiO with the positive charges. As a result of the introduction of the Pt-modified NiO layer, the rates of methanol oxidation and accompanying hydrogen evolution at zero bias voltage were improved by ∼3.5 times. The NiO layer may also protect the Au nanoparticles from self-oxidation.

Oxidation of multicarbon compounds to CO2 by photocatalysts with energy storage abilities.

Photocatalysts can be used for removal of harmful or odorous organic compounds, but only under illumination. We previously developed a TiO2/Ni(OH)2 photocatalyst with an oxidative energy storage ability, and used it for oxidation of monocarbon compounds such as methanol and formaldehyde to CO2 by the stored energy. Here, we report that TiO2/Ni(OH)2 charged with oxidative energy can also oxidize multicarbon compounds such as acetaldehyde, acetic acid and acetone to CO2 even in the dark. We also report that MnOx can be used as an oxidative energy storage material if it is not in direct contact with the TiO2 photocatalyst (e.g. TiO2/nanoporous SiO2/MnOx). Photocatalytically charged MnOx can also oxidize methanol, acetaldehyde, acetic acid and acetone to CO2.

Inactivation and spike protein denaturation of novel coronavirus variants by CuxO/TiO2 nano-photocatalysts.

In order to reduce infection risk of novel coronavirus (SARS-CoV-2), we developed nano-photocatalysts with nanoscale rutile TiO2 (4-8 nm) and CuxO (1-2 nm or less). Their extraordinarily small size leads to high dispersity and good optical transparency, besides large active surface area. Those photocatalysts can be applied to white and translucent latex paints. Although Cu2O clusters involved in the paint coating undergo gradual aerobic oxidation in the dark, the oxidized clusters are re-reduced under > 380 nm light. The paint coating inactivated the original and alpha variant of novel coronavirus under irradiation with fluorescent light for 3 h. The photocatalysts greatly suppressed binding ability of the receptor binding domain (RBD) of coronavirus (the original, alpha and delta variants) spike protein to the receptor of human cells. The coating also exhibited antivirus effects on influenza A virus, feline calicivirus, bacteriophage Qß and bacteriophage M13. The photocatalysts would be applied to practical coatings and lower the risk of coronavirus infection via solid surfaces.

Fast, cell-resolution, contiguous-wide two-photon imaging to reveal functional network architectures across multi-modal cortical areas.

Fast and wide field-of-view imaging with single-cell resolution, high signal-to-noise ratio, and no optical aberrations have the potential to inspire new avenues of investigations in biology. However, such imaging is challenging because of the inevitable tradeoffs among these parameters. Here, we overcome these tradeoffs by combining a resonant scanning system, a large objective with low magnification and high numerical aperture, and highly sensitive large-aperture photodetectors. The result is a practically aberration-free, fast-scanning high optical invariant two-photon microscopy (FASHIO-2PM) that enables calcium imaging from a large network composed of ∼16,000 neurons at 7.5 Hz from a 9 mm2 contiguous image plane, including more than 10 sensory-motor and higher-order areas of the cerebral cortex in awake mice. Network analysis based on single-cell activities revealed that the brain exhibits small-world rather than scale-free behavior. The FASHIO-2PM is expected to enable studies on biological dynamics by simultaneously monitoring macroscopic activities and their compositional elements.

Spectroelectrochemistry of P700 in native photosystem I particles and diethyl ether-treated thylakoid membranes from spinach and Thermosynechococcus elongatus.

The redox potentials (E(composite function')) of P700 in intact and diethyl ether-treated thylakoid membranes as well as native photosystem (PS) I particles from spinach and Thermosynechococcus elongatus have been measured by a spectroelectrochemistry with an error range of +/-2-3 mV. Stepwise removal of antenna pigments by ether treatment caused distinct shifts of the E( composite function') value with increasing degree of water saturation in ether; negatively from +471 to +428 mV for spinach, but positively from +423 to +436 mV for T. elongatus. Such a contrasting behavior is discussed by invoking the mode of action of ether on the microenvironments around P700.