Electron-Energy Dependent Excitation and Directional Far-Field Radiation of Resonant Mie Modes in Single Si Nanospheres.

High-energy electron beams with energies in the 15-30 keV range are used to excite optical Mie modes in crystalline Si nanospheres with radius 80-100 nm. Cathodoluminescence (CL) spectra show emission from resonant electric and magnetic dipole and quadrupole modes, with relative intensities that depend strongly on electron energy and impact parameter. The measured trends are explained by a coupling model in which the electron-energy dependent CL excitation probability-and thus the CL emission-is proportional to the Fourier transform of the modal electric field at a spatial frequency determined by the electron velocity.

Attonewton Force Resolution Measurements with Silicon Nanospheres at the Thermal Noise Limit in Ambient-Temperature Liquids.

Precise force measurements are crucial for understanding fundamental physics or nanoscale interactions, such as those of molecular machines in biology. Optical tweezers are versatile force transducers for such measurements, enabling meticulous manipulation of small particles. However, achieving high-resolution, subfemtonewton force measurements under physiological conditions remains challenging due to thermal fluctuations and instrument noise.

Achieving synergy between pollution reduction and carbon mitigation in the eco-industrial park: a multi-objective optimization framework.

Eco-Industrial Parks (EIPs) have emerged as a strategic approach to reconcile industrial development with environmental responsibility. However, optimizing their industrial structure remains complex due to the intertwined goals of economic growth, energy efficiency, and ecological sustainability. This study aims to develop a multi-objective optimization framework that systematically balances economic benefits, energy consumption, and waste management within EIPs.

Verification experiments on CO reduction planning from the estimated waste collection amount at waste stations using waste collection vehicle route log data.

In Japan, the municipal waste management sector, which accounts for approximately 3 % of the country's total greenhouse gas emissions, faces several challenges, including the need to decarbonize waste collection and shrinking labor force. In recent years, technologies such as the Internet of Things (IoT) and artificial intelligence have been investigated to improve the efficiency and decarbonization of waste management. This study installed IoT devices (known as a digital tachographs) in waste collection vehicles and containers in Matsuyama City to record their route log data.

Proposing adjustments to heat safety thresholds for junior high and high school sports clubs in Japan.

With higher temperatures expected in the future due to global climate change, addressing health risks such as heat illness is increasingly important. In Japan, thousands of heat illness cases occur annually during school sports club activities. The risk may vary by sport, location, and region, but how heat safety thresholds (HSTs) should be adjusted to provide effective guidelines remains uncertain.

Optical trapping-induced crystallization promoted by gold and silicon nanoparticles.

This study investigates the promotion of sodium chlorate (NaClO) crystallization through optical trapping, enhanced by the addition of gold nanoparticles (AuNPs) and silicon nanoparticles (SiNPs). Using a focused laser beam at the air-solution interface of a saturated NaClO solution with AuNPs or SiNPs, the aggregates of these particles were formed at the laser focus, the nucleation and growth of metastable NaClO (m-NaClO) crystals were induced. Continued laser irradiation caused these m-NaClO crystals to undergo repeated cycles of growth and dissolution, eventually transitioning to a stable crystal form.

Resources time footprint indicator extension for evaluating human interventions in provisioning ecosystem services supply.

The growing emphasis on ecosystem services (ES) has enhanced evaluation of their capacity. However, intensive human intervention in the provisioning ecosystem service (P-ES) supply driven by widening spatial gaps between supply sources and demand locations, compromises the long-term ES supply potential. The Resources Time Footprint (RTF) indicator provides numerical insights into these impacts in the form of occupancy rates by comparing resource utilization to allocated capacities over a person's lifespan.

Scattering/Fluorescence Dual-Mode Imaging in MnO-Coated Silicon Nanospheres for Cancer Cell Detection.

A tumor microenvironment (TME)-responsive nanoprobe composed of a fluorescent dye-decorated silicon (Si) nanosphere core and a thin MnO shell is proposed for simple and intelligent detection of cancer cells. The Si nanosphere core with diameters of 100-200 nm provides environment-independent Mie scattering imaging, while, simultaneously, the MnO shell provides the capability to switch the on/off state of the dye fluorescence reacted to the glutathione (GSH) and/or HO levels in a cancer cell. Si-MnO core-shell nanosphere probes are fabricated in a solution-based process from crystalline Si nanosphere cores.

Universal Click-Chemistry Approach for the DNA Functionalization of Nanoparticles.

Nanotechnology has revolutionized the fabrication of hybrid species with tailored functionalities. A milestone in this field is the deoxyribonucleic acid (DNA) conjugation of nanoparticles, introduced almost 30 years ago, which typically exploits the affinity between thiol groups and metallic surfaces. Over the last decades, developments in colloidal research have enabled the synthesis of an assortment of nonmetallic structures, such as high-index dielectric nanoparticles, with unique properties not previously accessible with traditional metallic nanoparticles.

Photoluminescence from FRET pairs coupled with Mie-resonant silicon nanospheres.

Optically resonant nanoparticles decorated with donor-acceptor molecular pairs have been attracting attention for applications as nanoprobes in bioimaging and biosensing. We produced composite nanoparticles composed of donor-acceptor molecular pairs and silicon nanospheres (Si NSs) with diameters of 100-200 nm exhibiting Mie resonances in the visible range and studied the effect of Mie resonances on their photoluminescence properties. We showed that the photoluminescence spectra are strongly modified by Mie resonances and the spectral shape is controlled in a wide range by the Si NS size; by controlling the size, we can achieve the photoluminescence maximum from that of a donor molecule to that of an acceptor molecule almost continuously.

Photosensitizing Metasurface Empowered by Enhanced Magnetic Field of Toroidal Dipole Resonance.

Photochemical reaction exploiting an excited triplet state (T ) of a molecule requires two steps for the excitation, i.e., electronic transition from the ground (S ) to singlet excited (S ) states and intersystem crossing to the T  state.

Helicity-Preserving Optical Metafluids.

A colloidal suspension of photonic nanostructures exhibiting optical magnetism is dubbed an optical metafluid. A promising constituent of a metafluid is a nanosphere of high-refractive index dielectrics having the magnetic-type Mie resonances in the optical frequency. At the Kerker conditions, a dielectric nanosphere satisfies the electromagnetic duality symmetry condition and preserves the handedness of circularly polarized incident light.

Visualizing the Nanoscopic Field Distribution of Whispering-Gallery Modes in a Dielectric Sphere by Cathodoluminescence.

A spherical dielectric particle can sustain the so-called whispering-gallery modes (WGMs), which can be regarded as circulating electromagnetic waves, resulting in the spatial confinement of light inside the particle. Despite the wide adoption of optical WGMs as a major light confinement mechanism in salient practical applications, direct imaging of the mode fields is still lacking and only partially addressed by simple photography and simulation work. The present study comprehensively covers this research gap by demonstrating the nanoscale optical-field visualization of self-interference of light extracted from excited modes through experimentally obtained photon maps that directly portray the field distributions of the excited eigenmodes.

Fluorophore-Decorated Mie Resonant Silicon Nanosphere for Scattering/Fluorescence Dual-Mode Imaging.

Inorganic nanoparticles with multiple functions have been attracting attention as multimodal nanoprobes in bioimaging, biomolecule detection, and medical diagnosis and treatment. A drawback of conventional metallic nanoparticle-based nanoprobes is the Ohmic losses that lead to fluorescence quenching of attached molecules and local heating under light irradiation. Here, metal-free nanoprobes capable of scattering/fluorescence dual-mode imaging are developed.

Mode Hybridization in Silicon Core-Gold Shell Nanosphere.

A dielectric core-metal shell nanosphere has attracted scientific and technological interests due to the unique optical resonances arising from the hybridization of surface plasmon modes and cavity modes. The previous studies focus on a low-index dielectric core without its own optical resonances. Here, optical resonances of a core-shell nanosphere with a high refractive index (n ≈ 4) core with the lowest order Mie resonances in the visible range are investigated theoretically and experimentally.

Resonance Couplings in Si@MoS Core-Shell Architectures.

Heterostructures of transition metal dichalcogenides and optical cavities that can couple to each other are rising candidates for advanced quantum optics and electronics. This is due to their enhanced light-matter interactions in the visible to near-infrared range. Core-shell structures are particularly valuable for their maximized interfacial area.

Disentangling Cathodoluminescence Spectra in Nanophotonics: Particle Eigenmodes vs Transition Radiation.

Cathodoluminescence spectroscopy performed in an electron microscope has proven a versatile tool for analyzing the near- and far-field optical response of plasmonic and dielectric nanostructures. Nevertheless, the transition radiation produced by electron impact is often disregarded in the interpretation of the spectra recorded from resonant nanoparticles. Here we show, experimentally and theoretically, that transition radiation can by itself generate distinct resonances that, depending on the time-of-flight of the electron beam inside the particle, can result from constructive or destructive interference in time.

Feasibility of the Olympic marathon under climatic and socioeconomic change.

There are concerns about the impact of climate change on Olympic Games, especially endurance events, such as marathons. In recent competitions, many marathon runners dropped out of their races due to extreme heat, and it is expected that more areas will be unable to host the Games due to climate change. Here, we show the feasibility of the Olympic marathon considering the variations in climate factors, socioeconomic conditions, and adaptation measures.

Optical spin sorting chain.

Transverse spin angular momentum of light is a key concept in recent nanophotonics to realize unidirectional light transport in waveguides by spin-momentum locking. Herein we theoretically propose subwavelength nanoparticle chain waveguides that efficiently sort optical spins with engineerable spin density distributions. By arranging high-refractive-index nanospheres or nanodisks of different sizes in a zigzag manner, directional optical spin propagation is realized.

Direct Excitation of Triplet State of Molecule by Enhanced Magnetic Field of Dielectric Metasurfaces.

Efficient excitation of a triplet (T ) state of a molecule has far-reaching effects on photochemical reaction and energy conversion systems. Because the optical transition from a ground singlet (S ) to a T state is spin-forbidden, a T state is generated via intersystem crossing (ISC) from an excited singlet (S ) state. Although the excitation efficiency of a T state can be increased by enhancing ISC utilizing a heavy atom effect, energy loss during S →T relaxation is inevitable.

Colloidal Mie resonant silicon nanoparticles.

Nano- and microstructures of silicon (Si) exhibit electric and magnetic Mie resonances in the optical regime, providing a novel platform for controlling light at the nanoscale and enhancing light-matter interactions. In this Review, we present recent development of colloidal Si nanoparticles (NPs) that have wide range of applications in nanophotonics. Following brief summary of synthesis methods of amorphous and crystalline Si particles with high sphericity, optical responses of single Si particles placed on a substrate are overviewed.

Solution-processed silicon quantum dot photocathode for hydrogen evolution.

The photoelectrochemical response of a photocathode made from a colloidal solution of boron (B) and phosphorus (P) codoped silicon (Si) quantum dots (QDs) 2-11 nm in diameters is studied. Since codoped Si QDs are dispersible in alcohol and water due to the hydrophilic surface, a photoelectrode with a smooth surface is produced by drop-coating the QD solution on an indium tin oxide substrate. The codoping provides high oxidation resistance to Si QDs and makes the electrode operate as a photocathode.