Gd2O3-mesoporous silica/gold nanoshells: A potential dual T1/T2 contrast agent for MRI-guided localized near-IR photothermal therapy.

A promising clinical trial utilizing gold-silica core-shell nanostructures coated with polyethylene glycol (PEG) has been reported for near-infrared (NIR) photothermal therapy (PTT) of prostate cancer. The next critical step for PTT is the visualization of therapeutically relevant nanoshell (NS) concentrations at the tumor site. Here we report the synthesis of PEGylated Gd2O3-mesoporous silica/gold core/shell NSs (Gd2O3-MS NSs) with NIR photothermal properties that also supply sufficient MRI contrast to be visualized at therapeutic doses (≥108 NSs per milliliter). The nanoparticles have r1 relaxivities more than three times larger than those of conventional T1 contrast agents, requiring less concentration of Gd3+ to observe an equivalent signal enhancement in T1-weighted MR images. Furthermore, Gd2O3-MS NS nanoparticles have r2 relaxivities comparable to those of existing T2 contrast agents, observed in agarose phantoms. This highly unusual combination of simultaneous T1 and T2 contrast allows for MRI enhancement through different approaches. As a rudimentary example, we demonstrate T1/T2 ratio MR images with sixfold contrast signal enhancement relative to its T1 MRI and induced temperature increases of 20 to 55 °C under clinical illumination conditions. These nanoparticles facilitate MRI-guided PTT while providing real-time temperature feedback through thermal MRI mapping.

A Quasi-Bound States in the Continuum Dielectric Metasurface-Based Antenna-Reactor Photocatalyst.

Metasurfaces are a class of two-dimensional artificial resonators, creating new opportunities for strong light-matter interactions. One type of nonradiative optical metasurface that enables substantial light concentration is based on quasi-Bound States in the Continuum (quasi-BIC). Here we report the design and fabrication of a quasi-BIC dielectric metasurface that serves as an optical frequency antenna for photocatalysis. By depositing Ni nanoparticle reactors onto the metasurface, we create an antenna-reactor photocatalyst, where the virtually lossless metasurface funnels light to drive a chemical reaction. This quasi-BIC-Ni antenna-reactor drives H2 dissociation under resonant illumination, showing strong polarization, wavelength, and optical power dependencies. Both E-field-induced electronic and photothermal heating effects drive the reaction, supported by load-dependent reactivity studies and our theoretical model. This study unlocks new opportunities for photocatalysis that employ dielectric metasurfaces for light harvesting in an antenna-reactor format.

Successive Rebounds of Impinging Water Droplets on Superhydrophobic Surfaces.

When a water droplet strikes a superhydrophobic surface, there may be several to a few tens of rebounds before it comes to rest. Although this intriguing multiphase flow phenomenon has received a great deal of attention from interfacial scientists and engineers, the underlying dynamics have not yet been completely resolved. In this paper, we report on an experimental investigation into the bouncing behavior of water droplets impinging on macroscopically flat superhydrophobic surfaces. We show that the restitution coefficient, which quantifies the energy consumed during impact and rebound, exhibits a nonmonotonic dependence on the Weber number. It is the droplet-surface friction that restricts the rebound height of the impinging droplet, so its restitution coefficient increases with the Weber number when the impact velocity is below a critical value. Above this value, the viscous friction within a thin liquid layer close to the superhydrophobic surface becomes dominant, and thus, the restitution coefficient decreases sharply. On the basis of energy analyses, semiempirical formulas are proposed to describe the restitution coefficient, and these can be employed to predict the number of successive rebounds of impinging droplets on superhydrophobic surfaces.

Compact Modeling of Advanced Gate-All-Around Nanosheet FETs Using Artificial Neural Network.

As the architecture of logic devices is evolving towards gate-all-around (GAA) structure, research efforts on advanced transistors are increasingly desired. In order to rapidly perform accurate compact modeling for these ultra-scaled transistors with the capability to cover dimensional variations, neural networks are considered. In this paper, a compact model generation methodology based on artificial neural network (ANN) is developed for GAA nanosheet FETs (NSFETs) at advanced technology nodes. The DC and AC characteristics of GAA NSFETs with various physical gate lengths (Lg), nanosheet widths (Wsh) and thicknesses (Tsh), as well as different gate voltages (Vgs) and drain voltages (Vds) are obtained through TCAD simulations. Subsequently, a high-precision ANN model architecture is evaluated. A systematical study on the impacts of ANN size, activation function, learning rate, and epoch (the times of complete pass through the entire training dataset) on the accuracy of ANN models is conducted, and a shallow neural network configuration for generating optimal ANN models is proposed. The results clearly show that the optimized ANN model can reproduce the DC and AC characteristics of NSFETs very accurately with a fitting error (MSE) of 0.01.

Fast Topology Optimization for Near-Field Focusing All-Dielectric Metasurfaces Using the Discrete Dipole Approximation.

Using an efficient implementation of the discrete dipole approximation and topology optimization, we design all-dielectric metasurfaces capable of focusing light into intense deep subwavelength hotspots. The light focusing of these metasurfaces far outweighs conventional lenses and can provide dramatic enhancements of processes that depend superlinearly on light intensity, such as light-powered membrane distillation and photocatalysis. Our approach can easily be generalized to optimize metasurfaces for other functionalities, such as nonlinear optics or photothermal conversion.

A 3D Plasmonic Antenna-Reactor for Nanoscale Thermal Hotspots and Gradients.

Plasmonic nanoantennas focus light below the diffraction limit, creating strong field enhancements, typically within a nanoscale junction. Placing a nanostructure within the junction can greatly enhance the nanostructure's innate optical absorption, resulting in intense photothermal heating that could ultimately compromise both the nanostructure and the nanoantenna. Here, we demonstrate a three-dimensional "antenna-reactor" geometry that results in large nanoscale thermal gradients, inducing large local temperature increases in the confined nanostructure reactor while minimizing the temperature increase of the surrounding antenna. The nanostructure is supported on an insulating substrate within the antenna gap, while the antenna maintains direct contact with an underlying thermal conductor. Elevated local temperatures are quantified, and high local temperature gradients that thermally reshape only the internal reactor element within each antenna-reactor structure are observed. We also show that high local temperature increases of nominally 200 °C are achievable within antenna-reactors patterned into large extended arrays. This simple strategy can facilitate standoff optical generation of high-temperature hotspots, which may be useful in applications such as small-volume, high-throughput chemical processes, where reaction efficiencies depend exponentially on local temperature.

A Novel Lightweight Polyurethane Composite for Application on Ultra-High-Voltage Insulator Core Filler.

This study aimed to prepare a new lightweight ultra-high-voltage insulator core filler composite, which can solve the problem of bulkiness. In this study, rigid polyurethane foam pellets with different densities are used as lightweight fillers and polyurethane resins to compound lightweight composite materials. On accounting for working conditions, the density, insulation, heat resistance, water absorption and mechanical properties are tested. The compressive properties of composites are determined by a foam skeleton and a process. Among three kinds of composites, in which the composites with the best comprehensive performance are materials filled with pellets to a density of 0.15g·cm-3. The density, surface resistance, volume resistance, leakage current, initial decomposition temperature, water absorption, force, rupture displacement and limiting oxygen index (LOI) of composites are 0.665 g·cm-3, 1.17 × 1014 Ω, 9.68 × 1014 Ω·cm, 0.079 mA, 208 °C, 0.047%, 2262 N, 2.54 mm, and 23.3%, respectively. The ultra-high-voltage insulator core filler in this study can reduce the weight of the solid core insulator crossarm for Ultra-High Voltage (UHV) by 50-75%.

Observation of Dicke cooperativity in magnetic interactions.

The interaction of N two-level atoms with a single-mode light field is an extensively studied many-body problem in quantum optics, first analyzed by Dicke in the context of superradiance. A characteristic of such systems is the cooperative enhancement of the coupling strength by a factor of N. In this study, we extended this cooperatively enhanced coupling to a solid-state system, demonstrating that it also occurs in a magnetic solid in the form of matter-matter interaction. Specifically, the exchange interaction of N paramagnetic erbium(III) (Er3+) spins with an iron(III) (Fe3+) magnon field in erbium orthoferrite (ErFeO3) exhibits a vacuum Rabi splitting whose magnitude is proportional to N. Our results provide a route for understanding, controlling, and predicting novel phases of condensed matter using concepts and tools available in quantum optics.