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A nanoindenter was used to compress individual particles of hydrogenated amorphous silicon (a-Si:H) ranging in diameter from 290 nm to 780 nm. The colloidal synthesis used to produce the particles enables the hydrogen content to be manipulated over a wide range, from about 5 at. % to 50 at. %, making these a-Si:H particles promising for applications in lithium ion batteries, hydrogen storage, and optical metamaterials. Force-displacement curves generated using a tungsten probe flattened with focused ion beam exhibited elastic and then plastic deformations, followed by fracture and crushing of the particles. For particles with 5% and 50% H, Young's moduli, yield strengths, and compressive strengths were 73.5(±19.5) GPa, 5.8 GPa, and 3.2(±0.1)–9.3(±0.6) GPa and 31.2(±9.0) GPa, 2.5 GPa, and 1.8 (±0.3)–5.3(±0.8) GPa, respectively. Particles with more hydrogen were significantly more compliant and weaker. This is consistent with atomistically detailed molecular dynamics simulations, which revealed compression forms of an interphase of H atom clusters that weakens the material. [ABSTRACT FROM AUTHOR]

A goal in the field of nanoscale optics is the fabrication of nanostructures with strong directional light scattering at visible frequencies. Here, the synthesis of Mie‐resonant core–shell particles with overlapping electric and magnetic dipole resonances in the visible spectrum is demonstrated. The core consists of silicon surrounded by a lower index silicon oxynitride (SiOxNy) shell of an adjustable thickness. Optical spectroscopies coupled to Mie theory calculations give the first experimental evidence that the relative position and intensity of the magnetic and electric dipole resonances are tuned by changing the core–shell architecture. Specifically, coating a high‐index particle with a low‐index shell coalesces the dipoles, while maintaining a high scattering efficiency, thus generating broadband forward scattering. This synthetic strategy opens a route toward metamaterial fabrication with unprecedented control over visible light manipulation. [ABSTRACT FROM AUTHOR]

Constructing colloidal particles into functional nanostructures, materials, and devices is a promising yet challenging direction. Many optical techniques have been developed to trap, manipulate, assemble, and print colloidal particles from aqueous solutions into desired configurations on solid substrates. However, these techniques operated in liquid environments generally suffer from pattern collapses, Brownian motion, and challenges that come with reconfigurable assembly. Here, we develop an all-optical technique, termed optothermally-gated photon nudging (OPN), for the versatile manipulation and dynamic patterning of a variety of colloidal particles on a solid substrate at nanoscale accuracy. OPN takes advantage of a thin surfactant layer to optothermally modulate the particle-substrate interaction, which enables the manipulation of colloidal particles on solid substrates with optical scattering force. Along with in situ optical spectroscopy, our non-invasive and contactless nanomanipulation technique will find various applications in nanofabrication, nanophotonics, nanoelectronics, and colloidal sciences. Particle manipulation is still challenging even with the many tools available, especially manipulating particles on a surface. Here, the authors report a technique for nanomanipulation of various objects on solid substrates by modulating particle-substrate interactions through laser-induced opto-thermal dynamics. [ABSTRACT FROM AUTHOR]

While lithium–sulfur (Li–S) batteries are poised to be the next generation of high-density energy storage devices, the intrinsic polysulfide shuttle has limited their practical applications. In order to fundamentally solve the problem, a well-designed host to simultaneously meet the requirements for both sufficient surface reaction and efficient conversion of polysulfides is urgently demanded. Herein, a 3D heterogeneous sulfur host, termed Ni-ZIF-8@CC, is fabricated by in situ deposition of nickel-doped zeolitic imidazolate framework-8 (Ni-ZIF-8) on carbon cloth (CC). Spectroscopic investigations show that polysulfides can be strongly adsorbed by the Ni-ZIF-8@CC host through the synergy between Ni–S and Li–N interactions, which is also verified by DFT simulations. The doped electrocatalytically active nickel species could furthermore significantly facilitate the kinetics of polysulfide redox reaction, attributed to fast lithium ion diffusion and reduced polarization potential. By combining these advantages, the electrodes exhibit a high areal capacity of up to 6.04 mA h cm−2 together with excellent cycling stabilities. [ABSTRACT FROM AUTHOR]

Inspired by the “tip effect”, we demonstrate that hollow cupric oxide spheres (HCOS) built from abundant protrusive crystal strips can be used as an effective host for Li–S batteries. The battery based on this novel host retained an excellent cycle performance over 500 cycles and delivered an improved rate capability. [ABSTRACT FROM AUTHOR]

A novel electrical current applied technique known as flash sintering has been applied to rapidly (within 10 min) densify electrolytes including Ce0.8Gd0.2O1.9 ( GDC20), Ce0.9Gd0.1O1.95 ( GDC10), and Ce0.8Sm0.2O1.9 ( SDC20) for application in Solid Oxide Fuel Cells ( SOFCs). The densification temperature for the three electrolytes was 554°C, 635°C, and 667°C, respectively, which is far below conventional sintering temperatures. All specimens after flash sintering maintained the pure fluorite structure and exhibited a well-densified microstructure. To investigate the flash-sintering mechanism, we have applied Joule heating effect with blackbody radiation theory, and found that this theory could reasonably interpret the flash-sintering phenomenon by matching theoretically calculated temperature with the real temperature. More importantly, one of the materials inherent properties, the electronic conductivity, has been found correlated with the onset of flash sintering, which indicates that the electrons and holes are the primary current carriers during the start of flash-sintering process. As a result, potential densification mechanisms have been discussed in terms of spark plasma discharge. [ABSTRACT FROM AUTHOR]

Sr2Fe1.5−xNixMo0.5O6−δ (x = 0, 0.05, 0.1, 0.2, 0.4) (SFNM) materials have been synthesized by a sol–gel combustion method and studied towards application as cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs). The crystal structure, microstructure, thermal expansion, element valence, conductivity and electrochemical properties have been characterized as a function of Ni content. The symmetrical structure of the cubic lattice in perovskite oxides is confirmed. SFNM powders possess the 3D interconnected network microstructure composed of nanoparticles. An increasing Ni substitution results in the unit cell shrinkage and the increase of thermal expansion coefficient (TEC). Furthermore, X-ray photoelectron spectroscopy (XPS) analysis shows that Ni basically exhibits a low oxidation state (Ni2+). Doped Ni2+ affects the equilibrium between Fe3+/Mo5+ and Fe2+/Mo6+, which is directly related to the conductivity. The SFNM conductivity was apparently improved, reaching 60 S cm−1 at 450 °C when x = 0.1, which is more than twice that of the Sr2Fe1.5Mo0.5O6−δ (SFM) sample. In addition, Sr2Fe1.4Ni0.1Mo0.5O6−δ (SFN0.1M) cathodes showed excellent electrochemical performance and lowest interface polarization resistance (Rp). The Rp of the SFN0.1M cathode was approximately 50% of that of the SFM cathode. Moreover, the maximum power densities of a single cell based on the SFN0.1M cathode were 0.92, 1.27 W cm−2 at 700, 750 °C, respectively. The SFNM material is a type of potential cathode for IT-SOFCs. [ABSTRACT FROM AUTHOR]

All-dielectric nanostructures have recently opened exciting opportunities for functional nanophotonics, owing to their strong optical resonances along with low material loss in the near-infrared range. Pushing these concepts to the visible range is hindered by their larger absorption coefficient, thus encouraging the search for alternative dielectrics for nanophotonics. Here, we employ bandgap engineering to synthesize hydrogenated amorphous Si nanoparticles (a-Si:H NPs) offering ideal features for functional nanophotonics. We observe significant material loss suppression in a-Si:H NPs in the visible range caused by hydrogenation-induced bandgap renormalization, producing strong higher-order resonant modes in single NPs with Q factors up to ~100 in the visible and near-IR range. We also realize highly tunable all-dielectric meta-atoms by coupling a-Si:H NPs to photochromic spiropyran molecules. ~70% reversible all-optical tuning of light scattering at the higher-order resonant mode under a low incident light intensity is demonstrated. Our results promote the development of high-efficiency visible nanophotonic devices. Large absorption of high-index semiconductors has hindered the application of all dielectric nanostructures in the visible range. Here, the authors present bandgap-engineered hydrogenated amorphous Si nanoparticles with Q-factors up to 100 and their integration with photochromic molecules as tunable meta-atoms. [ABSTRACT FROM AUTHOR]