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The ability to split an incident light beam into separate wavelength bands is central to a diverse set of optical applications, including imaging, biosensing, communication, photocatalysis, and photovoltaics. Entirely new opportunities are currently emerging with the recently demonstrated possibility to spectrally split light at a subwavelength scale with optical antennas. Unfortunately, such small structures offer limited spectral control and are hard to exploit in optoelectronic devices. Here, we overcome both challenges and demonstrate how within a single-layer metafilm one can laterally sort photons of different wavelengths below the free-space diffraction limit and extract a useful photocurrent. This chipscale demonstration of anti-Hermitian coupling between resonant photodetector elements also facilitates near-unity photon-sorting efficiencies, near-unity absorption, and a narrow spectral response (∼ 30 nm) for the different wavelength channels. This work opens up entirely new design paradigms for image sensors and energy harvesting systems in which the active elements both sort and detect photons. Subwavelength photon sorting in photodetection systems with a narrow spectral bandwidth has remained elusive. The authors spectrally sort and detect photons by suppressing the near-field interaction and maximizing the far-field interactions between photodetector elements, achieving a spectral separation of 30 nm.

In the development of hydrogen-based technology, a key challenge is the sustainable production of hydrogen in terms of energy consumption and environmental aspects. However, existing methods mainly rely on fossil fuels due to their cost efficiency, and as such, it is difficult to be completely independent of carbon-based technology. Electrochemical hydrogen production is essential, since it has shown the successful generation of hydrogen gas of high purity. Similarly, the photoelectrochemical (PEC) method is also appealing, as this method exhibits highly active and stable water splitting with the help of solar energy. In this article, we review recent developments in PEC water splitting, particularly those using metal-organic halide perovskite materials. We discuss the exceptional optical and electrical characteristics which often dictate PEC performance. We further extend our discussion to the material limit of perovskite under a hydrogen production environment, i.e., that PEC reactions often degrade the contact between the electrode and the electrolyte. Finally, we introduce recent improvements in the stability of a perovskite-based PEC device.

A universal increase in energy consumption and the dependency on fossil fuels have resulted in increasing severity of global warming, thus necessitating the search of new and environment-friendly energy sources. Hydrogen is as one of the energy sources that can resolve the abovementioned problems. Water splitting promotes ecofriendly hydrogen production without the formation of any greenhouse gas. The most common process for hydrogen production is electrolysis, wherein water molecules are separated into hydrogen and oxygen through electrochemical reactions. Solar-energy-induced chemical reactions, including photocatalysis and photoelectrochemistry, have gained considerable attention because of the simplicity of their procedures and use of solar radiation as the energy source. To improve performance of water splitting reactions, the use of catalysts has been widely investigated. For example, the novel-metal catalysts possessing extremely high catalytic properties for various reactions have been considered. However, due to the rarity and high costs of the novel-metal materials, the catalysts were considered unsuitable for universal use. Although other transition-metal-based materials have also been investigated, carbon-based materials, which are obtained from one of the most common elements on Earth, have potential as low-cost, nontoxic, high-performance catalysts for both photo and electrochemical reactions. Because abundancy, simplicity of synthesis routes, and excellent performance are the important factors for catalysts, easy optimization and many variations are possible in carbon-materials, making them more attractive. In particular, low-dimensional carbon materials, such as graphene and graphitic carbon nitride, exhibit excellent performance because of their unique electrical, mechanical, and catalytic properties. In this mini-review, we will discuss the performance of low-dimensional carbon-based materials for water splitting reactions.

The unique physical and chemical properties of spinels have made them highly suitable electrocatalysts in oxygen evolution reaction and oxygen reduction reaction (OER & ORR). Zinc–air batteries (ZABs), which are safer and more cost-effective power sources than commercial lithium-ion batteries, hinge on ORR and OER. The slow kinetics of the air electrode reduce its high theoretical energy density and specific capacity, which limits its practical applications. Thus, tuning the performance of the electrocatalyst and cathode architecture is vital for improving the performance of ZABs, which calls for exploring spinel, a material that delivers improved performance. However, the structure–activity relationship of spinel is still unclear because there is a lack of extensive information about it. This study was performed to address the promising potential of spinel as the bifunctional electrocatalyst in ZABs based on an in-depth understanding of spinel structure and active sites at the atomic level.

Among numerous approaches to assembling nanowires onto electrodes, dielectrophoresis (DEP) is a potential candidate to place the nanowires. However, its yield is still far from perfection, urging fundamental understanding of its dynamics. Here, the impact of a static electric field on dielectrophoretic nanowire assembly on gold electrodes is investigated. Specifically, a 4 peak‐to‐peak alternating voltage with 700 Hz is applied and modulate the offset voltage from 0 to 2V. The highest yield in the alignment of the nanowires at 0.5 V offset voltage is found. With the optical investigation of misaligned nanowires, it is found that rotating wires on top of electrodes, and the analysis of their angular velocity suggest the impact of the induced static charges. The numerical analysis quantifies the length scale of competing two forces, dielectrophoretic force and electric double layer force. This work suggests a quantitative understanding of the interplay between dielectrophoresis and electric double layer, which contributes to the advances in scalable nanowire fabrications. This research investigates the assembly of nanowires on gold electrodes using dielectrophoretic force, with an emphasis on static electric fields. An optimal nanowire alignment is achieved at a 0.5 V DC offset. Findings suggest that high offset voltages disrupt alignment by causing nanowire rotation, highlighting the need for a balance between dielectrophoretic and electric double‐layer forces for effective nanowire alignment.

Here we study single-crystalline silicon nanobeams having 470 nm width and 80 nm thickness cross section, where we produce tortuous thermal paths ( i . e . labyrinths) by introducing slits to control the impact of the unobstructed “line-of-sight” (LOS) between the heat source and heat sink. The labyrinths range from straight nanobeams with a complete LOS along the entire length to nanobeams in which the LOS ranges from partially to entirely blocked by introducing slits, s  = 95, 195, 245, 295 and 395 nm. The measured thermal conductivity of the samples decreases monotonically from ~47 W m −1  K −1 for straight beam to ~31 W m −1  K −1 for slit width of 395 nm. A model prediction through a combination of the Boltzmann transport equation and ab initio calculations shows an excellent agreement with the experimental data to within ~8%. The model prediction for the most tortuous path ( s  = 395 nm) is reduced by ~14% compared to a straight beam of equivalent cross section. This study suggests that LOS is an important metric for characterizing and interpreting phonon propagation in nanostructures.

Transmission electron microscopy (TEM) is arguably the most important tool for atomic‐scale material characterization. A significant portion of the energy of transmitted electrons is transferred to the material under study through inelastic scattering, causing inadvertent damage via ionization, radiolysis, and heating. In particular, heat generation complicates TEM observations as the local temperature can affect material properties. Here, the heat generation due to electron irradiation is quantified using both top‐down and bottom‐up approaches: direct temperature measurements using nanowatt calorimeters as well as the quantification of energy loss due to inelastic scattering events using electron energy loss spectroscopy. Combining both techniques, a microscopic model is developed for beam‐induced heating and to identify the primary electron‐to‐heat conversion mechanism to be associated with valence electrons. Building on these results, the model provides guidelines to estimate temperature rise for general materials with reasonable accuracy. This study extends the ability to quantify thermal impact on materials down to the atomic scale. Electron beam is converted to heat via inelastic scattering while traversing a solid‐state medium and the generated heat often complicates experimental analysis. A nanocalorimeter enables capturing heat generation induced by electron beams, and in parallel, the electron energy loss spectroscopy measurements reveal that a key energy conversion is to be responsible for the electrons in an outer shell.

Encapsulation of single- and double-wall carbon nanotubes in carbon nanocages, which may contain gadolinium or erbium, leads to a reduction of the thermal conductivity and an improved Seebeck coefficient. The potential impact of encapsulated molecules on the thermal properties of individual carbon nanotubes (CNTs) has been an important open question since the first reports of the strong modulation of electrical properties in 2002 1 , 2 . However, thermal property modulation has not been demonstrated experimentally because of the difficulty of realizing CNT-encapsulated molecules as part of thermal transport microstructures. Here we develop a nanofabrication strategy that enables measurement of the impact of encapsulation on the thermal conductivity ( κ ) and thermopower ( S ) of single CNT bundles that encapsulate C 60 , Gd@C 82 and Er 2 @C 82 . Encapsulation causes 35–55% suppression in κ and approximately 40% enhancement in S compared with the properties of hollow CNTs at room temperature. Measurements of temperature dependence from 40 to 320 K demonstrate a shift of the peak in the κ to lower temperature. The data are consistent with simulations accounting for the interaction between CNTs and encapsulated fullerenes.

Background This study aimed to evaluate the feasibility and effectiveness of ultrasound-guided charcoal tattooing in locating metastatic lymph nodes in robotic selective neck dissection (SND) for papillary thyroid carcinoma (PTC). Methods The overall study group comprised 21 patients with PTC who underwent robotic SND via a unilateral transaxillary approach for treatment of suspicious lymph node metastasis in the lateral compartment. Charcoal suspension was injected into 10 of the patients (total of 23 lesions) 1 day before robotic SND. The authors evaluated the location of the tattoos, the success rate of localization, the intraoperative detection rate, and the complications associated with the procedure. The perioperative results were compared with those in the control group of 11 patients who did not receive charcoal tattooing. Results Charcoal suspension was successfully injected into 22 of the 23 suspicious lymph nodes (95.7 %). The remaining lesion was located posterior to the internal jugular vein. Therefore, the charcoal was injected into the soft tissue around the lymph node. Ultrasound-guided injections were well tolerated in all the patients, and no major complications occurred. All the charcoal-tattooed lesions were identified intraoperatively by the surgeon. The number of harvested and metastatic lymph nodes in the lateral compartment was greater in the patients with charcoal tattoo localization than in the control group. The two groups did not differ in terms of perioperative complications, operation time, or volume of drainage. Conclusion Ultrasound-guided charcoal tattooing for localization of metastatic lymph nodes is feasible and effective in robotic SND for the treatment of PTC with lateral compartment lymph node metastasis.

Despite extensive research on quasi-ballistic phonon transport, anomalous phonon transport is still observed in numerous nanostructures. Herein, we investigate the transport characteristics of two sets of samples: straight beams and nanoladders comprising two straight beams orthogonally connected with bridges. A combination of experiments and analysis with a Boltzmann transport model suggests that the boundary scattering within the bridges considerably dictates the distribution of phonon mean free paths, despite its negligible contribution to the net heat flux. Statistical analysis of those boundary scatterings shows that phonons with large axial angles are filtered into bridges, creating dead spaces in the line-of-sight channels. Such redistribution induces Lévy walk conduction along the line-of-sight channels, causing the remaining phonons within the bridges to exhibit Brownian motion. Phonon conduction in the nanoladders is suppressed below that of the straight beams with equivalent cross-sectional areas due to trapped phonons within the bridges. Our work reveals the origin of unusual thermal conductivity suppression at the nanoscale, suggesting a method to modulate phonon conduction via systematic nanostructuring. Despite extensive previous research, the suppression in phonon conduction at the nanoscale still calls into questions on the interaction of phonons with various sources of boundary scatterings. In this work, a combination of Boltzmann transport model and the experiments finds that the bridges contribute to phonon mean free paths proportional to its volume fraction despite its negligible contribution to net heat flux. A statistical analysis of boundary scattering reveals that transport characteristics of phonon evolves from Brownian motion to Lévy walk due to phonons trapped within the bridges.