Abstract Nanoimprint lithography (NIL) has attracted attention recently as a promising fabrication method for dielectric metalenses owing to its low cost and high throughput, however, high aspect ratio (HAR) nanostructures are required to manipulate the full 2π phase of light. Conventional NIL using a hard-polydimethylsiloxane (h-PDMS) mold inevitably incurs shear stress on the nanostructures which is inversely proportional to the surface area parallel to the direction of detachment. Therefore, HAR structures are subjected to larger shear stresses, causing structural failure. Herein, we propose a novel wet etching NIL method with no detachment process to fabricate flawless HAR metalenses. The water-soluble replica mold is fabricated with polyvinyl alcohol (PVA) which is simpler than an h-PDMS mold, and the flexibility of the PVA mold is suitable for direct printing as its high tensile modulus allows high-resolution patterning of HAR metalenses. The diffraction-limited focusing of the printed metalenses demonstrates that it operates as an ideal lens in the visible regime. This method can potentially be used for manufacturing various nanophotonic devices that require HAR nanostructures at low cost and high throughput, facilitating commercialization.
In this study, an efficient hierarchical Co-Pi clusters/Fe 2 O 3 nanorods/FTO micropillars 3D branched photoanode was designed for enhanced photoelectrochemical performance. A periodic array of FTO micropillars, which acts as highly conductive “host” framework for uniform light scattering and extremely enlarged active area, was fabricated by direct printing and mist-CVD. Fe 2 O 3 nanorods that act as light absorber “guest” materials and Co-Pi clusters that give rise to random light scattering were synthesized via a hydrothermal reaction and photo-assisted electrodeposition, respectively. The hierarchical 3D branched photoanode exhibits enhanced light absorption efficiency because of multiple light scattering, which combined with the uniform light scattering of the periodic FTO micropillars and the random light scattering of the Fe 2 O 3 nanorods. Additionally, the large surface area of the 3D FTO micropillar together with the surface area provided by the one-dimensional Fe 2 O 3 nanorods contribute to a significant increase in the surface area of the photoanode. Due to these enhancement methods and the further decoration by the Co–Pi catalyst that enhances surface water oxidation, the photocurrent density of 3D branched Fe 2 O 3 photoanode reaches 1.51 mA cm −2 at 1.23 V RHE , which is 5.2 times higher than that of the flat non-decorated Fe 2 O 3 photoanode.
Abstract Daytime radiative cooling presents a compelling technology, noted for its efficiency and environmental friendliness. Recent studies have focused on not only the cooling capacity but also the applicability and versatility of this technology. This study introduces a daytime radiative cooler as a sheet with exceptional cooling performance. Its matrix is composed of polymethylmethacrylate (PMMA) and thermoplastic polyurethane (TPU), which are emerging organic materials suitable for radiative cooling. Furthermore, aluminum oxide (Al 2 O 3 ) is employed as a supporting dielectric particle to enhance cooling performance. An Al 2 O 3 ‐assisted organic composite (AOC) is created through electrospinning and hot‐pressing, resulting in a bendable sheet form. The AOC sheet demonstrates a light reflectance of 97.9% across the solar spectral region (0.3–2.5 µm) and an emissivity of 95.2% within the atmospheric transparency window (ATW) of 8–13 µm. The cooling power, derived from optical properties, is calculated to be 120.1 Wm −2 . Experimental findings confirm the AOC sheet's capability to achieve 4.9 °C below ambient temperature and, when applied to a car model, to reduce the interior temperature by 12.7 °C.
In this study, an efficient hierarchical Co-Pi cluster/Fe2O3 nanorod/fluorine-doped tin oxide (FTO) micropillar three-dimensional (3D) branched photoanode was designed for enhanced photoelectrochemical performance. A periodic array of FTO micropillars, which acts as a highly conductive "host" framework for uniform light scattering and provides an extremely enlarged active area, was fabricated by direct printing and mist-chemical vapor deposition (CVD). Fe2O3 nanorods that act as light absorber "guest" materials and Co-Pi clusters that give rise to random light scattering were synthesized via a hydrothermal reaction and photoassisted electrodeposition, respectively. The hierarchical 3D branched photoanode exhibited enhanced light absorption efficiency because of multiple light scattering, which was a combination of uniform light scattering from the periodic FTO micropillars and random light scattering from the Fe2O3 nanorods. Additionally, the large surface area of the 3D FTO micropillar, together with the surface area provided by the one-dimensional Fe2O3 nanorods, contributed to a remarkable increase in the specific area of the photoanode. Because of these enhancements and further improvements facilitated by decoration with a Co-Pi catalyst that enhanced water oxidation, the 3D branched Fe2O3 photoanode achieved a photocurrent density of 1.51 mA cm-2 at 1.23 VRHE, which was 5.2 times higher than that generated by the non-decorated flat Fe2O3 photoanode.
Young Stellar Objects (YSOs) in the early evolutionary stages are very embedded, and thus they emit most of their energy at long wavelengths such as far-infrared (FIR) and submillimeter (Submm). Therefore, the FIR observational data are very important to classify the accurate evolutionary stages of these embedded YSOs, and to better constrain their physical parameters in the dust continuum modeling. We selected 28 YSOs, which were detected in the AKARI Far-Infrared Surveyor (FIS), from the Spitzer c2d legacy YSO catalogs to test the effect of FIR fluxes on the classification of their evolutionary stages and on the constraining of envelope properties, internal luminosity, and UV strength of the Interstellar Radiation Field (ISRF). According to our test, one can mis-classify the evolutionary stages of YSOs, especially the very embedded ones if the FIR fluxes are not included. In addition, the total amount of heating of YSOs can be underestimated without the FIR observational data.
Colored radiative cooling (CRC) offers an attractive alternative for surface and space cooling, while preserving the aesthetics of an object. However, there has been no study on the CRC using phosphors in regard to vivid coloration, sophisticated performance investigation, retention of properties, functionality, and structural flexibility all at once. Thus, to manage the entire solar spectrum, a colored cooling structure comprising a near-infrared (NIR)-reflective bottom layer and a top colored layer with a phosphor-embedded polymer matrix is proposed. The structure is paintable, vividly colored, hydrophobic, and ultraviolet (UV) and water resistant. In the daytime outdoor measurement, the structure with red, orange, and yellow colors exhibited lower temperature than a control group using commercial white paint by 4.7 °C, 7.2 °C, and 7.4 °C, respectively. After precise theoretical and experimental time-tracing temperature validation, the CRC performance enhancement from NIR reflection and photoluminescence effects was thoroughly analyzed, and a temperature reduction of up to 16.1 °C was achieved for the orange-colored structure. Furthermore, experiments of hydrophobicity infusion and exposure to UV and deionized water verified the durability of the colored cooling structure. In addition, flexible-film-type colored cooling structures were demonstrated using different bottom reflective layers, such as a silver thin film and porous aluminum oxide particle-embedded poly(vinylidene fluoride-co-hexafluoropropylene), suggesting the potential applicability of these colored cooling structures for vivid-colored, functional, and durable CRC.
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