Abstract Electrically tunable graphene‐metal metasurfaces with controllable optical properties have attracted interest for straightforward manipulation of free space light. Their resonance tuning range depends on graphene's electrical transport characteristics, which are affected by its quality, operating conditions, and the device design. An important example of the latter is the direct contact of metallic antennas with the graphene layer that limits the extent to which a bias voltage can tune the metasurface's permittivity. In this work, this issue is resolved in a straightforward and fabrication‐efficient way for graphene‐metal hybrid metasurfaces with multiple plasmonic resonances. It is demonstrated that the incorporation of a 10 nm Al 2 O 3 barrier layer enhances the tuning range of mid‐infrared resonances compared to metasurfaces without barrier layer, i.e., from 300 to 700 nm for a 7.3 µm resonance and from 110 to 140 nm for a 4.7 µm resonance. The improved tunability of the metal/dielectric/graphene metasurface can be attributed to the reduced electrical coupling between metal and graphene, as confirmed by an equivalent circuit model. These results bring closer the use of active metasurfaces based on two‐dimensional materials under ambient conditions, with possible applications as optical filters, modulators, and information processing devices that require dynamic control of light.
In response to the escalating challenge of poor performance in pesticide wastewater treatment, ferromagnetic biochar derived from traditional Chinese medicine residues was added to an anaerobic membrane bioreactor (AnMBR, R2) to investigate reduced toxicity and increased gas production across different temperatures and hydraulic retention times (HRTs), compared with an AnMBR using non- ferromagnetic biochar (R1). The results demonstrated that ferromagnetic biochar significantly enhanced ethylene thiourea (ETU) removal efficiencies. Compared to R1, ETU removal in R2 increased from 40.7% to 61.0% at 10°C, from 64.6% to 71.6% at 15°C, from 76.9% to 87.0% at 25°C, and from 86.4% to 92.4% at 35°C. Similarly, COD removal in R2 with an HRT of 48 h at 15°C was comparable to the COD removal in R1 with an HRT of 48 h at 25°C, both achieving a removal efficiency of approximately 77.1±0.6%. Cyanide removal efficiency in R2 was 2.4% to 9.6% higher than in R1 across various temperatures. In addition, at an HRT of 18 h and 25°C, effluent concentrations of TMn in R2 were reduced by 378.8±96.2 mg/L compared to R1. The average enhancements of TZn removal efficiencies in R2 were higher than those in R1 by 6.5% at 10°C, 8.5% at 15°C, 3.7% at 25°C, and 4.2% at 35°C. Importantly, biogas production in R2 increased by 5.3% to 15.9% at 25°C. There were significant negative correlations between biogas production and the concentrations of ETU and cyanide. This highlights the dual benefit of R2 in enhancing pollutant degradation and energy recovery.
At present, COVID-19 is still spreading, and its transmission patterns and the main factors that affect transmission behavior still need to be thoroughly explored. To this end, this study collected the cumulative confirmed cases of COVID-19 in China by 8 April 2020. Firstly, the spatial characteristics of the COVID-19 transmission were investigated by the spatial autocorrelation method. Then, the factors affecting the COVID-19 incidence rates were analyzed by the generalized linear mixed effect model (GLMMs) and geographically weighted regression model (GWR). Finally, the geological detector (GeoDetector) was introduced to explore the influence of interactive effects between factors on the COVID-19 incidence rates. The results showed that: (1) COVID-19 had obvious spatial aggregation. (2) The control measures had the largest impact on the COVID-19 incidence rates, which can explain the difference of 34.2% in the COVID-19 incidence rates, while meteorological factors and pollutant factors can only explain the difference of 1% in the COVID-19 incidence rates. It explains that some of the literature overestimates the impact of meteorological factors on the spread of the epidemic. (3) The influence of meteorological factors was stronger than that of air pollution factors, and the interactive effects between factors were stronger than their individual effects. The interaction between relative humidity and NO2 was stronger. The results of this study will provide a reference for further prevention and control of COVID-19.
Performance of ozonation and an ozone/hydrogen peroxide process under a new concept centering on ozonation and/or ozone/hydrogen peroxide processes in sewage treatment processes comprising only physical and chemical processes are discussed, with focus on the removal of matrix organic compounds and emerging contaminants. Matrix organic compounds of filtrated primary sewage effluents were removed to as low as 3.2 mgC/L in the ozone/hydrogen peroxide process at an ozone consumption of around 400 mg/L. Linear relationships between ozone consumption and removal amounts of organic compounds were observed, in which the amounts of ozone required to remove 1 mg of organic carbon were 9.5 and 8.3 mg (2.4 and 2.1 mol-O3/mol-C) in ozonation and the ozone/hydrogen peroxide process, respectively. Ratios of hydroxyl radical exposure to ozone exposure were in the order of 10–9 to 10–8 for ozonation and 10–7 to 10–6 for the ozone/hydrogen peroxide process. Experiments and a kinetic evaluation showed that ozonation and/or the ozone/hydrogen peroxide process have high elimination capability for emerging contaminants, even in primary sewage effluent with the thorough removal of matrix organic compounds. Newly found reaction phenomena, the temporal increase and decrease of dissolved ozone and accumulation of hydrogen peroxide in the early stage of oxidation with the continuous feeding of hydrogen peroxide, were presented. Possible reaction mechanisms are also discussed.
Metallic nanostructures are becoming increasingly important for both fundamental research and practical devices. Many emerging applications employing metallic nanostructures often involve unconventional substrates that are flexible or nonplanar, making direct lithographic fabrication very difficult. An alternative approach is to transfer prefabricated structures from a conventional substrate; however, it is still challenging to maintain high fidelity and a high yield in the transfer process. In this paper, we propose a high-fidelity, clean nanotransfer lithography method that addresses the above challenges by employing a polyvinyl acetate (PVA) film as the transferring carrier and promoting electrostatic adhesion through triboelectric charging. The PVA film embeds the transferred metallic nanostructures and maintains their spacing with a remarkably low variation of <1%. When separating the PVA film from the donor substrate, electrostatic charges are generated due to triboelectric charging and facilitate adhesion to the receiver substrate, resulting in a high large-area transfer yield of up to 99.93%. We successfully transferred the metallic structures of a variety of materials (Au, Cu, Pd, etc.) with different geometries with a <50-nm spacing, high aspect ratio (>2), and complex 3D structures. Moreover, the thin and flexible carrier film enables transfer on highly curved surfaces, such as a single-mode optical fiber with a curvature radius of 62.5 μm. With this strategy, we demonstrate the transfer of metallic nanostructures for a compact spectrometer with Cu nanogratings transferred on a convex lens and for surface-enhanced Raman spectroscopy (SERS) characterization on graphene with reliable responsiveness.
Tunable Mid-Infrared Graphene–Metal Metasurfaces This cover illustrates the incorporation of a thin Al2O3 barrier layer for resolving current limitations of electrically tunable graphene–metal hybrid metasurfaces (article 2303085 by Fei Han, Xuezhi Zheng, Ewald Janssens, and co-workers). The authors' device improves the electronic doping ability of graphene, thereby enhancing the tuning range of mid-infrared metasurfaces. The straightforward approach is not only promising for future compact tunable optical devices, but it also provides guidelines for engineering future 2D material-based optoelectronics.
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