Geometry‐tunable substrates with abundant plasmon resonant structure are ideal to proffer high surface‐enhanced Raman scattering (SERS) activity for trace sensing including pollutants and toxics, whereas great challenge remains in creating high‐density “hotspots” in these structures for further improving Raman signals and detection sensitivity. Herein, one‐step dealloying strategy is proposed to fabricate free‐standing copper membranes with hierarchical porous architecture where a high density of inherent “hotspots” is built in the vicinity of secondary pores in 3D ligaments. The hierarchical nanoporous copper shows excellent SERS activity with an average enhancement factor of 6.4 × 109, originating from strong electromagnetic coupling effects induced by its highly dense “hotspots” and highly accessible surface. Moreover, the proposed one‐step dealloying strategy of dual‐phase binary alloys propounds an inexpensive yet effective route to construct ultrasensitive SERS substrate for trace detection and molecular diagnosis.
Intermetallic compounds formed from non-precious transition metals are promising cost-effective and robust catalysts for electrochemical hydrogen production. However, the development of monolithic nanoporous intermetallics, with ample active sites and sufficient electrocatalytic activity, remains a challenge. Here we report the fabrication of nanoporous Co7Mo6 and Fe7Mo6 intermetallic compounds via liquid metal dealloying. Along with the development of three-dimensional bicontinuous open porosity, high-temperature dealloying overcomes the kinetic energy barrier, enabling the direct formation of chemically ordered intermetallic phases. Unprecedented small characteristic lengths are observed for the nanoporous intermetallic compounds, resulting from an intermetallic effect whereby the chemical ordering during nanopore formation lowers surface diffusivity and significantly suppresses the thermal coarsening of dealloyed nanostructure. The resulting ultrafine nanoporous Co7Mo6 exhibits high catalytic activity and durability in electrochemical hydrogen evolution reactions. This study sheds light on the previously unexplored intermetallic effect in dealloying and facilitates the development of advanced intermetallic catalysts for energy applications.
a Although many efforts have been made to engineer Escherichia coli for fumaric acid production, the fumarate efflux system has not been investigated as an engineering target to improve fumaric acid production. In this work, we cloned and expressed C4-dicarboxylate transporters of different sources in a previously constructed fumaric-acid-producing strain to study their effects on the production of fumaric acid. In addition, each native C4-dicarboxylate transporter was deleted in separate experiments to investigate their individual effects on fumaric acid production. The results showed that the expression of the genes dcuB-Ec and dcuC-Ec can increase the fumaric acid yield by 48.5% and 53.1%, respectively.Fed-batch cultivations in a 5 L bioreactor of strain A-dcuB-Ec produced 9.42 g L À1 of fumaric acid after 50 hours.
Active wave manipulation by ultracompact meta-devices is highly embraced in recent years, but a major concern still exists due to the lack of functional reconfigurability. Moreover, the phase or amplitude discontinuities introduced by collective response of discrete meta-atoms make current meta-devices far from practical applications. Here, we demonstrate actively tunable wavefront control with high-efficiency by combining catenary-based meta-atoms for intrinsic continuous phase regulation with the chalcogenide phase change material (PCM) of Ge2Sb2Te5. First, switchable beam deflection is demonstrated in a wide mid-IR range between 8 μm and 9.5 μm with ‘on’ and ‘off’ states for beam steering between anomalous and normal specular reflections. Second, a switchable meta-axicon for zero order Bessel beam generation is demonstrated with full width at half maximum (FWHM) as small as ∼0.41 λ (λ = 12 µm). As a result, our scheme for active and continuous phase control potentially paves an avenue to construct active photonic devices especially for applications where large contrast ratio is highly desirable, such as optoelectronic integration, wavefront engineering and so on.
Oxidative stress has been implicated in the pathogenesis of various chronic diseases such as cardiovascular disease, cancer, coronary heart disease, and arthritis. The antioxidative bioactive macromolecules, as evidenced by substantial studies, can effectively scavenge reactive oxygen species (ROS) and free radicals or mediate the immune system of the body to regulate the redox level, arousing the concern of numerous researchers on their antioxidative activities. An overview was carried out in this paper emphasizing on the types, antioxidant activities, application fields, and preparation methods of antioxidative biomacromolecules, which is expected to provide theoretical basis for the development and utilization of antioxidative biomacromolecules, as well as their applications in the fields of biomedicine, functional foods and skin care products.
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