While various effects of physicochemical parameters (e.g., size, facet, composition, and internal structure) on the catalytic efficiency of nanozymes (i.e., nanoscale enzyme mimics) have been studied, the strain effect has never been reported and understood before. Herein, we demonstrate the strain effect in nanozymes by using Pd octahedra and icosahedra with peroxidase-like activities as a model system. Strained Pd icosahedra were found to display 2-fold higher peroxidase-like catalytic efficiency than unstrained Pd octahedra. Theoretical analysis suggests that tensile strain is more beneficial to OH radical (a key intermediate for the catalysis) generation than compressive strain. Pd icosahedra are more active than Pd octahedra because icosahedra amplify the surface strain field. As a proof-of-concept demonstration, the strained Pd icosahedra were applied to an immunoassay of biomarkers, outperforming both unstrained Pd octahedra and natural peroxidases. The findings in this research may serve as a strong foundation to guide the design of high-performance nanozymes.
Summary With the developing of exploration, ultra-deep fractured vuggy carbonate reservoir in Tarim Basin has become the key field of oil and gas exploration and development. Coherence attribute is used to characterize discontinuities in strata by measuring the amplitude and waveform transverse changes caused by tectonic discontinuity, stratigraphic discontinuity and pitch-out in seismic data, which is usually used to identify and image faults and river channels. But the low signal to noise ratio of ultra-deep seismic data has seriously interfered with the accuracy of coherence attribute's identification of reservoirs. In order to solve this problem, this paper proposes to introduce Karhunen-Loeve (KL) filter into FIC, and then adjust the proportion of C3 and eigenvector coherence in FIC by a scale factor, so as to realize the effective identification of "string beads", which is the seismic response of reservoir.
Strong light interaction with a subwavelength object has been a long pursuing goal with difficulties mainly arising from the diffraction limit. We propose a high finesse cavity with one mirror made of a subwavelength resonant particle as a platform to enhance this interaction. High-quality eigenmode solutions are obtained for such a highly non-paraxial cavity with a very high field concentration at the particle. The eigenmode solutions interact with the small particle in a more general way than by the electric dipole approximation. With the help of the anapole excitation in the dipole term, the particle is designed to scatter like a pure magnetic quadrupole, and in this way, it has anear-unity reflectivity when used as a mirror for the strongly focused field of the eigenmode. Light-matter interactions at the subwavelength scale can be greatly enhanced due to the small size of the particle and the high finesse of the cavity, which can be potentially interesting for applications in nano optics, quantum optomechanics, nonlinear optics, and subwavelength metrology beyond the electric dipole approximation.
Mid-air 360° videos are videos shot by placing the camera on the drone or helicopter. However, how the camera height of mid-air 360° videos affects user experience is unclear. The study explores whether the camera's height affects users' immersion, presence, and realism. Results suggest that when the camera height is higher, immersion decreases for acrophobic people while first drops and then rises for others because of the broad vision and beautiful scenery. Higher camera height brings a higher presence and worse realism, especially in distance details. Our work contributes to better understanding and designing of mid-air 360° video experiences.
We propose an optical antenna as a unidirectional surface plasmon polariton (SPP) mode launcher. Appropriate tuning of the transverse and longitudinal resonance of the antenna makes the scattered field pattern mimic that of the rotating dipole. An extinction ratio of 110 dB is achieved for the SPP launched via the optical antenna. The steering of the SPP propagation direction can be controlled by focusing on antennas with different orientations. The universal design can also be applied to unidirectional launching of the waveguide mode.
Abstract Noble‐metal nanostructures have emerged as a category of efficient and versatile peroxidase mimics in recent years. Enhancing their peroxidase‐like activities is essential to the realization of certain applications. In this review, we focus on how to engineer noble‐metal nanostructures with enhanced peroxidase‐like activities. The article is organized by introducing the impacts of surface capping ligands, particle size, shape, elemental composition, and internal structure as key parameters for the peroxidase‐like activity of noble‐metal nanostructures. Emphasis is given to the controlled synthesis of nanostructures and their peroxidase‐like catalytic efficiencies. At the end, we provide a perspective on future developments in the research relevant to peroxidase mimics of noble metals.
We report in this article a detailed study on how to stabilize a first-row transition metal (M) in an intermetallic L10-MPt alloy nanoparticle (NP) structure and how to surround the L10-MPt with an atomic layer of Pt to enhance the electrocatalysis of Pt for oxygen reduction reaction (ORR) in fuel cell operation conditions. Using 8 nm FePt NPs as an example, we demonstrate that Fe can be stabilized more efficiently in a core/shell structured L10-FePt/Pt with a 5 Å Pt shell. The presence of Fe in the alloy core induces the desired compression of the thin Pt shell, especially the two atomic layers of Pt shell, further improving the ORR catalysis. This leads to much enhanced Pt catalysis for ORR in 0.1 M HClO4 solution (at both room temperature and 60 °C) and in the membrane electrode assembly (MEA) at 80 °C. The L10-FePt/Pt catalyst has a mass activity of 0.7 A/mgPt from the half-cell ORR test and shows no obvious mass activity loss after 30 000 potential cycles between 0.6 and 0.95 V at 80 °C in the MEA, meeting the DOE 2020 target (<40% loss in mass activity). We are extending the concept and preparing other L10-MPt/Pt NPs, such as L10-CoPt/Pt NPs, with reduced NP size as a highly efficient ORR catalyst for automotive fuel cell applications.
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