Nano Letters最新文献

Titanium-based composites hold great promise in versatile functional application fields, including supercapacitors. However, conventional subtractive methods for preparing complex-shaped titanium-based composites generally suffer from several significant shortcomings, including low efficiency, strictly simple geometry, low specific surface area, and poor electrochemical performance of the products. Herein, three-dimensional composites of Ti/TiN nanotube arrays with hierarchically porous structures were prepared using the additive manufacturing method of selective laser melting combined with anodic oxidation and nitridation. The resultant Ti/TiN nanotube array composites exhibit good electrical conductivity, ultrahigh specific surface areas, and outstanding supercapacitor performances featuring the unique combination of a large specific capacitance of 134.4 mF/cm² and a high power density of 4.1 mW/cm², which was remarkably superior to that of their counterparts. This work is anticipated to provide new insights into the facile and efficient preparation of high-performance structural and functional devices with arbitrarily complex geometries and good overall performances.

Auger recombination is a pivotal process for semiconductor nanocrystals (NCs), significantly affecting charge carrier generation and collection in optoelectronic devices. This process depends mainly on the NCs' electronic structures. In our study, we investigated Auger recombination dynamics in manganese (Mn²⁺)-doped CsPbI₃ NCs using transient absorption (TA) spectroscopy combined with theoretical and experimental structural characterization. Our results show that Mn²⁺ doping accelerates Auger recombination, reducing the biexciton lifetime from 146 to 74 ps with increasing Mn doping concentration up to 10%. This accelerated Auger recombination in Mn-doped NCs is attributed to increased band edge wave function overlap of excitons and a larger density of final states of Auger recombination due to Mn orbital involvement. Moreover, Mn doping reduces the dielectric screening of the excitons, which also contributes to the accelerated Auger recombination. Our study demonstrates the potential of element doping to regulate Auger recombination rates by modifying the materials' electronic structure.

Optical multiplexing technology plays a crucial role in various fields such as data storage, anti-counterfeiting, and time-resolved biological imaging. Nevertheless, employing single-wavelength phosphorescence for multiplexing often results in spectral overlap among the emission peaks of various channels, which can precipitate crosstalk and misinterpretation in the information-decoding process, thereby compromising the integrity and precision of the encrypted data. This paper proposes a time-divided colorful multiplexing technology based on phosphorescent carbon nanodots with different colors and lifetimes. Using different luminescence colors to symbolize varying information levels helps achieve multitiered information encryption and storage. By modulation of the lifetime and the emission wavelength, intricate information can be encoded, thereby enhancing the intricacy and security of the encryption mechanism. By assigning different data bits to each color, more information can be encoded in the same physical space. This method enables higher-density information storage and fortifies encryption, ensuring the compactness and security of information.

Two-dimensional (2D) InSe and PtTe₂ have drawn extensive attention due to their intriguing properties. However, the InSe monolayer is an indirect bandgap semiconductor with a low hole mobility. van der Waals (vdW) heterostructures produce interesting electronic and optoelectronic properties beyond the existing 2D materials and endow totally new device functions. Herein, we theoretically investigated the electronic structures, transport behaviors, and electric field tuning effects of the InSe/PtTe₂ vdW heterostructures. The calculated results show that the direct bandgap type-II vdW heterostructures can be realized by regulating the stacking configurations of heterostructures. By applying an external electric field, the band alignment and bandgap of the heterostructures can also be flexibly modulated. Particularly, the hole mobility of the heterostructures is improved by 2 orders of magnitude to ∼10³ cm² V^-1 s^-1, which overcomes the intrinsic disadvantage of the InSe monolayer. The InSe/PtTe₂ vdW heterostructures have great potential applications in developing novel optoelectronic devices.

Magnetic topological materials with coexisting magnetism and nontrivial band structures exhibit many novel quantum phenomena, including the quantum anomalous Hall effect, the axion insulator state, and the Weyl semimetal phase. As a stoichiometric layered antiferromagnetic topological insulator, thin films of MnBi₂Te₄ show fascinating even-odd layer-dependent physics. In this work, we fabricate a series of thin-flake MnBi₂Te₄ devices using stencil masks and observe the Chern insulator state at high magnetic fields. Upon magnetic field training, a large exchange bias effect is observed in odd but not in even septuple layer (SL) devices. Through theoretical calculations, we attribute the even-odd layer-dependent exchange bias effect to the contrasting surface and bulk magnetic properties of MnBi₂Te₄ devices. Our findings reveal the microscopic magnetic configuration of MnBi₂Te₄ thin flakes and highlight the challenges in replicating the zero magnetic field quantum anomalous Hall effect in odd SL MnBi₂Te₄ devices.

The discovery of interfacial superconductivity in monolayer FeSe/oxides has spurred intensive research interest. Here we not only extend the FeSe/FeO_x superconducting interface to FeSe/NdFeO₃ but also establish robust interface-enhanced superconductivity at a very low doping level. Specifically, well-annealed FeSe/NdFeO₃ exhibits a low doping level of 0.038-0.046 e^-/Fe with a larger superconducting pairing gap without a nematic gap, indicating an enhancement of the enhanced superconducting pairing strength and suppression of nematicity by the FeSe/FeO_x interface compared with those of thick FeSe films. These results improve our understanding of the roles of the oxide interface in the low-electron-doped regime.

Chirality is inherent to a broad range of systems, including solid-state and wave physics. The precession (chiral motion) of the magnetic moments in magnetic materials, forming spin waves, has various properties and many applications in magnetism and spintronics. We show that an optical analogue of spin waves can be generated in arrays of plasmonic nanohelices. Such optical waves arise from the interaction between twisted helix eigenmodes carrying spin and orbital angular momenta. We demonstrate that these optical spin waves are reflected at the interface between successive domains of enantiomeric nanohelices, forming a heterochiral lattice regardless of the wave propagation direction within the lattice. Optical spin waves may be applied in techniques involving photon spin, ranging from data processing and storage to quantum optics.