Anisotropic fluid flows in black phosphorus nanochannels.

With the development of advanced micro/nanoscale technologies, two-dimensional materials have emerged from laboratories and have been applied in practice. To investigate the mechanisms of solid-liquid interactions in potential applications, molecular dynamics simulations are employed to study the flow behavior of n-dodecane (C12) molecules confined in black phosphorus (BP) nanochannels. Under the same external conditions, a significant difference in the velocity profiles of fluid molecules is observed when flowing along the armchair and zigzag directions of the BP walls. The average velocity of C12 molecules flowing along the zigzag direction is 9-fold higher than that along the armchair direction. The friction factor at the interface between C12 molecules and BP nanochannels and the orientations of C12 molecules near the BP walls are analyzed to explain the differences in velocity profiles under various flow directions, external driving forces, and nanochannel widths. The result shows that most C12 molecules are oriented parallel to the flow direction along the zigzag direction, leading to a relatively smaller friction factor hence a higher average velocity. In contrast, along the armchair direction, most C12 molecules are oriented perpendicular to the flow direction, leading to a relatively larger friction factor and thus a lower average velocity. This work provides important insights into understanding the anisotropic liquid flows in nanochannels.

Eggshell Biowaste-Derived Flexible and Self-Cleaning Films for Efficient Subambient Daytime Radiative Cooling.

The management of the abundant eggshell biowaste produced worldwide has become a problematic issue due to the generated odor and microorganisms after direct disposal of the eggshell biowaste in landfills. Herein, we propose a new method to convert the hazardous eggshell biowaste to valuable resources for energy management applications. Eggshell-based films are fabricated by embedding eggshell powders into a polymer matrix to achieve highly efficient subambient daytime radiative cooling. Benefiting from the Mie scattering of the eggshell particles/air pores in the solar spectrum and the strong emission of the eggshell in the mid-infrared (mid-IR) range, the eggshell-based films present a high reflection of 0.96 in the solar spectrum and a high emission of 0.95 in the mid-IR range, with notable average temperature reductions of 4.1 and 11 °C below the ambient temperature during daytime and nighttime, respectively. Moreover, the eggshell-based films exhibit excellent flexibility and self-cleaning properties, which are beneficial for practical long-term outdoor applications. Our proposed design provides a new means for environmentally friendly and sustainable management of eggshell biowaste.

Design of a High-Performance Titanium Nitride Metastructure-Based Solar Absorber Using Quantum Computing-Assisted Optimization.

Metastructures of titanium nitride (TiN), a plasmonic refractory material, can potentially achieve high solar absorptance while operating at elevated temperatures, but the design has been driven by expert intuition. Here, we design a high-performance solar absorber based on TiN metastructures using quantum computing-assisted optimization. The optimization scheme includes machine learning, quantum annealing, and optical simulation in an iterative cycle. It designs an optimal structure with solar absorptance > 95% within 40 h, much faster than an exhaustive search. Analysis of electric field distributions demonstrates that combined effects of Fabry-Perot interferences and surface plasmonic resonances contribute to the broadband high absorption efficiency of the optimally designed metastructure. The designed absorber may exhibit great potential for solar energy harvesting applications, and the optimization scheme can be applied to the design of other complex functional materials.

Suppressing Dendrite Growth and Side Reactions via Mechanically Robust Laponite-Based Electrolyte Membranes for Ultrastable Aqueous Zinc-Ion Batteries.

The development of aqueous zinc-ion batteries (AZIBs) faces significant challenges because of water-induced side reactions arising from the high water activity in aqueous electrolytes. Herein, a quasi-solid-state electrolyte membrane with low water activity is designed based on a laponite (LP) nanoclay for separator-free AZIBs. The mechanically robust LP-based membrane can perform simultaneously as a separator and a quasi-solid-state electrolyte to inhibit dendrite growth and water-induced side reactions at the Zn/electrolyte interface. A combination of density functional theory calculations, theoretical analyses, and experiments ascertains that the water activities associated with self-dissociation, byproduct formation, and electrochemical decomposition could be substantially suppressed when the water molecules are absorbed by LP. This could be attributed to the high water adsorption and hydration capabilities of LP nanocrystals, resulting from the strong Coulombic and hydrogen-binding interactions between water and LP. Most importantly, the separator-free AZIBs exhibit high capacity retention rates of 94.10% after 2,000 cycles at 1 A/g and 86.32% after 10,000 cycles at 3 A/g, along with enhanced durability and record-low voltage decay rates over a 60-day storage period. This work provides a fundamental understanding of water activity and demonstrates that LP nanoclay is promising for ultrastable separator-free AZIBs for practical energy storage applications.

Molecular Alignment-Mediated Stick-Slip Poiseuille Flow of Oil in Graphene Nanochannels.

The flow behavior of oil in nanochannels has attracted extensive attention for oil transport applications. In most, if not all, of the prior theoretical simulations, oil molecules were observed to flow steadily in nanochannels under pressure gradients. In this study, non-equilibrium molecular dynamics simulations are conducted to simulate the Poiseuille flow of oil with three different hydrocarbon chain lengths in graphene nanochannels. Contrary to the conventional perception of steady flows of oil in nanochannels, we find that oil molecules with the longest hydrocarbon chain (i.e., n-dodecane) exhibit notable stick-slip flow behavior. An alternation between the high average velocity of n-dodecane in the slip motion and the low average velocity in the stick motion is observed, with a drastic, abrupt velocity jolt of up to 40 times occurring at the transition in a stick-slip motion. Further statistical analyses show that the stick-slip flow behavior of n-dodecane molecules originates from the molecular alignment change of oil near the graphene wall. The molecular alignment of n-dodecane shows different statistical distributions under stick and slip motion states, leading to significant changes of friction forces and thus notable velocity fluctuations. This work provides new insights into the Poiseuille flow behavior of oil in graphene nanochannels and may offer useful guidelines for other mass transport applications.

An Overview of Electrochemical Sensors Based on Transition Metal Carbides and Oxides: Synthesis and Applications.

Sensors play vital roles in industry and healthcare due to the significance of controlling the presence of different substances in industrial processes, human organs, and the environment. Electrochemical sensors have gained more attention recently than conventional sensors, including optical fibers, chromatography devices, and chemiresistors, due to their better versatility, higher sensitivity and selectivity, and lower complexity. Herein, we review transition metal carbides (TMCs) and transition metal oxides (TMOs) as outstanding materials for electrochemical sensors. We navigate through the fabrication processes of TMCs and TMOs and reveal the relationships among their synthesis processes, morphological structures, and sensing performance. The state-of-the-art biological, gas, and hydrogen peroxide electrochemical sensors based on TMCs and TMOs are reviewed, and potential challenges in the field are suggested. This review can help others to understand recent advancements in electrochemical sensors based on transition metal oxides and carbides.

High-performance polarization-independent black phosphorus refractive index sensors enabled by a single-layer pattern design.

The in-plane orientation-dependent electrical and optical properties of two-dimensional (2D) anisotropic materials attract significant attention because of the intriguing underlying physics. However, this feature limits their further development in polarization-independent applications such as refractive index sensors and light absorbers. In this paper, polarization-independent optical properties of black phosphorous (BP) metadevices are achieved by the design of a single-layer pattern of 2D anisotropic material. Finite-difference time-domain (FDTD) simulation results indicate that the absorption spectrum remains unchanged as the polarization angle of the incident light varies from 0° to 360°. The performance of the BP metadevices when used as refractive index sensors is also studied. The results show that the polarization-independent BP sensors exhibit high sensitivity and figures of merit (FOMs). This work opens up the possibility of fabricating optically polarization-independent devices based on a single-layer pattern of 2D anisotropic material.