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Abstract In this work, we explore how the optical properties of isotropic materials can be modulated by adjacent anisotropic materials, providing new insights into anisotropic light-matter interactions in van der Waals heterostructures. Using a WS₂/ReS₂heterostructure, we systematically investigated the excitation angle-dependent photoluminescence (PL), differential reflectance, time-resolved PL, and power-dependent PL anisotropy of WS₂. Our findings reveal that the anisotropic optical response of WS₂, influenced by the crystallographically low symmetry and unique dielectric environment of ReS₂, significantly impacts both the optical and temporal behavior of WS₂. We observed that the emission anisotropy increases with optical power density, highlighting that anisotropic localization of photo-generated carriers and subsequent charge transfer dynamics are key contributors to the polarization-sensitive optical response. These findings provide a framework for leveraging optical density-sensitive anisotropy mirroring to design advanced anisotropic optoelectronic and photonic devices. 

Abstract Tightly bound electron-hole pairs (excitons) hosted in atomically-thin semiconductors have emerged as prospective elements in optoelectronic devices for ultrafast and secured information transfer. The controlled exciton transport in such excitonic devices requires manipulating potential energy gradient of charge-neutral excitons, while electrical gating or nanoscale straining have shown limited efficiency of exciton transport at room temperature. Here, we report strain gradient induced exciton transport in monolayer tungsten diselenide (WSe₂) across microns at room temperature via steady-state pump-probe measurement. Wrinkle architecture enabled optically-resolvable local strain (2.4%) and energy gradient (49 meV/μm) to WSe₂. We observed strain gradient induced flux of high-energy excitons and emission of funneled, low-energy excitons at the 2.5 μm-away pump point with nearly 45% of relative emission intensity compared to that of excited excitons. Our results strongly support the strain-driven manipulation of exciton funneling in two-dimensional semiconductors at room temperature, opening up future opportunities of 2D straintronic exciton devices. 

Abstract 2D van der Waals (vdW) materials are emerging as the next generation platform for optical and electronic devices with their wide coverage of the energy bandgaps. The strong light–matter interactions in 2D vdW layers allow for exploring novel optical and electronic phenomena such as 2D polaritons exhibiting ultrahigh field confinement, defects‐induced new quantum states, and strain‐modulated quantum confinement of 2D excitons. Far‐field optical imaging techniques are extensively used to characterize the 2D vdW materials so far, however, subdiffraction spatial resolution is required for comprehensive investigations of 2D vdW materials of which physical properties are greatly influenced by local defects and strain. This article aims to cover historical advances, fundamental principles, and distinct features of emerging near‐field optical imaging techniques: scattering‐type scanning near‐field optical microscopy, tip‐enhanced Raman spectroscopy, tip‐enhanced photoluminescence techniques, and photo‐induced force microscopy. The recent developments toward spectroscopic analysis of near‐field imaging and applications for unveiling unique properties of 2D polaritons, nanoscale defects, and mechanical strains in 2D vdW materials, are also discussed. This review article provides an understanding of emerging near‐field imaging techniques and suggests prospective applications for exploring 2D vdW materials. 

Abstract Abundant Li resources in the ocean are promising alternatives to refining ore, whose supplies are limited by the total amount and geopolitical imbalance of reserves in Earth's crust. Despite advances in Li⁺extraction using porous membranes, they require screening other cations on a large scale due to the lack in precise control of pore size and inborn defects. Herein, MoS₂nanoflakes on a multilayer graphene membrane (MFs‐on‐MGM) that possess ion channels comprising i) van der Waals interlayer gaps for optimal Li⁺extraction and ii) negatively charged vertical inlets for cation attraction, are reported. Ion transport measurements across the membrane reveal ≈6‐ and 13‐fold higher selectivity for Li⁺compared to Na⁺and Mg²⁺, respectively. Furthermore, continuous, stable Li⁺extraction from seawater is demonstrated by integrating the membrane into a H₂and Cl₂evolution system, enabling more than 10⁴‐fold decrease in the Na⁺concentration and near‐complete elimination of other cations. 

Abstract The past decade has witnessed a rapid growth of graphene plasmonics and their applications in different fields. Compared with conventional plasmonic materials, graphene enables highly confined plasmons with much longer lifetimes. Moreover, graphene plasmons work in an extended wavelength range, i.e., mid-infrared and terahertz regime, overlapping with the fingerprints of most organic and biomolecules, and have broadened their applications towards plasmonic biological and chemical sensors. In this review, we discuss intrinsic plasmonic properties of graphene and strategies both for tuning graphene plasmons as well as achieving higher performance by integrating graphene with plasmonic nanostructures. Next, we survey applications of graphene and graphene-hybrid materials in biosensors, chemical sensors, optical sensors, and sensors in other fields. Lastly, we conclude this review by providing a brief outlook and challenges of the field. Through this review, we aim to provide an overall picture of graphene plasmonic sensing and to suggest future trends of development of graphene plasmonics. 

Stretchable and free‐form displays receive significant attention as they hold immense potential for revolutionizing future display technologies. These displays are designed to conform to irregular surfaces and endure mechanical strains, making them well suited for applications in wearable electronics, biomedical devices, and interactive displays. Traditional light‐emitting devices typically employ brittle inorganic and metallic materials, which are not conducive to stretchability. However, replacing these nonflexible components with flexible/stretchable nanomaterials, soft organic materials, or their composites improves the overall flexibility and stretchability of devices. In this review, the roles and opportunities of nanomaterials, such as thin films, 1D nanofibrous materials, and micro/nanoparticles, are highlighted for enhancing the stretchability and overall performance of various types of light‐emitting devices. By leveraging the unique mechanical and electrical properties of nanomaterials, various efforts emerge to push the boundaries of stretchable display technologies and further realize their full potential for diverse applications.