Gold nanorods (NRs), pseudo-one-dimensional rod-shaped nanoparticles (NPs), have become one of the burgeoning materials in the recent years due to their anisotropic shape and adjustable plasmonic properties. With the continuous improvement in synthetic methods, a variety of materials have been attached around Au NRs to achieve unexpected or improved plasmonic properties and explore state-of-the-art technologies. In this review, we comprehensively summarize the latest progress on Au NRs, the most versatile anisotropic plasmonic NPs. We present a representative overview of the advances in the synthetic strategies and outline an extensive catalogue of Au-NR-based heterostructures with tailored architectures and special functionalities. The bottom-up assembly of Au NRs into preprogrammed metastructures is then discussed, as well as the design principles. We also provide a systematic elucidation of the different plasmonic properties associated with the Au-NR-based structures, followed by a discussion of the promising applications of Au NRs in various fields. We finally discuss the future research directions and challenges of Au NRs.

The recent discovery of topological semimetals has stimulated extensive research interest due to their unique electronic properties and novel transport properties related to a chiral anomaly. However, the studies to date are largely limited to bulk crystals and exfoliated flakes. Here, we report the controllable synthesis of ultrathin two-dimensional (2D) platinum telluride (PtTe) nanosheets with tunable thickness and investigate the thickness-dependent electronic properties. We show that PtTe nanosheets can be readily grown, using a chemical vapor deposition approach, with a hexagonal or triangular geometry and a lateral dimension of up to 80 μm, and the thickness of the nanosheets can be systematically tailored from over 20 to 1.8 nm by reducing the growth temperature or increasing the flow rate of the carrier gas. X-ray-diffraction, transmission-electron microscopy, and electron-diffraction studies confirm that the resulting 2D nanosheets are high-quality single crystals. Raman spectroscopic studies show characteristics E and A vibration modes at ∼109 and ∼155 cm, with a systematic red shift with increasing nanosheet thickness. Electrical transport studies show the 2D PtTe nanosheets display an excellent conductivity up to 2.5 × 10 S m and show strong thickness-tunable electrical properties, with both the conductivity and its temperature dependence varying considerably with the thickness. Moreover, 2D PtTe nanosheets show an extraordinary breakdown current density up to 5.7 × 10 A/cm, the highest breakdown current density achieved in 2D metallic transition-metal dichalcogenides to date.

Two-dimensional layered materials (2DLMs) have attracted considerable recent interest for their layer-number-dependent physical and chemical properties, as well as potential technological opportunities. Here we report the synthesis of two-dimensional layered cadmium iodide (CdI) nanoplates using a vapor transport and deposition approach. Optical microscopy and scanning electron microscopy studies show that the resulting CdI nanoplates predominantly adopt hexagonal and triangular morphologies with a lateral dimension of ∼2-10 μm. Atomic force microscopy studies show that the resulting nanoplates exhibit a thickness in the range of 5-220 nm with a relatively smooth surface. X-ray diffraction studies reveal highly crystalline CdI in hexagonal phase, which is also confirmed by the characteristic Raman A mode at 110 cm. High-resolution transmission electron microscopy and selected area electron diffraction reveal that the resulting CdI nanoplates are single crystals. Taking a step further, we show the CdI nanoplates were readily grown on other 2DLMs (e.g., WS, WSe, MoS), forming diverse van der Waals heterostructures. Using prepatterned WS monolayer square arrays as the nucleation and growth templates, we also show that regular arrays of CdI/WS vertical heterostructures can be prepared. The synthesis of the CdI nanoplates, heterostructures, and heterostructure arrays offers a valuable material system for 2D materials science and technology.

Two-dimensional layered materials (2DLMs) have attracted considerable recent interest as a new material platform for fundamental materials science and potential new technologies. Here we report the growth of layered metal halide materials and their optoelectronic properties. BiI nanoplates can be readily grown on SiO /Si substrates with a hexagonal geometry, with a thickness in the range of 10-120 nm and a lateral dimension of 3-10 µm. Transmission electron microscopy and electron diffraction studies demonstrate that the individual nanoplates are high quality single crystals. Micro-Raman studies show characteristic A band at ≈115 cm with slight red-shift with decreasing thickness, and micro-photoluminescence studies show uniform emission around 690 nm with blue-shift with decreasing thickness. Electrical transport studies of individual nanoplates show n-type semiconductor characteristics with clear photoresponse. Further, the BiI can be readily grown on other 2DLMs (e.g., WSe ) to form van der Waals heterostructures. Electrical transport measurements of BiI /WSe vertical heterojunctions demonstrate p-n diode characteristics with gate-tunable rectification behavior and distinct photovoltaic effect. The synthesis of the BiI nanoplates can expand the library of 2DLMs and enable a wider range of van der Waals heterostructures.

The recent progress in the use of surface plasmons to improve the performance of two-dimensional material-based optoelectronic devices is discussed.