Pressure exerts a profound influence on atomic configurations and interlayer interactions, thereby modulating the electronic and structural properties of materials. While high pressure has been observed to induce a structural phase transition in bulk PdSe₂ crystals, leading to a transition from semiconductor to metal, the high-pressure behavior of few-layer PdSe₂ remains elusive. Here, employing diamond anvil cell (DAC) techniques and high-pressure Raman spectroscopy, we investigate the structural evolution of layer-dependent PdSe₂ under high pressure. We reveal that pressure significantly enhances interlayer coupling in PdSe₂, driving structural phase transitions from an orthorhombic to a cubic phase. We demonstrate that PdSe₂ crystals exhibit distinct layer-dependent pressure thresholds during the phase transition, with the decrease of transition pressure as the thickness of PdSe₂ increases. Furthermore, our results of polarized Raman spectra confirm a reduction in material anisotropy with increasing pressure. This study offers crucial insights into the structural evolution of layer-dependent van der Waals materials under pressure, advancing our understanding of their pressure-induced behaviors.

Neuromorphic computing systems, which mimic the operation of neurons and synapses in the human brain, are seen as an appealing next-generation computing method due to their strong and efficient computing abilities. Two-dimensional (2D) materials with dangling bond-free surfaces and atomic-level thicknesses have emerged as promising candidates for neuromorphic computing hardware. As a result, 2D neuromorphic devices may provide an ideal platform for developing multifunctional neuromorphic applications. Here, we review the recent neuromorphic devices based on 2D material and their multifunctional applications. The synthesis and next micro–nano fabrication methods of 2D materials and their heterostructures are first introduced. The recent advances of neuromorphic 2D devices are discussed in detail using different operating principles. More importantly, we present a review of emerging multifunctional neuromorphic applications, including neuromorphic visual, auditory, tactile, and nociceptive systems based on 2D devices. In the end, we discuss the problems and methods for 2D neuromorphic device developments in the future. This paper will give insights into designing 2D neuromorphic devices and applying them to the future neuromorphic systems.

Featured with high thermal decomposition temperature and layered structure, violet phosphorus (VP) offers an unparalleled stable allotrope of phosphorus to demonstrate the optoelectronic device and photonics elements with high performance at the nanoscale. Here, we report few-layer and hundreds of nanometer-sized VP with robust stability in different solvents and ambient conditions by ultrasound-assisted liquid phase exfoliation approach. For the first time, the ultrafast carrier dynamics and third-order nonlinear optical response of VP were investigated. Sub-picosecond timescale ultrafast carrier dynamic and ultrafast nonlinear saturable absorption of VP were demonstrated. Our findings demonstrated that VP possessed a promising potential for use in ultrafast nonlinear photonic applications such as saturable absorbers and optical switches.

An emerging subclass of transition-metal dichalcogenides (TMDs), noble-transition-metal dichalcogenides (NMDs), has led to an increase in nanoscientific research in two-dimensional (2D) materials. NMDs feature a unique structure and several useful properties. 2D NMDs are promising candidates for a broad range of applications in areas such as photodetectors, phototransistors, saturable absorbers, and meta optics. In this review, the state of the art of 2D NMDs research, their structures, properties, synthesis, and potential applications are discussed, and a perspective of expected future developments is provided.