Theoretical and Experimental Advances in High-Pressure Behaviors of Nanoparticles

Using compressive mechanical forces, such as pressure,to inducecrystallographic phase transitions and mesostructural changes whilemodulating material properties in nanoparticles (NPs) is a uniqueway to discover new phase behaviors, create novel nanostructures,and study emerging properties that are difficult to achieve underconventional conditions. In recent decades, NPs of a plethora of chemicalcompositions, sizes, shapes, surface ligands, and self-assembled mesostructureshave been studied under pressure by in-situ scattering and/or spectroscopytechniques. As a result, the fundamental knowledge of pressure-structure-propertyrelationships has been significantly improved, leading to a betterunderstanding of the design guidelines for nanomaterial synthesis.In the present review, we discuss experimental progress in NP high-pressureresearch conducted primarily over roughly the past four years on semiconductorNPs, metal and metal oxide NPs, and perovskite NPs. We focus on thepressure-induced behaviors of NPs at both the atomic- and mesoscales,inorganic NP property changes upon compression, and the structuraland property transitions of perovskite NPs under pressure. We furtherdiscuss in depth progress on molecular modeling, including simulationsof ligand behavior, phase-change chalcogenides, layered transitionmetal dichalcogenides, boron nitride, and inorganic and hybrid organic-inorganicperovskites NPs. These models now provide both mechanistic explanationsof experimental observations and predictive guidelines for futureexperimental design. We conclude with a summary and our insights onfuture directions for exploration of nanomaterial phase transition,coupling, growth, and nanoelectronic and photonic properties.