Nanocrystal Synthesis within Solid-State Confinement

Abstract

Designing, synthesizing, and modifying nanomaterials (below 100nm in size) are at the leading edge of emerging nanoscience and nanotechnology due to exhibiting a wide range of enhanced and new physicochemical properties such as mechanical, thermal, electronic, optical properties which are significantly different from their bulk counterparts. It makes these materials superior and indispensable in many modern technological applications. By taking advantage of the unique physicochemical properties of nanocrystals, different synthetic strategies, bottom-up and top-down approach, have been developed. Among those synthetic methods, solution-based process to synthesize nanocrystals have been mostly employed with a specific precursor, stabilizing and/or capping agent. Despite remarkable advances in wet-chemical syntheses for precisely synthesizing and tailoring nanocrystals, solution-based procedures are still restricted to preparing a wider variety of nanocrystals owing to limited available precursors, organic surfactants, and reaction conditions. Unlike well-established solution-based process, solid-state reaction, which allows us to synthesize almost unrestricted metal-combinations and alloys, has been scarcely employed to synthesize nanocrystals due to inevitable sintering and aggregation during the conventional solid-state reaction process required high-temperature (>300 °C). Recently, high-temperature solid-state reaction with different type of templates for synthesizing nanocrystals has been devised, which could provide a potential novel nanoparticles not synthesized via conventional solution-based chemical reaction. This review will summarize syntheses of various nanocrystals through high-temperature solid-state reaction with spatial confinement strategy. The discussion will develop to the crucial examples of synthesizing nanocrystals through solid-state reaction pathway, which involves growing crystals spatially restricted within thermally stable porous materials, nanoparticles, or two-dimensional substrates.