Pressure Induced Assembly and Coalescence of Lead Chalcogenide Nanocrystals

Abstract

We report here pressure induced nanocrystal coalescence of ordered lead chalcogenide nanocrystal arrays into one-dimensional (1D) and 2D nanostructures. In particular, atomic crystal phase transitions and mesoscale coalescence of PbS and PbSe nanocrystals have been observed and monitored in situ respectively by wide- and small-angle synchrotron X-ray scattering techniques. At the atomic scale, both nanocrystals underwent reversible structural transformations from cubic to orthorhombic at significantly higher pressures than those for the corresponding bulk materials. At the mesoscale, PbS nanocrystal arrays displayed a superlattice transformation from face-centered cubic to lamellar structures, while no clear mesoscale lattice transformation was observed for PbSe nanocrystal arrays. Intriguingly, transmission electron microscopy showed that the applied pressure forced both spherical nanocrystals to coalesce into single crystalline 2D nanosheets and 1D nanorods. Our results confirm that pressure can be used as a straightforward approach to manipulate the interparticle spacing and engineer nanostructures with specific morphologies and, therefore, provide insights into the design and functioning of new semiconductor nanocrystal structures under high-pressure conditions.

Overview of HPCAT and capabilities for studying minerals and various other materials at high-pressure conditions

“…In the setup, a Pilatus 100 K is used for wide-angle x-ray scattering (WAXS) and a MAR345 image plate ~ 3 m from sample is used for SAXS. Meng et al combined HP XRD and SAXS to characterize the structural and morphological changes in PbS and PbSe nanocrystals and demonstrated that the applied pressure induced a reversible atomic phase transition of the nanocrystals under hydrostatic pressure (Meng et al 2021 ).…”

Theoretical and Experimental Advances in High-Pressure Behaviors of Nanoparticles

“…Among semiconductor NCs, PbS and PbSe are two of the most widely studied materials; they possess unique properties, including large Bohr radii of excitons, tunable absorption ranges, and focused emission colors, making them suitable for a wide range of emerging optoelectronic applications. − Although the atomic phase behaviors of these lead-chacolgenide NCs of different shapes and sizes under high pressures have been thoroughly investigated, − studies on ordered assembly at the mesoscale and pressure-induced coalescence are limited to a couple of reports on PbS nanospheres and nanocubes. , Meng et al recently reported the synthesis of 1.6 nm PbS spherical NCs and 12.1 nm PbSe nanocubes and their self-assembly into ordered arrays via slow solvent evaporation methods . Both NCs exist in RS crystal structures at ambient pressure and self-assemble into fcc superlattices.…”

“…Morphologies of NCs after compression: (A) TEM images of 2D PbS NSs and lamellar structures (inset); (B) HRTEM image of the circled area in (A) and the corresponding FFT pattern (inset); (C, D) TEM and HRTEM images of 1D PbS short NWs; (E–H) TEM, HRTEM, and FFT (inset) images of 1D PbSe NRs. Reproduced with permission from ref . Copyright 2021 American Chemical Society.…”

Silicic Acid Polymerization and SiO2 Nanoparticle Growth in Hydrothermal Solution

“…Hydrothermal synthesis of SiO 2 nanoparticles is the new technological method with a low production cost, high density of silanol groups, low toxicity, excluding the use of chemical reagents and other green chemistry methods of nanoparticle synthesis [ 1 , 2 , 3 ], and allows to obtain different forms of nanosilica—sols, gels, powders, products of the sol-gel process applied in concrete, agricultural plants, medicines, and other materials [ 4 , 5 , 6 , 7 ]. The technology of hydrothermal synthesis includes the stages of OSA polymerization, ultrafiltration membrane concentration of nanoparticles, the sol-gel process, vacuum sublimation, and others [ 4 , 5 , 6 ].…”