Nanocrystals with Metastable High-Pressure Phases Under Ambient Conditions

Tianyuan Xiao, Yasutaka Nagaoka, Xirui Wang, Tian Jiang, Derek LaMontagne, Qiang Zhang, Can Cao, Xizheng Diao, Jiahua Qiu, Yiruo Lu, Zhongwu Wang, Y. Charles Cao

This groundbreaking work was supported by a collaboration between the PI an collaborators and CHEXS scientist Zhongwu Wang, spanning many years, across the former CHESS “B-line” beamline and the new CHEXS HPBio facilities. This work was enabled by custom diamond anvil cells with large opening angles for simultaneous SAXS / WAXS measurements, and by in-situ spectroscopy techniques deployed at CHESS

pressure picture

Pressure-engineering of designer solids creates a metastable materials with structure and properties made-to-order, formed under pressure and harvested at ambient conditions, enabling real-world use of new materials for scientific innovation and technological development.

What did the scientists discover?

Pressure processing is a fast and efficient method for materials discovery and property manifestation. Upon application of pressure, soft graphite transforms to superhard diamond, while insulting sulfur turns a superconductor. Unfortunately, unlike diamond that remains stable at ambient conditions, most high-pressure phases can not be preserved upon release of pressure. The desire to harvest metastable materials and exploit their properties for real-world application is the motivation behind a recent paper from the research group of University of Florida professor Charles Cao, appearing in the journal Science this month.  In collaboration with CHEXS scientists, the team combined nanocrystal-based designer solids with controlled pressure processing and recovered high-pressure metastable phases to ambient conditions. Beyond the technological breakthrough, the team also identified the mechanisms that allowed them to retain stability of high-pressure phases, including the interplay between nanocrystals and surface-coating molecules, and the role of the 3D inter-connected nanocrystal architecture.  

The cover of the science magazine in which this work appears

Why is this important? What are the broader impacts of this work?

This new solid-solid transition pathway provides a design principle for controlled fabrication of a new generation of advanced materials. Unlike historical “trial-and-error” materials discovery, pressure-enabled discovery involves design, fabrication, and assembly of nanocrystals with desired chemical compositions and surface molecular decoration. Pressure-engineering of designer solids creates a metastable materials with structure and properties made-to-order, formed under pressure and harvested at ambient conditions, enabling real-world use of new materials for scientific innovation and technological development.

Why did this research need CHESS?

This groundbreaking work was supported by a collaboration between the PI an collaborators and CHEXS scientist Zhongwu Wang, spanning many years, across the former CHESS “B-line” beamline and the new CHEXS HPBio facilities. This work was enabled by custom diamond anvil cells with large opening angles for simultaneous SAXS / WAXS measurements, and by in-situ spectroscopy techniques deployed at CHESS to complement the information gleaned from x-ray scattering, enabling multi-modal measurements during high-pressure materials processing.     

Graphs of ligand reversibility versus solid-phase transformation
Figure 1. Ligand-tailorable reversibility of the RS-ZB solid-phase transformation in superlattices of 4.8-nm WZ CdSe nanocrystals. (A to C) WAXS and SAXS patterns collected during compression and decompression (de) at different pressures. CdSe NCs were functionalized with octylamine of (A) 92% surface coverage and of (B) 62% surface coverage and (C) capped with a mixture of octylamine and CTAB (with a molar ratio of 5:1) of 63% surface coverage in terms of hydrocarbon chains. SAXS patterns are shown in green. WAXS diffraction patterns from the WZ/ZB structure and from the RS structure are shown in blue and red, respectively. 

How was the work funded?

This research conducted jointly by a group of scientists at U. Florida and Cornell U. was supported by the National Science Foundation (NSF) under awards of DMR-1829070, DMR1710509, DMR1309798, DMR-1332208.

Popular Summary

Making the most of metastability

Wendy L. Mao and Yu Lin

Science 377, 6608, 814-815 (2022); https://doi.org/10.1126/science.add5433

Reference:

Nanocrystals with metastable high-pressure phases under ambient conditions

T Xiao, Y Nagaoka, X Wang, T Jiang, D LaMontagne, Q Zhang, C Cao, X Diao, J Qiu, Y Lu, Z Wang and Y. Charles Cao

Science 377, 6608, 870-874 (2022); https://doi.org/10.1126/science.abq7684