Leslie Yeo

Professor

Micro/Nanophysics Research Laboratory

School of Engineering.

Royal Melbourne Institute of Technology (RMIT University)

Australia

Personal homepage

Title: High-Frequency Nanoelectromechanical Interactions Between Sound and Matter: A New Method for the Synthesis, Processing and Manipulation of Two‐Dimensional and Bulk Crystals

Abstract: We demonstrate the intriguing possibility of harnessing phonon sources, in particular, high frequency (10 MHz order) surface and hybrid acoustic waves, for synthesizing and manipulating two-dimensional and bulk crystals. In particular, we show that the large mechanical stresses that arise from the extraordinary surface acceleration of the acoustic wave—on the order of 10 million g’s, together with the intense electric field inherent in its electromechanical coupling, are capable of facilitating rapid synthesis of organic and inorganic crystals, as well as those of metal–organic frameworks (MOFs), often yielding novel crystal morphologies and structures. Moreover, the same process can be deployed to rapidly exfoliate bulk three-dimensional crystalline transitional metal dichalcogenides (TMDs; e.g., MoS2) and carbides/nitrides (MXenes) into monolayer and few-layer nanosheets and quantum dots with high yield. Finally, the acoustic wave can be exploited for the manipulation of quasiparticles in these two-dimensional materials. For example, we show the possibility for reversibly modulating trion to exciton transition, and their subsequent transport and hence spatial separation within the material. In the case of the TMDs, we show with convincing evidence, that such novel phenomena can be attributed to their unique piezoelectric property, particularly when they exist in odd number of layers due to their broken crystallographic centrosymmetry.

Representative papers:
[1] AR Rezk, H Ahmed, S Ramesan, LY Yeo. High Frequency Sonoprocessing: A New Field of Cavitation-Free Acoustic Materials Synthesis, Processing and Manipulation. Adv Sci 8, 2001983 (2021)..
[2] H Ahmed, H Alijani, A El-Ghazaly, J Halim, BJ Murdoch, Y Ehrnst, E Massahud, AR Rezk, J Rosen, LY Yeo. Recovery of Oxidized Two-Dimensional MXenes Through High Frequency Nanoscale Electromechanical Vibration. Nature Commun 14, 3 (2023).
[3] A El Ghazaly, H Ahmed, A Rezk, J Halim, P Persson, LY Yeo, J Rosen. Ultrafast, One-Step, Salt-Solution-Based Acoustic Synthesis of Ti3C2 MXene. ACS Nano 15, 4287-4293 (2021).
[4] H Ahmed, AR Rezk, JJ Richardson, LK Macreadie, R Babarao, ELH Mayes, L Lee, LY Yeo. Acoustomicrofluidic Assembly of Oriented and Simultaneously Activated Metal-Organic Frameworks. Nature Commun 10, 2282 (2019).
[5] H Ahmed, AR Rezk, BJ Carey, Y Wang, M Mohiuddin, KJ Berean, SP Russo, K Kalantar-zadeh, LY Yeo. Ultrafast Acoustofluidic Exfoliation of Stratified Crystals. Adv Mater 30, 1704756 (2018).