Photochromism in sound-induced alignment of a diarylethene supramolecular nanofibre

A photochromic supramolecular nanofibre, composed of a diarylethene derivative, exhibits hydrodynamic alignment upon exposure to the audible sound.

Interplay Between Mechanochemistry and Sonochemistry

Ultrasonic irradiation-based mechanochemical strategies have recently been the subject of intensive investigation because of the advantages they offer. These include simplicity, energy savings and wide applicability. Traditional areas of sonoprocessing such as cleaning, efficient mixing and solid activation have been extended to both macromolecular and micro/nanostructures, some of which are biologically significant, ultrasound-responsive actuators and crystal design, among others. Unlike conventional mechanochemical protocols, which require little solvent usage if any at all, mechanical (and chemical) effects promoted by ultrasound are observed in a liquid medium. Tensile forces, which share similarities with solid mechanochemistry, are generated by virtue of nonlinear effects, notably cavitation, when high-amplitude waves propagate in a fluid. This work aims to provide insight into some recent developments in the multifaceted field of sono-mechanochemistry using various examples that illustrate the role of ultrasonic activation, which is capable of boosting hitherto sterile transformations and inventing new crafts in applied chemistry. After a preliminary discussion of acoustics, which is intended to provide a mechanistic background, we mainly focus on experimental developments, while we often mention emerging science and occasionally delve into theoretical models and force simulations.

Spectroscopic visualization of sound-induced liquid vibrations using a supramolecular nanofibre

The question of whether sound vibration of a medium can bring about any kind of molecular or macromolecular events is a long-standing scientific controversy. Although it is known that ultrasonic vibrations with frequencies of more than 1 MHz are able to align certain macromolecules in solution, no effect has yet been reported with audible sound, the frequency of which is much lower (20-20,000 Hz). Here, we report on the design of a supramolecular nanofibre that in solution becomes preferentially aligned parallel to the propagation direction of audible sound. This phenomenon can be used to spectroscopically visualize sound-induced vibrations in liquids and may find application in a wide range of vibration sensing technologies.