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Keywords:

  • acoustic alignment;
  • linear dichroism;
  • nanofibers;
  • sound;
  • supramolecular chemistry

Abstract

Audible sound with a low-frequency vibration brings about hydrodynamic alignment of a supramolecular nanofiber in solution. Design of the nanoscale molecules and molecular assemblies, which can sense a wide range of frequencies of the audible sound wave with high sensitivity, develops sound-driven molecular machines and sound-responsive nanomaterials, and is also interesting for investigation of unknown physical interactions between the molecules and audible sound vibrations. In this study, it was found that a supramolecular nanofiber, composed of an anthracene derivative AN, in an n-hexane solution aligned upon exposure to an audible sound wave at frequencies up to 1000 Hz, with quick responses to the sound and silence, and to amplitude and frequency changes of the sound wave. These properties are of great advantage to sense dynamic changes of fluid flows, such as those induced by the sound of music. Music is composed of multiple complex sounds and silence, which characteristically change in the course of its playing time. When classical music was playing, the AN nanofiber aligned itself in harmony with the sound of the music. Time course linear dichroism spectroscopy revealed the dynamic acoustic alignments of the AN nanofiber in the solution upon playing the music. The sound vibrations of music, which generate acoustic streaming flows in liquid media, allowed shear-induced alignments of the nanofiber.