Relationship between tribology and optics in thin films of mechanically oriented nanocrystals

Liana Wong, Chunhua Hu, Ruthanne Paradise, Zina Zhu, Alexander Shtukenberg, Bart Kahr

Research output: Contribution to journalArticlepeer-review


Many crystalline dyes, when rubbed unidirectionally with cotton on glass slides, can be organized as thin films of highly aligned nanocrystals. Commonly, the linear birefringence and linear dichroism of these films resemble the optical properties of single crystals, indicating precisely oriented particles. Of 186 colored compounds, 122 showed sharp extinction and 50 were distinctly linearly dichroic. Of the latter 50 compounds, 88% were more optically dense when linearly polarized light was aligned with the rubbing axis. The mechanical properties of crystals that underlie the nonstatistical correlation between tribological processes and the direction of electron oscillations in absorption bands are discussed. The features that give rise to the orientation of dye crystallites naturally extend to colorless molecular crystals.

Original languageEnglish (US)
Pages (from-to)12245-12251
Number of pages7
JournalJournal of the American Chemical Society
Issue number29
StatePublished - Jul 25 2012

ASJC Scopus subject areas

  • Catalysis
  • General Chemistry
  • Biochemistry
  • Colloid and Surface Chemistry


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