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Structural coloration has been reported for many types of two-dimensional materials including metal oxide nanosheets. In particular, metal oxide nanosheets are featured by a wealth of composition and structure, but their impact on structural color has not been explored. In the current study, we report structural coloration observed for aqueous suspensions of three types of transition metal oxide nanosheets (Ti1.73O41.08−, TiNbO5−, and Ti2NbO7−) obtained via exfoliation of precursory layered compounds with tetramethylammonium hydroxide (TMAOH). It was revealed that a minute amount of TMA+ was retained even after deionization via repeated centrifugation, acting as counter cations to the negatively charged nanosheets. This residual TMA+ ions contributed to stabilize the dispersion of nanosheets under low ionic strength conditions, while the intersheet spacing was expanded to a magnitude comparable to the wavelength of the visible light range, resulting in the structural coloration. The wavelength of structural colors was dependent not only on nanosheet concentration, but also on the type of nanosheets, correlating with the charge (zeta potential) and thickness of the nanosheets, as well as amounts of TMA+ dissociated from the nanosheet surfaces. Specifically, TiNbO5− was featured with the highest amount of TMA+ in the solution, which screened the negative charge of the nanosheets and resulted in the smallest intersheet spacing. On the other hand, when the dissociated amount of TMA+ was diminished, Ti2NbO7− with a larger thickness yielded a larger intersheet spacing than that of Ti1.73O41.08−. These findings provide a valuable clue to rational control of structural colors derived from nanosheets with different composition and structure for a wide range of applications.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: Structural coloration, Liquid crystallinity, Metal oxide nanosheets, Surface charge, Ionic strength

Date published: 2025-10-27

Publisher: American Chemical Society (ACS)

Journal:

• JACS Au (ISSN: 26913704) vol. 5 issue. 10 p. 5207-5216

Funding:

• Core Research for Evolutional Science and Technology JPMJCR17N1
• Core Research for Evolutional Science and Technology JPMJCR22B1
• Japan Society for the Promotion of Science 22H01916

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1021/jacsau.5c01152

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Updated at: 2025-10-29 12:30:10 +0900

Published on MDR: 2025-10-29 12:17:10 +0900