Surface Dissociation Effect on Phosphonic Acid Self-Assembled Monolayer Formation on ZnO Nanowires

Kentaro Nakamura, Tsunaki Takahashi, Takuro Hosomi, Yu Yamaguchi, Wataru Tanaka, Jiangyang Liu, Masaki Kanai, Kazuki Nagashima, Takeshi Yanagida

Research output: Contribution to journalArticlepeer-review

Abstract

Understanding the formation process of self-assembled monolayers (SAMs) of organophosphonic acids on ZnO surfaces is essential to designing their various applications, including solar cells, heterogeneous catalysts, and molecular sensors. Here, we report the significant effect of surface dissociation on SAM formation of organophosphonic acids on single-crystalline ZnO nanowire surfaces using infrared spectroscopy. When employing the most conventional solvent-methanol (relative permittivity ϵr = 32.6), the production of undesired byproducts (layered zinc compounds) on the surface was identified by infrared spectral data and microscopy. On the other hand, a well-defined SAM structure with a tridentate coordination of phosphonic acids on the surface was confirmed when employing toluene (ϵr = 2.379) or tert-butyl alcohol (ϵr = 11.22-11.50). The observation of layered zinc compounds as byproducts highlights that the degree of Zn2+ dissociation from the ZnO solid surface into a solvent significantly affects the surface coordination of phosphonic acids during the SAM formation process. Although the ZnO nanowire surface (m-plane) is hydrophilic, the present results suggest that a weaker solvent polarity is preferred to form well-defined phosphonic acid SAMs on ZnO nanowire surfaces without detrimental surface byproducts.

Original languageEnglish
Pages (from-to)1462-1467
Number of pages6
JournalACS Omega
Volume7
Issue number1
DOIs
Publication statusPublished - Jan 11 2022

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Chemical Engineering(all)

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