Tailoring Morphology and Wetting Behavior of Films of Ionic Liquid Mixtures

• Type: Article in International Scientific Journal
• Date: 2025

Authors

Silva, SRMR (Author) Other; Carvalho, RM (Author) Other; Bondarchuk, O (Author) Other; Oliveira, GNP (Author) Other; Araújo, JP (Author) Other; Bastos, M (Author) Other; Luis M N B F Santos (Author) FCUP; Costa, JCS (Author) Other

Journal

Title: Langmuir

Vol. 41

Pages: 9086-9099

ISSN: 0743-7463

Publisher: American Chemical Society

Indexing

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Other information

Authenticus ID: P-018-FZJ

DOI: 10.1021/acs.langmuir.5c00653

Abstract (EN): Extensive research has focused on films formed by pure ionic liquids (ILs). However, growing interest in IL mixtures and their synergistic properties presents new opportunities for targeted applications and fundamental scientific investigations. This study explores the morphology of films composed of mixtures of two ILs, [C2C1im][OTf] and [C8C1im][OTf], co-deposited via physical vapor deposition (PVD)/vacuum thermal evaporation. The primary objective was understanding how varying the IL ratio influences droplet formation, surface coverage, and overall film structure. Thin-film growth was examined on glass substrates coated with indium tin oxide (ITO) and ITO/glass surfaces coated with metallic films (Au and Ag). Film morphology was characterized using optical and high-resolution scanning electron microscopy (SEM), while elemental composition was analyzed via X-ray photoelectron spectroscopy (XPS). The results show that IL mixture morphology is strongly influenced by both IL composition and substrate type. Increasing [C8C1im][OTf] content led to larger microstructures due to improved wetting, particularly on Au surfaces, resulting in nearly fully coalesced films. Metallic surfaces near ITO significantly impacted droplet behavior, with ILs exhibiting a strong affinity for metals, especially when the long-chain IL dominated the mixture. The IL-assisted crystallization of rubrene, a high-performance organic semiconductor (OSC) that typically exhibits poor crystallinity when deposited via PVD, highlights the potential of IL mixtures to enhance organic film quality. X-ray diffraction (XRD) confirmed that [C2C1im][OTf] and [C8C1im][OTf] mixtures significantly improved rubrene crystallinity, demonstrating their potential to create an optimal environment for OSC solubility and crystallization.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 14