1
|
Carvalho RM, Santos LMNBF, Bastos M, Costa JCS. Carbon-Induced Changes in the Morphology and Wetting Behavior of Ionic Liquids on the Mesoscale. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024. [PMID: 38343280 PMCID: PMC10883047 DOI: 10.1021/acs.langmuir.4c00102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/25/2024]
Abstract
Thin films of ionic liquids (ILs) have gained significant attention due to their unique properties and broad applications. Extensive research has focused on studying the influence of ILs' chemical composition and substrate characteristics on the structure and morphology of IL films at the nano- and mesoscopic scales. This study explores the impact of carbon-coated surfaces on the morphology and wetting behavior of a series of alkylimidazolium-based ILs. Specifically, this work investigates the effect of carbon coating on the morphology and wetting behavior of short-chain ([C2C1im][NTf2] and [C2C1im][OTf]) and long-chain ([C8C1im][NTf2] and [C8C1im][OTf]) ILs deposited on indium tin oxide (ITO), silver (Ag), and gold (Au) substrates. A reproducible vapor deposition methodology was utilized for the deposition process. High-resolution scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy were used to analyze the morphological and structural characteristics of the substrates and obtained IL films. The experimental data revealed that the IL films deposited on carbon-coated Au substrates showed minor changes in their morphology compared to that of the films deposited on clean Au surfaces. However, the presence of carbon coatings on the ITO and Ag surfaces led to significant morphological alterations in the IL films. Specifically, for short-chain ILs, the carbon film surface induced 2D growth of the IL film, followed by subsequent island growth. In contrast, for long-chain ILs deposited on carbon surfaces, layer-by-layer growth occurred without island formation, resulting in highly uniform and coalesced IL films. The extent of morphological changes observed in the IL films was found to be influenced by two crucial factors: the thickness of the carbon film on the substrate surface and the amount of IL deposition.
Collapse
Affiliation(s)
- Rita M Carvalho
- CIQUP, Institute of Molecular Sciences (IMS), Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do Campo Alegre s/n, P4169-007 Porto, Portugal
| | - Luís M N B F Santos
- CIQUP, Institute of Molecular Sciences (IMS), Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do Campo Alegre s/n, P4169-007 Porto, Portugal
| | - Margarida Bastos
- CIQUP, Institute of Molecular Sciences (IMS), Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do Campo Alegre s/n, P4169-007 Porto, Portugal
| | - José C S Costa
- CIQUP, Institute of Molecular Sciences (IMS), Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do Campo Alegre s/n, P4169-007 Porto, Portugal
| |
Collapse
|
2
|
Sambe K, Takeda T, Hoshino N, Matsuda W, Miura R, Tsujita K, Maruyama S, Yamamoto S, Seki S, Matsumoto Y, Akutagawa T. Ferroelectric Organic Semiconductor: [1]Benzothieno[3,2- b][1]benzothiophene-Bearing Hydrogen-Bonding -CONHC 14H 29 Chain. ACS APPLIED MATERIALS & INTERFACES 2023; 15:58711-58722. [PMID: 38055344 DOI: 10.1021/acsami.3c14476] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/08/2023]
Abstract
An alkylamide-substituted [1]benzothieno[3,2-b][1]benzothiophene (BTBT) derivative of BTBT-CONHC14H29 (1) and C8H17-BTBT-CONHC14H29 (2) were prepared to design the multifunctional organic materials, which can show both ferroelectric and semiconducting properties. Single-crystal X-ray structural analyses of short-chain (-CONHC3H7) derivatives revealed the coexistence of two-dimensional (2D) electronic band structures brought from a herringbone arrangement of the BTBT π core and the one-dimensional (1D) hydrogen-bonding chains of -CONHC3H7 chains. The thin films of 1 and 2 fabricated on the Si/SiO2 substrate surface have monolayer and bilayer structures, respectively, resulting in conducting layers parallel to the substrate surface, which is suitable for a channel layer of organic field-effect transistors (OFETs). The thin film of 1 indicated a hole mobility μFET = 2.4 × 10-5 cm2 V-1 s-1 and threshold voltage VTh = - 29 V, whereas that of 2 showed a μFET = 2.1 × 10-2 cm2 V-1 s-1 and threshold voltage VTh = -9.7 V. Both 1 and 2 formed the smectic E (SmE) phase above 410 and 369 K, respectively, where the existence of a hole transport pathway was confirmed in the SmE phase. The ferroelectric hysteresis behavior was observed in bulk 1 and 2 in the polarization-electric field (P-E) curves at the SmE phase. 1 showed the remanent polarization Pr = 2.3 μC cm-2 and coercive electric field Ec = 5.2 V μm-1, whereas the Pr and Ec of 2 were 3.4 μC cm-2 and 7.0 V μm-1 at the conditions of 453 K and 1 Hz. Introduction of alkylamide units into the BTBT π core has the potential to develop the external stimulus-responsive organic semiconductors brought from both ferroelectricity and semiconducting properties.
Collapse
Affiliation(s)
- Kohei Sambe
- Graduate School of Engineering, Tohoku University, 6-6-07 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8579, Japan
| | - Takashi Takeda
- Graduate School of Engineering, Tohoku University, 6-6-07 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8579, Japan
- Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
- Department of Chemistry, Faculty of Science, Shinshu University, 3-1-1 Asahi, Matsumoto 390-8621, Japan
| | - Norihisa Hoshino
- Department of Materials Science and Technology, Faculty of Engineering, Niigata University, 8050 Ikarashi-2, Niigata 9050-2181, Japan
| | - Wakana Matsuda
- Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Riku Miura
- Graduate School of Engineering, Tohoku University, 6-6-07 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8579, Japan
| | - Kanae Tsujita
- Graduate School of Engineering, Tohoku University, 6-6-07 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8579, Japan
| | - Shingo Maruyama
- Graduate School of Engineering, Tohoku University, 6-6-07 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8579, Japan
| | - Shunsuke Yamamoto
- Graduate School of Engineering, Tohoku University, 6-6-07 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8579, Japan
| | - Shu Seki
- Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Yuji Matsumoto
- Graduate School of Engineering, Tohoku University, 6-6-07 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8579, Japan
| | - Tomoyuki Akutagawa
- Graduate School of Engineering, Tohoku University, 6-6-07 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8579, Japan
- Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
| |
Collapse
|
3
|
Chon S, Nakayama R, Iwamoto S, Kobayashi S, Shimizu R, Hitosugi T. Orientation Control of a Two-Dimensional Conductive Metal-Organic Framework Thin Film by a Pyridine Vapor-Assisted Dry Process. ACS APPLIED MATERIALS & INTERFACES 2023; 15:56057-56063. [PMID: 38009945 DOI: 10.1021/acsami.3c14401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
Metal-organic frameworks (MOFs) are attractive materials with periodic pore structures constructed by coordinating metal ions and organic ligands. Recently, Cu3(HHTP)2 (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene), a two-dimensional conductive MOF, has attracted attention as a promising device material. Owing to the anisotropy of Cu3(HHTP)2 properties, oriented thin films of this MOF are desired for evaluating its physical properties and device integration. To date, wet processes have been used to fabricate Cu3(HHTP)2 films, whereas dry processes are essential for high-quality devices. However, oriented Cu3(HHTP)2 thin films have not yet been fabricated by using dry processes. In this study, we succeed in fabricating an orientation-controlled Cu3(HHTP)2 film on Al2O3 (001) by using a two-step dry process involving (1) the multilayer deposition of copper acetate and HHTP using a vapor deposition system and (2) pyridine vapor-assisted annealing. In-plane and out-of-plane X-ray diffraction patterns confirm the successful fabrication of the (001)-oriented Cu3(HHTP)2 films. The conductivity evaluated by four-probe measurements is 2.6 × 10-2 S cm-1, comparable to that of films fabricated by wet processes. This study provides a novel guideline for the orientation control of two-dimensional conductive MOF thin films via a dry process.
Collapse
Affiliation(s)
- Seoungmin Chon
- School of Materials and Chemical Technology, Tokyo Institute of Technology, Tokyo 152-8552, Japan
| | - Ryo Nakayama
- Department of Chemistry, The University of Tokyo, Tokyo 113-0033, Japan
| | - Shunta Iwamoto
- School of Materials and Chemical Technology, Tokyo Institute of Technology, Tokyo 152-8552, Japan
| | - Shigeru Kobayashi
- Department of Chemistry, The University of Tokyo, Tokyo 113-0033, Japan
| | - Ryota Shimizu
- School of Materials and Chemical Technology, Tokyo Institute of Technology, Tokyo 152-8552, Japan
- Department of Chemistry, The University of Tokyo, Tokyo 113-0033, Japan
| | - Taro Hitosugi
- School of Materials and Chemical Technology, Tokyo Institute of Technology, Tokyo 152-8552, Japan
- Department of Chemistry, The University of Tokyo, Tokyo 113-0033, Japan
| |
Collapse
|
4
|
Zhang W, Komatsu H, Maruyama S, Kaminaga K, Matsumoto Y. Ionic Liquid Crystal Thin Film as Switching Layer in Nonvolatile Resistive Memory. ACS APPLIED MATERIALS & INTERFACES 2023. [PMID: 37910855 DOI: 10.1021/acsami.3c13980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2023]
Abstract
In this study, we propose the use of an ionic liquid crystal (ILC) as a new resistive switching layer in nonvolatile resistive random-access memory (ReRAM) devices. The high-quality vacuum-deposited ILC films of 1-hexadecyl-3-methylimidazolium hexafluorophosphate ([C16mim][PF6]) enabled to demonstrate the first operation of ReRAM devices with a low set voltage of ∼1 V and stable switching behavior for up to ∼44 cycles. The key to the successful operation is that the ILC layer is in the liquid crystal phase (smectic A), where the electric double layers formed at the electrode-ILC interfaces play a significant role. The results of basic electrical properties and I-V curve fittings suggested the following operation principle: the formation and rupture of charge-composed filaments within the ILC film, where the current conduction is primarily governed by the trap charge limited current (TCLC) mechanism. These achievements will pave the way for advanced studies of ILC-based electronic devices.
Collapse
Affiliation(s)
- Wenzhong Zhang
- Department of Applied Chemistry, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan
| | - Haruka Komatsu
- Department of Applied Chemistry, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan
| | - Shingo Maruyama
- Department of Applied Chemistry, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan
| | - Kenichi Kaminaga
- Department of Applied Chemistry, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan
| | - Yuji Matsumoto
- Department of Applied Chemistry, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan
| |
Collapse
|
5
|
Matsumoto Y. Recent Progress in Vacuum Engineering of Ionic Liquids. Molecules 2023; 28:1991. [PMID: 36838981 PMCID: PMC9966320 DOI: 10.3390/molecules28041991] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Revised: 02/13/2023] [Accepted: 02/14/2023] [Indexed: 02/22/2023] Open
Abstract
Since the discovery of ionic liquids (ILs) as a new class of liquid that can survive in a vacuum at room temperature, they have been aimed at being characterized with vacuum analysis techniques and used in vacuum processes for the last two decades. In this review, our state-of-the-art of the vacuum engineering of ILs will be introduced. Beginning with nanoscale vacuum deposition of IL films and their thickness-dependent ionic conductivity, there are presented some new applications of the ellipsometry to in situ monitoring of the thickness of IL films and their glass transitions, and of the surface thermal fluctuation spectroscopy to investigation of the rheological properties of IL films. Furthermore, IL-VLS (vapor-liquid-solid) growth, a vacuum deposition via IL, has been found successful, enhancing the crystallinity of vacuum-deposited crystals and films, and sometimes controlling their surface morphology and polymorphs. Among recent applications of ILs are the use of metal ions-containing IL and thin film nano IL gel. The former is proposed as a low temperature evaporation source of metals, such as Ta, in vacuum deposition, while the latter is demonstrated to work as a gate electrolyte in an electric double layer organic transistor.
Collapse
Affiliation(s)
- Yuji Matsumoto
- Department of Applied Chemistry, School of Engineering, Tohoku University, 6-6-07 Aramaki-Aza-Aoba, Aoba-ku, Sendai 980-8579, Japan
| |
Collapse
|
6
|
Nucleation, Coalescence, and Thin-Film Growth of Triflate-Based Ionic Liquids on ITO, Ag, and Au Surfaces. COLLOIDS AND INTERFACES 2022. [DOI: 10.3390/colloids6030046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
This study investigates the nucleation and growth of micro-/nanodroplets of triflate-based ionic liquids (ILs) fabricated by vapor deposition on different surfaces: indium tin oxide (ITO); silver (Ag); gold (Au). The ILs studied are constituted by the alkylimidazolium cation and the triflate anion—[CnC1im][OTF] series. One of the key issues that determine the potential applications of ILs is the wettability of surfaces. Herein, the wetting behavior was evaluated by changing the cation alkyl chain length (C2 to C10). A reproducible control of the deposition rate was conducted employing Knudsen cells, and the thin-film morphology was evaluated by high-resolution scanning electron microscopy (SEM). The study reported here for the [CnC1im][OTF] series agrees with recent data for the [CnC1im][NTf2] congeners, highlighting the higher wettability of the solid substrates to long-chain alkylimidazolium cations. Compared to [NTf2], the [OTF] series evidenced an even more pronounced wetting ability on Au and coalescence processes of droplets highly intense on ITO. Higher homogeneity and film cohesion were found for cationic groups associated with larger alkyl side chains. An island growth was observed on both Ag and ITO substrates independently of the cation alkyl chain length. The Ag surface promoted the formation of smaller-size droplets. A quantitative analysis of the number of microdroplets formed on Ag and ITO revealed a trend shift around [C6C1im][OTF], emphasizing the effect of the nanostructuration intensification due to the formation of nonpolar continuous domains.
Collapse
|
7
|
Costa JCS, Alves A, Bastos M, Santos LMNBF. The impact of the cation alkyl chain length on the wettability of alkylimidazolium-based ionic liquids at the nanoscale. Phys Chem Chem Phys 2022; 24:13343-13355. [PMID: 35608141 DOI: 10.1039/d2cp01868c] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ionic liquids (ILs) have been widely used for energy storage and conversion devices due to their negligible vapor pressure, high thermal stability, and outstanding interfacial properties. Notably, the interfacial nanostructure and the wettability of thin ionic liquid films on solid surfaces are of utmost relevance in nanosurface science and technology. Herein, a reproducible physical vapor deposition methodology was used to fabricate thin films of four alkylimidazolium bis(trifluoromethylsulfonyl)imide ILs. The effect of the cation alkyl chain length on the wettability of ILs was explored on different surfaces: gold (Au); silver (Ag); indium-tin oxide (ITO). High-resolution scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to evaluate the morphology of the produced micro- and nanodroplets and films. SEM and AFM results revealed an island growth for all the ILs deposited on ITO and Ag surfaces, with a lower minimum free area to promote nucleation (MFAN) in Ag and higher wettability for ILs having larger non-polar domains. The low wettability of ITO by the studied ILs was highlighted. For long-chain ILs, nucleation and growth mechanisms were strongly conditioned by coalescence processes. The results also supported the higher affinity of the ILs to the Au surface. The increase in the length of the cation alkyl chain was found to promote a better film adhesion inducing a 2D growth and higher wetting ability.
Collapse
Affiliation(s)
- José C S Costa
- CIQUP, Institute of Molecular Sciences (IMS), Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, P4169-007, Porto, Portugal.
| | - Alexandre Alves
- CIQUP, Institute of Molecular Sciences (IMS), Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, P4169-007, Porto, Portugal.
| | - Margarida Bastos
- CIQUP, Institute of Molecular Sciences (IMS), Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, P4169-007, Porto, Portugal.
| | - Luís M N B F Santos
- CIQUP, Institute of Molecular Sciences (IMS), Department of Chemistry and Biochemistry, Faculty of Science, University of Porto, Rua do Campo Alegre, P4169-007, Porto, Portugal.
| |
Collapse
|
8
|
Ishikawa Y, Maruyama S, Matsumoto Y. In situ vacuum ellipsometry approach to investigation of glass transition behavior in ionic liquid thin films. Chem Phys Lett 2020. [DOI: 10.1016/j.cplett.2020.137691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
9
|
Campos RM, Alves ACPM, Lima MAL, Farinha AFM, Cardoso JPS, Mendes A, Costa JCS, Santos LMNBF. Morphology, Structure, and Dynamics of Pentacene Thin Films and Their Nanocomposites with [C
2
C
1
im][NTf
2
] and [C
2
C
1
im][OTF] Ionic Liquids. Chemphyschem 2020; 21:1814-1825. [DOI: 10.1002/cphc.202000431] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 06/18/2020] [Indexed: 11/09/2022]
Affiliation(s)
- Ricardo M. Campos
- CIQUP – Centro de Investigação em Química Departamento de Química e Bioquímica Faculdade de Ciências Universidade do Porto Portugal
| | - Alexandre C. P. M. Alves
- CIQUP – Centro de Investigação em Química Departamento de Química e Bioquímica Faculdade de Ciências Universidade do Porto Portugal
| | - Marco A. L. Lima
- CIQUP – Centro de Investigação em Química Departamento de Química e Bioquímica Faculdade de Ciências Universidade do Porto Portugal
| | - Artur F. M. Farinha
- CIQUP – Centro de Investigação em Química Departamento de Química e Bioquímica Faculdade de Ciências Universidade do Porto Portugal
| | - João P. S. Cardoso
- CIQUP – Centro de Investigação em Química Departamento de Química e Bioquímica Faculdade de Ciências Universidade do Porto Portugal
| | - Adélio Mendes
- LEPABE – Laboratory for Process Engineering, Environment, Biotechnology and Energy Faculdade de Engenharia Universidade do Porto Portugal
| | - José C. S. Costa
- CIQUP – Centro de Investigação em Química Departamento de Química e Bioquímica Faculdade de Ciências Universidade do Porto Portugal
- LEPABE – Laboratory for Process Engineering, Environment, Biotechnology and Energy Faculdade de Engenharia Universidade do Porto Portugal
| | - Luís M. N. B. F. Santos
- CIQUP – Centro de Investigação em Química Departamento de Química e Bioquímica Faculdade de Ciências Universidade do Porto Portugal
| |
Collapse
|
10
|
Wang YL, Li B, Sarman S, Mocci F, Lu ZY, Yuan J, Laaksonen A, Fayer MD. Microstructural and Dynamical Heterogeneities in Ionic Liquids. Chem Rev 2020; 120:5798-5877. [PMID: 32292036 PMCID: PMC7349628 DOI: 10.1021/acs.chemrev.9b00693] [Citation(s) in RCA: 197] [Impact Index Per Article: 49.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Indexed: 12/11/2022]
Abstract
Ionic liquids (ILs) are a special category of molten salts solely composed of ions with varied molecular symmetry and charge delocalization. The versatility in combining varied cation-anion moieties and in functionalizing ions with different atoms and molecular groups contributes to their peculiar interactions ranging from weak isotropic associations to strong, specific, and anisotropic forces. A delicate interplay among intra- and intermolecular interactions facilitates the formation of heterogeneous microstructures and liquid morphologies, which further contributes to their striking dynamical properties. Microstructural and dynamical heterogeneities of ILs lead to their multifaceted properties described by an inherent designer feature, which makes ILs important candidates for novel solvents, electrolytes, and functional materials in academia and industrial applications. Due to a massive number of combinations of ion pairs with ion species having distinct molecular structures and IL mixtures containing varied molecular solvents, a comprehensive understanding of their hierarchical structural and dynamical quantities is of great significance for a rational selection of ILs with appropriate properties and thereafter advancing their macroscopic functionalities in applications. In this review, we comprehensively trace recent advances in understanding delicate interplay of strong and weak interactions that underpin their complex phase behaviors with a particular emphasis on understanding heterogeneous microstructures and dynamics of ILs in bulk liquids, in mixtures with cosolvents, and in interfacial regions.
Collapse
Affiliation(s)
- Yong-Lei Wang
- Department
of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Bin Li
- School
of Chemical Engineering and Technology, Sun Yat-sen University, Zhuhai 519082, P. R. China
| | - Sten Sarman
- Department
of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Francesca Mocci
- Department
of Chemical and Geological Sciences, University
of Cagliari, I-09042 Monserrato, Italy
| | - Zhong-Yuan Lu
- State
Key Laboratory of Supramolecular Structure and Materials, Institute
of Theoretical Chemistry, Jilin University, Changchun 130021, P. R. China
| | - Jiayin Yuan
- Department
of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Aatto Laaksonen
- Department
of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
- State
Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University, Nanjing 210009, P. R. China
- Centre of
Advanced Research in Bionanoconjugates and Biopolymers, Petru Poni Institute of Macromolecular Chemistry Aleea Grigore Ghica-Voda, 41A, 700487 Iasi, Romania
- Department
of Engineering Sciences and Mathematics, Division of Energy Science, Luleå University of Technology, SE-97187 Luleå, Sweden
| | - Michael D. Fayer
- Department
of Chemistry, Stanford University, Stanford, California 94305, United States
| |
Collapse
|
11
|
Wu B, Breen JP, Xing X, Fayer MD. Controlling the Dynamics of Ionic Liquid Thin Films via Multilayer Surface Functionalization. J Am Chem Soc 2020; 142:9482-9492. [PMID: 32349470 DOI: 10.1021/jacs.0c03044] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The structural dynamics of planar thin films of an ionic liquid (IL) 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BmimNTf2) as a function of surface charge density and thickness were investigated using two-dimensional infrared (2D IR) spectroscopy. The films were made by spin coating a methanol solution of the IL on silica substrates that were functionalized with alkyl chains containing head groups that mimic the IL cation. The thicknesses of the ionic liquid films ranged from ∼50 to ∼250 nm. The dynamics of the films are slower than those in the bulk IL, becoming increasingly slow as the films become thinner. Control of the dynamics of the IL films can be achieved by adjusting the charge density on substrates through multilayer network surface functionalization. The charge density of the surface (number of positively charged groups in the network bound to the surface per unit area) is controlled by the duration of the functionalization reaction. As the charge density is increased, the IL dynamics become slower. For comparison, the surface was functionalized with three different neutral groups. Dynamics of the IL films on the functionalized neutral surfaces are faster than on any of the ionic surfaces but still slower than the bulk IL, even for the thickest films. These results can have implications in applications that employ ILs that have electrodes, such as batteries, as the electrode surface charge density will influence properties like diffusion close to the surface.
Collapse
Affiliation(s)
- Boning Wu
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - John P Breen
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Xiangyu Xing
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Michael D Fayer
- Department of Chemistry, Stanford University, Stanford, California 94305, United States
| |
Collapse
|
12
|
Maruyama S, Sannodo N, Harada R, Anada Y, Takahashi R, Lippmaa M, Matsumoto Y. Pulsed laser deposition with rapid beam deflection by a galvanometer mirror scanner. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2019; 90:093901. [PMID: 31575232 DOI: 10.1063/1.5104291] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Accepted: 08/21/2019] [Indexed: 06/10/2023]
Abstract
A pulsed laser deposition system with rapid beam deflection (RBD-PLD) by a galvanometer mirror scanner has been developed for alternating ablation of multiple targets with a single laser instrument. In this system, the alternating deposition of different target materials is carried out by scanning the laser beam between the positionally fixed targets with a galvanometer mirror instead of mechanically switching the target positions on a fixed optical path of the laser beam as is done in conventional pulsed laser deposition (PLD) systems. Thus, the "wait" time required for switching target materials to be deposited, which typically takes several seconds in a conventional system, can be made as short as a few milliseconds. We demonstrate some of the advantages of this PLD system in several technologically important aspects of thin film synthesis: (1) fast fabrication of binary alloy films, (2) preparation of natural composition spread libraries, (3) effect of the target switching time on the deposition of volatile compounds, (4) control of the degree of mixing of two different materials in a film, and (5) efficient growth of compositionally graded thin films.
Collapse
Affiliation(s)
- S Maruyama
- Department of Applied Chemistry, Tohoku University, Sendai, Miyagi, 980-8579, Japan
| | - N Sannodo
- Department of Applied Chemistry, Tohoku University, Sendai, Miyagi, 980-8579, Japan
| | - R Harada
- Department of Applied Chemistry, Tohoku University, Sendai, Miyagi, 980-8579, Japan
| | - Y Anada
- Department of Applied Chemistry, Tohoku University, Sendai, Miyagi, 980-8579, Japan
| | - R Takahashi
- Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Chiba 277-8581, Japan
| | - M Lippmaa
- Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Chiba 277-8581, Japan
| | - Y Matsumoto
- Department of Applied Chemistry, Tohoku University, Sendai, Miyagi, 980-8579, Japan
| |
Collapse
|
13
|
Maruyama S, Prastiawan IBH, Toyabe K, Higuchi Y, Koganezawa T, Kubo M, Matsumoto Y. Ionic Conductivity in Ionic Liquid Nano Thin Films. ACS NANO 2018; 12:10509-10517. [PMID: 30199622 DOI: 10.1021/acsnano.8b06386] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Thin film approaches are powerful methods for gaining a nanoscale understanding of interfacial ionic liquids (ILs) in the vicinity of solids. These approaches are used to directly elucidate the interfacial contributions to the physical properties of ILs as nanoscale thin films have significant proportions of the surface or interface region with respect to their total volume. Here, we report the growth of a uniform [emim][TFSA] thin film ionic liquid on a chemically modified, well-wettable sapphire, thereby allowing the in situ measurement of its ionic conductivity on the nanoscale. We observed the thickness-dependent behavior of the ionic conductivity, which gradually decreased especially when the thickness was less than 10 nm, and found it to be quantitatively analyzed well by using an empirical two-layer model. The molecular dynamics (MD) simulations show that the thickness-dependent ionic conductivity originates from the solid-like structuring of the IL near the substrate, reproducing a thickness-dependent ionic conductivity. The MD simulation results suggest that the thickness of the low conductivity region determined in the two-layer model should roughly correspond to the thickness of the solid-like structuring of the IL near the substrate.
Collapse
Affiliation(s)
- Shingo Maruyama
- Department of Applied Chemistry, School of Engineering , Tohoku University , Sendai 980-8579 , Japan
| | | | - Kaho Toyabe
- Department of Applied Chemistry, School of Engineering , Tohoku University , Sendai 980-8579 , Japan
| | - Yuji Higuchi
- Institute for Materials Research , Tohoku University , Sendai 980-8577 , Japan
| | - Tomoyuki Koganezawa
- Japan Synchrotron Radiation Research Institute (JASRI) , SPring-8, 1-1-1 Kouto , Sayo , Hyogo 679-5198 , Japan
| | - Momoji Kubo
- Institute for Materials Research , Tohoku University , Sendai 980-8577 , Japan
| | - Yuji Matsumoto
- Department of Applied Chemistry, School of Engineering , Tohoku University , Sendai 980-8579 , Japan
| |
Collapse
|
14
|
Nishida J, Breen JP, Wu B, Fayer MD. Extraordinary Slowing of Structural Dynamics in Thin Films of a Room Temperature Ionic Liquid. ACS CENTRAL SCIENCE 2018; 4:1065-1073. [PMID: 30159404 PMCID: PMC6107873 DOI: 10.1021/acscentsci.8b00353] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Indexed: 05/03/2023]
Abstract
The role that interfaces play in the dynamics of liquids is a fundamental scientific problem with vast importance in technological applications. From material science to biology, e.g., batteries to cell membranes, liquid properties at interfaces are frequently determinant in the nature of chemical processes. For most liquids, like water, the influence of an interface falls off on a ∼1 nm distance scale. Room temperature ionic liquids (RTILs) are a vast class of unusual liquids composed of complex cations and anions that are liquid salts at room temperature. They are unusual liquids with properties that can be finely tuned by selecting the structure of the cation and anion. RTILs are being used or developed in applications such as batteries, CO2 capture, and liquids for biological processes. Here, it is demonstrated quantitatively that the influence of an interface on RTIL properties is profoundly different from that observed in other classes of liquids. The dynamics of planar thin films of the room temperature ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BmimNTf2), were investigated using two-dimensional infrared spectroscopy (2D IR) with the CN stretch of SeCN- as the vibrational probe. The structural dynamics (spectral diffusion) of the thin films with controlled nanometer thicknesses were measured and compared to the dynamics of the bulk liquid. The samples were prepared by spin coating the RTIL, together with the vibrational probe, onto a surface functionalized with an ionic monolayer that mimics the structure of the BmimNTf2. Near-Brewster's angle reflection pump-probe geometry 2D IR facilitated the detection of the exceedingly small signals from the films, some of which were only 14 nm thick. Even in quarter micron (250 nm) thick films, the observed dynamics were much slower than those of the bulk liquid. Using a new theoretical description, the correlation length (exponential falloff of the influence of the interfaces) was found to be 28 ± 5 nm. This very long correlation length, ∼30 times greater than that of water, has major implications for the use of RTILs in devices and other applications.
Collapse
|
15
|
Sitaputra W, Stacchiola D, Wishart JF, Wang F, Sadowski JT. In Situ Probing of Ion Ordering at an Electrified Ionic Liquid/Au Interface. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29:1606357. [PMID: 28498642 DOI: 10.1002/adma.201606357] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Revised: 01/27/2017] [Indexed: 06/07/2023]
Abstract
Charge transport at the interface of electrodes and ionic liquids is critical for the use of the latter as electrolytes. A room-temperature ionic liquid, 1-ethyl-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide (EMMIM TFSI), is investigated in situ under applied bias voltage with a novel method using low-energy electron and photoemission electron microscopy. Changes in photoelectron yield as a function of bias applied to electrodes provide a direct measure of the dynamics of ion reconfiguration and electrostatic responses of the EMMIM TFSI. Long-range and correlated ionic reconfigurations that occur near the electrodes are found to be a function of temperature and thickness, which, in turn, relate to ionic mobility and different configurations for out-of-plane ordering near the electrode interfaces, with a critical transition in ion mobility for films thicker than three monolayers.
Collapse
Affiliation(s)
- Wattaka Sitaputra
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - Dario Stacchiola
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - James F Wishart
- Chemistry Division, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - Feng Wang
- Sustainable Energy Technologies Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - Jerzy T Sadowski
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY, 11973, USA
| |
Collapse
|
16
|
Miyadera T, Sugita T, Tampo H, Matsubara K, Chikamatsu M. Highly Controlled Codeposition Rate of Organolead Halide Perovskite by Laser Evaporation Method. ACS APPLIED MATERIALS & INTERFACES 2016; 8:26013-26018. [PMID: 27611007 DOI: 10.1021/acsami.6b07837] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Organolead-halide perovskites can be promising materials for next-generation solar cells because of its high power conversion efficiency. The method of precise fabrication is required because both solution-process and vacuum-process fabrication of the perovskite have problems of controllability and reproducibility. Vacuum deposition process was expected to achieve precise control; however, vaporization of amine compound significantly degrades the controllability of deposition rate. Here we achieved the reduction of the vaporization by implementing the laser evaporation system for the codeposition of perovskite. Locally irradiated continuous-wave lasers on the source materials realized the reduced vaporization of CH3NH3I. The deposition rate was stabilized for several hours by adjusting the duty ratio of modulated laser based on proportional-integral control. Organic-photovoltaic-type perovskite solar cells were fabricated by codeposition of PbI2 and CH3NH3I. A power-conversion efficiency of 16.0% with reduced hysteresis was achieved.
Collapse
Affiliation(s)
- Tetsuhiko Miyadera
- National Institute of Advanced Industrial Science and Technology (AIST) , 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan
| | - Takeshi Sugita
- National Institute of Advanced Industrial Science and Technology (AIST) , 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan
| | - Hitoshi Tampo
- National Institute of Advanced Industrial Science and Technology (AIST) , 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan
| | - Koji Matsubara
- National Institute of Advanced Industrial Science and Technology (AIST) , 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan
| | - Masayuki Chikamatsu
- National Institute of Advanced Industrial Science and Technology (AIST) , 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan
| |
Collapse
|
17
|
Costa JCS, Mendes A, Santos LMNBF. Morphology of Imidazolium-Based Ionic Liquids as Deposited by Vapor Deposition: Micro-/Nanodroplets and Thin Films. Chemphyschem 2016; 17:2123-7. [DOI: 10.1002/cphc.201600198] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Indexed: 11/10/2022]
Affiliation(s)
- José C. S. Costa
- Centro de Investigação em Química (CIQ); Departamento de Química e Bioquímica; Faculdade de Ciências; Universidade do Porto; Rua do Campo Alegre, 687 4169-007 Porto Portugal
- Laboratory for Process Engineering, Environment, Biotechnology and Energy (LEPABE); Faculdade de Engenharia; Universidade do Porto; Rua Dr. Roberto Frias 4200-465 Porto Portugal
| | - Adélio Mendes
- Laboratory for Process Engineering, Environment, Biotechnology and Energy (LEPABE); Faculdade de Engenharia; Universidade do Porto; Rua Dr. Roberto Frias 4200-465 Porto Portugal
| | - Luís M. N. B. F. Santos
- Centro de Investigação em Química (CIQ); Departamento de Química e Bioquímica; Faculdade de Ciências; Universidade do Porto; Rua do Campo Alegre, 687 4169-007 Porto Portugal
| |
Collapse
|
18
|
Feng G, Zhao W, Cummings PT, Li S. Molecular simulation study of dynamical properties of room temperature ionic liquids with carbon pieces. Sci China Chem 2016. [DOI: 10.1007/s11426-016-5580-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
|
19
|
Feng G, Jiang X, Qiao R, Kornyshev AA. Water in ionic liquids at electrified interfaces: the anatomy of electrosorption. ACS NANO 2014; 8:11685-94. [PMID: 25341189 DOI: 10.1021/nn505017c] [Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Complete removal of water from room-temperature ionic liquids is nearly impossible. For the electrochemical applications of ionic liquids, how water is distributed in the electrical double layers when the bulk liquids are not perfectly dry can potentially determine whether key advantages of ionic liquids, such as a wide electrochemical window, can be harnessed in practical systems. In this paper, we study the adsorption of water on electrode surfaces in contact with humid, imidazolium-based ionic liquids using molecular dynamics simulations. The results revealed that water molecules tend to accumulate within sub-nanometer distance from charged electrodes. At low amount of water in the bulk, the distributions of ions and of electrostatic potential in the double layer are affected weakly by the presence of water, but the spatial distribution of water molecules is strongly dependent on both. The preferential positions of water molecules in double layers are determined by the balance of several factors: the tendency to follow the positions of the maximal absolute value of the electrical field, the association with their ionic surroundings, and the propensity to settle at positions where more free space is available. The balance between these factors changes with charging the electrode, but the adsorption of water generally increases with voltage. The ion specificity of water electrosorption is manifested in the stronger presence of water near positive electrodes (where anions are the counterions) than near negative electrodes (where cations are counterions). These predictions await experimental verification.
Collapse
Affiliation(s)
- Guang Feng
- State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology (HUST) , Wuhan 430074, China
| | | | | | | |
Collapse
|
20
|
Takeyama Y, Mantoku S, Maruyama S, Matsumoto Y. Growth behaviours of pentacene films confined in engineered shapes of ionic-liquid in vacuum. CrystEngComm 2014. [DOI: 10.1039/c3ce41473f] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
21
|
Zhou H, Rouha M, Feng G, Lee SS, Docherty H, Fenter P, Cummings PT, Fulvio PF, Dai S, McDonough J, Presser V, Gogotsi Y. Nanoscale perturbations of room temperature ionic liquid structure at charged and uncharged interfaces. ACS NANO 2012; 6:9818-27. [PMID: 23092400 DOI: 10.1021/nn303355b] [Citation(s) in RCA: 103] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The nanoscale interactions of room temperature ionic liquids (RTILs) at uncharged (graphene) and charged (muscovite mica) solid surfaces were evaluated with high resolution X-ray interface scattering and fully atomistic molecular dynamics simulations. At uncharged graphene surfaces, the imidazolium-based RTIL ([bmim(+)][Tf(2)N(-)]) exhibits a mixed cation/anion layering with a strong interfacial densification of the first RTIL layer. The first layer density observed via experiment is larger than that predicted by simulation and the apparent discrepancy can be understood with the inclusion of, dominantly, image charge and π-stacking interactions between the RTIL and the graphene sheet. In contrast, the RTIL structure adjacent to the charged mica surface exhibits an alternating cation-anion layering extending 3.5 nm into the bulk fluid. The associated charge density profile demonstrates a pronounced charge overscreening (i.e., excess first-layer counterions with respect to the adjacent surface charge), highlighting the critical role of charge-induced nanoscale correlations of the RTIL. These observations confirm key aspects of a predicted electric double layer structure from an analytical Landau-Ginzburg-type continuum theory incorporating ion correlation effects, and provide a new baseline for understanding the fundamental nanoscale response of RTILs at charged interfaces.
Collapse
Affiliation(s)
- Hua Zhou
- Chemical Science and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
22
|
Maruyama S, Taniguchi H, Takeyama Y, Itoh M, Matsumoto Y. High-throughput CW-IR laser deposition and laser microscope imaging of binary ionic liquids in vacuum. SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 2011; 12:054204. [PMID: 27877431 PMCID: PMC5074425 DOI: 10.1088/1468-6996/12/5/054204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Revised: 12/02/2011] [Accepted: 10/07/2011] [Indexed: 06/06/2023]
Abstract
A combinatorial library of binary mixtures of ionic liquids with various mixing ratios was fabricated on a single sapphire substrate using the composition-spread technique combined with a continuous-wave infrared (CW-IR) laser deposition method; the mixtures were condensed in the form of micro-scale droplets. The mixing ratio within the droplets was examined by Raman spectroscopy. The contact angle of the droplets was found to systematically vary with the mixing ratio. Their thermal behavior was characterized with an ultrahigh-vacuum laser microscope, revealing the dependence of the evaporation rate on the mixing ratio.
Collapse
Affiliation(s)
| | | | | | | | - Yuji Matsumoto
- Materials and Structures Laboratory, Tokyo Institute of Technology, Tokyo, Japan
| |
Collapse
|
23
|
Takeyama Y, Maruyama S, Matsumoto Y. Development of compact CW-IR laser deposition system for high-throughput growth of organic single crystals. SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 2011; 12:054210. [PMID: 27877437 PMCID: PMC5074431 DOI: 10.1088/1468-6996/12/5/054210] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2011] [Revised: 12/28/2011] [Accepted: 10/25/2011] [Indexed: 06/06/2023]
Abstract
We developed a compact continuous-wave infrared (CW-IR) laser deposition system for the high-throughput growth of organic single crystals. In this system, two CW-IR lasers are used for the sample heating and thermal evaporation of materials. The CW-IR laser heating is simple and allows good control of the deposition rate and growth temperature, in response to the on/off laser switching. Six samples can be loaded simultaneously in a chamber, which allows one-by-one sequential deposition for high-throughput experiments, without breaking the vacuum. Using this setup, we studied the effect of ionic liquids on the growth of C60 crystals in vacuum.
Collapse
|
24
|
Cremer T, Stark M, Deyko A, Steinrück HP, Maier F. Liquid/solid interface of ultrathin ionic liquid films: [C1C1Im][Tf2N] and [C8C1Im][Tf2N] on Au(111). LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:3662-71. [PMID: 21361299 DOI: 10.1021/la105007c] [Citation(s) in RCA: 134] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Ultrathin films of two imidazolium-based ionic liquids (IL), [C(1)C(1)Im][Tf(2)N] (= 1,3-dimethylimidazolium bis(trifluoromethyl)imide) and [C(8)C(1)Im][Tf(2)N] (= 1-methyl-3-octylimidazolium bis(trifluoromethyl)imide) were prepared on a Au(111) single-crystal surface by physical vapor deposition in ultrahigh vacuum. The adsorption behavior, orientation, and growth were monitored via angle-resolved X-ray photoelectron spectroscopy (ARXPS). Coverage-dependent chemical shifts of the IL-derived core levels indicate that for both ILs the first layer is formed from anions and cations directly in contact with the Au surface in a checkerboard arrangement and that for [C(8)C(1)Im][Tf(2)N] a reorientation of the alkyl chain with increasing coverage is found. For both ILs, geometry models of the first adsorption layer are proposed. For higher coverages, both ILs grow in a layer-by-layer fashion up to thicknesses of at least 9 nm (>10 ML). Moreover, beam damage effects are discussed, which are mainly related to the decomposition of [Tf(2)N](-) anions directly adsorbed at the gold surface.
Collapse
Affiliation(s)
- T Cremer
- Lehrstuhl für Physikalische Chemie II and Erlangen Catalysis Resource Center, Friedrich-Alexander-Universität, Erlangen-Nürnberg Egerlandstrasse 3, 91058 Erlangen, Germany
| | | | | | | | | |
Collapse
|