Bilayer Formation vs Molecular Exchange in Organic Heterostructures: Strong Impact of Subtle Changes in Molecular Structure

Wang, Qi; Franco-Cañellas, Antoni; Ji, Penghui; Bürker, Christoph; Wang, Rongbin; Broch, Katharina; Thakur, P.; Lee, Tien‐Lin; Zhang, Haiming; Gerlach, Alexander; Chi, Lifeng; Duhm, Steffen; Schreiber, Frank

doi:10.1021/acs.jpcc.8b01529

Cited by 28 publications

(68 citation statements)

References 98 publications

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“…In the present case, no information on the surface tension of 2H-TPP is available. In line with earlier studies on exchange processes in organic bilayers, 10,27−30 it seems reasonable to assume that the determining factor for the replacement of [C 8 C 1 Im][PF 6 ] by 2H-TPP at the IL/metal interface is the stronger binding of porphyrin to the metal surface.…”

Section: Resultssupporting

confidence: 69%

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Stability and Exchange Processes in Ionic Liquid/Porphyrin Composite Films on Metal Surfaces

et al. 2019

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In light of increasing interest in the development of organic–organic multicomponent heterostructures on metals, this molecular-scale study investigates prototypical composite systems of ultrathin porphyrin and ionic liquid (IL) films on metallic supports under well-defined ultrahigh vacuum conditions. By means of angle-resolved X-ray photoelectron spectroscopy, we investigated the adsorption, stability, and thermal exchange of the resulting films after sequential physical vapor deposition of the free-base porphyrin 5,10,15,20-tetraphenylporphyrin, 2H-TPP, and the IL 1-methyl-3-octylimidazolium hexafluorophosphate, [C8C1Im][PF6], on Ag(111) and Au(111). 2H-TPP shows two-dimensional growth of up to two closed molecular layers on Ag(111) and Au(111) and three-dimensional island growth for thicker films. IL films on top of a monolayer of 2H-TPP exhibit Stranski–Krastanov-like growth and are stable up to 385 K. The 2H-TPP layer leads to destabilization of the IL films, compared to the IL in direct contact with the bare metals, by inhibiting the specific adsorption of the ions on the metal surfaces. When the porphyrin is deposited on top of [C8C1Im][PF6] at low temperature, the 2H-TPP molecules adsorb on top of the IL film at first but replace the IL at the IL/metal interfaces upon heating above 240 K. This exchange process is most likely driven by the higher adsorption energy of 2H-TPP on Ag(111) and Au(111) surfaces, as compared to the IL. The behavior observed on Ag(111) and Au(111) is identical. The results are highly relevant for the stability of porphyrin/IL-based thin film catalyst systems and molecular devices, and more generally, stacked organic multilayer architectures.

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Section: Resultssupporting

confidence: 69%

“…They found that P2O is exchanged by Cu-Pc on the Ag(111) surface, whereas for P4O, no exchange occurs, that is, Cu-Pc remains on top of the P4O layer. 27…”

Section: Introductionmentioning

confidence: 99%

Stability and Exchange Processes in Ionic Liquid/Porphyrin Composite Films on Metal Surfaces

et al. 2019

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“…In analogy to molecular exchange and preferential adsorption processes after sequential deposition of two different ILs on Ag(111) [81,82], exchange processes have also been reported for organic bilayers on metals involving porphyrins and related aromatic molecules [156][157][158][159][160][161][162][163][164]. These investigations highlight the importance of the strength of the organic-metal interaction and its correlation to the stability and arrangement in stacked multilayer architectures [156,161,162,[164][165][166][167][168][169][170]. Although combinations of porphyrins and ILs were already realized for catalysis [171] and dye-sensitized solar cell technologies [40,41], dedicated interface studies of porphyrin/IL hybrid systems are still missing.…”

Section: Replacement Of Ionic Liquids By Porphyrins At Metal Interfacesmentioning

confidence: 85%

Ultrathin ionic liquid films on metal surfaces: adsorption, growth, stability and exchange phenomena

Lexow

Maier

Steinrück

2020

Advances in Physics: X

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The interface of ionic liquids (ILs) with solid surfaces is of pivotal interest for many applications, ranging from sensors, lubrication, separation technology, and electronics to electrochemistry and catalysis. We present a short review on ultrathin layers of ionic liquids on metal surfaces using a surface science approach. We mainly focus on specific examples of imidazolium-based ionic liquids on Ag(111) and Au(111) studied by angle-resolved X-ray photoelectron spectroscopy, and relate the obtained results to existing literature. We address a variety of phenomena on the molecular level, namely, (i) the adsorption, growth and wetting behavior of ILs, (ii) the thermal stability and desorption of ILs, (iii) exchange processes of anions and cations at the IL/solid interface, and (iv) the replacement of ILs from the IL/solid interface by porphyrins.

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“…We superimposed the STM image by the contours of the two molecules in the unit cell as well as the adsorbate lattice as determined by LEED. A DBP molecule is characterized by four bright protrusions, which correspond to the phenyl substituents oriented nearly perpendicular to the aromatic backbone and two smaller double lobes which correspond to the bisbenz [5,6]indeno end groups [26].…”

Section: Lateral Structurementioning

confidence: 99%

“…Some applications, however, require to preserve the intrinsic properties of the molecules such as the typically rather narrow optical absorption and/or emission bands. To achieve this, one needs to electronically decouple the molecules from the substrate, which can be achieved through different ways such as the usage of wide-band-gap insulator thin films (e.g., oxides, alkali halides) [ 3 – 4 ], a molecular spacer layer [ 5 – 6 ], or sp 2 -hybridized two-dimensional interlayers (e.g., graphene and hexagonal boron nitride (h-BN)) [ 7 – 8 ]. The advantageous properties of an h-BN monolayer on metal single crystals are the high crystal quality, chemical inertness and the wide band gap of approx.…”

Section: Introductionmentioning

confidence: 99%

Hybridization vs decoupling: influence of an h-BN interlayer on the physical properties of a lander-type molecule on Ni(111)

Schaal¹,

Aihara²,

Gruenewald³

et al. 2020

Beilstein J. Nanotechnol.

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2D materials such as hexagonal boron nitride (h-BN) are widely used to decouple organic molecules from metal substrates. Nevertheless, there are also indications in the literature for a significant hybridization, which results in a perturbation of the intrinsic molecular properties. In this work we study the electronic and optical properties as well as the lateral structure of tetraphenyldibenzoperiflanthene (DBP) on Ni(111) with and without an atomically thin h-BN interlayer to investigate its possible decoupling effect. To this end, we use in situ differential reflectance spectroscopy as an established method to distinguish between hybridized and decoupled molecules. By inserting an h-BN interlayer we fabricate a buried interface and show that the DBP molecules are well decoupled from the Ni(111) surface. Furthermore, a highly ordered DBP monolayer is obtained on h-BN/Ni(111) by depositing the molecules at a substrate temperature of 170 °C. The structural results are obtained by quantitative low-energy electron diffraction and low-temperature scanning tunneling microscopy. Finally, the investigation of the valence band structure by ultraviolet photoelectron spectroscopy shows that the low work function of h-BN/Ni(111) further decreases after the DBP deposition. For this reason, the h-BN-passivated Ni(111) surface may serve as potential n-type contact for future molecular electronic devices.

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Bilayer Formation vs Molecular Exchange in Organic Heterostructures: Strong Impact of Subtle Changes in Molecular Structure

Cited by 28 publications

References 98 publications

Stability and Exchange Processes in Ionic Liquid/Porphyrin Composite Films on Metal Surfaces

Stability and Exchange Processes in Ionic Liquid/Porphyrin Composite Films on Metal Surfaces

Ultrathin ionic liquid films on metal surfaces: adsorption, growth, stability and exchange phenomena

Hybridization vs decoupling: influence of an h-BN interlayer on the physical properties of a lander-type molecule on Ni(111)

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