- Modular Assembly of Vibrationally and Electronically Coupled Rhenium Bipyridine Carbonyl Complexes on Silicon
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Hybrid inorganic/organic heterointerfaces are promising systems for next-generation photocatalytic, photovoltaic, and chemical-sensing applications. Their performance relies strongly on the development of robust and reliable surface passivation and functionalization protocols with (sub)molecular control. The structure, stability, and chemistry of the semiconductor surface determine the functionality of the hybrid assembly. Generally, these modification schemes have to be laboriously developed to satisfy the specific chemical demands of the semiconductor surface. The implementation of a chemically independent, yet highly selective, standardized surface functionalization scheme, compatible with nanoelectronic device fabrication, is of utmost technological relevance. Here, we introduce a modular surface assembly (MSA) approach that allows the covalent anchoring of molecular transition-metal complexes with sub-nanometer precision on any solid material by combining atomic layer deposition (ALD) and selectively self-assembled monolayers of phosphonic acids. ALD, as an essential tool in semiconductor device fabrication, is used to grow conformal aluminum oxide activation coatings, down to sub-nanometer thicknesses, on silicon surfaces to enable a selective step-by-step layer assembly of rhenium(I) bipyridine tricarbonyl molecular complexes. The modular surface assembly of molecular complexes generates precisely structured spatial ensembles with strong intermolecular vibrational and electronic coupling, as demonstrated by infrared spectroscopy, photoluminescence, and X-ray photoelectron spectroscopy analysis. The structure of the MSA can be chosen to avoid electronic interactions with the semiconductor substrate to exclusively investigate the electronic interactions between the surface-immobilized molecular complexes.
- Allegretti, Francesco,Amati, Matteo,Barth, Johannes V.,Bartl, Johannes D.,Bondino, Federica,Cattani-Scholz, Anna,Deimel, Peter S.,Gregoratti, Luca,Henning, Alex,Magnano, Elena,Nickel, Bert,Ober, Martina F.,Ochsenfeld, Christian,Paulus, Claudia,Rieger, Bernhard,Savasci, G?kcen,Sharp, Ian D.,Stutzmann, Martin,Thomas, Christopher,Yazdanshenas, Bahar,Zeller, Patrick
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supporting information
p. 19505 - 19516
(2021/11/26)
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- Copper oxide surfaces modified by alkylphosphonic acids with terminal pyridyl-based ligands as a platform for supported catalysis
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Self-assembled monolayer (SAM) films of phosphonates have been successfully formed via reaction of 11-hydroxyundecylphosphonic acid or 4,4′-di(methylenephosphonic acid)-2,2′-bipyridine with the oxide layer of copper via the Tethering by Aggregation and Growth (TBAG) deposition method. The hydroxyl-terminated SAM was further modified with isonicotinic acid or 4,4′-dicarboxy-2,2′-bipyridine through a Steglich esterification reaction. These three surfaces derivatized with pyridyl-based ligands are potential platforms for supported catalysis. As a proof of concept, [Ru(CO)3Cl2]2 was bound to the surfaces through the pyridyl-based ligands to yield tethered analogs of the known carbon dioxide reduction catalyst, [Ru(bpy)(CO)2Cl2]. Surface modification reactions were confirmed through specular reflectance infrared (IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Characteristic core binding energies were observed in the XPS analyses for phosphorus (P 2p), nitrogen (N 1s), and ruthenium (Ru 3p and Ru 3d), verifying the presence of the various surface functionalizations. IR and XPS data indicate that the phosphonate binding to the copper surface is tridentate in nature.
- Andrews, Brooke,Almahdali, Sarah,James, Karmel,Ly, Sandrine,Crowder, Katherine N.
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p. 360 - 369
(2016/07/06)
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- Rapid in situ generation of two patterned chemoselective surface chemistries from a single hydroxy-terminated surface using controlled microfluidic oxidation
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In this work, we develop a new, rapid and inexpensive method to generatespatially controlled aldehyde and carboxylic acid surface groups by mic rofluidic oxidation of 11-hydroxyundecylphosphonic acid self-assembled monolayers (SAMs) on indium tin oxide (ITO) surfaces. SAMs are activated and patterned using a reversibly sealable, elastomeric polydimethylsiloxane cassette, fabricated with preformed micropatterns by soft lithography. By flowing the mild oxidant pyridinium chlorochromate through the microchannels, only selected areas of the SAM are chemically altered. This microfluidic oxidation strategy allows for ligand immobilization by two chemistries originating from a single SAM composition. ITO is robust, conductive, and transparent, making it an ideal platform for studying interfacial interactions. We display spatial control over the immobilizationof a variety of ligands on ITO and characterize the resulting oxime and amide linkages by electrochemistry, X-ray photoelectron spectroscopy, c ontact angle, fluorescence microscopy, and atomic force microscopy. Thisgeneral method may be used with many other materials to rapidly generat e patterned and tailored surfaces for studies ranging from molecular electronics to biospecific cell-based assays and biomolecular microarrays.
- Pulsipher, Abigail,Westcott, Nathan P.,Luo, Wei,Yousaf, Muhammad N.
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experimental part
p. 7626 - 7632
(2009/10/17)
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- Detection of discrete interactions upon rupture of au microcontacts to self-assembled monolayers terminated with -S(CO)CH3 or -SH
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Pulloff forces were measured under solvent for Au-coated atomic force microscopy (AFM) tips in contact with -S-acetate-, -O-acetate-, -SH-, or -OH-terminated self-assembled monolayers (SAMs). The SAMs were formed by adsorption of ω-functionalized undecylphosphonic acids on metal oxide substrates. In ethanol and hexadecane, the mean force required to rupture Au/S-acetate microcontacts was 7 times greater than the mean force required to break Au/O-acetate contacts, consistent with the known affinity of S-containing functional groups for Au. Further, rupture force histograms for Au/S-acetate microcontacts under ethanol or hexadecane showed 0.1 nN periodicity. Rupture forces for Au/-SH microcontacts were 4 times greater than for Au/-OH microcontacts under ethanol, and the rupture force histograms showed the same 0.1 nN periodicity. We have assigned this 0.1 nN force quantum to rupture of individual chemical bonds and have estimated the bond energy to be on the order of 10 kJ/mol. The specific interaction corresponding to this energy appears to be abstraction of Au atoms from the tip surface upon pulloff. Our ability to detect these discrete interactions was a function of the solvent in which the measurements were made. For example, in water there was no difference in the mean pulloff force for Au/S-acetate and Au/O-acetate contacts and the histograms did not exhibit periodicity. In general, mean rupture forces for tip-SAM microcontacts are strongly solvent-dependent. To observe single bond rupture forces directly, we argue that the tip-substrate interfacial energy must be negative and larger in absolute value than the substrate-solvent and tip-solvent interfacial energies [i.e., |γsubstrate-tip| > (γtip-solvent + γsubstrate-solvent)]. Otherwise, nonspecific solvent exclusion effects dominate the microcontact adhesion. These measurements show that, whereas rupture forces for tip-SAM microcontacts are solvent-dependent, these forces can be sensitive, under the right conditions, to fluctuations in the number of discrete chemical interactions.
- Skulason, Hjalti,Frisbie, C. Daniel
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p. 9750 - 9760
(2007/10/03)
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