Amine‐Directed Hydrogen‐Bonded Two‐Dimensional Supramolecular Structures

Afsari, Sepideh; Li, Zhihai; Borguet, Eric

doi:10.1002/cphc.201600686

Cited by 9 publications

(5 citation statements)

References 37 publications

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“…47 For example, if hydrogen bonding occurs between the ion pairs of the electronegative nitrogen atoms and the hydrogen atoms of neighboring surface groups after the NH 3 * pulse, and these groups get isolated after the precursor pulse, this could explain the observed frequency shift (Figure 7). 48,49 The broad band at 1100−1200 cm −1 in Figure 6 is located in the spectral region where we expect to find the C−F and C−N stretching vibrations. 45 This band could arise from C−F stretches, resulting from defluorination of the fod ligand of adsorbed precursor molecules or fragments.…”

Section: ■ Results and Discussionmentioning

confidence: 90%

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Plasma-Enhanced Atomic Layer Deposition of Silver Using Ag(fod)(PEt₃) and NH₃-Plasma

et al. 2017

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A plasma-enhanced atomic layer deposition (ALD) process using the Ag(fod)(PEt 3 ) precursor [(triethylphosphine) (6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5octanedionate)silver(I)] in combination with NH 3 -plasma is reported. The steady growth rate of the reported process (0.24 ± 0.03 nm/cycle) was found to be 6 times larger than that of the previously reported Ag ALD process based on the same precursor in combination with H 2 -plasma (0.04 ± 0.02 nm/ cycle). The ALD characteristics of the H 2 -plasma and NH 3plasma processes were verified. The deposited Ag films were polycrystalline face-centered cubic Ag for both processes. The film morphology was investigated by ex situ scanning electron microscopy and grazing-incidence small-angle X-ray scattering, and it was found that films grown with the NH 3 -plasma process exhibit a much higher particle areal density and smaller particle sizes on oxide substrates compared to those deposited using the H 2 -plasma process. This control over morphology of the deposited Ag is important for applications in catalysis and plasmonics. While films grown with the H 2 -plasma process had oxygen impurities (∼9 atom %) in the bulk, the main impurity for the NH 3 -plasma process was nitrogen (∼7 atom %). In situ Fourier transform infrared spectroscopy experiments suggest that these nitrogen impurities are derived from NH x surface groups generated during the NH 3 -plasma, which interact with the precursor molecules during the precursor pulse. We propose that the reaction of these surface groups with the precursor leads to additional deposition of Ag atoms during the precursor pulse compared to the H 2 -plasma process, which explains the enhanced growth rate of the NH 3 -plasma process.

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Section: ■ Results and Discussionmentioning

confidence: 90%

“…For example, if hydrogen bonding occurs between the ion pairs of the electronegative nitrogen atoms and the hydrogen atoms of neighboring surface groups after the NH 3 * pulse, and these groups get isolated after the precursor pulse, this could explain the observed frequency shift (Figure ). , …”

Section: Results and Discussionmentioning

confidence: 99%

Plasma-Enhanced Atomic Layer Deposition of Silver Using Ag(fod)(PEt₃) and NH₃-Plasma

et al. 2017

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“…Furthermore, external “stimuli” could be essential in controlling the formation of surface nanomaterials. These external “stimuli” can be solution pH, temperature, , solvent of solutions, , electrochemical potential, etc.…”

Section: Introductionmentioning

confidence: 99%

Probing Molecular Nanostructures of Aromatic Terephthalic Acids Triggered by Intermolecular Hydrogen Bonds and Electrochemical Potential

et al. 2019

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Self-assembly provides unique routes to create supramolecular nanostructures at well-defined surfaces. In the present work, we employed scanning tunneling microscopy (STM) in combination with electrochemical techniques to explore the adsorption and phase formation of a series of aromatic carboxylic acids (ACAs) at Au(111)/0.1 M HClO4. Specific goals are to elucidate the roles of electrochemical potential and directional hydrogen-bonding on the structures and orientation of individual ACAs that form nanoarchitectures. ACAs are prototype materials for supramolecular self-assemblies via stereospecific hydrogen bonds between neighboring molecules. In this study, we mainly focus on a special ACA, terephthalic acid (TPA), which is almost insoluble in water, making the assembly of this molecule from aqueous solution challenging. Depending on the applied electric field, TPA molecules form distinctly different, highly ordered adlayers on Au(111) triggered by directional intermolecular hydrogen bonds. At low electrochemical potentials, TPA molecules are planar oriented, forming a potentially infinite hydrogen-bonded adlayer without any observed domain boundaries. The increase of the electrode potential triggers the deprotonation of one carboxylic acid functional group of TPA; additionally, this is accompanied by an orientation change of molecules from planar to perpendicular. In contrast, structural “defects” and multiple domain boundaries were found at this positively charged surface. The assembled nanostructures of TPA are compared with other ACAs (trimesic acid, benzoic acid, and isophthalic acid), and corresponding adsorption models were built for all molecular adlayers, showing that intermolecular hydrogen-bonding plays a determining role in the formation of two-dimensional ACA nanostructures.

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“…As one category of AHC molecules, benzenecarboxylic acids, which are composed of a single benzene ring and a different number of carboxylic acid functional groups, have been intensively studied because benzenecarboxylic acids represent the smallest and a model-type of AHCs, i.e., studying the smallest AHC model can help in understanding the expanded forms of AHC such as pyrenes, , naphthalenes, and coronenes . Among the studies of benzenecarboxylic acids, most reports are focused on 1,3,5-benzenetricarboxylic acid (trimesic acid, TMA) ,− because each TMA molecule has three carboxylic acid functional groups. The multiple −COOH functional groups allow TMA molecules to form intermolecular hydrogen bonds stabilizing the molecular adlayer on a metal substrate or at liquid–metal interfaces.…”

Section: Introductionmentioning

confidence: 99%

Revealing the Structural Complex of Adsorption and Assembly of Benzoic Acids at Electrode–Electrolyte Interfaces Using Electrochemical Scanning Tunneling Microscopy

et al. 2019

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Self-assembly of benzenecarboxylic acids on well-defined noble metals has been intensively investigated using surface-sensitive techniques. However, most studies were focused on the formation of nanostructures via benzenetricarboxylic and benzenedicarboxylic acids, which are composed of multiple carboxylic acid functional groups in either the meta or para positions of the benzene ring, allowing the formation of long-range ordered molecular arrays through −COOH-mediated intermolecular hydrogen bonds. Two-dimensional nanostructures of benzoic acid molecules that are composed of a single carboxylic acid functional group on the phenyl ring at metal–electrolyte interfaces were rarely reported using scanning tunneling microscopy (STM) because there is only one carboxylic acid functional group for each benzoic acid available to form intermolecular hydrogen bonds, making it difficult to construct long-range ordered nanoarchitectures. In this work, we employed electrochemical scanning tunneling microscopy (EC-STM) in combination with electrochemical cyclic voltammetry (CV) techniques to explore the adsorption and phase formation of benzoic acids (BZAs) at Au(111)/electrolyte interfaces. Our experiments show how the electrolyte, molecular concentration, electrochemical potential, and co-adsorption of aqueous ions affect the adsorption and self-assembly of BZA molecules. It is found that the BZA molecules are not assembled into long-range ordered structures in the presence of a sulfuric acid electrolyte due to the strong competing co-adsorption of sulfate ions on a gold electrode. BZA molecules can form flat-oriented ordered adlayers in a perchloric acid electrolyte (containing weakly adsorbed ClO4 – ions) at a negatively charged surface only when the concentration of the molecular solution reaches above 6 mM. Below 6 mM, the CVs of BZA on Au(111) in 0.1 M HClO4 show only one pair of adsorption/desorption peaks. When the BZA concentration increases to 6 mM, the voltammogram exhibits three pairs of peaks, corresponding to the structural transformation of disordered phase [phase I, E sample (E S): −0.600 to −0.190 V], linear stripe pattern (phase II, E S: −0.190 to 0.108 V), zigzag pattern (phase III, E S: −0.108 to −0.066 V), and upright packing pattern (phase IV, E S: −0.066 to 0.300 V). These phases and molecular adlayers were revealed by STM in the four electrochemical potential regions. Effect of parameters (electrolyte ions, concentration, and electrochemical potential) explored in this study will provide valuable information for the formation of molecular adlayers, adsorption and self-assembly, materials, corrosion inhibition, and molecular devices.

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Amine‐Directed Hydrogen‐Bonded Two‐Dimensional Supramolecular Structures

Cited by 9 publications

References 37 publications

Plasma-Enhanced Atomic Layer Deposition of Silver Using Ag(fod)(PEt₃) and NH₃-Plasma

Plasma-Enhanced Atomic Layer Deposition of Silver Using Ag(fod)(PEt₃) and NH₃-Plasma

Probing Molecular Nanostructures of Aromatic Terephthalic Acids Triggered by Intermolecular Hydrogen Bonds and Electrochemical Potential

Revealing the Structural Complex of Adsorption and Assembly of Benzoic Acids at Electrode–Electrolyte Interfaces Using Electrochemical Scanning Tunneling Microscopy

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Amine‐Directed Hydrogen‐Bonded Two‐Dimensional Supramolecular Structures

Cited by 9 publications

References 37 publications

Plasma-Enhanced Atomic Layer Deposition of Silver Using Ag(fod)(PEt3) and NH3-Plasma

Plasma-Enhanced Atomic Layer Deposition of Silver Using Ag(fod)(PEt3) and NH3-Plasma

Probing Molecular Nanostructures of Aromatic Terephthalic Acids Triggered by Intermolecular Hydrogen Bonds and Electrochemical Potential

Revealing the Structural Complex of Adsorption and Assembly of Benzoic Acids at Electrode–Electrolyte Interfaces Using Electrochemical Scanning Tunneling Microscopy

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Plasma-Enhanced Atomic Layer Deposition of Silver Using Ag(fod)(PEt₃) and NH₃-Plasma

Plasma-Enhanced Atomic Layer Deposition of Silver Using Ag(fod)(PEt₃) and NH₃-Plasma