scholarly journals Mechanistic Study of Silane Alcoholysis Reactions with Self-Assembled Monolayer-Functionalized Gold Nanoparticle Catalysts

Catalysts ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 908
Author(s):  
Katsuhiro Isozaki ◽  
Tomoya Taguchi ◽  
Kosuke Ishibashi ◽  
Takafumi Shimoaka ◽  
Wataru Kurashige ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Metallic Nanoparticles ◽  
Molecular Structures ◽  
Critical Parameters ◽  
Mechanistic Study ◽  
Self Assembled Monolayer ◽  
Mechanistic Investigation ◽  
Self Assembled ◽  
20 Nm ◽  
Silane Alcoholysis

The self-assembled monolayer (SAM)-modified metallic nanoparticles (MNPs) often exhibit improved chemoselectivity in various catalytic reactions by controlling the reactants’ orientations adsorbed in the SAM; however, there have been a few examples showing that the reaction rate, i.e., catalytic activity, is enhanced by the SAM-modification of MNP catalysts. The critical parameters that affect the catalytic activity, such as the supports, nanoparticle size, and molecular structures of the SAM components, remain uninvestigated in these sporadic literature precedents. Here, we report the mechanistic investigation on the effects of those parameters on the catalytic activity of alkanethiolate SAM-functionalized gold nanoparticles (AuNPs) toward silane alcoholysis reactions. The evaluation of the catalytic reaction over two-dimensionally arrayed dodecanethiolate SAM-functionalized AuNPs with different supports revealed the electronic interactions between AuNPs and the supports contributing to the rate enhancement. Additionally, an unprecedented size effect appeared—the AuNP with a 20 nm radius showed higher catalytic activity than those at 10 and 40 nm. Infrared reflection–absorption spectroscopy revealed that the conformational change of alkyl chains of the SAM affects the entrapment of reactants and products inside the SAM, and therefore brings about the acceleration effect. These findings provide a guideline for further applying the SAM-functionalization technique to stereoselective organic transformations with designer MNP catalysts.

Surfaces Matter

2009 ◽  
Vol 1209 ◽  
Author(s):  
Eric L. Bruner
Keyword(s):  
Self Assembly ◽  
Scratch Resistance ◽  
Consumer Products ◽  
Molecular Structures ◽  
Self Assembled Monolayer ◽  
Phosphonic Acids ◽  
Princeton University ◽  
Self Assembled ◽  
Strong Attachment ◽  
Functional Areas

AbstractAculon, Inc. specializes in inventing and commercializing unique molecular-scale surface and interfacial coatings leveraging nanotechnology discoveries made at Princeton University. These coatings can be classified into three functional areas; non-stick, pro-stick/adhesion, and anti-corrosion. The company has formulated coating solutions and processes for numerous markets including optical, display, electronics, consumer products and industrial coatings. These specialized coatings outperform all known alternatives in characteristics such as adhesion, stain resistance, and scratch resistance. Fueling the company’s commercialization efforts are its proprietary Self-Assembled Monolayer of Phosphonates (SAMP) technology. The commercialization of SAMP treatments can be used for a variety of applications including imparting hydrophobicity, adhesion, or corrosion inhibition to numerous substrates. For surface treatments to be effective, they must be mechanically and chemically stable under conditions experienced in the intended area of use. Aculon’s proprietary Self-Assembled Monolayer of Phosphonates methodology can impart any of these properties as desired to metals, metal oxides and even some polymer surfaces by drawing on its library of structurally tailored phosphonic acids. The secret to the commercialization is covalent bonding, which creates a uniquely strong attachment between the SAMP and the substrate. Because the SAMP is one approximately 1.5 nm thick, it completely covers the material to which it is applied, and assures total surface coverage regardless of the type or texture of that material. The composition of the SAMP determines the properties that it imparts to its substrate. In 1998, Professor Jeffery Schwartz of Princeton University discovered that well-ordered monolayers of phosphonates could be formed by self-assembly on a wide variety of oxide and oxide-terminated surfaces. At that time Professor Schwartz and his team also discovered that a simple dip process enabled SAMP formation on substrates of complex structures and geometries, as well as traditionally “unreactive” surfaces. The research showed that SAMP adhesion to oxides was mechanically strong and resisted removal by hydrolysis and oxidation. It showed further that by using the dip method, SAMPs of a variety of molecular structures, including aliphatic, aromatic, and heteroaromatic, could be prepared. Commercialization of SAMPs proves that such surface-bound phosphonates can dictate control of the surface properties of myriad substrates and that they can be implemented using well-known industrial techniques and conditions. These processes can be scaled to meet the needs of large or small facilities, and can be applied to surfaces of nearly any size or shape without special needs. Based on the needs of the producer, surface modification can be completed during the time of manufacturing or can be performed as a post-production step.

scholarly journals Nanoscale patterning of a self-assembled monolayer by modification of the molecule–substrate bond

2014 ◽  
Vol 5 ◽  
pp. 258-267 ◽  
Author(s):  
Cai Shen ◽  
Manfred Buck
Keyword(s):  
Structural Phase ◽  
Lateral Diffusion ◽  
Scanning Tunneling ◽  
Self Assembled Monolayer ◽  
Nanoscale Patterning ◽  
Interfacial Structures ◽  
Self Assembled ◽  
The Difference ◽  
20 Nm ◽  
Induced Defects

The intercalation of Cu at the interface of a self-assembled monolayer (SAM) and a Au(111)/mica substrate by underpotential deposition (UPD) is studied as a means of high resolution patterning. A SAM of 2-(4'-methylbiphenyl-4-yl)ethanethiol (BP2) prepared in a structural phase that renders the Au substrate completely passive against Cu-UPD, is patterned by modification with the tip of a scanning tunneling microscope. The tip-induced defects act as nucleation sites for Cu-UPD. The lateral diffusion of the metal at the SAM–substrate interface and, thus, the pattern dimensions are controlled by the deposition time. Patterning down to the sub-20 nm range is demonstrated. The difference in strength between the S–Au and S–Cu bond is harnessed to develop the latent Cu-UPD image into a patterned binary SAM. Demonstrated by the exchange of BP2 by adamantanethiol (AdSH) this is accomplished by a sequence of reductive desorption of BP2 in Cu free areas followed by adsorption of AdSH. The appearance of Au adatom islands upon the thiol exchange suggests that the interfacial structures of BP2 and AdSH SAMs are different.

Enhanced Catalytic Activity of Self-Assembled-Monolayer-Capped Gold Nanoparticles

2012 ◽  
Vol 24 (48) ◽  
pp. 6462-6467 ◽  
Author(s):  
Tomoya Taguchi ◽  
Katsuhiro Isozaki ◽  
Kazushi Miki
Keyword(s):  
Gold Nanoparticles ◽  
Catalytic Activity ◽  
Self Assembled Monolayer ◽  
Self Assembled

Photo and Scanning Probe Lithography Using Alkylsilane Self-Assembled Monolayers

1999 ◽  
Vol 584 ◽  
Author(s):  
H. Sugimura ◽  
T. Hanji ◽  
O. Takai ◽  
K. Fukuda ◽  
H. Misawa
Keyword(s):  
Vacuum Ultraviolet ◽  
Scanning Probe ◽  
Self Assembled Monolayers ◽  
Self Assembled Monolayer ◽  
Scanning Probe Lithography ◽  
Si Substrates ◽  
Atomic Force ◽  
Assembled Monolayers ◽  
Self Assembled ◽  
20 Nm

AbstractAn organic film of a few nm in thickness was applied as a resist for photolithography and scanning probe lithography. This resist film was prepared on an oxide-covered Si substrate through chemisorption and spontaneous organization of organosilane molecules, e.g., n-octadecyltrimethoxysilane. The film belongs to a class of materials referred to as self-assembled monolayer (SAM). A SAM/Si sample was irradiated through a photomask with vacuum ultraviolet (VUV) light at a wavelength of 172 nm. The photomask image was transferred to the SAM through the decomposition of the SAM. Furthermore, we demonstrate nano-scale patterning of the SAM using an atomic force microscope (AFM) with an electrically conductive probe. The SAM was electrochemically degraded in the region where the AFM probe had been scanned. Both the photo-printed and AFM-genereated patterns were successfully transferred into the Si substrates based on wet chemical etching or on dry plasma etching. At present, using these VUV and AFM-based lithographies, we have succeeded in fabricating minute features of 2 μm and 20 nm in width, respectively.

Self-Assembled Fluid Phase Floating Membranes with Tuneable Water Interlayers

2019 ◽  
Author(s):  
Luke Clifton ◽  
Nicoló Paracini ◽  
Arwel V. Hughes ◽  
Jeremy H. Lakey ◽  
Nina-Juliane Seinke ◽  
...  
Keyword(s):  
Fluid Phase ◽  
Interlayer Thickness ◽  
Supported Bilayers ◽  
Self Assembled Monolayer ◽  
High Coverage ◽  
Nano Technology ◽  
Surface Distance ◽  
Potential Applications ◽  
Self Assembled ◽  
Coated Surfaces

<p>We present a reliable method for the fabrication of fluid phase unsaturated bilayers which are readily self-assembled on charged self-assembled monolayer (SAM) surfaces producing high coverage floating supported bilayers where the membrane to surface distance could be controlled with nanometer precision. Vesicle fusion was used to deposit the bilayers onto anionic SAM coated surfaces. Upon assembly the bilayer to SAM solution interlayer thickness was 7-10 Å with evidence suggesting that this layer was present due to SAM hydration repulsion of the bilayer from the surface. This distance could be increased using low concentrations of salts which caused the interlayer thickness to enlarge to ~33 Å. Reducing the salt concentration resulted in a return to a shorter bilayer to surface distance. These accessible and controllable membrane models are well suited to a range of potential applications in biophysical studies, bio-sensors and Nano-technology.</p><br>

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