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Self-assembled monolayers of thiolates on metals as a form of nanotechnology.

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New approaches to nanofabrication: molding, printing, and other techniques.

In this work, we show the strong resistance of zwitterionic phosphorylcholine (PC) self-assembled monolayers (SAMs) to protein adsorption and examine key factors leading to their nonfouling behavior using both experimental and molecular simulation techniques. Zwitterions with a balanced charge and minimized dipole are excellent candidates as nonfouling materials due to their strong hydration capacity via electrostatic interactions.

Strong resistance of phosphorylcholine self-assembled monolayers to protein adsorption: insights into nonfouling properties of zwitterionic materials.

The ability to tailor the chemical composition and structure of a surface at the sub-100-nm length scale is important for studying topics ranging from molecular electronics to materials assembly, and for investigating biological recognition at the single biomolecule level. Dip-pen nanolithography (DPN) is a scanning probe microscopy-based nanofabrication technique that uniquely combines direct-write soft-matter compatibility with the high resolution and registry of atomic force microscopy (AFM), which makes it a powerful tool for depositing soft and hard materials, in the form of stable and functional architectures, on a variety of surfaces. The technology is accessible to any researcher who can operate an AFM instrument and is now used by more than 200 laboratories throughout the world. This article introduces DPN and reviews the rapid growth of the field of DPN-enabled research and applications over the past several years.

Applications of dip-pen nanolithography.

Patterning self-assembled monolayers

This Account focuses on our recent and systematic effort in the development of generic scanning probe lithography (SPL)-based methodologies to produce nanopatterns of self-assembled monolayers (SAMs). The key to achieving high spatial precision is to keep the tip−surface interactions strong and local. The approaches used include two AFM-based methods, nanoshaving and nanografting, which rely on the local force, and two STM-based techniques, electron-induced diffusion and desorption, which use tunneling electrons for fabrication. In this Account we discuss the principle of these procedures and the critical steps in controlling local tip−surface interactions. The advantages of SPL will be illustrated through various examples of production and modification of SAM nanopatterns and their potential applications.

Nanofabrication of Self-Assembled Monolayers Using Scanning Probe Lithography

While the structures of self-assembled monolayers (SAMs) of alkanethiols on Au(111) are extensively studied and well-known, new structures and complex phase behavior have been progressively discovered when coverage of these layers falls below saturation. Structures and phase transitions of annealed decanethiol monolayers on Au(111) surfaces were systematically investigated using scanning tunneling microscopy (STM) under ultrahigh vacuum (UHV) conditions. Rich structures were revealed as a result of annealing in UHV. At temperatures below 345 K, no significant changes in coverage were observed, although the size of two-dimensional crystalline c(4√3 × 2√3)R30° domains increases as annealing progresses. A two-dimensional melting occurs at 345 ± 5 K and was captured in situ from time-dependent STM studies. Above 400 K, significant desorption takes place. In the temperature range of 345−400 K, within which desorption progresses to gradually decrease the surface coverage, a variety of striped phases have been o...

Structures of Annealed Decanethiol Self-Assembled Monolayers on Au(111): an Ultrahigh Vacuum Scanning Tunneling Microscopy Study

Self-assembled monolayers (SAMs) of 4-[4‘-(phenylethynyl)-phenylethynyl]-benzenethiols on Au(111) surfaces are investigated by scanning tunneling microscopy (STM) under ultrahigh vacuum. STM images reveal long-range order in these SAMs with a rectangular unit cell containing two molecules. In high-resolution images, two new structural features are resolved, which cannot be explained by the previously proposed (√3 × 2√3)R30° commensurate structure which consists of three equivalent domains. First, six equivalent domains are present, and the orientations of these domains with respect to the three 〈121〉 directions of Au(111) are ±5°. Second, superstructures are observed. Periodical ridges are observed as a modulation of the STM imaging contrast within the ordered domains. A new model is proposed, which is very similar to the crystalline structure of p-terphenyl. The closest-packed row is aligned along the next-nearest neighbor or 〈121〉 direction of Au(111) with phenyl planes arranged in a herringbone fashion...

Yile Qian

Papers

Nanofabrication of Self-Assembled Monolayers Using Scanning Probe Lithography

Structures of Annealed Decanethiol Self-Assembled Monolayers on Au(111): an Ultrahigh Vacuum Scanning Tunneling Microscopy Study

Arenethiols form ordered and incommensurate self-assembled monolayers on Au(111) surfaces

Nanofabrication of Self‐Assembled Monolayers Using Scanning Probe Lithography