Real-Space Imaging of the Atomic Structure of Organic-Inorganic Perovskite.

Organic-inorganic perovskite is a promising class of materials for photovoltaic applications and light emitting diodes. However, so far commercialization is still impeded by several drawbacks. Atomic-scale effects have been suggested to be possible causes, but an unequivocal experimental view at the atomic level is missing.

Flat-lying semiconductor-insulator interfacial layer in DNTT thin films.

The molecular order of organic semiconductors at the gate dielectric is the most critical factor determining carrier mobility in thin film transistors since the conducting channel forms at the dielectric interface. Despite its fundamental importance, this semiconductor-insulator interface is not well understood, primarily because it is buried within the device. We fabricated dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT) thin film transistors by thermal evaporation in vacuum onto substrates held at different temperatures and systematically correlated the extracted charge mobility to the crystal grain size and crystal orientation.

Self-assembly of semiconductor/insulator interfaces in one-step spin-coating: a versatile approach for organic field-effect transistors.

Self-assembly of interfaces is of great interest in physical and chemical domains. One of the most challenging targets is to obtain an optimal interface structure showing good electronic properties by solution-processing. Interfaces of semiconductor/semiconductor, semiconductor/insulator and insulator/insulator have been successfully manipulated to obtain high-performance devices.

Langmuir nanoarchitectonics: one-touch fabrication of regularly sized nanodisks at the air-water interface.

In this article, we propose a novel methodology for the formation of monodisperse regularly sized disks of several nanometer thickness and with diameters of less than 100 nm using Langmuir monolayers as fabrication media. An amphiphilic triimide, tri-n-dodecylmellitic triimide (1), was spread as a monolayer at the air-water interface with a water-soluble macrocyclic oligoamine, 1,4,7,10-tetraazacyclododecane (cyclen), in the subphase. The imide moieties of 1 act as hydrogen bond acceptors and can interact weakly with the secondary amine moieties of cyclen as hydrogen bond donors.

Silica-based gene reverse transfection: an upright nanosheet network for promoted DNA delivery to cells.

A method for substrate-mediated reverse gene transfection was developed using a silica film composed of an upright-sheet network. The silica film with a dense upright-sheet network shows approximately double higher transgene expression efficiency than that of solution-based transfection.

The initiation mechanisms for surface hydrosilylation with 1-alkenes.

Hydrosilylation provides a route to form substituted silanes in solution. A similar reaction has been observed in the formation of covalent organic monolayers on a hydrogen-terminated silicon surface and is called thermal hydrosilylation. In solution, the mechanism requires a catalyst to add the basal silicon and saturating hydrogen to the C=C double bond.

Recent developments in supramolecular approach for nanocomposites.

One of the most efficient ways to create new materials is the fabrication of nanocomposites and/or nanohybrids. Composites adopt some characteristics from the components that compose it; synergistic effects can also produce properties not present in any of the parts. A union of the worlds of organic, biological, and inorganic materials merges the versatility, fine structural precision, and mechanical and chemical stability of these respective areas.

Characteristic IR C=C stretch enhancement in monolayers by nonconjugated, noncumulated unsaturated bonds.

Control over and understanding of single-molecule covalent coatings becomes increasingly important in tailoring surfaces during the fabrication of nanoscale electrical or optical elements, such as organic field-effect transistors and light-emitting devices as well as microelectromechanical systems as the relevant feature sizes decrease. In this work, we develop a model based on IR spectra from public databases and DFT calculations that can be used to semiquantitatively assess the level of double bonds in monolayer coatings. We use the model to show the enhancement of the C=C vibrational mode due to silicon substitution and also from additional unsaturated bonds.

Two-dimensional nanoarchitectonics based on self-assembly.

Top-down nanofabrication techniques, especially photolithography, have advanced nanotechnology to a point where system-process integration with bottom-up self-assembly is now required. Because most lithographic techniques are constrained to two-dimensional planes, investigation of integrated self-assembly systems should focus on two-dimensional organization. In this review, research on two-dimensional nanoartchitectonics is classified and summarized according to the type of interface used.

Unanticipated C=C bonds in covalent monolayers on silicon revealed by NEXAFS.

Interfaces are crucial to material properties. In the case of covalent organic monolayers on silicon, molecular structure at the interface controls the self-assembly of the monolayers, which in turn influences the optical properties and electrical transport. These properties intrinsically affect their application in biology, tribology, optics, and electronics.

Studies on Langmuir monolayers of polyprenyl phosphates towards a possible scenario for origin of life.

Although some biological components such as RNA are believed to play a crucial role in the processes which led to the formation of the first living systems, we cannot ignore the importance of lipids in the genesis of cell membranes. To answer the fundamental question of what the oldest cell-forming components were the Ourisson/Nakatani group has extensively investigated the origin of lipids and they have proposed polyprenyl phosphates and related molecules as plausible candidates for precursors of modern lipids. These molecules have been demonstrated as being capable of forming vesicle structures, and this feature has been extended to preparation of Langmuir monolayers of polyprenyl phosphates in collaboration with the Ourisson/Nakatani group.

Challenges and breakthroughs in recent research on self-assembly.

The controlled fabrication of nanometer-scale objects is without doubt one of the central issues in current science and technology. However, existing fabrication techniques suffer from several disadvantages including size-restrictions and a general paucity of applicable materials. Because of this, the development of alternative approaches based on supramolecular self-assembly processes is anticipated as a breakthrough methodology.

Chemomechanical nanolithography: nanografting on silicon and factors impacting linewidth.

We present a two-fold extension of previous work on Atomic Force Microscope-based chemomechanical functionalization: (1) chemomechanical nanografting, which extends chemomechanical functionalization to a more stable initial surface, and (2) linewidth studies that show the impact of force and Atomic Force Microscope probe tip wear on patterning resolution. Alkene, alcohol, and alkyl halide molecules were nanografted to silicon and imaged with in situ atomic force microscopy, time-of-flight secondary ion mass spectrometry with Automated eXpert Spectrum Image Analysis, and scanning electron microscopy. Chemomechanical nanografting demonstrated linewidths down to 50 nm.

Chemomechanical functionalization and patterning of silicon.

The chemomechanical method has emerged as a straightforward and convenient tool for simultaneously functionalizing and patterning silicon. This technique simply consists of wetting (or exposing) a silicon surface to a reactive chemical and then scribing. Scribing activates the surface and leads to monolayer formation.

Molecular modeling of alkyl monolayers on the Si(100)-2 x 1 surface.

Molecular modeling was used to simulate various surfaces derived from the addition of 1-alkenes and 1-alkynes to Si=Si dimers on the Si(100)-2 x 1 surface. The primary aim was to better understand the interactions between adsorbates on the surface and distortions of the underlying silicon crystal due to functionalization. Random addition of ethylene and acetylene was used to determine how the addition of an adduct molecule affects subsequent additions for coverages up to one molecule per silicon dimer, that is, 100% coverage.