Although a molecular monolayer is only a few nanometers thick it can completely change the properties of a surface. Molecular monolayers can be readily prepared using the Langmuir-Blodgett methodology or by chemisorption on metal and oxide surfaces. This Review focuses on the use of chemisorbed self-assembled monolayers (SAMs) as a platform for the functionalization of silicon oxide surfaces. The controlled organization of molecules and molecular assemblies on silicon oxide will have a prominent place in bottom-up nanofabrication, which could revolutionize fields such as nanoelectronics and biotechnology in the near future. In recent years, self-assembled monolayers on silicon oxide have reached a high level of sophistication and have been combined with various lithographic patterning methods to develop new nanofabrication protocols and biological arrays. Nanoscale control over surface properties is of paramount importance to advance from 2D patterning to 3D fabrication.

Engineering silicon oxide surfaces using self-assembled monolayers.

The homogeneous combination of inorganic and organic moieties in a single-phase material provides unique possibilities to tailor the mechanical, electrical, and optical properties with respect to numerous applications. The synthetic pathway follows the well-known sol−gel procedure. Nevertheless, the establishment of defined hybrid products necessitates a basic understanding of the underlying chemistry as well as of the parameters influencing the processing techniques. Modern spectroscopy provides versatile tools, e.g., multinuclear NMR experiments and Raman scattering to investigate the sol−gel processing of organo(alkoxy)silanes in their co-condensation reactions with main group or transition metal alkoxides as well as in their copolymerization reactions with each other or with organic molecules. This almost infinite modular design concept has led to the industrial application of coatings for transparent plastics, glasses, and metals to prevent these substrates from mechanical abrasion, permeation, or co...

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Hybrid Sol−Gel-Derived Polymers: Applications of Multifunctional Materials

By using mass spectrometry to analyze the atomic and molecular secondary ions that are emitted from a solid surface when bombarded with ions, one obtains detailed information about the chemical composition of the surface. A time-of-flight mass spectrometer is especially suitable for the analysis of secondary ions because of its high transmission, high mass resolution, and ability to detect ions of different masses simultaneously. By using a finely focused primary ion beam it is also possible to analyze microareas and generate surface images with a lateral resolution of 0.1 μm or less. Static time-of-flight secondary ion mass spectrometry (TOF-SIMS) allows monolayer imaging and local analysis of monolayers with high sensitivity, a wide mass range, high mass resolution, and high lateral resolution. Besides information on elements and isotopes, the technique yields direct information on the molecular level and can also be used to analyze surface species of high molecular mass that are thermally unstable and cannot be vaporized. The method can be applied to practically all types of materials and sample forms, including insulators in particular. In this article the basic principles of TOF-SIMS are explained, and its analytical capabilities for both large area and imaging applications are illustrated by examples. These include silicon surfaces (both uniform and structured), thermally unstable organic molecules on surfaces, synthetic polymers, and synthetically prepared molecular surface films, particles, and fibers. Emitted neutral particles can also be analyzed by postionization with a laser, and the possibilities of this technique are discussed.

Chemical Analysis of Inorganic and Organic Surfaces and Thin Films by Static Time‐of‐Flight Secondary Ion Mass Spectrometry (TOF‐SIMS)

Chapter 1 – Fully Condensed Polyhedral Oligosilsesquioxanes (POSS): From Synthesis to Application

The chemistry of polyhedral oligomeric silsesquioxanes (POSS) has taken a tremendous leap over the past decade. New synthetic approaches have been developed, and new complexes based on elements throughout the periodic table have been synthesized and applied in catalytic processes such as alkene epoxidation, Oppenauer oxidation, alkene polymerization, Diels−Alders reactions and alkene metathesis. The use of silsesquioxane ligands as models for silica surface has provided an intimate knowledge of the reactions on the surface of this much-used support. New methods have been developed to incorporate silsesquioxanes into new materials. Encapsulation in siloxane polymers has provided precision supports for catalysts and controlled calcination has produced materials with well-defined metal oxide particles. This paper reviews the history and the latest developments of silsesquioxane chemistry. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

The Dynamic Status Quo of Polyhedral Silsesquioxane Coordination Chemistry

Octakis-(dimethylphosphanoethyl)-octasilsesquioxane-synthesis, characterization and reactivity

Ein Verfahren zur FeCl3-katalysierten Hydrolyse von Trichlorsilanen im Zweiphasensystem wird untersucht und das dargestellte, neue Silasesquioxan (BrCH2CH2CH2)8Si8O12 isoliert und charakterisiert.



Synthesis and Structures of γ-Halopropyl-octa(silasesquioxanes)



As a more rapid and versatile synthetic approach, we have studied the FeCl3-catalyzed hydrolytic polycondensation of suited trichlorosilanes in a biphasic system which yields e.g. the new octa(silasesquioxane) (BrCH2CH2CH2)8Si8O12.

Synthese und Struktur von γ‐Halogenpropyl‐octa(silasesquioxanen)

Surface investigations of silylated substrates by TOF‐SIMS

Results of an extensive examination concerning effectiveness and durability of two different commercial organosilicon impregnating mixtures applied to Obernkirchener sandstone are presented briefly. Hygric tests and contact angle measurements prior to spectroscopic surface investigations of a propyl/octylsilane mixture and a methyl/octylsiloxane mixture reveal different long-term stability of the protective organosilicon coatings. General surface characteristics of the coatings were elucidated by time-of-flight secondary ion mass spectrometry (TOF-SIMS). The measurements on freshly soaked stone slabs give evidence of spherical silsesquioxanes and their homoderivatives only of the precursor compound with the shorter alkyl chain. Investigations on the weathered coatings (8 years) show the presence of silsesquioxanes only in case of the silane system. Additional DRIFT (diffuse reflectance FT-IR) measurements on both freshly soaked and exposed material confirm the presence of the coating in case of the silane mixture, but not in case of the siloxane mixture.

Examination of organosilicon impregnating mixtures by static SIMS and diffuse reflectance FT-IR

Anwendungsnahe Grundlagenforschung bedarf wegen der Komplexitat der Probleme und der zur Losung erforderlichen Spezialkenntnisse mehr denn je der interdisziplinaren Kooperation. In diesem Bericht wird eine fruchtbare Zusammenarbeit dreier Forschungsgruppen der Westfalischen Wilhelms-Universitat Munster auf dem Gebiet des Bautenschutzes mit siliciumorganischen Schutzstoffen vorgestellt.

Karl Stoppek‐Langner

Papers

Octakis-(dimethylphosphanoethyl)-octasilsesquioxane-synthesis, characterization and reactivity

Synthese und Struktur von γ‐Halogenpropyl‐octa(silasesquioxanen)

Surface investigations of silylated substrates by TOF‐SIMS

Examination of organosilicon impregnating mixtures by static SIMS and diffuse reflectance FT-IR

Grundlagenforschung im Dienst des Bautenschutzes