C3-C3' and C6-C6' Oxidative Couplings of Carbazoles

9-Substituted carbazoles are widely used units in materials science, and their oxidative reactions have been utilized for the synthesis and characterization of polymers. Though the oxidative mechanism of carbazoles has been known for a few decades, structural definition has remained difficult, because their polymers are generally insoluble with incomplete characterization and unknown dependence of the electrochemical potentials. The oxidative reactions of 9-substituted carbazoles should be carefully considered under specific oxidative conditions; otherwise, structure definitions could be wrong, because the IR and NMR spectra used previously cannot quantitatively analyze 3,3'-coupling and 6,6'-coupling of carbazoles. In this review, the best understanding of the C3-C3' and C6-C6' oxidative couplings of 9-substituted carbazoles is presented, and the benefit of these oxidative reactions from the viewpoints of electrochemical synthesis, film engineering, and the synthesis and processing of polymers is highlighted.

Electroreductive Coupling Layer-by-Layer Assembly

Rapid and covalent layer-by-layer (LbL) assembly is of significance for practical applications because of superior chemical and mechanical stability. The electrochemical LbL assembly via an accelerating trigger can be automated and programmable in response to electrical signals to in situ fabricate covalently layered thin films with chemical and mechanical stability. In this paper, electroreductive coupling layer-by-layer assembly is introduced as both covalent and rapid methodology for preparing layered thin films. This assembly is triggered by C-C coupling of peripheral alkynyls, which have own absorption below 300 nm and can transform to optical and electrical inert double/single or triple/single alternative bonding formations significantly without optical or electric alternations of desirable photoelectric building blocks, superior to other linkers among covalent LbL assemblies. Not limited to fabrication of optical thin films, this assembly is readily available for oxygen sensitive substrates or materials and also a powerful addition to electrooxidative coupling LbL assembly for developing the economically dynamoelectric LbL machines without moving or changing experimental gears.

Review of Electrochemically Triggered Macromolecular Film Buildup Processes and Their Biomedical Applications

Macromolecular coatings play an important role in many technological areas, ranging from the car industry to biosensors. Among the different coating technologies, electrochemically triggered processes are extremely powerful because they allow in particular spatial confinement of the film buildup up to the micrometer scale on microelectrodes. Here, we review the latest advances in the field of electrochemically triggered macromolecular film buildup processes performed in aqueous solutions. All these processes will be discussed and related to their several applications such as corrosion prevention, biosensors, antimicrobial coatings, drug-release, barrier properties and cell encapsulation. Special emphasis will be put on applications in the rapidly growing field of biosensors. Using polymers or proteins, the electrochemical buildup of the films can result from a local change of macromolecules solubility, self-assembly of polyelectrolytes through electrostatic/ionic interactions or covalent cross-linking between different macromolecules. The assembly process can be in one step or performed step-by-step based on an electrical trigger affecting directly the interacting macromolecules or generating ionic species.

Building High-Coverage Monolayers of Covalently Bound Magnetic Nanoparticles

This work presents an approach for producing a high-coverage single monolayer of magnetic nanoparticles using "click chemistry" between complementarily-functionalized nanoparticles and a flat substrate. This method highlights essential aspects of the functionalization scheme for substrate surface and nanoparticles to produce exceptionally high surface coverage without sacrificing selectivity or control over the layer produced. The deposition of one single layer of magnetic particles without agglomeration, over a large area, with a nearly 100% coverage is confirmed by electron microscopy. Spectroscopic techniques, supplemented by computational predictions, are used to interrogate the chemistry of the attachment and to confirm covalent binding, rather than attachment through self-assembly or weak van der Waals bonding. Density functional theory calculations for the surface intermediate of this copper-catalyzed process provide mechanistic insight into the effects of the functionalization scheme on surface coverage. Based on this analysis, it appears that steric limitations of the intermediate structure affect nanoparticle coverage on a flat solid substrate; however, this can be overcome by designing a functionalization scheme in such a way that the copper-based intermediate is formed on the spherical nanoparticles instead. This observation can be carried over to other approaches for creating highly-controlled single- or multilayered nanostructures of a wide range of materials to result in high coverage and possibly, conformal filling.

Nanoarchitectonics for Dynamic Functional Materials from Atomic-/Molecular-Level Manipulation to Macroscopic Action

Objects in all dimensions are subject to translational dynamism and dynamic mutual interactions, and the ability to exert control over these events is one of the keys to the synthesis of functional materials. For the development of materials with truly dynamic functionalities, a paradigm shift from "nanotechnology" to "nanoarchitectonics" is proposed, with the aim of design and preparation of functional materials through dynamic harmonization of atomic-/molecular-level manipulation and control, chemical nanofabrication, self-organization, and field-controlled organization. Here, various examples of dynamic functional materials are presented from the atom/molecular-level to macroscopic dimensions. These systems, including atomic switches, molecular machines, molecular shuttles, motional crystals, metal-organic frameworks, layered assemblies, gels, supramolecular assemblies of biomaterials, DNA origami, hollow silica capsules, and mesoporous materials, are described according to their various dynamic functions, which include short-term plasticity, long-term potentiation, molecular manipulation, switchable catalysis, self-healing properties, supramolecular chirality, morphological control, drug storage and release, light-harvesting, mechanochemical transduction, molecular tuning molecular recognition, hand-operated nanotechnology.

Nanoparticle layer deposition for highly controlled multilayer formation based on high- coverage monolayers of nanoparticles

This paper establishes a strategy for chemical deposition of functionalized nanoparticles onto solid substrates in a layer-by-layer process based on self-limiting surface chemical reactions leading to complete monolayer formation within the multilayer system without any additional intermediate layers - nanoparticle layer deposition (NPLD). This approach is fundamentally different from previously established traditional layer-by-layer deposition techniques and is conceptually more similar to well-known atomic and molecular - layer deposition processes. The NPLD approach uses efficient chemical functionalization of the solid substrate material and complementary functionalization of nanoparticles to produce a nearly 100% coverage of these nanoparticles with the use of "click chemistry". Following this initial deposition, a second complete monolayer of nanoparticles is deposited using a copper-catalyzed "click reaction" with the azide-terminated silica nanoparticles of a different size. This layer-by-layer growth is demonstrated to produce stable covalently-bound multilayers of nearly perfect structure over macroscopic solid substrates. The formation of stable covalent bonds is confirmed spectroscopically and the stability of the multilayers produced is tested by sonication in a variety of common solvents. The 1-, 2- and 3-layer structures are interrogated by electron microscopy and atomic force microscopy and the thickness of the multilayers formed is fully consistent with that expected for highly efficient monolayer formation with each cycle of growth. This approach can be extended to include a variety of materials deposited in a predesigned sequence on different substrates with a highly conformal filling.