The layer-by-layer (LbL) adsorption technique offers an easy and inexpensive process for multilayer formation and allows a variety of materials to be incorporated within the film structures. Therefore, the LbL assembly method can be regarded as a versatile bottom-up nanofabrication technique. Research fields concerned with LbL assembly have developed rapidly but some important physicochemical aspects remain uninvestigated. In this review, we will introduce several examples from physicochemical investigations regarding the basics of this method to advanced research aimed at practical applications. These are selected mostly from recent reports and should stimulate many physical chemists and chemical physicists in the further development of LbL assembly. In order to further understand the mechanism of the LbL assembly process, theoretical work, including thermodynamics calculations, has been conducted. Additionally, the use of molecular dynamics simulation has been proposed. Recently, many kinds of physicochemical molecular interactions, including hydrogen bonding, charge transfer interactions, and stereo-complex formation, have been used. The combination of the LbL method with other fabrication techniques such as spin-coating, spraying, and photolithography has also been extensively researched. These improvements have enabled preparation of LbL films composed of various materials contained in well-designed nanostructures. The resulting structures can be used to investigate basic physicochemical phenomena where relative distances between interacting groups is of great importance. Similarly, LbL structures prepared by such advanced techniques are used widely for development of functional systems for physical applications from photovoltaic devices and field effect transistors to biochemical applications including nano-sized reactors and drug delivery systems.

Layer-by-Layer Assembly as a Versatile Bottom-Up Nanofabrication Technique for Exploratory Research and Realistic Application

Creating functional electrical circuits using individual or ensemble molecules, often termed as “molecular-scale electronics”, not only meets the increasing technical demands of the miniaturization of traditional Si-based electronic devices, but also provides an ideal window of exploring the intrinsic properties of materials at the molecular level. This Review covers the major advances with the most general applicability and emphasizes new insights into the development of efficient platform methodologies for building reliable molecular electronic devices with desired functionalities through the combination of programmed bottom-up self-assembly and sophisticated top-down device fabrication. First, we summarize a number of different approaches of forming molecular-scale junctions and discuss various experimental techniques for examining these nanoscale circuits in details. We then give a full introduction of characterization techniques and theoretical simulations for molecular electronics. Third, we highlig...

Molecular-Scale Electronics: From Concept to Function

Materials fabrication with nanoscale structural precision based on bottom-up-type self-assembly has become more important in various current disciplines in chemistry including materials chemistry, ...

Layer-by-layer Nanoarchitectonics: Invention, Innovation, and Evolution

Layer-by-layer assembly: from conventional to unconventional methods

Unimolecular electrical rectifiers.

This report describes synthesis and characterization of a molecular diode based upon a diblock conjugated oligomer system. This system consists of two conjugated blocks with opposite electronic demand. The molecular structure exhibits a built-in electronic asymmetry, much like a semiconductor p−n junction. Electrical measurements by scanning tunneling spectroscopy (STS) clearly revealed a pronounced rectifying effect. Definitive proof for the molecular nature of the rectifying effect in this conjugated diblock molecule is provided by control experiments with a structurally similar reference compound.

Molecular diodes based on conjugated diblock co-oligomers.

This paper reports a simple method for the multilayer immobilization of conjugated polymers, gold nanoparticles on solid supports. Poly(phenylenevinylene) functionalized with aldehyde and aminooxy groups was chemoselectively immobilized onto both glass and gold substrates via layer-by-layer deposition. The physical properties of the thin films were characterized by grazing angle IR, TM-AFM, fluorescence, and UV-visible spectroscopy. This methodology was also successfully applied to prepare polymer/gold nanocluster alternating multilayers. The results show that this methodology provides a general route for preparing robust and functionalizable multilayer films on solid substrates with molecular-level thickness control.

A novel layer-by-layer approach to immobilization of polymers and nanoclusters.

Site-specific reaction of hyperthermal O+ with a self-assembled monolayer is described. Isotopic labeling experiments reveal the percentage of abstraction products formed from hydrogen atoms bound originally to the top three carbon atoms in the chain.

Site-selective abstraction in the reaction of 5-20 eV O+ with a self-assembled monolayer.

Cofacial porphyrin multilayers via layer-by-layer assembly.

This Letter reports a novel approach to the fabrication of a biomimicking surface by modification of an end-functionalizable smooth polymer cushion constructed via chemoselective ligation with a phospholipid-like molecule containing oxyamine groups. The mobility of a phospholipid bilayer formed by vesicle fusion on the phospholipid-like molecule terminated polymer film was characterized by fluorescence recovery after bleaching. Platelet adhesion, as one measure of biocompatibility of the film was also studied and compared to other surfaces such as polyethylene or poly(dimethylsiloxane). The results show that the end-functionalized smooth polymer cushion has potential as a biocompatible platform to reconstitute membrane proteins.

Dong-Chan Lee

Papers

Molecular diodes based on conjugated diblock co-oligomers.

A novel layer-by-layer approach to immobilization of polymers and nanoclusters.

Site-selective abstraction in the reaction of 5-20 eV O+ with a self-assembled monolayer.

Cofacial porphyrin multilayers via layer-by-layer assembly.

Polymer cushions functionalized with lipid molecules.