Waka Nakanishi

Nanoarchitectonics: a new materials horizon for nanotechnology

Nanoarchitectonics is introduced as a rising tide within current nanomaterials science. Physical phenomena operate quite differently at the nanoscale (compared to in the macroscopic and microscopic regimes) with behaviours of nanoscopic objects being strongly influenced by thermal/statistical fluctuations and mutual interactions between components. Nanoarchitectonic methods, and the materials that they produce, contrast strongly with those of conventional nanotechnology. In this review, to illustrate the potential of nanoarchitectonics for future technologies, examples of nanoarchitectonics are introduced which are categorized as (i) atomic or molecular manipulation as a route to leading nanotechnologies, (ii) materials creation in the realization of materials nanoarchitectonics, and (iii) advanced device materials.

Highly Ordered 1D Fullerene Crystals for Concurrent Control of Macroscopic Cellular Orientation and Differentiation toward Large‐Scale Tissue Engineering

A highly aligned 1D fullerene whisker (FW) scaffold in a centimeter area is fabricated by interfacial alignment. The resulting aligned FW scaffold enables concurrent control over cellular orientation and differentiation to muscle cells. This aligned FW scaffold is made by a facile method, and hence the substrate is a promising alternative to other cell scaffolds for tissue engineering.

Mechanochemical Tuning of the Binaphthyl Conformation at the Air–Water Interface†

Gradual and reversible tuning of the torsion angle of an amphiphilic chiral binaphthyl, from -90° to -80°, was achieved by application of a mechanical force to its molecular monolayer at the air-water interface. This 2D interface was an ideal location for mechanochemistry for molecular tuning and its experimental and theoretical analysis, since this lowered dimension enables high orientation of molecules and large variation in the area. A small mechanical energy (<1u2005kcalu2009mol(-1) ) was applied to the monolayer, causing a large variation (>50u2009%) in the area of the monolayer and modification of binaphthyl conformation. Single-molecule simulations revealed that mechanical energy was converted proportionally to torsional energy. Molecular dynamics simulations of the monolayer indicated that the global average torsion angle of a monolayer was gradually shifted.

Vortex-Aligned Fullerene Nanowhiskers as a Scaffold for Orienting Cell Growth

A versatile method for the rapid fabrication of aligned fullerene C60 nanowhiskers (C60NWs) at the air-water interface is presented. This method is based on the vortex motion of a subphase (water), which directs floating C60NWs to align on the water surface according to the direction of rotational flow. Aligned C60NWs could be transferred onto many different flat substrates, and, in this case, aligned C60NWs on glass substrates were employed as a scaffold for cell culture. Bone forming human osteoblast MG63 cells adhered well to the C60NWs, and their growth was found to be oriented with the axis of the aligned C60NWs. Cells grown on aligned C60NWs were more highly oriented with the axis of alignment than when grown on randomly oriented nanowhiskers. A study of cell proliferation on the C60NWs revealed their low toxicity, indicating their potential for use in biomedical applications.

Thin Film Nanoarchitectonics

A paradigm shift from nanotechnology to nanoarchitectonics is necessary. Individual nano-objects are required to be constructed into functional nanoarchitectures in order to develop this field and its potential applications. According to nanoarchitectonic strategies, materials are formed based on manipulation of atoms, molecules, or their assemblies and through synergetic combinations of chemical nanofabrication, self-organization, and field-controlled organization. In this review, nanoarchitectonics involving films are summarized, in which both nano-level material (i.e. molecular) interactions and external stimuli are utilized in a harmonized manner. In film nanoarchitectonics, three major strategies are used for thin film preparation: self-assembled monolayer (SAM) technique, Langmuir–Blodgett (LB) method, and layer-by-layer (LbL) assembly. The SAM method is a powerful and precise strategy for surface nanoarchitectures that is advantageous for introduction of functionality to device structures and for preparation of biocompatible surfaces. LbL assembly and LB techniques both provide effective methods for preparing controlled layered nanoarchitectures. LbL assembly is somewhat more versatile being useful for preparing a wide range of layered nanoarchitectures and has been rapidly taken up for various applications. On the other hand, the LB method is unique for its utilization of a dynamic interface in production processes. Thin film nanoarchitectonics is an excellent prototypical method for formation of three-dimensional nanoarchitectures.

Mechanically Induced Opening-Closing Action of Binaphthyl Molecular Pliers: Digital Phase Transition vs. Continuous Conformational Change

Reversible dynamic control of structure is a significant challenge in molecular nanotechnology. Previously, we have reported a mechanically induced continuous (analog) conformational variation in an amphiphilic binaphthyl, where closing of molecular pliers was achieved by compression of a molecular monolayer composed of these molecules at the air-water interface. In this work we report that a phase transition induced by an applied mechanical stress enables discontinuous digital (1/0) opening of simple binaphthyl molecular pliers. A lipid matrix at the air-water interface promotes the formation of quasi-stable nanocrystals, in which binaphthyl molecules have an open transoid configuration. The crystallization/dissolution of quasi-stable binaphthyl crystals with accompanying conformational change is reversible and repeatable.

Determination of blood potassium using a fouling-resistant PVDF–HFP-based optode

Monitoring potassium levels in blood is a significant aspect of clinical analysis. For this reason, polymeric bulk optodes have received much attention for their use in portable and easy-to-use analysis systems in situ determination without additional calibration. However, blood contamination on the detection area of the sensor can hinder accurate sensing and also increases risk of infection from the wounds. In this paper, we report a system for determination of potassium in blood which has the additional advantage of being blood-fouling resistant. We have replaced the generally used poly(vinyl chloride) (PVC) with hydrophobic fluorinated poly(vinylidene fluoride–hexafluoropropylene) (PVDF–HFP) for preparation of a polymeric bulk optode. Sensing ability in the visual range of the polymeric bulk optode was retained despite the variation of the polymer matrix. These polymeric bulk optodes are suitable for potassium determination in blood with the PVDF–HFP-based optode possessing better blood antifouling properties than the PVC-based optode. The blood monitoring system described here represents the basis for functionalization of the optode toward safe and easily implementation in blood and in situ sensing applications.

Nano Trek Beyond: Driving Nanocars/Molecular Machines at Interfaces

In 2016, the Nobel Prize in Chemistry was awarded for pioneering work on molecular machines. Half a year later, in Toulouse, the first molecular car race, a nanocar race, was held by using the tip of a scanning tunneling microscope as an electrical remote control. In this Focus Review, we discuss the current state-of-the-art in research on molecular machines at interfaces. In the first section, we briefly explain the science behind the nanocar race, followed by a selection of recent examples of controlling molecules on surfaces. Finally, motion synchronization and the functions of molecular machines at liquid interfaces are discussed. This new concept of molecular tuning at interfaces is also introduced as a method for the continuous modification and optimization of molecular structure for target functions.

Disilanyl Double-Pillared Bisternaphthyl (SiDPBT): Synthesis and Interfused Packing Structures with Herringbone and π-Stack Motifs

A silacyclophane molecule with two disilanyl pillars and two oligoarylene units was synthesized. The molecule was packed in a single crystal with a new motif interfusing π-stack and herringbone packing structures. The hole transporting ability of the solid was revealed by using the flash-photolysis time-resolved microwave conductivity method. The molecular structure, albeit a singly-bonded arylene macrocycle, was rigidified by the unique packing array, which favorably contributed to the hole transporting ability of the solid via the small reorganization energy through the charge transport.