Materials innovation through interfacial physics and chemistry

Katsuhiko Ariga
World Premier International (WPI) Research Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Japan

Improvements in our day-to-day quality of life require materials innovations. As is well known, the development of advanced devices, machines, or even computing programs is an important aspect of social advancement. Efficiently functioning automata or high-density information processing in computing devices are based on the discovery, synthesis, fabrication, and selection of the optimum materials. In addition, we need to conserve important material resources and carefully consider the environmental impact of research, development and application activities. Thus, optimization of the use of highly functional materials will become crucial in the near future and materials innovations will enhance our lives.

A most effective strategy in materials innovation would be material production including fine nanostructure control. Based on well considered internal structures including atomic composition, molecular arrangement, nanopatterning, and mesoscopic structures, the new materials might possess highly advanced properties and functions. However, control and fabrication of three-dimensional nanostructures in bulk materials is not a simple task except in a few fortuitous examples such as self-assembled porous structures. We can access materials and control structures only from surfaces and interfaces. Therefore, the contributions due to interface physics and chemistry are important factors in materials innovation under nanostructure control. In particular, low-dimensional materials such as two-dimensional thin films and one-dimensional fibers consist mostly of surface or, in other words, an interface. Therefore, interfacial sciences play a central role in the preparation and functionalization of these low-dimensional materials, and so are anticipated to promote nanotechnology-driven materials innovation.

However, designing interfacial systems can be challenging since unusual phenomena based on specific physical and chemical interactions operate. Molecules align and orient in particular directions, atoms have higher energies, forces and fields possess anisotropies, and anomalous behaviour often occurs at interfaces although they may be not so notable in conventional bulk materials. Therefore, innovative and highly functional materials should be designed and synthesized based on a deep understanding of interfacial physics and chemistry. Interfaces are not limited to bulk visible media such as gas–solid and liquid–liquid interfaces. Invisible interfaces, including surfaces of molecular assemblies or molecule/molecule interfaces can also play important roles in materials' preparation and properties. Through specific interactions, various materials such as mesoporous solids, layered assemblies, and shape-defined nanomaterials can be created. Recent studies in these areas have certainly illustrated the importance of interfacial physics and chemistry.

This Themed Issue is expected to be of wide general interest to physicists and chemists in nano-related and materials-related disciplines since the various contributions report accounts from the vanguard of their respective research fields.

This issue features some exciting reviews on innovative interfacial science and technology. For example, in their comprehensive review Vollhardt et al. describe chiral discrimination in mesoscopic aggregates, which may lead to the development of a new paradigm for large area patterning using the Langmuir–Blodgett (LB) technique (DOI: 10.1039/c0cp02196b). Wang et al. comprehensively review polymer assemblies at interfaces (DOI: 10.1039/c0cp02287j) where the assembled polymer objects can be used for stimuli-responsive cargo release. Conceptual innovation in the use of interfacial environments to drive nano and molecular machines by macroscopic mechanical forces is proposed by Ariga et al. (DOI: 10.1039/c0cp02040k).

This issue also contains original contributions from various fields of interface and materials chemistry and physics. The contributions are roughly categorized under three headings: (i) characterization and basic investigations of interfaces; (ii) novel materials creation and fabrication; (iii) advanced nanotechnology and unique functions.

Advanced professional analyses on interfacial phenomena and nanomaterials are included. For example, Enders et al. investigated interface-grown plasmonic gold island films by surface-enhanced ATR-IR spectroscopy (DOI: 10.1039/c0cp01450h). Vasko et al. report chemical reactions occurring near a tip–sample interface (DOI: 10.1039/c0cp02150d). An electrochemical impedance spectroscopic and voltammetric study on gold nanoparticles with sizes ranging from 2 to 50 nm is reported by Bonanni et al. (DOI: 10.1039/c0cp01209b). Analyses of fundamental interfacial phenomena are also included. For example, a detailed analysis of initiation mechanisms of surface hydrosilylation with 1-alkenes on a silicone surface was conducted by Lee et al. (DOI: 10.1039/c0cp01992e). Also, Hirata et al. reported surface segregation of poly(2-methoxyethyl acrylate) in a mixture with poly(methyl methacrylate) (DOI: 10.1039/c0cp02101f).

Fabrication of nanomaterials based on interfacial science is a hot topic of this issue. Examples of new inorganic nanomaterials are given by the synthesis of nitrogen and sulfur co-doped TiO2 nanosheets reported in the article by Xiang et al. (DOI: 10.1039/c0cp01459a), where investigations of visible-light promoted photocatalytic activity of the novel materials is presented. Garcia et al. demonstrated the synthesis of platinum nanowheels using an inhomogeneous reaction environment with bicelle templates (DOI: 10.1039/c0cp01930e). Several examples of organic nanomaterials are also reported. Millimeter-scale crystalline sheets of fullerene derivatives with high charge mobility are reported by Babu et al. (DOI: 10.1039/c0cp02265a). Richards et al. report the preparation of organic nanotubes composed of pyrazinacene molecules through hierarchic self-assembly (DOI: 10.1039/c0cp02025g). Vijayakumar et al. present oligo(p-phenylenevinylene) based organogels (DOI: 10.1039/c0cp02110e), where excitation energy migration assisted energy transfer (ET) properties were studied using picosecond time-resolved emission spectroscopy. The highly sensitive photoalignment of liquid crystals with the assistance of axis-selective triplet energy transfer is demonstrated by Furumi and Ichimura (DOI: 10.1039/c0cp02016h). The preparation of polymer meshes by stretching and photo-crosslinking of poly(1,2-butadiene) honeycomb films is presented in an article by Yabu et al. (DOI: 10.1039/c0cp01945c). This Themed Issue also contains work on interfacial techniques for the fabrication of composites and hybrids. For example, Fernandes et al. report details of gelatin–sepiolite structural bionanocomposites at interfacial media (DOI: 10.1039/c0cp00882f). Ke et al. used the layer-by-layer (LbL) assembly technique for the preparation of patterned porous films (DOI: 10.1039/c0cp01229g).

Interfacial media often provide opportunities for advanced nanotechnology and observation of unique properties. Jensen et al. present an article on the preparation of gold nanoparticle electrochemical arrays on plastic using an inkjet printing technique (DOI: 10.1039/c0cp01755h). The arrays were demonstrated for use in immunodetection of a cancer biomarker protein. Micromachine manipulation using solvent responsive polymers was challengingly proposed by Tian et al. (DOI: 10.1039/c0cp02006k) while Michinobu et al. successfully demonstrate control of chiral sensing of amino acids using macroscopic manipulation of a cholesterol-armed cyclen molecular machine at the air–water interface (DOI: 10.1039/c0cp01990a). Although I am not able to highlight all of the contributions to the Themed Issue here, I am certain that all of the research described represents an important step forward for materials innovation through interfacial physics and chemistry.

Finally, I would like to express my deep gratitude to all authors who submitted their work to this Themed Issue of PCCP and also to the staff of the journal for their assistance during its preparation. In addition, I would like to thank all the referees who anonymously contributed through their conscientious examination and assessment of the manuscripts.

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