Introduction to the themed issue on Advanced Complex Inorganic Nanomaterials

Energy, environmental issues and health care are amongst the top priorities of modern society. Such strategic issues have sparked phenomenal interest in inorganic nanomaterials as they hold great promise to develop new advanced devices and equipment which could revolutionise the way we live. Investigating the structuration of materials on the nanoscale has revealed unprecedented physical (optics, magnetism, etc.) and chemical (e.g. catalysis) properties that are absent in bulk matter of the same chemical composition. These specific functionalities are the consequence of a complex multi-level organisation (chemical, structural, textural) of the architecture of inorganic nanomaterials. The global properties and functional performances largely depend on the extent to which these levels are mastered during the synthesis process.

A new forum to discuss the evolution and extraordinary revolution brought by such nanomaterials was most welcome. This was the scope of the second International Conference on Advanced Complex Inorganic Nanomaterials (ACIN) held in Namur (Belgium), July 15–19, 2013, which was jointly organised by the Laboratory of Inorganic Materials Chemistry at the University of Namur and the Institute of Condensed Matter and Nanosciences (IMCN) at the University Catholique de Louvain. This meeting gathered an impressive set of renowned international speakers (Michael Graetzel, Zhong Lin Wang, Susumu Kitagawa, Mathias Driess, Xinhe Baho, Marie-Paule Pileni, Leone Spiccia, Lee Cronin, Min Gu, Paolo Samori, Mir Wais Hosseini, Shin-ichi Ohkoshi and Di Zhang, to name but a few) including Nobel Prize winner Jean Marie Lehn, who presented original results.

To celebrate this international inorganic chemistry event, New Journal of Chemistry (CNRS and RSC Publishing) present a themed issue gathering original contributions presented as 4 NJC Letters, 25 full papers, 4 Focus reviews and 6 Perspective reviews. This forum offers an update of recent innovations in both fundamental and applied aspects of inorganic nanomaterials (inorganics, ceramics, complexes, hybrids and bio-inspired materials).

The latest advances and progress on advanced preparation methods are discussed. In particular, hydrothermal routes are largely used to produce Bi₂WO₆ microspheres (Zhou et al.), BaTiO₃ tube-like arrays (Lamberti et al.), as well as NH₄V₃O₈ microcrystals or V₂O₅ (Vernardou et al.) and H₂V₃O₈ nanowire bundles (Han, Mai et al.) to improve electrochemical performances. Microwave assisted methods are employed to prepare EuPO₄·H₂O nanostructures (Tran Thu et al.) and layered simple hydroxides (Rogez et al.). Template assisted methods are followed to synthesise ZnO nanostructures/nanowires (Stassi, Cauda et al.) or porous BN and Si/B/C/N monoliths (Miele et al.). We can also point out an original self-assembly route combined with a ship-in-a-bottle method for mesoporous catalysts (Sun et al.), and a surface modification method to functionalize a graphite electrode (Toda, Hayami et al.). Finally, ion exchange methods to produce hollow micro/nanostructures materials are reviewed by Yan and Rosei.

The active field of coordination polymers (CPs)/MOFs and hybrids is also covered. In their review, Van der Voort et al. provide a useful survey of vanadium MOFs and their applications in adsorption, separation and catalysis, whereas Janiak, Henninger et al. highlight novel industrial applications of MOFs for heat transformation. Oshio et al. disclose the crystal structure of an achiral CP whereas Chen et al. present a flexible CP based on a rare heptanuclear Zn^II cluster featuring selective adsorption properties of alkylbenzene isomers, which are widely used in the chemical industry. Potential Mg precursors to MOFs are also presented (Wilson et al.). Non-siliceous hybrid organic–inorganic nanostructures are reviewed by Yuan et al. whereas Tremel et al. present the immobilisation of Au@MnO nanoflowers onto TiO₂ nanowires.

Spin crossover (SCO) nanomaterials are the focus of rising interest. Insights into complex cooperative mechanisms of SCO phenomena could be gained by Kitazawa et al. who present a Hofman like CP showing a two-step SCO with multiple phase transitions whereas Weber et al. have studied the effect of a short alkyl chain of amphiphilic Fe complexes. Halcrow surveys recent developments in the chemistry of 2,6-dipyrazol pyridine transition metal complexes and their SCO/luminescent properties. Other heterocycles are used either to reduce the metal–metal distance in dinuclear Ru^II complexes (Escriche, Albrecht et al.) or to prepare Fe^III polynuclear clusters with a ring structure (Clemente-León, Coronado et al.). Understanding thermal and photoswitchable SCO properties after size reduction is addressed respectively in the Focus reviews by Bousseksou et al. and Tissot. Tallon, Brooker et al. point out the importance of scan rate in the study of hysteretic Co SCO complexes whereas Ohkoshi et al. underline how relative humidity can tune hysteresis widths, which is of major importance for applications in display and data processing.

Several papers focus on heterogeneous catalysis. T. Zhang, Mou et al. investigate supported Au/Pd nanocatalysts, Lamonier et al. study hierarchically porous Nb–TiO₂ catalysts, whereas the effect of doping a titania catalytic support with vanadium oxide is reported by Siffert et al. Ru nanocrystal catalysts are described by J. Zhang, Ma et al. and Visart de Bocarmé developed impressive field emission techniques to study Pd and Pt nanocrystallites. Photocatalysis is also covered with Zn–TiO₂ mesoporous materials (Blin et al.) whereas Driess et al. stress the relevance of multi-faceted morphology of Ag₃PO₄ microparticles for water splitting. Other important properties are discussed: electrolytes (Laberty-Robert et al.) and photoanodes (Bein, Fattakhova-Rohlfing et al.) for dye-sensitised solar cells, plasmonic materials obtained with halloysite nanotubes decorated with Au (Hueso, Santamaría et al.) and a semiconducting charge transfer salt (Liu et al.).

From the large number of participants as well as from the appreciation received by the two chairmen, the success of this second edition of ACIN 2013 has been well recognised. Participants mentioned the highly stimulating exchange of ideas, the outstanding quality of the oral program and the impressive list of invited speakers, as well as the variety of themes and high level of organisation. ‘A conference from which we learn and we are ready to revisit’. ACIN has raised high expectations within the nanomaterials community about the next edition of the series, which will soon be announced. We wish to take the opportunity to thank all contributors and reviewers, and sincerely hope that you will enjoy reading this themed issue.

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