Preface

Inorganic nanomaterials are an extremely broad, diverse and versatile class of materials, often endowed with outstanding functional properties (e.g., optical, magnetic, semiconducting, electric, thermoelectric, electronic, etc.). They are typically characterised by enhanced chemical, thermal and mechanical stability with respect to their organic counterparts, which make them appealing candidates for a very wide range of technological applications. The current energy transition, renewable energy sources, advanced catalysis and electronics are all technologies that rely strongly on the availability of inorganic materials, typically in their nanostructured form.

Green synthesis, being more environmentally sustainable and lowering the environmental burden of materials production, could represent a required competitive advantage. As the recent scientific literature demonstrates, there are increasing endeavours to develop sustainable, green and easy syntheses of inorganic nanomaterials using approaches relying on unconventional conditions (e.g., confined spaces, non-standard temperature and pressure, etc.). Indeed, although several chemical processes have been established for the synthesis of the ever-increasing and expanding portfolio of nanomaterials, there has been a considerable amount of recent interest in developing more sustainable routes to produce inorganic nanomaterials, and also to explore unconventional synthesis pathways.

The motivation behind the planning of this book was many-fold. From one perspective, the book aims to cover an emerging area of inorganic synthesis, that is, the green and/or unconventional synthesis of metal nanoparticles, metal oxides, chalcogenides and halides, as well as composite and hybrid materials (see Chapter 1, for example). All of these are interesting for the different properties they display and the very broad range of applications they exhibit, ranging from catalysis, to electronics, optics and nanomedicine. The second motivation is to fill a cultural and technological gap, showing how it is possible to combine environmental and economical sustainability. The third and final aim is to provide the reader with a state-of-the-art and updated overview of less-known and emerging synthesis routes for inorganic nanomaterials, and to stimulate the inorganic chemistry community in relation to topics such as sustainability in synthesis, as well as the exploration of novel and challenging preparation methods. As such, we believe this book offers something quite different to the many other volumes regarding synthetic methods.

Selected green and/or unconventional wet-chemistry routes for the synthesis of functional inorganic nanostructures will be thoroughly described and discussed, by outlining their green and/or unconventional features. For each explored method, a brief background and state-of-the-art of the synthetic route are provided, followed by a detailed description of the procedure and a discussion of the roles of the synthetic parameters involved. Where possible, insight into how these parameters influence the final products will be given. Each chapter also includes a detailed description of the state-of-the-art concerning the compounds that can be obtained, as well as the potential scalability in an industrial environment.

The book is organised into six chapters. Chapters 1–4 are each devoted to a specific synthetic approach, each being characterised by some unconventional feature: nucleation and growth under confined space afforded by micro- and miniemulsion droplets (Chapter 1), use of biogenic agents (Chapter 2), use of supercritical fluids (Chapter 3), and use of microwaves (Chapter 4). Chapter 5 deals with advanced approaches for the in situ synthesis of hybrid nanocomposites based on graphene derivatives and inorganic nanoparticles for advanced applications. Chapter 6 collects together, in a short and concise form, further synthesis methods that are not covered in the previous chapters, i.e., hydrothermal, polyol-assisted, continuous-flow and sonochemical methods, as well as radiochemistry and laser ablation in liquid media. Also in Chapter 6, a theoretical background is provided for each method, along with a detailed survey of the applications for the synthesis of different classes of inorganic nanomaterials.

Silvia Gross