Sustainable and Very-Low-Temperature Wet-Chemistry Routes for the Synthesis of Crystalline Inorganic Nanostructures

Abstract

In this chapter, selected low (T < 200 °C)-temperature wet-chemistry routes for the synthesis of crystalline inorganic compounds are described and reviewed, outlining their main features and application fi elds. In particular, the chosen approaches are hydro/solvothermal synthesis, template-assisted approaches, nucleation and growth in solution/suspension, microemulsion and miniemulsion. The described synthetic strategies have been selected since all of them, once optimized the experimental set-up and conditions, comply with the paradigms of green chemistry, being based on low (or even room) temperature of processing, on low chemical consumption (they are all bottom-up approach), in many cases having water as solvent or dispersing medium. In this regard, environmentally friendly methodologies for the controlled synthesis of inorganic nanostructures represent a stimulating research playground, since the use of environmentally friendly, green, cost-effective and technically sound approaches to inorganic crystalline nanostructures does not necessarily imply to sacrifi ce the sample crystallinity, purity, and monodispersity.

Pursuing the Crystallization of Mono- and Polymetallic Nanosized Crystalline Inorganic Compounds by Low-Temperature Wet-Chemistry and Colloidal Routes

“…As outlined at the very beginning, the underlying concept of this review is to focus on low-temperature-based routes, “low” intended as lower than 200 °C, since this further constraint not only complies with one of the principles of green chemistry − but also enables unusual crystallization pathways to be explored. In relation to that, the other focus of the review is the achievement of “crystalline” inorganic nanomaterials.…”

“…Green chemistry is based on “the utilization of a set of principles that reduces or eliminates the use or generation of hazardous substances in the design, manufacture and application of chemical products” . This is an already established and spreading concept in the field of preparative chemistry, and the implementation of these paradigms to inorganic chemistry represents one of most bewitching developments . In this framework, environmentally friendly methodologies encompass not only the control of the final composition but also, and more importantly, a fine tuning of the obtained materials in terms of crystallinity (crystalline phase, crystallite size), shape, and morphology.…”

“…Several synthetic approaches to crystalline inorganic nanostructured compounds, either metallic or binary (oxides, chalcogenides, halides), have been extensively described in several books and excellent reviews. − In particular, Caruso , and Günter Schmid collected in their papers and books a comprehensive collection of the main synthetic approaches to colloids, colloids assemblies, and nanostructures, together with a thorough overview on their properties and applications.…”

“…Among the various synthetic routes which can be used for the preparation of inorganic compounds, wet-chemistry routes and solution-phase methods, i.e., the focus of this review, are usually preferable with respect to solid-state methods, due to the greater control they afford over the reaction pathways, the much greater uniformity in the yielded products, and the generally lower temperatures involved. ,,,,, In truth, solution-phase methods should be better referred as “liquid phase methods” or, even better, as “wet synthesis routes” since, in many cases, colloidal systems (i.e., suspensions) instead of molecularly homogeneous solutions are involved. These methods include sol–gel, ,,− , nonaqueous sol–gel, − hydrothermal and solvothermal, templated synthesis, − micro- , and miniemulsion, − as well as biomimetic/biomineralization approaches, − ,, which have been the topic of extensive reviews and books.…”

“…1 This is an already established and spreading concept in the field of preparative chemistry, and the implementation of these paradigms to inorganic chemistry represents one of most bewitching developments. 2 In this framework, environmentally friendly methodologies encompass not only the control of the final composition but also, and more importantly, a fine tuning of the obtained materials in terms of crystallinity (crystalline phase, crystallite size), shape, and morphology. In fact, control over structure, size, shape, and morphology combined with mild processing conditions (mainly in terms of temperature and pressure) are not only important requirements to be met for sustainable and cost-efficient production of functional inorganic materials but, as outlined in a following section (section 2), also afford enhanced functional properties which are related to the crystalline habitus of the obtained material.…”