Greener synthesis at different scales

Abstract The dwindling supply of renewables, coupled with the alarming negative impacts of the available resources raises serious concerns about the sustainability of the chemical and physical processes. Thus, it becomes imperative to find alternative options to such processes to make the processes greener and hence more sustainable. Though the sustainable approaches, especially in the context of synthetic procedures, involve the greener routes, the special mention seems apt due to the sharp growth of the associated fields in recent past. As the utilization of inexpensive, earth-abundant, and environmentally benign precursors is the primary objective of these approaches, it is impossible to generalize this with a single strategy and hence a further categorization is necessary. In this context, the current chapter aims to introduce the topic of greener synthetic routes with a classification based on the relation between the size/dimensionality (microscale and nanoscale) as well as the prevalence of the materials with the reported greener synthetic approaches. In each category, the materials are further classified based on their composition and types, and the development of greener synthetic strategies for the preparation of materials (from each category) is described in details. The extrapolation of such approaches for the potential industrial applications is also evaluated. At the end of each section, the present status, current challenges, and possible solutions are highlighted. Special care has been taken to avoid overlap with other chapters from the rest of the book and the primary objective of the chapter is suitably emphasized wherever needed. The authors truly believe that the choice of the topic/subtopics of this chapter makes this a unique one and the current chapter will surely help both the experts and nonexperts who are really interested in exploring the greener synthetic approaches for the preparation of materials of various shape, sizes, functionalities, and properties.