A Proposed Taxonomy and Classification Strategy for Well‐Defined, Soft‐Matter Nanoscale Building Blocks

The field of nanoscience has evolved explosively over the last two decades, generating a vast number of nanoscale structures and objects. These nanoconstructs may be derived from covalently bound molecules in the classical chemical sense or they may be supramolecular, self-assembled structures. That withstanding, in either case “well-defined nanostructures/objects” may be formed from the smaller discrete building blocks (i.e., atoms, small molecules, monomers, polymers, etc.) if certain “bottom-up” assembly processes are involved that ensure structure control of critical nanoscale design parameters (CNDPs) such as (a) size, (b) shape, (c) surface chemistry, (d) flexibility/rigidity, (e) architecture, and (f) composition. These resulting discrete, homogeneous nanostructures/objects constitute an important category of nanomaterials and are distinguished from other heterogeneous nano-assemblies by expressing well-defined interrelationship patterns and quantized stoichiometries with each other [1, 2]. The quantized stoichiometries and interparticle relationships exhibited by these well-defined nano-entities are a consequence of their structure-controlled precursor building blocks and their ability to transfer important critical atomic design parameters (CADPs) or critical molecular design parameters (CMDPs) to the nanoscale level. This structural information is routinely transferred with high integrity to higher complexity in biological systems via certain evolutionary/genealogical aufbau strategies as described in Figure 1.8 and 1.1. Joyce [3, 4] has clearly demonstrated (a) the importance of these genealogical/evolutionary aufbau patterns involving well-defined nanoscale building blocks such as proteins, RNA, and DNA and (b) their ultimate role in the diversification of life. In the case of abiotic systems, unique structure controlled synthetic strategies and construction rules are usually involved in the formation of these well-defined nanostructures/objects. The importance of understanding these bottomup construction rules and aufbau patterns cannot be overstated. They will be invaluable for developing classification and taxonomy schemes to define key nano-building blocks (i.e., nano-elements), as well as their hybridization pathways to (i.e., nano-compounds/assemblies) and synthetic evolution to higher complexity in the nanoscale region. In many respects, our present insights are similar to previous historical growth phases in traditional chemistry during the nineteenth century that led to the Mendeleev Periodic Table in 1869. In essence, the patterns and categorization of atomic elements in Mendeleev’s periodic table constituted an elegant classification or taxonomy for all the known atomic elements [5,6]. Mendeleev’s seminal atomic element taxonomy [7] has provided powerful insights and critical information useful for a priori predictions of elemental physicochemical behavior, as well as chemical reactivity, stoichiometries, assembly patterns, and so on, leading to the formation of traditional small molecular structures and assemblies as illustrated in Figure 1.2. The idea of classifying atomic elements or small molecules according to chosen criteria of similarity features or as a function of their interrelationships patterns/trends is not new. In fact, Swedish botanist Carl von Linnaeus (1707–1778), the “father of taxonomy,” initiated such a