ABSTRACT
Perhaps the most influential force to have guided the advancement of traditional 19th-century atomic/molecular chemistry/physics theory to its current 21st-century maturity was the evolution of a “central paradigm/dogma.” Based on a shared consensus by both chemists and physicists, a similar central dogma for guiding/unifying nanoscience is emerging (Tomalia, 2009, 2010; Tomalia and Khanna, 2014, 2016). This new paradigm is based on the same first principles as traditional atomic/molecular theory and involves discrete nanoclusters of atoms [i.e., quantized building blocks (QBBs)] reminiscent of picoscale atoms. By analogy to traditional inorganic or organic elemental categories, they are referred to as hard or soft superatoms, respectively. These hard/soft superatoms have been observed and reported by both chemists and physicists. They are quantized, nanoscale atom clusters that behave as discrete atom-like units by mimicking unique nanoscale shell-filling (i.e., aufbau) features, as well as exhibiting discrete chemical combining properties leading to stoichiometric nano-compounds/supramolecular assemblies (Tomalia, 2009, 2010; Tomalia and Khanna, 2014, 2016). Perhaps most compelling is that each of these hard and soft superatom categories exhibits unique nanoperiodic property patterns, much like traditional inorganic and organic type atomic elements. Intrinsic properties manifested by these hard/soft superatoms, as well as new emerging properties associated with chemical/supramolecular combinations of these nanoscale superatoms exhibit these periodic patterns. Much like the first list of 20 atomic elements and proposed stoichiometric combinations (i.e., compound atoms) published by Dalton in 1808 (Pullman, 1998) (Figure 18.1a), a preliminary roadmap of nanoscale elemental analog categories has been described. It currently consists of six major hard and six soft nano-element (i.e., hard/soft superatom) categories; however, these categories are expected to be expanded in the future. Furthermore, well-defined combinatorial libraries of potential nano-element compound/assemblies, nanoperiodic property patterns, nanoscale rules and proposed Mendeleev-like nanoperiodic tables are emerging as described in Figure 18.1b.
