The unified electronic nature of nanomaterial surface science
The properties of inorganic nanomaterials in adsorption, catalysis, and photoluminescence are commonly affected or dominated by particle size, surface ligand, and ligand coverage; however, it has been long remaining challenging to generally understand underlying physical and chemical principles with a unified model. In this review the electronic-level principle that can unify the structure-property relationships concerning nanomaterial surface science is systematically illustrated, based on a chemisorption model through competitive orbital redistribution from bulk energy bands into surface chemisorption bonds. The physical nature of enhanced surface reactivity by size reduction lies in weakening lattice confinement on surface atomic orbitals and amplifying the effects of other structural factors such as defects. Nanoscale cooperative chemisorption (NCC) model reveals the general physical principles driving size- and coverage-dependent ligand-nanomaterial interactions owing to orbital competitions between bulk energy bands and surface adsorption bonds. NCC theory can interpret the impacts and trends of ligand-induced surface effects on electronic states, bonding strength, and the emission energy and quantum yield of both surface fluorescence like ligand-capped Au nanoclusters and bulk intraband fluorescence like CdSe quantum dots. Competitive orbital redistribution provides a new electronic perspective to unify the physical principles driving nanomaterial surface science.