Surface-Engineering Enhanced Charge Injection and Recombination of Silver Nanoclusters in an Aqueous Medium

An effective way to enhance the charge injection and the radiative recombination within atomically precise nanoclusters (NCs) is proposed with Ag29(BDT)12 (BDT = 1,3-benzenedithiol) and Ag29(BDT)12(TPP)4 (TPP = triphenylphosphine) as models. Surface-engineering Ag29(BDT)12 with phosphine ligands can passivate the four naked Ag atom sites on the surface of Ag29(BDT)12 and circumvent the geometric packing limitation induced by the wide footprint of BDT, which endows Ag29(BDT)12(TPP)4 with enhanced electrochemical redox for improved charge injection as well as boosted photoluminescence (PL) and electrochemiluminescence (ECL) for enhanced radiative charge recombination. The surface-engineering process demonstrates a negligible effect on the charge-injection potentials as well as the excited state emission for PL and ECL. Ag29(BDT)12 and Ag29(BDT)12(TPP)4 can be injected with holes and electrons via similar electrochemical redox processes; both annihilation ECL and co-reactant ECL of Ag29(BDT)12 and Ag29(BDT)12(TPP)4 match well with their valence (VB) hole/conduction (CB) electron injection-related oxidative/reductive processes and are of similar wavebands with a maximum emission wavelength around 795 nm.