Transitions in Discrete Absorption Bands of Au₁₃₀ Clusters upon Stepwise Charging by Spectroelectrochemistry

Abstract

Rich and tunable physicochemical properties make noble metal clusters promising candidates as novel nanomolecules for a variety of applications. Spectroelectrochemistry analysis is employed to resolve previously inaccessible electronic transitions in Au130 clusters stabilized by a monolayer of di- and monothiolate ligands. Well-defined quantized double-layer charging of the Au core and oxidizable ligands make this Au130 nanocluster unique among others and enable selective electrolysis to different core and ligand charge states. Subsequent analysis of the corresponding absorption changes reveals that different absorption bands originate from different electronic transitions involving both metal core energy states and ligand molecular orbitals. Besides the four discrete absorption bands in the steady-state UV-visible-near-IR absorption spectrum, additional transitions otherwise not detectable are resolved upon selective addition/removal of electrons at cores and ligand energy states, respectively, upon electrolysis. An energy diagram is proposed that successfully explains the major features observed in electrochemistry and absorption spectroscopy. Those assignments are believed applicable and effective to explain similar transitions observed in some other Au thiolate clusters.

Near Infrared Electrochemiluminescence of Rod-Shape 25-Atom AuAg Nanoclusters That Is Hundreds-Fold Stronger Than That of Ru(bpy)3 Standard

“…The energetics of metal NCs depend on their specific compositions and structures. From the well-established monometallic Au NCs − and Ag NCs, , to the recent alloy NCs, − their electronic properties can be tuned from molecular-liked behavior, such as HOMO–LUMO (highest occupied and lowest unoccupied molecular orbital) transitions, to semiconductor or metallic-like quantized single-electron charging . The wavelength or energy of the photoluminescence is insensitive to the overall energy diagram, displaying a broad near-IR emission at 700–900 nm range mostly.…”

“…From the well-established monometallic Au NCs 33−35 and Ag NCs, 36,37 to the recent alloy NCs, 38−40 their electronic properties can be tuned from molecular-liked behavior, such as HOMO−LUMO (highest occupied and lowest unoccupied molecular orbital) transitions, 20 to semiconductor or metallic-like quantized singleelectron charging. 33 The wavelength or energy of the photoluminescence is insensitive to the overall energy diagram, displaying a broad near-IR emission at 700−900 nm range mostly. Although the fundamental mechanism remains to be unveiled, 41 the available energy states for near-IR photoluminescence suggest the feasibility to generate near-IR ECL.…”

Kinetics of Quantized Charging of Au144 Nanoclusters

“…Quantification of the ET processes can offer fundamental insights into Au MPC energetics and applications in catalysis, electrogenerated chemiluminescence , and other MPC‐mediated electrochemical systems . A number of electrochemical techniques, including cyclic voltammetry, AC impedance, pulse voltammetry, electric conductance measurement, and chronoamperometry, have been used to characterize the ET processes in Au MPCs .…”

Controlling magnetism of Au133(TBBT)52 nanoclusters at single electron level and implication for nonmetal to metal transition

“…The similarity between the absorption spectra of [Au 133 (TBBT) 52 ] 0 and [Au 133 (TBBT) 52 ] + may be ascribed to the much less perturbation of one electron loss in Au 133 (1 out 81e) than Au 25 (1 out of 8e) as well as possibly less structural distortion in Au 133 than Au 25 when switching the charge state. 46,56,57 We also performed electrochemical oxidation of [Au 133 (-TBBT) 52 ] 0 by applying positive voltages and monitored the optical spectra in situ, 68,69 but no change in optical spectra was found, even aer applying a 1 V bias for 90 min (Fig. S1 †).…”