Photodynamics of a Molecular Water-Soluble Nanocluster Identified as Au₁₃₀(pMBA)₅₀

Abstract

Photodynamics of a highly monodisperse sample of a water-soluble gold nanocluster tentatively identified as Au 130 (pMBA) 50 (pMBA = p-mercaptobenzoic acid) was studied by mid-IR transient absorption spectroscopy with visible excitation. The observed long-lived excited states (>1 ns) indicate a molecular behavior of the cluster. By combining the transient absorption data with DFT calculation results the observed relaxation dynamics could be fully explained by identifying several relaxation processes involving singlet and triplet manifolds. The results indicate that the cluster may have interesting transient magnetic properties due to a long-lived triplet population.

Anomalous phonon relaxation in Au 333 (SR) 79 nanoparticles with nascent plasmons

“…Steadystate absorption spectra revealed two absorption peaks at 442 and 498 nm at 80 K, which is different from the case of typical plasmonic nanoparticles. The laser fluence dependence of both peaks indicates that both are plasmon peaks (as opposed to excitons) (11)(12)(13)40). The dual plasmons indicate a nonspherical shape of Au 333 .…”

“…On the other hand, metal nanoclusters in nonmetallic (excitonic) state show multiple ground state-bleaching (GSB) bands (like organic molecules) upon photoexcitation (11)(12)(13)36). The photogenerated exciton experiences a relaxation process of electron-hole recombination, and its lifetime depends on the size and structure.…”

“…For example, SPR disappears when the size goes down below 2 nm due to quantum confinement effect and quantization of the conduction band (7). Unlike the conventional, plasmonic gold nanoparticles of facecentered cubic structure, the ultrasmall gold nanoparticles (socalled nanoclusters) with discrete energy levels exhibit unique geometrical (8)(9)(10) and electronic structures (11)(12)(13), and novel properties for applications in biomedicine (14,15), optoelectronics (16,17), and catalysis (18,19).…”

On the Non‐Metallicity of 2.2 nm Au246(SR)80 Nanoclusters

“…Finally, the last 78 ps should be assigned to the hot ground state relaxation. Previous studies by Pettersson and co‐workers reported that molecular‐like gold nanoclusters exhibit slower electronic relaxation (a few nanoseconds), in contrast to metallic gold nanoparticles (ca. 100 ps energy dissipation).…”

The unique electrochemical reactivity of small metal nanoparticles.

“…The desired ligand could be added at the initial step of the synthesis or later (post-synthesis) by a ligand exchange approach. 47 The ligand shell has several roles in control of the nanoparticle solubility, 48 functionality (targeting biomolecules), 49 and electronic properties. 50 Table 1.1 shows common stabilizing ligands used in nanoparticle syntheses.…”