Unraveling the Effect of Single Atom Doping on the Carrier Relaxation Dynamics of MAg₂₄^n– Nanoclusters

Abstract

Precisely doped metal nanoclusters (NCs) are currently emerging nanomaterials for their unique photophysical properties. Here, we report the influence of single atom doping on the excited state relaxation dynamics of a series of MAg 24 (2,4-Me 2 PhS) 18 n− NCs where M is Ag, Au, Pd, and Pt. The NCs with a group 11 metal (Ag and Au) as central atoms exhibit dual emission at NIR and visible range, whereas it shows only NIR emission for group 10 metal (Pd and Pt) doped NCs. Global target analyses of transient absorption (TA) data reveal the three-state relaxation, i.e., initially excited state (S n ), ligand-centered charge transfer (CT) state (S L ), and metal-centered lowest excited state (S 1 ). Apart from the HOMO−LUMO (H−L) energy gap, the electron affinity of the central metal atom and rigidity of the NC structural framework influence the relaxation processes of the NCs. The extensive study into the relaxation dynamics will bestow the single atomic level modulation of photophysical properties.

Experimental and computational insights into luminescence in atomically precise bimetallic Au6−nCun(MPA)5 (n = 0–2) clusters

“…The physical properties of metal NCs can be tuned at the atomic level via engineering their surface and core structures. [1][2][3][4][5][6] These NCs are made up of tens to hundreds of metal atoms with a size near the electron's Fermi wavelength (size o 2 nm). 3,[7][8][9] Metal NCs exhibit fascinating properties like a distinctive HOMO-LUMO gap, tunable photoluminescence properties, and biocompatibility, which endow them with broad applications in optoelectronics, drug delivery, sensing, and bioimaging.…”

Understanding the Photoelectrochemical Behavior of Metal Nanoclusters: A Perspective

“…The doping of NCs is perhaps the easiest variable to control for tuning NCs for photoelectrochemical (PEC) applications. − Doping NCs, even with a single heteroatom, can cause a dramatic shift in their properties. , The introduction of a single Ag atom into Au 18 (SR) 14 increases its extinction coefficient, photoluminescence (PL) lifetime, and recombination resistance . Doping is also significant for PEC from a design perspective because dye–TiO 2 photoelectrodes usually require a cocatalyst for effective PEC applications.…”

Electronegativity of the Substituent on Surface Motifs Influences the Ultrafast Relaxation Dynamics of Ag44(SR)304– Nanoclusters

“…41−43 In our earlier work, we investigated the single-atom doping effect on the excited-state dynamics of MAg 24 n− NCs (M = Ag, Au, Pd, and Pt). 44 However, the effect of substituent groups of the surface staple motifs on relaxation dynamics is still unexplored.…”

“…Change in the surface ligand often shows structural distortion, such that sharing of surface motifs becomes different in the crystal structure, which governs their excited-state dynamics. , Excited-state dynamics are highly influenced by different arrangements of the shell having two completely different ligands although consisting of the same core . Even though recent intense theoretical and experimental research works highlighted the effect of the number of valence electrons, structural isomerism, charge state, shape of the crystal structure, surface ligand, and core structure of Au NCs, the underlying mechanism remains obscured, especially for Ag NCs. − There are very few reports that explain the role of the core structure having a common shell on the relaxation dynamics and the nonmetallic behavior of NCs. − In our earlier work, we investigated the single-atom doping effect on the excited-state dynamics of MAg 24 n – NCs (M = Ag, Au, Pd, and Pt) . However, the effect of substituent groups of the surface staple motifs on relaxation dynamics is still unexplored.…”