Rationale Strategy to Tune the Optical Properties of Gold Catenane Nanoclusters by Doping with Silver Atoms

Abstract

We report the chemical substitution mediated doping of silver atoms into the Au10SG10 (SG: glutathione) catenane nanoclusters in a controllable manner. Two levels of doping were conducted leading to two silver-doped Au10-xAgxSG10 nanoclusters (with x=0-2 and x=1-4). Optical studies reveal that nanoclusters with high level of doping (x=1-4) feature a blue shift in absorption and a significant red shift of ~ 50 nm in the two-photon excited emission spectrum with respect to pristine Au10SG10. The preservation of the catenane structure is confirmed by comparing experimental and computational X-ray diffraction patterns and absorption spectra of Au10SG10 and its silver-doped analogues. In order to better address the structure-property relationship in such catenane clusters, further theoretical investigations were performed at DFT level. A high-energy shift of the S1 state is evidenced in the calculated one-photon absorption spectra due to a larger s to d gap in silver caused by smaller relativistic effects in comparison to the gold atoms. Furthermore, the red-shift in the two-photon excited emission band of the clusters is due to significantly larger calculated relaxation of the first excited state in nanoclusters with high level of silver doping.

Effects of Single Platinum Atom Doping on Stability and Nonlinear Optical Properties of Ag29 Nanoclusters

“…8 The nature and position of lowest excited electronic states are also sensitive to silver doping. 9 Other factors like relativistic effects (mainly due to the Au atoms), the exact position of metal dopants, and heteronuclear Au−Ag bonds 10 can affect the fluorescence intensity of gold-doped nanoclusters. 11 While most of doping of nanoclusters with heteroatoms was done with the highly stable single thiolated (SR) Au 25 SR 18 , 12−18 and Ag 25 SR 18 , 19,20 dithiolated (SSR) Ag 29 SSR 12 nanoclusters 21−26 are another interesting candidate for doping strategies.…”

“…29 Also, the exact spatial position of metal dopants and the heteronuclear bimetallic bonds have a profound effect on the nanocluster's properties, in particular, their optical properties. 10,11 Moroever, doping of metal nanohybrid systems with another metal has been demonstrated to lead to enhanced nonlinear optical properties. In particular, silver-doped gold− cysteine supramolecular assemblies, 30 response).…”

“…The setup for 2PEPL has been described in detail in a previous study. 10 The 2PEPL cross sections are extracted using the reference method and is calculated using fluorescein as a reference according to the following equation:…”

Origin of luminescence properties and synthetic methods for gold- and bimetallic gold-based nanomaterials

“…In the case of Au 10− x Ag x SG 10 ( x = 1–4), the improved relaxation of the first excited state (S 1 ) of silver-doped AuNCs may be the prime reason behind the shifting of the two-photon excited fluorescence (TPEF) towards a longer wavelength. 146…”

Controlling the Chemistry of Nanoclusters: From Atomic Precision to Controlled Assembly

“…To this end, Antoine and co-workers reported the systematic doping of Au 10 NCs stabilized by glutathione molecules. 1–3 silver atoms have been doped into Au 10 NCs, displacing equivalent number of gold atoms from the clusters, which led to gradual variation in the two-photon excited fluorescence of the clusters [ 89 ].…”