The solely motif-doped Au_36−xAg_x(SPh-tBu)₂₄(x = 1–8) nanoclusters: X-ray crystal structure and optical properties

Abstract

We report the observation of new doping behavior in Au36-xAgx(SR)24 nanoclusters (NCs) with x = 1 to 8. The atomic arrangements of Au and Ag atoms are determined by X-ray crystallography. The new gold-silver bimetallic NCs share the same framework as that of the homogold counterpart, i.e. possessing an fcc-type Au28 kernel, four dimeric AuAg(SR)3 staple motifs and twelve simple bridging SR ligands. Interestingly, all the Ag dopants in the Au36-xAgx(SR)24 NCs are selectively incorporated into the surface motifs, which is in contrast to the previously reported Au-Ag alloy structures with the Ag dopants preferentially displacing the core gold atoms. This distinct doping behavior implies that the previous assignments of an fcc Au28 core with four dimers and 12 bridging thiolates for Au36(SR)24 are more justified than other assignments of core vs. surface motifs. The UV-Vis adsorption spectrum of Au36-xAgx(SR)24 is almost the same as that of Au36(SR)24, indicating that the Ag dopants in the motifs do not change the optical properties. The similar UV-Vis spectra are further confirmed by TD-DFT calculations. DFT also reveals that the energies of the HOMO and LUMO of the motif-doped AuAg alloy NC are comparable to those of the homogold Au36 NC, indicating that the electronic structure is not disturbed by the motif Ag dopants. Overall, this study reveals a new silver-doping mode in alloy NCs.

Atomically Precise Alloy Nanoclusters

“…Figure20A shows the optical absorption spectra of [Au 36 (TBBT) 24 ] 0 and [Au 36Àx Ag x (TBBT) 24 ] 0 (x = 2.83). [156] Both spectra are generally similar, indicating that the substitution of Au by Ag in [Au 36 (TBBT) 24 ] 0 has no marked effecto nt he optical absorption spectra.I nc ontrast, these NCs showed clear differences in the relaxation times from their excited states (Figure 20 B). Ag substitution shortened the lifetimeo ft he excited state.…”

“…[155] Synthesis of alloy NCs by substitution of some of the Au atoms of [Au 36 (SR) 24 ] 0 with Ag or Cu has also been reported. In 2016, Zhu et al [156] synthesized [Au 36Àx Ag x (TBBT) 24 ] 0 (x = 1-8) by the reconstruction method. Dass and co-workerss ynthesized [Au 36Àx Ag x (TBBT) 24 ] 0 (x = 2.83) in 2019 by ad ifferent reconstruction method.…”

“…It is expectedt hat ad eeper understanding of this behavior will be obtained in the future by considering the differences in the synthesis processes. [38,39,156,157] Figure 19 Cd epicts the geometricals tructure of [Au 36Àx Cu x (m-MBT) 24 ] 0 (x = 1-3). The framework structure of theseNCs is generally similar to that of [Au 36 (SR) 24 ] 0 .C ui sl ocated at fourteen metal sites, six of which are in the subsurface of the metal core and eight of which are in the staples.…”

The mechanism of metal exchange in non-metallic nanoclusters

“…We apologize for the wrong results due to the lack of experience in the treatment of alloy clusters at the early stage of our study in this area. 41 In order to study the metal exchange behaviour in fccstructured gold nanoclusters, Ag(I)-SR (where SR ¼ TBBT) is used as the heterometal source. Besides, UV/Vis and ESI-TOF-MS spectroscopy methods are applied to monitor the metal exchange reaction.…”

Photoinduced Oxidation Catalysis by Au25‐xAgx(SR)18 Nanoclusters

“…Ag doped nanoclusters (NCs) have emerged as a new class of nanomaterials along with the booming of atomically precise gold NCs. In the past decade, a range of alloyed Au/Ag NCs have been prepared and crystallized like Au 15 Ag 3 , Ag x Au 25‐x , Au 36‐x Ag x , Au 38‐x Ag x , Au 3 Ag 38 , Au 24 Ag 20 , Au 12 Ag 32 , Au 9 Ag 36 , Au x Ag 50‐x , Au 34 Ag 28 , Ag 46 Au 24 , Au 80 Ag 30. Due to the luminescence and synergy effect, they are valuable for biolabeling and catalysis .…”