A metal exchange method based upon atomically precise gold nanoclusters (NCs) as templates is devised to obtain alloy NCs including CuxAu25-x(SR)18, AgxAu25-x(SR)18, Cd1Au24(SR)18, and Hg1Au24(SR)18 via reaction of the template with metal thiolate complexes of Cu(II), Ag(I), Cd(II), and Hg(II) (as opposed to common salt precursors such as CuCl2, AgNO3, etc.). Experimental results imply that the exchange between gold atoms in NCs and those of the second metal in the thiolated complex does not necessarily follow the order of metal activity (i.e., galvanic sequence). In addition, the crystal structure of the exchange product (Cd1Au24(SR)18) is successfully determined, indicating that the Cd is in the center of the 13-atom icosahedral core. This metal exchange method is expected to become a versatile new approach for synthesizing alloy NCs that contain both high- and low-activity metal atoms.

The larger size gold nanoparticles typically adopt a face-centered cubic (fcc) atomic packing, while in the ultrasmall nanoclusters the packing styles of Au atoms are diverse, including fcc, hexagonal close packing (hcp), and body-centered cubic (bcc), depending on the ligand protection. The possible conversion between these packing structures is largely unknown. Herein, we report the growth of a new Au21(S-Adm)15 nanocluster (S-Adm = adamantanethiolate) from Au18(SR)14 (SR = cyclohexylthiol), with the total structure determined by X-ray crystallography. It is discovered that the hcp Au9-core in Au18(SR)14 is transformed to a fcc Au10-core in Au21(S-Adm)15. Combining with density functional theory (DFT) calculations, we provide critical information about the growth mechanism (geometrical and electronic structure) and the origin of fcc-structure formation for the thiolate-protected gold nanoclusters.

The concept of aggregation-induced emission (AIE) has been exploited to render non-luminescent Cu(I) SR complexes strongly luminescent. The Cu(I) SR complexes underwent controlled aggregation with Au(0) . Unlike previous AIE methods, our strategy does not require insoluble solutions or cations. X-ray crystallography validated the structure of this highly fluorescent nanocluster: Six thiolated Cu atoms are aggregated by two Au atoms (Au2 Cu6 nanoclusters). The quantum yield of this nanocluster is 11.7 %. DFT calculations imply that the fluorescence originates from ligand (aryl groups on the phosphine) to metal (Cu(I) ) charge transfer (LMCT). Furthermore, the aggregation is affected by the restriction of intramolecular rotation (RIR), and the high rigidity of the outer ligands enhances the fluorescence of the Au2 Cu6 nanoclusters. This study thus presents a novel strategy for enhancing the luminescence of metal nanoclusters (by the aggregation of active metal complexes with inert metal atoms), and also provides fundamental insights into the controllable synthesis of highly luminescent metal nanoclusters.

In this study, we successfully synthesized the rod-like [Au 25 (PPh 3 ) 10 (SePh) 5 Cl 2 ] q (q = +1 or +2) nanoclusters through kinetic control. The single crystal X-ray crystallography determined their formulas to be [Au 25 (PPh 3 ) 10 (SePh) 5 Cl 2 ]-(SbF 6 ) and [Au 25 (PPh 3 ) 10 (SePh) 5 Cl 2 ](SbF 6 )(BPh 4 ), respectively. Compared to the previously reported Au 25 coprotected by phosphine and thiolate ligands (i.e., [Au 25 (PPh 3 ) 10 (SR) 5 Cl 2 ] 2+ ), the two new rod-like Au 25 nanoclusters show some interesting structural differences. Nonetheless, each of these three nanoclusters possesses two icosahedral Au 13 units (sharing a vertex gold atom) and the bridging "Au−Se(S)−Au" motifs. The compositions of the two new nanoclusters were characterized with ESI-MS and TGA. The optical properties, electrochemistry, and magnetism were studied by EPR, NMR, and SQUID. All these results demonstrate that the valence character significantly affects the properties of the "non-superatom" Au 25 nanoclusters, and the changes are different from the previously reported "superatom" Au 25 nanoclusters. Theoretical calculations indicate that the extra electron results in the half occupation of the highest occupied molecular orbitals in the rod-like Au 25 + nanoclusters and, thus, significantly affects the electronic structure of the "non-superatom" Au 25 nanoclusters. This work offers new insights into the relationship between the properties and the valence of the "non-superatom" gold nanoclusters.

Tailoring the nanocluster at an atomic level leads to a tetrahedron-shaped FCC Pt1Ag28(S-Adm)18(PPh3)4 nanocluster and a large enhancement in photoluminescence.

The crystal structure of the [Ag62S12(SBu(t))32](2+) nanocluster (denoted as NC-I) has been successfully determined, and it shows a complete face-centered-cubic (FCC) Ag14 core structure with a Ag48(SBu(t))32 shell configuration interconnected by 12 sulfide ions, which is similar to the [Ag62S13(SBu(t))32](4+) structure (denoted as NC-II for short) reported by Wang. Interestingly, NC-I exhibits prominent differences in the optical properties in comparison with the case of the NC-II nanocluster. We employed femtosecond transient absorption spectroscopy to further identify the differences between the two nanoclusters. The results show that the quenching of photoluminescence in NC-I in comparison to that of NC-II is caused by the free valence electrons, which dramatically change the ligand to metal charge transfer (LMCT, S 3p → Ag 5s). To get further insight into these, we carried out time-dependent density functional theory (TDDFT) calculations on the electronic structure and optical absorption spectra of NC-I and NC-II. These findings offer a new insight into the structure and property evolution of silver cluster materials.

A large thiolate/phosphine coprotected Ag(Dppm)(SR) nanocluster was synthesized through the further growth of Ag(SR) nanocluster and characterized by X-ray photoelectron spectroscopy (XPS), electrospray ionization mass spectrometry (ESI-MS), and single-crystal X-ray analysis. This new nanocluster comprised a 32-metal-atom dodecahedral kernel and two symmetrical Ag(SR)P ring motifs. The 20 valence electrons correspond to shell closure in the Jellium model. Moreover, this nanocluster could be alloyed by templated/galvanic metal exchange to the homologue AuAg(Dppm)(SR) nanocluster; the latter showed much higher thermal stability than the Ag(Dppm)(SR) nanocluster. Further experiments were conducted to study the optical, electrical, and photoluminescence properties of both nanoclusters. Our work not only reports two new larger size nanoclusters but also reveals a new way to synthesize larger size silver and alloy nanoclusters, that is, controlled growth/alloying.

Exploring intermetallic synergy has allowed a series of alloy nanoparticles with prominent chemical–physical properties to be produced. However, precise alloying based on a maintained template has long been a challenging pursuit, and little has been achieved for manipulation at the atomic level. Here, a nanosystem based on M29(S-Adm)18(PPh3)4 (where S-Adm is the adamantane mercaptan and M is Ag/Cu/Au/Pt/Pd) has been established, which leads to the atomically precise operation on each site in this M29 template. Specifically, a library of 21 species of nanoclusters ranging from monometallic to tetrametallic constitutions has been successfully prepared step by step with in situ synthesis, target metal-exchange, and forced metal-exchange methods. More importantly, owing to the monodispersity of each nanocluster in this M29 library, the synergetic effects on the optical properties and stability have been mapped out. This nanocluster methodology not only provides fundamental principles to produce alloy nanoclusters with multimetallic compositions and monodispersed dopants but also provides an intriguing nanomodel that enables us to grasp the intermetallic synergy at the atomic level.