The metal-exchange reaction is a powerful means to generate atomically precise alloy nanoclusters. Both galvanic and antigalvanic exchange strategies have been devised to produce various doped metal nanoclusters with atomic precision. Here we report new insights into the metal-exchange synthesis of MAg24(SPhMe2)18 (M = Ni, Pd, Pt) nanoclusters. Based on the redox potential comparison of the Ag25 template with metal ion dopants, we reveal that the metal-exchange reaction is a redox potential-driven process and propose a two-step metal-exchange model that includes dopant deposition and host dissolution steps. With the help of a co-reductant and a counterion, the high-yield metal-exchange syntheses of MAg24(SPhMe2)18 nanoclusters are demonstrated, yielding center-doped [NiAg24(SPhMe2)18]0, [PdAg24(SPhMe2)18]2–, and [PtAg24(SPhMe2)18]2– nanoclusters in >70% yield. Voltammetric and density functional investigations reveal that [NiAg24(SPhMe2)18]0 is a six-electron superatom having a distorted core due to the Jahn–Teller effect. The neutral [NiAg24(SPhMe2)18]0 becomes an eight-electron [NiAg24(SPhMe2)18]2– superatom upon chemical reduction, which has an isotropic core as confirmed by single-crystal X-ray diffraction.

Heterometal doping is apowerful method for tuning the physicochemical properties of metal nanoclusters.W hile the heterometals doped into such nanoclusters predominantly include transition metals with closed d-shells,t he doping of open d-shell metals remains largely unexplored. Herein, we report the first synthesis of a[ RhHAg 24 (SPhMe 2 ) 18 ] 2À nanocluster,i nw hich aR ha tom with open d-shells ([Kr]4d 8 5s 1 )i s incorporated into the Ag 24 framework by forming aR hH superatom with closed d-shells ([Kr]4d 10 ). Combined experimental and theoretical investigations showed that the Ag 24 framework was co-doped with Rh and hydride and that the RhH dopant was as uperatomic construct of aP da tom. Additional studies demonstrated that the [RhHAg 24 -(SPhMe 2 ) 18 ] 2À nanocluster was isoelectronic to the [PdAg 24 -(SPhMe 2 ) 18 ] 2À nanocluster with the superatomic 8-electron configuration (1S 2 1P 6 ). This study demonstrated for the first time that as uperatom could be incorporated into ac luster superatom to generate astable superatom-in-superatom nanocluster.

Electrocatalytic CO 2 reduction reaction (CO 2 RR) is greatly facilitated by Au surfaces. However, large fractions of underlying Au atoms are generally unused during the catalytic reaction, which limits mass activity. Herein, we report a strategy for preparing efficient electrocatalysts with high mass activities by the atomic-level transplantation of Au active sites into a Ni 4 nanocluster (NC). While the Ni 4 NC exclusively produces H 2 , the Au-transplanted NC selectively produces CO over H 2 . The origin of the contrasting selectivity observed for this NC is investigated by combining operando and theoretical studies, which reveal that while the Ni sites are almost completely blocked by the CO intermediate in both NCs, the Au sites act as active sites for CO 2 -to-CO electroreduction. The Au-transplanted NC exhibits a remarkable turnover frequency and mass activity for CO production (206 mol CO /mol NC /s and 25,228 A/g Au , respectively, at an overpotential of 0.32 V) and high durability toward the CO 2 RR over 25 h.

Accurate measurements of intracellular pH are of crucial importance in understanding the cellular activities and in the development of intracellular drug delivery systems. Here we report a highly sensitive pH probe based on a fluorescein-conjugated Au nanocluster. Steady-state photoluminescence (PL) measurements have shown that, when conjugated to Au, fluorescein exhibits more than 160-fold pH-contrasting PL in the pH range of 4.3-7.8. Transient absorption measurements show that there are two competing ultrafast processes in the fluorescein-conjugated Au nanocluster: the intracore-state relaxation and the energy transfer from the nonthermalized states of Au to fluorescein. The latter becomes predominant at a higher pH, leading to dramatic PL enhancement of fluorescein. In addition to the intrinsically low toxicity, fluorescein-conjugated Au nanoclusters exhibit high pH sensitivity, wide dynamic range, and excellent photostability, providing a powerful tool for the study of intracellular processes.

We report a new strategy in which a thiolate‐protected Ag25 nanocluster can be doped with open d‐shell group 8 (Ru, Os) and 9 (Ir) metals by forming metal hydride (RuH2, OsH2, IrH) superatoms with a closed d‐shell. Structural analyses using various experimental and theoretical methods revealed that the Ag25 nanoclusters were co‐doped with the open d‐shell metal and hydride species to produce superatom‐in‐superatom nanoclusters, establishing a novel superatom doping phenomenon for open d‐shell metals. The synthesized superatom‐in‐superatom nanoclusters exhibited dopant‐dependent photoluminescence (PL) properties. Comparative PL lifetime studies of the Ag25 nanoclusters doped with 8–10 group metals revealed that both radiative and nonradiative processes were significantly dependent on the dopant. The former is strongly correlated with the electron affinity of the metal dopant, whereas the latter is governed predominantly by the kernel structure changed upon the doping of the metal hydride(s).