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Magic-sized (CdSe)13 clusters (MSCs) represent a material class at the boundary between molecules and quantum dots that exhibit a pronounced and well separated excitonic fine structure. The characteristic photoluminescence is composed of exciton bandgap emission and a spectrally broad mid-gap emission related to surface defects. Here, we report on a thermally activated energy transfer from fine-structure split exciton states to surface states by using temperature dependent photoluminescence excitation spectroscopy. We demonstrate that the broad mid-gap emission can be suppressed by a targeted Mn-doping of the MSC leading to the characteristic orange luminescence of the 4T1 → 6A1 Mn2+ transition. The energy transfer to the Mn2+ states is found to be significantly different than the transfer to the surface defect states, as the activation of the dopant emission requires a spin-conserving charge carrier transfer that only dark excitons can provide. [ABSTRACT FROM AUTHOR]

The chemical synthesis of (CdSe)13 magic-sized clusters (MSCs) allows the replacement of host atoms by individual transition metals such as Mn. By analyzing the spectral fingerprints of the Mn2+ photoluminescence (PL) in MSCs with different dopant concentrations, we are able to distinguish between single Mn2+ ions and coupled Mn2+ pairs. In case of Mn2+ pair emission, temperature-dependent studies show a pronounced red shift, followed by a distinct blue shift of the PL energy upon heating. This is related to a spin ladder formation of the ground and excited states due to Mn2+–Mn2+ exchange interaction at cryogenic temperatures, which is assumed to vanish at higher temperatures. In contrast, single Mn2+ ion PL exhibits a unique redshift with increasing temperature, which can be attributed to a particularly strong coupling to vibronic modes due to the ultimate small size of the MSCs. [ABSTRACT FROM AUTHOR]

Ligand protected metal nanoclusters (NCs) are an emerging class of functional materials with intriguing photophysical and chemical properties. The size and molecular structure play an important role in endowing NCs with characteristic optical and electronic properties. Modulation of these properties through the chemical reactivity of NCs is largely unexplored. Here, we report on the synthesis of self-assembled Ag2Cl2(dppe)2 clusters through the ligand-exchange-induced transformation of [Pt2Ag23Cl7(PPh3)10] NCs [(dppe): 1,2-bis(diphenylphosphino)ethane; (PPh3): triphenylphosphine]. The single crystal x-ray structure reveals that two Ag atoms are bridged by one dppe and two Cl ligands, forming a Ag2Cl2(dppe) cluster, which is subsequently self-assembled through dppe ligands to form [Ag2Cl2(dppe)2]n. Importantly, the Ag2Cl2(dppe)2 cluster assembly exhibits high photoluminescence quantum yield: ∼18%, which is attributed to the metallophilic interactions and rigidification of the ligand shell. We hope that this work will motivate the exploitation of the chemical reactivity of NCs as a new path to attain cluster assemblies endowed with enhanced photophysical properties. [ABSTRACT FROM AUTHOR]

Although atomically precise metalloid nanoclusters (NCs) of identical size with distinctly different molecular structures are highly desirable to understand the structural effects on the optical and photophysical properties, their synthesis remains highly challenging. Herein, we employed phosphine and thiol capping ligands featuring appropriate steric effects and synthesized a charge‐neutral Ag NC with the formula Ag44(EBT)26(TPP)4 (EBT: 2‐ethylbenzenethiolate; TPP: triphenylphosphine). The single‐crystal X‐ray structure reveals that this NC has a hollow metal core of Ag12@Ag20 and a metal–ligand shell of Ag12(EBT)26(TPP)4. The presence of mixed ligands and long V‐shaped metal–ligand motifs on this NC has resulted in an enhancement of the NIR‐II photoluminescence quantum yield by >25‐fold compared to an all‐thiolate‐stabilized anionic [Ag44(SR)30]4− NC (SR: thiolate). Time‐dependent density‐functional calculations show that our Ag44 NC is an 18‐electron superatom with a modulated electronic structure as compared to the [Ag44(SR)30]4− anion, significantly influencing its optical properties. [ABSTRACT FROM AUTHOR]

The chemical synthesis of (CdSe)13 magic-sized clusters (MSCs) allows the replacement of host atoms by individual transition metals such as Mn. By analyzing the spectral fingerprints of the Mn2+ photoluminescence (PL) in MSCs with different dopant concentrations, we are able to distinguish between single Mn2+ ions and coupled Mn2+ pairs. In case of Mn2+ pair emission, temperature-dependent studies show a pronounced red shift, followed by a distinct blue shift of the PL energy upon heating. This is related to a spin ladder formation of the ground and excited states due to Mn2+-Mn2+ exchange interaction at cryogenic temperatures, which is assumed to vanish at higher temperatures. In contrast, single Mn2+ ion PL exhibits a unique redshift with increasing temperature, which can be attributed to a particularly strong coupling to vibronic modes due to the ultimate small size of the MSCs., (© 2023 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).)

Quantum dots (QDs) are a promising material for photoelectrochemical (PEC) hydrogen (H 2 ) production because of their attractive optical properties including high optical absorption coefficient, band-gap tunability, and potential multiple exciton generation. To date, QDs containing toxic elements such as Cd or Pb have been mainly investigated for PEC H 2 production, which cannot be utilized in practice because of the environmental issue. Here, we demonstrate a highly efficient type II heterojunction photoanode of nontoxic CuIn 1.5 Se 3 (CISe) QDs and a mesoporous TiO 2 film. In addition, ZnS/SiO 2 double overlayers are deposited on the photoanodes to passivate surface defect sites on the CISe QDs, leading to the enhancement of both photocurrent density and photostability. Due to a combination of a wide light absorption range of the CISe QDs and the reduced interfacial charge recombination by the overlayers, a remarkable photocurrent density of 8.5 mA cm -2 (at 0.5 V RHE ) is obtained under 1 sun illumination, which is a record for the PEC sulfite oxidation based on nontoxic QD photoanodes.

Ligand protected metal nanoclusters (NCs) are an emerging class of functional materials with intriguing photophysical and chemical properties. The size and molecular structure play an important role in endowing NCs with characteristic optical and electronic properties. Modulation of these properties through the chemical reactivity of NCs is largely unexplored. Here, we report on the synthesis of self-assembled Ag 2 Cl 2 (dppe) 2 clusters through the ligand-exchange-induced transformation of [Pt 2 Ag 23 Cl 7 (PPh 3 ) 10 ] NCs [(dppe): 1,2-bis(diphenylphosphino)ethane; (PPh 3 ): triphenylphosphine]. The single crystal x-ray structure reveals that two Ag atoms are bridged by one dppe and two Cl ligands, forming a Ag 2 Cl 2 (dppe) cluster, which is subsequently self-assembled through dppe ligands to form [Ag 2 Cl 2 (dppe) 2 ] n . Importantly, the Ag 2 Cl 2 (dppe) 2 cluster assembly exhibits high photoluminescence quantum yield: ∼18%, which is attributed to the metallophilic interactions and rigidification of the ligand shell. We hope that this work will motivate the exploitation of the chemical reactivity of NCs as a new path to attain cluster assemblies endowed with enhanced photophysical properties.

Although atomically precise metalloid nanoclusters (NCs) of identical size with distinctly different molecular structures are highly desirable to understand the structural effects on the optical and photophysical properties, their synthesis remains highly challenging. Herein, we employed phosphine and thiol capping ligands featuring appropriate steric effects and synthesized a charge-neutral Ag NC with the formula Ag 44 (EBT) 26 (TPP) 4 (EBT: 2-ethylbenzenethiolate; TPP: triphenylphosphine). The single-crystal X-ray structure reveals that this NC has a hollow metal core of Ag 12 @Ag 20 and a metal-ligand shell of Ag 12 (EBT) 26 (TPP) 4 . The presence of mixed ligands and long V-shaped metal-ligand motifs on this NC has resulted in an enhancement of the NIR-II photoluminescence quantum yield by >25-fold compared to an all-thiolate-stabilized anionic [Ag 44 (SR) 30 ] 4- NC (SR: thiolate). Time-dependent density-functional calculations show that our Ag 44 NC is an 18-electron superatom with a modulated electronic structure as compared to the [Ag 44 (SR) 30 ] 4- anion, significantly influencing its optical properties., (© 2021 Wiley-VCH GmbH.)

Atomically precise coinage metal (Au, Ag, and Cu) nanoclusters (NCs) have been the subject of immense interest for their intriguing structural, photophysical, and catalytic properties. However, the synthesis of Cu NCs is highly challenging because of low reduction potential and high reactivity of copper, demonstrating the need for new synthetic methods using appropriate ligand combinations. By designing a diamine-assisted synthetic strategy, here we report the synthesis and total structure characterization of a box-like dianionic Cu NC [Cu 32 (PET) 24 H 8 Cl 2 ](PPh 4 ) 2 coprotected by 2-phenylethanethiolate (PET), hydride, and chloride ligands. Its crystal structure comprises a rare bisquare antiprismatic Cu 14 H 8 core, assembled by two square antiprisms by edge sharing, followed by hydride binding. The rod-shaped Cu 14 H 8 core is clamped by two complex Cu 7 (PET) 11 Cl and two simple Cu 2 PET metal ligand frameworks, constructing the complete structure of Cu 32 NC. The presence, number, and location of hydrides are established by combined experimental and density functional theory results. The electronic structure calculations show the cluster as a zero-free-electron system, reproduce well the measured optical absorption spectrum, and explain the main absorption features. Furthermore, the Cu 32 cluster is found to be a highly active homogeneous catalyst for C-N bond formation in aniline carbonylation reactions at room temperature. We hope that new findings in this work will stimulate and expand the research on Cu and other active metal NCs.