The bottom-up assembly of nanoparticles into diverse ordered solids is a challenge because it requires nanoparticles, which are often quasi-spherical, to have interaction anisotropy akin to atoms and molecules. Typically, anisotropy has been introduced by changing the shape of the inorganic nanoparticle core. Here, we present the design, self-assembly, optical properties, and total structural determination of Ag29(BDT)12(TPP)4, an atomically precise tetravalent nanocluster (NC) (BDT, 1,3-benzenedithiol; TPP, triphenylphosphine). It features four unique tetrahedrally symmetrical binding surface sites facilitated by the supramolecular assembly of 12 BDT (wide footprint bidentate thiols) in the ligand shell. When each of these sites was selectively functionalized by a single phosphine ligand, particle stability, synthetic yield, and the propensity to self-assemble into macroscopic crystals increased. The solid crystallized NCs have a substantially narrowed optical band gap compared to that of the solution state, suggesting strong interparticle electronic coupling occurs in the solid state.

A high quantum yield (QY) of photoluminescence (PL) in nanomaterials is necessary for a wide range of applications. Unfortunately, the weak PL and moderate stability of atomically precise silver nanoclusters (NCs) suppress their utility. Herein, we accomplished a ≥26-fold PL QY enhancement of the Ag29 (BDT)12 (TPP)4 cluster (BDT: 1,3-benzenedithiol; TPP: triphenylphosphine) by doping with a discrete number of Au atoms, producing Ag29-x Aux (BDT)12 (TPP)4 , x=1-5. The Au-doped clusters exhibit an enhanced stability and an intense red emission around 660 nm. Single-crystal XRD, mass spectrometry, optical, and NMR spectroscopy shed light on the PL enhancement mechanism and the probable locations of the Au dopants within the cluster.

The properties of atomically monodisperse noble metal nanoclusters (NCs) are intricately intertwined with their precise molecular formula. The vast majority of size-specific NC syntheses start from the reduction of the metal salt and thiol ligand mixture. Only in gold was it recently shown that ligand-exchange could induce the growth of NCs from one atomically precise species to another; a process of yet unknown reversibility. Here, we present a process for the ligand-exchange-induced growth of atomically precise silver NCs, in a biphasic liquid-liquid system, which is particularly of interest because of its complete reversibility and ability to occur at room temperature. We explore this phenomenon in-depth using Ag 35 (SG) 18

Atomically precise thiolate-protected noble metal molecular nanoparticles are a promising class of model nanomaterials for catalysis, optoelectronics, and the bottom-up assembly of true molecular crystals. However, these applications have not fully materialized due to a lack of ligand exchange strategies that add functionality, but preserve the properties of these remarkable particles. Here we present a method for the rapid (<30 s) and complete thiolate-for-thiolate exchange of the highly sought after silver molecular nanoparticle [Ag44(SR)30](-4). Only by using this method were we able to preserve the precise nature of the particles and simultaneously replace the native ligands with ligands containing a variety of functional groups. Crucially, as a result of our method we were able to process the particles into smooth thin films, paving the way for their integration into solution-processed devices.

We report the synthesis of atomically monodisperse thiol-protected silver nanoclusters [Ag 44 (SR) 30 ] m , (SR ¼ 5mercapto-2-nitrobenzoic acid) in which the product nanocluster is highly stable in contrast to previous preparation methods. The method is one-pot, scalable, and produces nanoclusters that are stable in aqueous solution for at least 9 months at room temperature under ambient conditions, with very little degradation to their unique UV-Vis optical absorption spectrum. The composition, size, and monodispersity were determined by electrospray ionization mass spectrometry and analytical ultracentrifugation. The produced nanoclusters are likely to be in a superatom charge-state of m ¼ 4À, due to the fact that their optical absorption spectrum shares most of the unique features of the intense and broadly absorbing nanoparticles identified as [Ag 44 (SR) 30 ] 4À by Harkness et al. (Nanoscale, 2012, 4, 4269). A protocol to transfer the nanoclusters to organic solvents is also described. Using the disperse nanoclusters in organic media, we fabricated solid-state films of [Ag 44 (SR) 30 ] m that retained all the distinct features of the optical absorption spectrum of the nanoclusters in solution. The films were studied by X-ray diffraction and photoelectron spectroscopy in order to investigate their crystallinity, atomic composition and valence band structure. The stability, scalability, and the film fabrication method demonstrated in this work pave the way towards the crystallization of [Ag 44 (SR) 30 ] m and its full structural determination by single crystal X-ray diffraction. Moreover, due to their unique and attractive optical properties with multiple optical transitions, we anticipate these clusters to find practical applications in light-harvesting, such as photovoltaics and photocatalysis, which have been hindered so far by the instability of previous generations of the cluster.

Achieving water splitting at low overpotential with high oxygen evolution efficiency and stability is important for realizing solar to chemical energy conversion devices. Herein we report the synthesis, characterization and electrochemical evaluation of highly active nickel nanoclusters (Ni NCs) for water oxidation at low overpotential. These atomically precise and monodisperse Ni NCs are characterized by using UV-visible absorption spectroscopy, single crystal X-ray diffraction and mass spectrometry. The molecular formulae of these Ni NCs are found to be Ni4(PET)8 and Ni6(PET)12 and are highly active electrocatalysts for oxygen evolution without any pre-conditioning. Ni4(PET)8 are slightly better catalysts than Ni6(PET)12 and initiate the oxygen evolution at an amazingly low overpotential of ~1.51 V (vs RHE; η ≈ 280 mV). The peak oxygen evolution current density (J) of ~150 mA cm -2 at 2.0 V (vs. RHE) with a Tafel slope of 38 mV dec -1 is observed using Ni4(PET)8. These results are comparable to the state-of-the art RuO2 electrocatalyst, which is highly expensive and rare compared to Ni-based materials. Sustained oxygen generation for several hours with an applied current density of 20 mA cm -2 demonstrates the long-term stability and activity of these Ni NCs towards electrocatalytic water oxidation. This unique approach provides a facile method to prepare cost-effective, nanoscale and highly efficient electrocatalysts for water oxidation.

Ah igh quantum yield (QY) of photoluminescence (PL) in nanomaterials is necessary for aw ide range of applications.U nfortunately,t he weak PL and moderate stability of atomically precise silver nanoclusters (NCs) suppress their utility.Herein, we accomplished a ! 26-fold PL QY enhancement of the Ag 29 (BDT) 12 (TPP) 4 cluster (BDT:1 ,3-benzenedithiol;T PP:t riphenylphosphine) by doping with adiscrete number of Au atoms,producing Ag 29Àx Au x (BDT) 12 -(TPP) 4 ,x= 1-5. The Au-doped clusters exhibit an enhanced stability and an intense red emission around 660 nm. Singlecrystal XRD,m ass spectrometry,o ptical, and NMR spectroscopys hed light on the PL enhancement mechanism and the probable locations of the Au dopants within the cluster.Noble-metal nanoclusters (NCs), consisting of ap recise number of metal atoms and ligands,exhibit unique molecular, optical, and physicochemical properties because of their distinct electronic structures.[1] Thetypical size of NCs lies in between atoms and plasmonic nanoparticles. [1a,2] Particularly, NCs of gold, silver, and their alloys are being investigated for their potential for light-energy conversion applications, [3] in addition to their catalytic activity, [4] biocompatibility, [5] and tunable emissions in the visible and near-infrared (NIR) regions.[6] Thephotophysical properties of NCs were found to be influenced by their intrinsic structure,c omposition, core size,a nd environment, including solvent and protecting ligand. [1c, 7] While luminescent NCs are in high demand, the origin of luminescence is not fully elucidated-with some studies implicating ligand-to-metal charge transfer (LMCT) and/or ligand-to-metal-metal charge transfer (LMMCT). [8] Thepivotal roles of the nature of metal atoms and the ligands signify the opportunity to tune the photoluminescence (PL) quantum yield (QY) of NCs for practical applications. [8,9] In this direction, various research groups followed the surface functionalization of NCs with diverse protecting environments,i ncluding polymers, [10] thiols, [11] and proteins.[12]Another approach is the alloying or doping of the metal core of aN Cw ith another suitable metal; [13] this method is attractive not only because of the control it affords over the number of alloying atoms,b ut also because it opens the opportunity to gain fundamental insights into the PL evolution with doping at as ingle-atom level. Fori nstance,a200-fold PL QY enhancement was observed when Au 25 NCs were doped with 13 silver atoms.[14] However,the role of doping on well-characterized Ag NCs-materials that would benefit immensely from enhancing their QY and stability-is still unknown.Among thoroughly characterized (including X-ray structure) visible-light-emitting Ag NCs,t he Ag 29 (BDT) 12 (TPP) 4 cluster (BDT:1 ,3-benzenedithiol;T PP:t riphenylphosphine) has moderate stability and weak PL QY (0.9 %), where PL is too weak to perceive by the naked eye. [15] In this work, we demonstrate the PL QY enhancement of Ag 29 NCs by doping with ad istinct number of Au a...

Efficient absorption of visible light and a long-lived excited state lifetime of silver nanoclusters (Ag29 NCs) are integral properties for these new clusters to serve as light-harvesting materials. Upon optical excitation, electron injection at Ag29 NC/methyl viologen (MV(2+)) interfaces is very efficient and ultrafast. Interestingly, our femto- and nanosecond time-resolved results demonstrate clearly that both dynamic and static electron transfer mechanisms are involved in photoluminescence quenching of Ag29 NCs.