Rapid Dissolution of Gold in Alcohols by In-Situ Generation of Halogens.

The dissolution of elemental gold is a fundamental step in its recycling by hydrometallurgy but has a significant environmental impact due to the use of strong acids or highly toxic reagents. Herein, it is shown that mixtures of acetyl halides and hydrogen peroxide in alcohols promote the rapid room-temperature dissolution of gold by halogenation to form Au(III) metalates. After leaching, distillation of the alcohol and re-dissolution in dilute HCl, the gold was refined through its precipitation by a simple diamide ligand; this method was also applied to separate gold from a mixture of metals.

Efficient Recycling of Gold and Copper from Electronic Waste by Selective Precipitation.

The recycling of metals from electronic waste (e-waste) using efficient, selective, and sustainable processes is integral to circular economy and net-zero aspirations. Herein, we report a new method for the selective precipitation of metals such as gold and copper that offsets the use of organic solvents that are traditionally employed in solvent extraction processes. We show that gold can be selectively precipitated from a mixture of metals in hydrochloric acid solution using triphenylphosphine oxide (TPPO), as the complex [(TPPO) (H O )][AuCl ].

Rapid Dissolution of Noble Metals in Organic Solvents.

The dissolution of elemental noble metals (NMs) such as gold, platinum, palladium, and copper is necessary for their recycling but carries a high environmental burden due to the use of strong acids and toxic reagents. Herein, a new approach was developed for the rapid dissolution of elemental NMs in organic solvents using mixtures of triphenylphosphine dichloride or oxalyl chloride and hydrogen peroxide, forming metal chloride salts directly. Almost quantitative dissolution of metallic Au, Pd, and Cu was observed within minutes at room temperature.

Assembling Atomically Precise Noble Metal Nanoclusters Using Supramolecular Interactions.

Supramolecular chemistry (SC) of noble metal nanoclusters (NMNCs) is one of the fascinating areas of contemporary materials science. It is principally concerned with the noncovalent interactions between NMNCs, as well as between NMNCs and molecules or nanoparticles. This review focuses on recent advances in the supramolecular assembly of NMNCs and applications of the resulting structures.

Ligand structure and charge state-dependent separation of monolayer protected Au clusters using non-aqueous reversed-phase HPLC.

The synthesis of atomically precise noble metal clusters using various protocols often results in a mixture of clusters with different cores. Hence, it is important to isolate such clusters in their pure form in terms of composition especially for crystallization. High-performance liquid chromatography (HPLC) is a powerful tool to achieve this.

A covalently linked dimer of [Ag(DMBT)].

We report the first example of a covalently bound dimer of monolayer protected atomically precise silver nanocluster [Ag25(DMBT)18]- (DMBT stands for 2,4-dimethylbenzenethiol). Covalently linked dimers could be important to design new cluster assembled materials with composite properties.

Rapid isotopic exchange in nanoparticles.

Rapid solution-state exchange dynamics in nanoscale pieces of matter is revealed, taking isotopically pure atomically precise clusters as examples. As two isotopically pure silver clusters made of Ag and Ag are mixed, an isotopically mixed cluster of the same entity results, similar to the formation of HDO, from HO and DO. This spontaneous process is driven by the entropy of mixing and involves events at multiple time scales.

Approaching Materials with Atomic Precision Using Supramolecular Cluster Assemblies.

Supramolecular chemistry is a major area of chemistry that utilizes weaker non-covalent interactions between molecules, including hydrogen bonding, van der Waals, electrostatic, π···π, and C-H···π interactions. Such forces have been the basis of several molecular self-assemblies and host-guest complexes in organic, inorganic, and biological systems. Atomically precise nanoclusters (NCs) are materials of growing interest that display interesting structure-property correlations.

Camouflaging Structural Diversity: Co-crystallization of Two Different Nanoparticles Having Different Cores But the Same Shell.

Two ligand-protected nanoscale silver moieties, [Ag (SPhMe ) (PPh ) ](NO ) and [Ag (SPhMe ) (PPh ) ](NO ) (abbreviated as Ag and Ag , respectively) with almost the same shell but different cores were synthesized simultaneously. As their external structures are identical, the clusters were not distinguishable and become co-crystallized. The occupancy of each cluster was 50 %.

Isomerism in Supramolecular Adducts of Atomically Precise Nanoparticles.

We present isomerism in a few supramolecular adducts of atomically precise nanoparticles, [Ag(BDT)∩(CD) ] ( n = 1-6), abbreviated as I where BDT and CD are 1,3-benzenedithiol and cyclodextrins (α, β and γ), respectively; ∩ symbolizes an inclusion complex. The different host-guest complexes of I were characterized in the solution state as well as in the gas phase. The CDs (α, β and γ) encapsulate a pair of BDT ligands protecting the Ag core.

Monolayer-Protected Noble-Metal Clusters as Potential Standards for Negative-Ion Mass Spectrometry.

A detailed mass-spectrometric study of atomically precise monolayer-protected clusters revealed the potential application of such materials as mass-spectrometric standards, mostly in negative-ion mode and in the high-mass range. To date, very few molecules are known that can be efficiently ionized and detected at lower concentrations as negative ions with high signal intensities beyond m/ z 3000. Noble-metal clusters are molecules with definite masses, sizes, and shapes, which makes them excellent candidates to choose as standards over conventional low-molecular-weight polymers or clusters of ionic salts.

Bent Keto Form of Curcumin, Preferential Stabilization of Enol by Piperine, and Isomers of Curcumin∩Cyclodextrin Complexes: Insights from Ion Mobility Mass Spectrometry.

A detailed examination of collision cross sections (CCSs) coupled with computational methods has revealed new insights into some of the key questions centered around curcumin, one of the most intensively studied natural therapeutic agents. In this study, we have distinguished the structures and conformers of the well-known enol and the far more elusive keto form of curcumin by using ion mobility mass spectrometry (IM MS). The values of the theoretically predicted isomers were compared with the experimental CCS values to confirm their structures.

Polymorphism of Ag(BDT)(TPP) cluster: interactions of secondary ligands and their effect on solid state luminescence.

We present the first example of polymorphism (cubic & trigonal) in single crystals of an atomically precise monolayer protected cluster, Ag29(BDT)12(TPP)43-. We demonstrate that C-Hπ interactions of the secondary ligands (TPP) are dominant in a cubic lattice compared to a trigonal lattice, resulting in a greater rigidity of the structure, which in turn, results in a higher luminescence efficiency in it.

Understanding proton capture and cation-induced dimerization of [Ag(BDT)] clusters by ion mobility mass spectrometry.

Proton transfer reactions have been a topic of fundamental interest in several areas of chemistry and biology. However, such reactivity has not been explored in detail for nanoscale materials. In this article, we present a unique reaction of an atomically precise monolayer-protected silver nanocluster, [Ag(BDT)], with a proton (H).

Fullerene-Functionalized Monolayer-Protected Silver Clusters: [Ag(BDT)(C) ] ( n = 1-9).

We report the formation of supramolecular adducts between monolayer-protected noble metal nanoclusters and fullerenes, specifically focusing on a well-known silver cluster, [Ag(BDT)], where BDT is 1,3-benzenedithiol. We demonstrate that C molecules link with the cluster at specific locations and protect the fragile cluster core, enhancing the stability of the cluster. A combination of studies including UV-vis, high-resolution electrospray ionization mass spectrometry, collision-induced dissociation, and nuclear magnetic resonance spectroscopy revealed structural details of the fullerene-functionalized clusters, [Ag(BDT)(C) ] ( n = 1-9).

Sequential Dihydrogen Desorption from Hydride-Protected Atomically Precise Silver Clusters and the Formation of Naked Clusters in the Gas Phase.

We report the formation of naked cluster ions of silver of specific nuclearities, uncontaminated by other cluster ions, derived from monolayer-protected clusters. The hydride and phosphine co-protected cluster, [Ag(TPP)H] (TPP, triphenylphosphine), upon activation produces the naked cluster ion, Ag, exclusively. The number of metal atoms present in the naked cluster is almost the same as that in the parent material.

[Ag(2,5-DCBT)]: a new cluster and a precursor for three well-known clusters.

We report the synthesis of a new silver cluster, [Ag(2,5-DCBT)] (I) (2,5-DCBT: 2,5-dichlorobenzenethiol), which acts as a precursor for the synthesis of three well-known silver clusters, [Ag(2,4-DCBT/4-FTP)] (II) (4-FTP: 4-fluorothiophenol and 2,4-DCBT: 2,4-dichlorobenzenethiol), [Ag(2,4-DMBT)] (III) (2,4-DMBT: 2,4-dimethylbenzenethiol) and [Ag(1,3-BDT)(PPh)] (IV) (1,3-BDT: 1,3-benzenedithiol and PPh: triphenylphosphine). This newly synthesized silver cluster, I, is characterized using UV-vis absorption studies, high resolution electrospray ionization mass spectrometry (ESI MS) and other analytical tools. The optical absorption spectrum shows distinct features which are completely different from the previously reported silver clusters.

Genomic expression of mesenchymal stem cells to altered nanoscale topographies.

The understanding of cellular response to the shape of their environment would be of benefit in the development of artificial extracellular environments for potential use in the production of biomimetic surfaces. Specifically, the understanding of how cues from the extracellular environment can be used to understand stem cell differentiation would be of special interest in regenerative medicine. In this paper, the genetic profile of mesenchymal stem cells cultured on two osteogenic nanoscale topographies (pitted surface versus raised islands) are compared with cells treated with dexamethasone, a corticosteroid routinely used to stimulate bone formation in culture from mesenchymal stem cells, using 19k gene microarrays as well as 101 gene arrays specific for osteoblast and endothelial biology.