A highly luminescent (quantum yield 21%) mixed chalcogenide silver cluster, Ag56Se13S15 cluster of Ag2X stoichiometry, protected with a 4-tert-butylbenzyl mercaptan ligand has been synthesized and characterized. Investigation using diverse tools of analysis such as mass spectrometry, elemental analysis, thermogravimetry and X-ray diffraction confirmed this composition. The cluster emits in solution and in the solid state and has been deposited on oxide supports to get red emitting films. The specificity of cluster emission to the mercuric ion Hg(ii), among a range of heavy metal ions, was used to develop a sensor, which shows sensitivity down to 1 ppb. A pH paper like visual detector was developed by combining the Hg(ii)-sensitive emission of the cluster and the insensitive emission of fluorescein isothiocyanate. The test strip showed visual detection down to 1 ppb in real water samples. © 2016 The Royal Society of Chemistry.

Pradeep Thalappil

Department Of Chemistry

C. K. Manju

Heavy metals

Luminescence

Mass spectrometry

Metal ions

Metals

Oxide films

Thermogravimetric analysis

X ray diffraction

fluorescein isothiocyanate

OXIDE SUPPORTS

PAPER-LIKE

REAL WATER SAMPLES

RED-EMITTING

SILVER CLUSTER

TEST STRIPS

VISUAL DETECTION

Mercury (metal)

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Journal of Materials Chemistry C

Enormous developments in the area of soluble noble metal clusters protected with monolayers are discussed. Mass spectrometry has been the principal tool with which cluster growth has been examined. The composition and chemistry of clusters have been examined extensively by mass spectrometry. Besides gold, silver, platinum, copper and iron clusters have been examined. Clusters have also been examined by tandem mass spectrometry and the importance of ligands in understanding closed shell electronic structure is understood from such studies. Protein protected noble metal clusters belong to a new group in this family of materials. Naked metal clusters bearing the same core composition as that of monolayer protected clusters is another class in this area, which have been discovered by laser desorption ionization from protein templates. © The Royal Society of Chemistry 2016.

Fulltext

SPR Nanoscience

Evolution of atomically precise clusters through the eye of mass spectrometry

Atomically precise monolayer protected clusters are molecules comprising a few-atom cluster core of a noble metal, typically Au or Ag, surrounded by a protective layer of ligands, exhibiting many special optical, electrical, catalytic, and magnetic properties, and are emerging as important materials in biology, medicine, catalysis, energy conversion and storage, and sensing. The structural diversity of these clusters or aspicules, as we definitively term them, meaning shielded molecules, combining the Greek word aspis (shield) with molecule, is rapidly increasing due to new compositions and modification routes such as ligand-exchange, alloying, or supramolecular functionalization. We present a structural analysis of the most stable cluster of this kind, Au25(SR)18, and propose a Borromean rings diagram for the cluster, showing its topological configuration of three interlocked (Au8S6)-rings. This simplified two-dimensional diagram is used to represent its structure and modifications via ligand or metal atom substitution uniquely. We enumerate and name its isomers with two-ligand or metal atom substituents. Among the several structural insights obtained, the identification of the Borromean rings-interlocked configuration in Au25(SR)18 may explain its high geometric stability and indicate a possible general unified structural viewpoint for these clusters without the division between core and staple motifs. On the basis of our structural analysis, we developed a structure-based nomenclature system that can be applied to both describe and understand the structure and modifications of gold thiolate clusters, AuM(SR)N, and is adaptable to the general case of MM(X)N (M, metal and X, ligand). The application of structural analysis and diagrams to Au38(SR)24 and Au102(SR)44, revealing the possible formation of the cluster core by stacking or growth of rings of metal atoms, is also presented. © 2015 American Chemical Society.

Journal of Physical Chemistry C

A Unified Framework for Understanding the Structure and Modifications of Atomically Precise Monolayer Protected Gold Clusters

We report a one-step and high yield synthesis of a red-luminescent silver cluster with the molecular formula, Ag11(SG)7 (SG: glutathionate) via reduction of silver ions by sodium borohydride in the presence of the tripeptide, glutathione (GSH). The as-prepared cluster shows prominent absorption features at 485 and 625 nm in its UV-vis absorption spectrum. Aging of the as-prepared cluster solution led to the disappearance of the 625 nm peak, followed by broadening of the 485 nm peak to give three maxima at ∼487, 437, and 393 nm in its absorption spectrum. These peaks remain unchanged even after polyacrylamide gel electrophoresis (PAGE), where a single band was observed confirming high purity of the cluster formed. Electrospray ionization mass spectrometry (ESI MS) reveal the composition of the cluster to be Ag11(SG)7 with multiple sodium attachments to the ligand to give -3 and -2 charged species. These compositions match well with their calculated isotope patterns. Extensive MS/MS was performed to understand the fragmentation. Potential atomic structures are discussed based on density functional theory calculations and comparisons for optical absorption spectra using Ag11(SCH3)7 as the model. Photoluminescence of this cluster was selectively quenched in the presence of Hg(II) and Cu(II) separately. Detection limit was found to be below their permissible limits in drinking water set by US EPA. Ag11(SR)7 cluster is reported for the first time. © 2014 American Chemical Society.

Ag11(SG)7: A new cluster identified by mass spectrometry and optical spectroscopy

Sub-nanometer-sized metal clusters, having dimensions between metal atoms and nanoparticles, have attracted tremendous attention in the recent past due to their unique physical and chemical properties. As properties of such materials depend strongly on size, development of synthetic routes that allows precise tuning of the cluster cores with high monodispersity and purity is an area of intense research. Such materials are also interesting owing to their wide variety of applications. Novel sensing strategies based on these materials are emerging. Owing to their extremely small size, low toxicity, and biocompatibility, they are widely studied for biomedical applications. Primary focus of this review is to provide an account of the recent advances in their applications in areas such as environment, energy, and biology. With further experimental and theoretical advances aimed at understanding their novel properties and solving challenges in their synthesis, an almost unlimited field of applications can be foreseen. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Particle and Particle Systems Characterization

Noble metal clusters: Applications in energy, environment, and biology

A new strategy to synthesize a diverse array of organic-soluble, atomically precise silver clusters has been developed. The technique is based on the miscibility principle of solvents and uses no phase-transfer agents; various clusters of masses 8.0, 13.4, 22.8, 29.2, and 34.4 kDa were synthesized by changing the reactant composition. We have also synthesized the well-known Au<inf>25</inf>(SR)<inf>18</inf> cluster by the same method. Among the silver clusters formed, we have studied the new 13.4 kDa species, which has unique steplike features in its UV/Vis spectrum, in detail by mass spectrometry and other analytical techniques. The compound has been assigned as Ag<inf>68</inf>(SR)<inf>34</inf>, which is reported for the first time. By time-dependent studies, we have shown that the synthetic route follows the bottom-up approach. The material forms microcrystals. We hope that the proposed synthetic strategy will extend the area of atomically precise clusters. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

European Journal of Inorganic Chemistry

Synthesis of atomically precise silver clusters by using the miscibility principle

Highly luminescent monolayer protected Ag56Se13S15 clusters

Journal	Data powered by TypesetJournal of Materials Chemistry C
Publisher	Data powered by TypesetRoyal Society of Chemistry
ISSN	20507534
Open Access	No