Events Calendar

 
Seminar

Chemistry of Atomically Precice Clusters of Noble Metals

Tuesday, 24 November 2015, 11:00-12:30
Institute of Nanotechnology !! Seminar room 0-341 !!
Talk given by Prof. T. Pradeep DST Unit of Nanoscience (DST UNS) and Thematic Unit of Excellence (TUE) Department of Chemistry Indian Institute of Technology Madras Chennai, India Abstract: 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. We present some of the examples of novel chemistry with these clusters. The structural diversity of these clusters or aspicules, as we 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 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. The application of structural analysis and diagrams to Au38(SR)24 and Au102(SR)44 is also presented. Among 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. This structure-based nomenclature system can be applied to both describe and understand the structure and modifications of gold thiolate clusters, AuM(SR)N, or more generally AuM(X)N. Some key references: 1. Two luminescent silver clusters by interfacial synthesis, T. U. B. Rao and T. Pradeep, Angew. Chem. Int. Ed., 49 (2010) 3525-3529. 2. Ag9 quantum cluster through a solid state route, T. U. B. Rao, B. Nataraju and T. Pradeep, J. Am. Chem. Soc., 132 (2010) 16304-16307. 3. Understanding the evolution of luminescent gold quantum clusters in protein templates, K. Chaudhari, P.L. Xavier, T. Pradeep, ACS Nano, 5 (2011) 8816-8827. 4. Ag7Au6: A 13 atom alloy quantum cluster, T. U. B. Rao, Y. Sun, N. Goswami, S. K. Pal, K. Balasubramanian, and T. Pradeep, Angew. Chem. Int. Ed., 51 (2012) 2155-2159. 5. Selective visual detection of TNT at the sub-zeptomole level, Ammu Mathew, P. R. Sajanlal, and T. Pradeep, Angew. Chem. Int. Ed., 51 (2012) 9596-9600. 6. The superstable 25-kDa monolayer protected silver nanoparticle: Measurements & interpretation as an icosahedral Ag152(SCH2CH2Ph)60 cluster, I. Chakraborty, A. Govindarajan, J. Erusappan, A. Ghosh, B. Yoon, R. L. Whetten, U. Landman and T. Pradeep, Nano Lett., 12 (2012), 5861-5866. 7. New protocols for the synthesis of stable Ag and Au nanocluster molecules, T. Udayabhaskararao and T. Pradeep, J. Phys. Chem. Lett., 4 (2013) 1553-1564 8. Separation of precise compositions of noble metal clusters protected with mixed ligands Yoshiki Niihori, Miku Matsuzaki, T. Pradeep and Yuichi Negishi, J. Am. Chem. Soc., 135 (2013) 4946-4949. 9. Supramolecular functionalization and concomitant enhancement in properties of Au25 clusters, Ammu Mathew, Ganapati Natarajan, Lauri Lehtovaara, Hannu Häkkinen, Ravva Kumar, Venkatesan Subramanian, Abdul Jaleel, T. Pradeep, ACS Nano, 2014, 8, 139-152. 10. Emergence of metallicity in silver clusters in the 150 atom regime: A study of differently sized silver clusters, Indranath Chakraborty, Jayanthi Erusappan, Anuradha Govindarajan, K. S. Sugi, Thumu Udayabhaskararao, Atanu Ghosh and T. Pradeep, Nanoscale, 2014, 6, 8024–8031. 11. A unified framework for understanding the structure and modifications of atomically precise monolayer protected gold clusters, G. Natarajan, A. Mathew, Y. Negishi, R. L. Whetten and T. Pradeep, J. Phys. Chem. C, 2015 (in press). DOI: 10.1021/acs.jpcc.5b08193.
This event is part of the eventgroup INT Talks
Speaker
Prof. T. Pradeep

Indian Institute of Technology Madras, Chennai, India
http://www.dstuns.iitm.ac.in/pradeep-research-group.php
Organizer
Prof. Dr.-Ing. Horst Hahn
Institute of Nanotechnology (INT)
Karlsruhe Institute of Technology (KIT)
Eggenstein-Leopoldshafen
Mail: horst hahn does-not-exist.kit edu
Targetgroup
Interested / Everyone
Service-Menu