Chemistry Colloquium by Dr. Sukhendu Mandal on 14th May 2019 on 'Transformation Chemistry at Nanoscale' | Shiv Nadar University
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Chemistry Colloquium by Dr. Sukhendu Mandal on 14th May 2019 on 'Transformation Chemistry at Nanoscale'

Achieving atomic precision and molecular purity is routine in organic chemistry, it is by no means so in nanochemistry, because nanoparticle growth is extremely complicated and remains the least understood.1 Recent years have witnessed significant advances in controlling gold nanoparticles with atomic precision. Atom precise metal nanocluster is essential for understanding the evolution of physiochemical properties from atomic to metallic state.  These interesting properties originate from their remarkable stability and distinct optical, electronic, electrochemical and biolabelling properties. Structure of these clusters consists of a gold kernel protected by the RS-Au-SR monomer units and RS-Au-SR-Au-SR dimer or higher staple like surface motifs.2 The unique staple motif set the basis for the design and interpretation of surface reactivity on thiolate protected gold nanoclusters through thiol exchange reactions. Ligand exchange can induce size and structural transformation and, accordingly to procure new Aun(SR)m nanoclusters.  Here we will discuss the ligand exchange induced transformation from an icosahedral Au25(SR)18 (where SR = 2-phenylethanethiol (PET)) cluster to a bitetrahedral Au22(SR)4(SR’)14 (where SR’ = 4-tert-butylbenzenethiol (TBBT)) (Fig. 1).3 This partial exchange of the ligand was achieved by controlling the concentration of the incoming TBBT ligand. Time dependent mass spectrometry and optical spectroscopy revealed the dissociation of the parent cluster and also gave a deep insight on the ligand exchange mechanism. Theoretical calculations and extended X-ray absorption fine structure (EXAFS) studies confirm the formation of Au22 structure. Identifying the atomic structure of the intermediate species opens a new avenue to study the transformation of one cluster to another.4  

Event Date: 
Tuesday, May 14, 2019 -
Tuesday 14, May 2019
11:30 AM - 12:30 PM