We report a joint experimental and theoretical study of two luminescent molecular quantum clusters of silver, Ag7(H2MSA) 7 and Ag8(H2MSA)8 (H2MSA is the dicarboxylic acid of mercaptosuccinic acid in thiolate form). Global optimizations and property calculations are performed in the framework of density-functional theory (DFT-PBE) to search for the leading candidates with the lowest energy. The simulated excitation spectra of these two clusters are in good agreement with the corresponding experimental spectra. The presence of -RS-Ag-RS- as a stable motif has been confirmed in all of the lowest energy structures. © 2011 American Chemical Society.

Pradeep Thalappil

Department Of Chemistry

Thumu Udaya Bhaskara Rao

dicarboxylic acid

Excitation spectrum

EXPERIMENTAL SPECTRA

First-principles study

Fluorescence spectra

LOWEST ENERGY STRUCTURE

MERCAPTOSUCCINIC ACIDS

QUANTUM CLUSTERS

theoretical study

THIOLATES

Luminescence

Density functional theory

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 Physical Chemistry C

Clusters composed of a 32 silver atom core, protected with thiolates of glutathione (GSH) and N-(2-mercaptopropionyl)glycine (MPGH), were synthesized by a solid-state route in milligram scale. They do not exhibit surface plasmon resonance unlike their larger sized nanoparticle analogues but show molecule-like features in absorption and luminescence spectra, falling in the visible window. The compositions Ag32SG19 (SG: thiolate of glutathione) and Ag32MPG19 (MPG: thiolate of MPGH) were identified from electrospray ionization mass spectrometry (ESI MS). Matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) was not successful for -SG protected clusters as reported before, but for Ag 32MPG19 a peak at 6.1 kDa was seen at a threshold laser intensity. This peak shifted to low mass region with increasing laser intensity due to systematic losses of Ag2S. Further confirmation of the composition Ag32SG19 was made using various studies such as XPS and EDAX. One-dimensional (1D) and two-dimensional (2D) NMR spectroscopic investigations of Ag32SG19 provided interesting spectral features which indicated the dominant -[SR-Ag-SR]- structural motif. This structural motif as the predominant entity is found for the first time in silver clusters. © The Royal Society of Chemistry 2013.

Fulltext

Nanoscale

Thiolate-protected Ag32 clusters: Mass spectral studies of composition and insights into the Ag-thiolate structure from NMR

Brightly luminescent, atomically precise subnanometer clusters of silver protected by glutathione were covalently functionalized by solution phase thiolated graphene using ligand exchange. A hybrid molecule was formed, which was obtained in a nearly pure form by phase transfer from the aqueous to the organic phase. The resulting hybrid exhibited properties of both of these nanoscale materials. UV-vis, luminescence, XPS, EDAX, TEM, and Raman spectroscopy were used to characterize the hybrid structure, which showed the spectroscopic characteristics of both the constituents. The luminescence of the cluster was retained in the hybrid, along with features characteristic of graphene. Atomically precise clusters with covalently linked graphene will be useful for new applications in the areas of drug delivery, sensors, and catalysis. © 2012 American Chemical Society.

Luminescent silver clusters with covalent functionalization of graphene

A silver cluster having the composition Ag9(H 2MSA)7 (H2MSA = mercaptosuccinic acid) was synthesized in macroscopic quantities using a solid-state route. The clusters were purified by PAGE and characterized by UV-vis, FTIR, luminescence, and NMR spectroscopy, TEM, XPS, XRD, TG, SEM/EDAX, elemental analysis, and ESI MS. The solid-state route provides nearly pure Ag9 clusters, and nanoparticle contamination was insignificant for routine studies. Formation of various clusters was observed by modifying the conditions. The effect of ligands on the synthesis was checked. The cluster decomposed slowly in water, and the decomposition followed first-order kinetics. However, it could be stabilized in solvent mixtures and in the solid state. Such materials may be important in cluster research because of their characteristic absorption profiles, which are similar to those of Au25 and Au38. The cluster showed luminescence with a quantum yield of 8 × 10-3 at 5 °C. © 2010 American Chemical Society.

Journal of the American Chemical Society

Ag9 quantum cluster through a solid-state route

SpringerReference

Meselson-Radding Model Of Recombination (1975 Proc Natl Acad Sci USA 72:358)

The Journal of Physical Chemistry C

Silver Nanoclusters: Single-Stage Scaleable Synthesis of Monodisperse Species and Their Chirooptical Properties

High Yield, Large Scale Synthesis of Thiolate-Protected Ag7Clusters

Angewandte Chemie International Edition

Silver Nanoparticles with Broad Multiband Linear Optical Absorption

First principles studies of two luminescent molecular quantum clusters of silver, Ag7(H2MSA)7 and Ag8(H 2MSA)8, based on experimental fluorescence spectra

Journal	Journal of Physical Chemistry C
ISSN	19327447
Open Access	No