A selenolate-protected Ag-Pd alloy cluster was synthesized using a one-pot solution-phase route. The crude product upon chromatographic analyses under optimized conditions gave three distinct clusters with unique optical features. One of these exhibits a molecular peak centered at m/z 2839, in its negative ion mass spectrum assigned to Ag5Pd4(SePh)12-, having an exact match with the corresponding calculated spectrum. Tandem mass spectrometry of the molecular ion peak up to MS9 was performed. Complex isotope distributions in each of the mass peaks confirmed the alloy composition. We find the Ag3Pd3- core to be highly stable. The composition was further supported by scanning electron microscopy, energy-dispersive spectroscopy, and X-ray photoelectron spectroscopy. (Graph Presented). © 2014 American Chemical Society.

Pradeep Thalappil

Department Of Chemistry

TANDEM MASS SPECTROMETRIC

Fulltext

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 Letters

Isolation and tandem mass spectrometric identification of a stable monolayer protected silver-palladium alloy cluster

We report the systematic appearance of a plasmon-like optical absorption feature in silver clusters protected with 2-phenylethanethiol (PET), 4-flurothiophenol (4-FTP) and (4-(t-butyl)benzenethiol (BBS) as a function of cluster size. A wide range of clusters, namely, Ag44(4-FTP) 30, Ag55(PET)31, ∼Ag75(PET) 40, ∼Ag114(PET)46, Ag152(PET) 60, ∼Ag202(BBS)70, ∼Ag 423(PET)105, and ∼Ag530(PET)100 were prepared. The UV/Vis spectra show multiple features up to ∼Ag 114; and thereafter, from Ag152 onwards, the plasmonic feature corresponding to a single peak at ∼460 nm evolves, which points to the emergence of metallicity in clusters composed of ∼150 metal atoms. A minor blue shift in the plasmonic peak was observed as cluster sizes increased and merged with the spectrum of plasmonic nanoparticles of 4.8 nm diameter protected with PET. Clusters with different ligands, such as 4-FTP and BBS, also show this behavior, which suggests that the 'emergence of metallicity' is independent of the functionality of the thiol ligand. © 2014 the Partner Organisations.

Nanoscale

Emergence of metallicity in silver clusters in the 150 atom regime: A study of differently sized silver clusters

A blue luminescent 11-atom platinum cluster showing step-like optical features and the absence of plasmon absorption was synthesized. The cluster was purified using high performance liquid chromatography (HPLC). Electrospray ionization (ESI) and matrix assisted laser desorption ionization (MALDI) mass spectrometry (MS) suggest a composition, Pt11(BBS)8, which was confirmed by a range of other experimental tools. The cluster is highly stable and compatible with many organic solvents. This journal is © the Partner Organisations 2014.

Blue emitting undecaplatinum clusters

An atomically precise silver cluster, Ag152 protected with thiolate ligands, was used as a surface-enhanced Raman scattering (SERS) substrate. The cluster shows intense enhancement of Raman signals of crystal violet with an enhancement factor of 1.58 × 109. Adaptability of the substrate for a wide range of systems starting from dyes to biomolecules is demonstrated. Solid-state drop casting method was used here, and SERS signals were localized on the Ag152 crystallites, confirmed from Raman images. Excellent periodicity of clusters, their plasmonic nature, and absence of visible luminescence are the main reasons for this kind of large enhancement. SERS was compared with smaller clusters and larger nanoparticles, and the size regime of Ag152 was found to be optimum. Several control experiments were done to understand the SERS activity in detail. The method has wide adaptability as the cluster can be easily drop-casted on any surface like paper, cotton, and so forth to produce effective SERS media. The work suggests that atomically precise clusters, in general, can show SERS activity. © 2013 American Chemical Society.

Atomically precise silver clusters as new SERS substrates

A copper cluster protected with 2-phenylethanethiol (PET) exhibiting distinct optical features in UV/Vis spectroscopy is reported. Matrix-assisted laser desorption ionisation mass spectrometry of the cluster shows a well-defined molecular ion peak at m/z 5,800, assigned to ~Cu 38(PET)25. Fragmented ions from the cluster show the expected isotope patterns in electrospray ionisation mass spectrometry. The as-synthesized cluster was well-characterised using other tools as well. Clusters undergo decomposition in about 2 h after synthesis as a metallic few-atom core of copper is highly unstable. The products of decomposition were also characterised. © 2013 Springer Science+Business Media Dordrecht.

Journal	Data powered by TypesetJournal of Physical Chemistry Letters
Publisher	Data powered by TypesetAmerican Chemical Society
ISSN	19487185
Open Access	No