chemical equation presentation Interfacial etching of silver nanoparticles and separation of the products by Polyacrylamide gel electrophoresis afforded Ag8 and Ag7 clusters with red and bluegreen fluorescence emission, respectively (see picture). The strongly temperaturedependent emission of the clusters suggests potential applications, whilst their facile phase transfer to organic media facilitates further studies. © 2010 Wiley-VCH Verlag GmbH &amp; Co. KCaA, weinheim.

Pradeep Thalappil

Department Of Chemistry

T. Udaya Bhaskara Rao

Chemical equations

Cluster compounds

Fluorescence emission

Interfacial reactions

Organic media

PHASE TRANSFER

polyacrylamide gel electrophoresis

Potential applications

Silver nanoparticles

Temperature dependent

Electrophoresis

Gels

Luminescence

Nanoparticles

Synthesis (chemical)

Silver

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

Angewandte Chemie - International Edition

Mass spectrometry (MS), a hundred-year-old subject, has been a technique of profound importance to molecular science. Its impact in solid-state materials science has not been evident, although many materials of modern science, such as fullerenes, have their origins in MS. Of late, mass spectrometric interface with materials is increasingly strengthened with advances in atomically precise clusters of noble metals. Advances in instrumentation along with recent developments in synthetic approaches have expanded the chemistry of clusters, and new insights into matter at the nanoscale are emerging. High-resolution MS coupled with soft ionization techniques enable efficient characterization of atomically precise clusters. Apart from that, techniques such as ion mobility, tandem MS, etc. reveal structural details of these systems. Growth, nucleation, and reactivity of clusters are also probed by MS. Some of the recent advancements in this field include the development of new hyphenated techniques. Finer structural details may be obtained by coupling MS with spectroscopic tools, such as photoelectron spectroscopy, vacuum ultraviolet spectroscopy, etc. With such advancements in instrumentation, MS can evolve into a universal tool for the characterization of materials. The present review captures highlights of this area. © 2019, The Author(s).

Fulltext

NPG Asia Materials

The emerging interface of mass spectrometry with materials

Reactivity of monolayer protected atomically precise clusters of noble metals is of significant research interest. To date very few experimental data are available on the reaction thermodynamics of such clusters. Here we report a calorimetric study of the reaction of glutathione (GSH) protected silver clusters in the presence of excess ligand, GSH, using isothermal titration calorimetry (ITC). We have studied Ag11(SG)7 and Ag32(SG)19 clusters and compared their reactivity with GSH protected silver nanoparticles (AgNPs) and silver ions. Clusters show intermediate reactivity toward excess ligand compared to nanoparticles and silver ions. Several control experiments were performed to understand the degradation mechanism of these silver clusters and nanoparticles. The effect of dissolved oxygen in the degradation process was studied in detail, and it was found that it did not have a significant role, although alternate pathways of degradation with the involvement of oxygen cannot be ruled out. Direct confirmation of the fact that functionalized metal clusters fall in-between NPs and atomic systems in their stability is obtained experimentally for the first time. Several other thermophysical parameters of these clusters were also determined, including density, speed of sound, isentropic compressibility, and coefficient of thermal expansion. © 2017 American Chemical Society.

Journal of Physical Chemistry C

Reactivity of Monolayer Protected Silver Clusters toward Excess Ligand: A Calorimetric Study

Reactivity of two different nanosystems of silver, namely nanoparticles and atomically precise clusters, toward 1D tellurium nanowires (NWs) was probed and compared with the reaction of silver ions. While the reaction of nanoparticles and ions led to silver telluride nanowires, a different reactivity was exhibited by clusters which resulted in silver islands at different positions on the Te NWs. These hybrid Ag nodule-decorated Te NWs are sensitive to temperature, and they transform to dumbbell-shaped silver-tipped Te NWs upon solution phase annealing. Differences in chemical reactivity of nanoparticles of two different size regimes with nanowires are demonstrated. Synthetic methods of this kind will be useful in creating complex nanostructures which are difficult to be made in the solution phase. © 2014 American Chemical Society.

Chemistry of Materials

Manifestation of the difference in reactivity of silver clusters in contrast to its ions and nanoparticles: The growth of metal tipped Te nanowires

The cluster Ag44SePh30, originally prepared from silver selenolate, upon oxidative decomposition by H2O2 gives the same cluster back, in an apparently reversible synthesis. Such an unusual phenomenon was not seen for the corresponding thiolate analogues. From several characterization studies such as mass spectrometry, Raman spectroscopy, etc., it has been confirmed that the degraded and as-synthesized selenolates are the same in nature, which leads to the reversible process. The possibility of making clusters from the degraded material makes cluster synthesis economical. This observation makes one to consider cluster synthesis to be a reversible chemical process, at least for selenolates. © The Royal Society of Chemistry 2014.

Nanoscale

Reversible formation of Ag44 from selenolates

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.

Journal of Physical Chemistry Letters

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

We synthesized fluorescent, porphyrin-anchored, Au 22 clusters in a single step, starting from well-characterized Au 25 clusters protected with glutathione (-SG) by a combined core reduction/ligand exchange protocol, at a liquid-liquid interface. The prepared cluster was characterized by UV/vis, photoluminescence, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy, elemental analysis, and matrix-assisted laser desorption ionization mass spectrometry. The absence of a 672 nm intraband transition of Au 25 and the simultaneous emergence of new characteristic peaks at 520 and 635 nm indicate the formation of the Au 22 core. An increase in the binding energy of 0.4 eV in Au 4f core-level peaks confirmed the presence of a reduced core size. Quantitative XPS confirmed the Au/S ratio. The presence of a free base, tetraphenylporphyrin (H 2TPPOAS-), on the Au 22 core was confirmed by fluorimetric titrations with Cu 2+ and Zn 2+ ions. From all of these, the composition of the cluster was determined to be Au 22[(-SG) 15(-SAOPPTH 2) 2], which was supported by mass spectrometry and elemental analysis. We utilized the fluorescence nature of these water-soluble clusters for the fabrication of fluorescent patterns by soft lithography. The patterns were studied using tapping-mode atomic force microscopy and confocal fluorescence imaging. © 2009 American Chemical Society.

ACS Applied Materials and Interfaces

Functionalized Au 22 clusters: Synthesis, characterization, and patterning

A novel interfacial route has been developed for the synthesis of a bright-red-emitting new subnanocluster, Au23, by the core etching of a widely explored and more stable cluster, Au25SG18 (in which SG is glutathione thiolate). A slight modification of this procedure results in the formation of two other known subnanoclusters, Au22 and Au33. Whereas Au22 and Au23 are water soluble and brightly fluorescent with quantum yields of 2.5 and 1.3%, respectively, Au33 is organic soluble and less fluorescent, with a quantum yield of 0.1%. Au23 exhibits quenching of fluorescence selectively in the presence of Cu2+ ions and it can therefore be used as a metal-ion sensor. Aqueous- to organic-phase transfer of Au23 has been carried out with fluorescence enhancement. Sol-vent dependency on the fluorescence of Au23 before and after phase transfer has been studied extensively and the quantum yield of the cluster varies with the solvent used. The temperature response of Au23 emission has been demonstrated. The inherent fluorescence of Au23 was used for imaging human hepatoma cells by employing the avidin-biotin interaction. © 2009 Wiley-VCH Verlag GmbH &amp; Co. KGaA.

Chemistry - A European Journal

Bright, NIR-emitting Au23 from Au25: Characterization and applications including biolabeling

Journal	Angewandte Chemie - International Edition
ISSN	14337851
Open Access	No