Nanometer sized gold and silver clusters protected with 2- mercaptobenzothiazole monolayers have been prepared and characterized by various spectroscopic methods. Optical absorption spectra show features assigned to charge-transfer excitation between the monolayer and the cluster, in addition to a red shifting and reduction of plasmon absorption. The monolayers on clusters are compared with the corresponding 2D-monolayers investigated previously. The dominant adsorbate geometries on these clusters are different. Whereas the temperature dependent dynamics are minimal for 2D- SAMs, they are significant for monolayers on 3D surfaces, which is attributed to the decreased packing density on the cluster surfaces. The thermal stability of these monolayers is high and comparable to that of alkanethiolate monolayers. The monolayers undergo irreversible structural changes upon heating, which have been studied by differential scanning calorimetry and IR spectroscopy.

Pradeep Thalappil

Department Of Chemistry

benzothiazole derivative

Gold

Silver

article

Differential scanning calorimetry

heating

infrared spectroscopy

nanoparticle

synthesis

thermostability

X ray spectrometry

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 Materials Chemistry

Researchers reported about the systematic size evolution of an organic-soluble, atomically precise silver cluster. Evolution of precise silver cluster larger nanoparticles was observed by mass spectrometry, while the formation of nanoparticles and crystals was investigated by electron microscopy. A solid-state route was used to synthesize atomically precise clusters and conduct the investigations. The method involves grinding the precursors in a mortar and pestle to form silver thiolates. Addition of sodium borohydride in the solid state to this mixture with continued grinding produced well-defined clusters that were extracted with suitable solvents. A mixture of AgNO3 and tetraoctyl ammonium bromide (TOABr) was taken in an agate mortar and ground uniformly. The product was extracted in ethanol and centrifuged to remove extra thiol in the supernatant and finally the residue was extracted in toluene, which gave reddish-brown solution.

Particle and Particle Systems Characterization

Evolution of atomically precise silver clusters to superlattice crystals

Water is one of the essential enablers of life on earth. Beginning with the origin of the earliest form of life in seawater, it has been central to the evolution of human civilizations. Noble metals have been similarly associated with the prosperity of human civilizations through their prominent use in jewellery and medical applications. The most important reason for the use of noble metals is the minimal reactivity at the bulk scale, which can be explained by a number of concepts such as electrochemical potential, relativisitic contraction, molecular orbital theory, etc. Recently, water quality has been associated with the development index of society. A number of chemical and biological contaminants have endangered the quality of drinking water. An overview of important events during last 200 years in the area of drinking water purification is presented. Realizing the molecular nature of contamination in drinking water, significant progress has been made to utilize the chemistry of nanomaterials for water purification. This article summarizes recent efforts in the area of noble metal nanoparticle synthesis and the origin of their reactivity at the nanoscale. The application of noble metal nanoparticle based chemistry for drinking water purification is summarized for three major types of contaminants: halogenated organics including pesticides, heavy metals and microorganisms. Recent efforts for the removal, as well as ultralow concentration detection of such species, using noble metal nanoparticles are summarized. Important challenges during the commercialization of nano-based products are highlighted through a case study of pesticide removal using noble metal nanoparticles. Recent efforts in drinking water purification using other forms of nanomaterials are also summarized. The article concludes with recent investigations on the issue of nanotoxicity and its implications for the future. © 2009 Elsevier B.V. All rights reserved.

Thin Solid Films

Noble metal nanoparticles for water purification: A critical review

Alkyl-chain dynamics in monolayer protected metal cluster systems of gold have been studied by the quasielastic neutron scattering technique. Measurements have been carried out with 6, 12, and 18 carbon-long thiolate protected gold clusters of 4 nm core diameter. Dynamics of the monolayers in these systems, as indicated by the quasielastic broadening, were found to evolve continuously with increase in temperature from 270 to 400 K. Analysis of the elastic incoherent structure factor showed that while only a small portion of each chain is dynamically active at low temperature, the dynamics extend to almost the whole chain at 400 K. Although an improved model compared to our earlier reports, involving precessional motion of the chains on a cone is found to explain the observed data, a further improvement with reorientation of the chain around its axis with additional body axis fluctuation was most consistent with the experiment. The studies revealed the existence of complex dynamical motions of alkyl chains on the clusters. The studies suggest that repeated washings provide more space for the monolayer chains as a result of the removal of the phase transfer catalysts between the alkyl chains on the cluster surface. This provides space for greater orientational freedom, resulting in the observed dynamics even at lower temperatures. © 2007 The American Physical Society.

Physical Review B - Condensed Matter and Materials Physics

Evolution of the alkyl-chain dynamics in monolayer-protected gold clusters

We report the generation of a potential difference, of the order of tens of millivolts, induced by the flow of polar liquids over an assembly of gold nanoparticles. The device consisted of two conducting glass plates, one of which contained the gold nanoparticle multilayer assembly. The potential generated is in transverse direction to the flow and is dependent on the nature of the flowing liquid. We propose a simple theoretical model to account qualitatively for the generation of the flow-induced transverse potential. © 2005 The American Physical Society.

Physical Review Letters

Flow-induced transverse electrical potential across an assembly of gold nanoparticles

Alkancthiol protected gold clusters of 29 kDa were prepared and separated by column chromatography. Laser desorption mass spectra of these clusters have been investigated. In the gas phase, monolayer-monolayer interaction leads to clustering of the protected clusters. Role of different matrices and effect of alkanethiol chain length on this process have been investigated. © World Scientific Publishing Company.

Journal	Journal of Materials Chemistry
ISSN	09599428
Open Access	No