Stable silver nanoparticles were generated in aqueous medium by amine, hydroxy and carboxylate terminated poly(amidoamine) (PAMAM) dendrimers in the absence of conventional reducing agents and light irradiation. Mechanistic studies suggest that, in spite of their lower pKa values, tertiary amines present in the dendritic structures act as the reducing agent. Dynamic light scattering and electron microscopic studies reveal that PAMAM dendrimers aggregate in presence of silver ions and the aggregation propensity plays a pivotal role in altering the size and shape of the nanoparticles generated in the dendritic milieu. The formation of metal nanoparticles with uniform size and shape by amine terminated PAMAM dendrimer is attributed to the unique aggregation propensity of amine terminated PAMAM. ©2009 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim.

Edamana Prasad

Department Of Chemistry

C. Vijayan

Department Of Physics

Manniledam Kavitha

Manas R. Parida

P. C. Deshmukh

Ag nanoparticle

Aggregation behavior

Aggregation propensity

aqueous medium

Dendritic structures

Light irradiations

mechanistic studies

Metal nanoparticles

Microscopic study

PAMAM dendrimer

Polyamidoamine dendrimers

Silver ions

Silver nanoparticles

Size and shape

SIZE DEPENDENCE

TERTIARY AMINE

Uniform size

Amines

Carboxylation

Light transmission

Metal ions

Nanoparticles

Organic compounds

REDUCING AGENTS

Silver

Dendrimers

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

Macromolecular Chemistry and Physics

Dendrimers have recently been shown to be excellent templates for synthesizing nanoparticles in view of their unique structural features. The present study, we report on nonlinear absorption and optical limiting properties of dendrimer-embedded silver nanoclusters and their linear and nonlinear optical (NLO) properties. Optical absorption spectroscopy reveals prominent plasmon peaks indicating quantum confinement. Z-scan experiments using pulsed laser excitation within the tail region of Plasmon absorption in the nanosecond regimes reveal evidence of strong nonlinear absorption involving two photo absorption followed by saturation absorption. The third ordered susceptibility (Χ(3)) measured using four wave degenarated four wave mixing tecnquie (FWDM). © 2010 SPIE.

Proceedings of SPIE - The International Society for Optical Engineering

Linear and nonlinear optical properties of dendrimer-based nanoclusters

Solvent-induced aggregation and its effect on the intrinsic emission properties of amine, hydroxy and carboxylate terminated, poly(amidoamine) (PAMAM) dendrimers have been investigated in glycerol, ethylene glycol, methanol, ethylene diamine and water. Altering the solvent medium induces remarkable changes in the intrinsic emission properties of the PAMAM dendrimers at identical concentration. Upon excitation at 370 nm, amine terminated PAMAM dendrimer exhibits an intense emission at 470 nm in glycerol, ethylene glycol as well as glycerol-water mixtures. Conversely, weak luminescence is observed for hydroxy and carboxylate terminated PAMAM dendrimers in the same solvent systems. When the solvent is changed to ethylene diamine, hydroxy terminated PAMAM exhibits intense blue emission at 425 nm. While the emission intensity is varied when the solvent milieu is changed, excited state lifetime values of PAMAM dendrimers remain independent of the solvent used. UV-visible absorption and dynamic light scattering (DLS) experiments confirm the formation of solvent-controlled dendrimer aggregates in the systems. Comparison of the fluorescence and DLS data reveals that the size distribution of the dendrimer aggregates in each solvent system is distinct, which control the intrinsic emission intensity from PAMAM dendrimers. The experimental results suggest that intrinsic emission intensity from PAMAM dendrimers can be regulated by proper selection of solvents at neutral conditions and room temperature. © 2008 Elsevier B.V. All rights reserved.

Journal of Luminescence

Effect of solvent-controlled aggregation on the intrinsic emission properties of PAMAM dendrimers

Amines are used extensively as reductants and subsequent capping agents in the synthesis of metal nanoparticles, especially gold, due to its affinity to nitrogen. Taking 2-methyl aniline as an example, we show that metal reduction is followed by polymerization of the amine, while part of it covers the nanoparticle surface another fraction deposits in the solution. It is found that the oxidative polymerization of the amine goes in step with the formation of gold nanoparticles. The gold nanoparticles thus formed have a mean diameter of 20 nm. The polymerized amine encapsulates the gold nanoparticle forming a robust shell of about 5 nm thickness, making the gold core inert towards mineralizing agents such as chloroform, bromoform, sodium cyanide, benzylchloride, etc. which react with the naked gold nanoparticles. The deposited polymer is largely protonated, taking up protons from the medium during its formation. Similar results have been observed in the case of aniline also. The materials have been fully characterized by spectroscopy and microscopy. © Springer 2005.

Journal of Nanoparticle Research

On the formation of protected gold nanoparticles from AuCl 4 - By the reduction using aromatic amines

Macromol. Chem. Phys. 22/2008

Chemistry - A European Journal

Switchable Nanoassemblies from Macroions and Multivalent Dye Counterions

Nanotechnology

Precise size control of hydrophobic gold nanoparticles using cooperative effect of refluxing ripening and seeding growth

Generation of Ag nanoparticles by PAMAM dendrimers and their size dependence on the aggregation behavior of dendrimersa

Journal	Data powered by TypesetMacromolecular Chemistry and Physics
Publisher	Data powered by TypesetWiley
ISSN	10221352
Open Access	No