A. Biswas

Tunable multiple plasmon resonance wavelengths response from multicomponent polymer-metal nanocomposite systems

A method of vapor phase codeposition has been used at elevated target temperature coupled with selective masking technique to produce a multicomponent optical material with seven different ultraviolet-visible optical active planes. Such a system consists of different nanocomposites of Teflon AF/Ag, Teflon AF/Au, and Teflon AF/Cu with sharp interfaces. The fabricated system has regions of single nanocomposite plane together with multilayer structures facilitating tunable multiple particle plasmon resonance wavelength response from a single system. Distinct double and triple plasmon wavelength resonance absorptions could be obtained from such interfaces forming multilayers of either two or three nanocomposite structures.

Controlled growth of nano-size metal clusters on polymers by using VPD method

A completely dry technique (VPD) for the preparation of a metal cluster onto a polymer surface or between two polymer layers opens up very good possibilities to control the two dimensional dispersion of the metal clusters and their size during variation of the deposition parameters or the polymer surface treatment. The kinetics of heterogenous nucleation and the growth of nano-size metal clusters (Ni, Ag, Cu, Au) on polymers with different chemical composition (PMDA-ODA polyimide, polystyrene and Teflon AF) are studied by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). In contrast to preferred nucleation and significantly incomplete condensation on the surface of Teflon AF and PS random nucleation and well defined cluster distribution was observed on PMDA-ODA polyimide. It was shown that cluster size and cluster distribution can be influenced in a wide range (some order of magnitude) by the variation of the preparation parameters. Ar ion beam treatment of polymers with low ion dose (10 12 –10 16 cm � 2 ) as well as predeposition of a trace amount of a reactive metal can be successfully used to prepare a definite cluster structure due to creation of adsorption sites on polymer surface. 2003 Elsevier Science B.V. All rights reserved.

Recrystallization in polyvinylidene fluoride upon low fluence swift heavy ion impact

Thin films (9 μm) of polyvinylidene fluoride (PVDF) are irradiated by swift heavy ions (180 MeV Ag14+) in the fluence range 1×1010–1×1012ions/cm2 with an electronic linear energy transfer LET∼11 keV/nm. In sharp contrast to the previous results, the most characteristic crystalline asymmetric and symmetric “CH2” doublets (located at 3025 and 2985 cm−1), have shown remarkable increase in their respective Fourier transform infrared (FTIR) absorbance intensities upon low fluence ion impact (1010 ions/cm2). This increase in absorbance is in consonance with the simultaneous decrease of the transmission intensities of other crystalline bending vibration bands located at 532 (CF2 bending), 614, 796, and 975 cm−1 (all due to CH2 bending) at the similar ion fluence. It appears most probable from the results that, being a polar polymer, the molecular dipoles in PVDF forming a hydrogen bond network get realigned upon irradiation into a highly ordered state of chain molecules in the crystalline regions and create volu...

Nanocomposites of vapour phase deposited Teflon AF containing Ni clusters

Two component nanocomposites of polymer containing 3d transition metal clusters are of immense interest because of their potential future applications in magnetic high frequency or data storage media, in particular: However, nanoscale engineering of such airstable 3d clusters protected in polymer layers is a major technological challenge, given the readily reactive nature of such nanoparticles. In this invited paper, we introduce relatively simple vapour phase deposition as a powerful solvent free technique to prepare polymer nanocomposites containing 3d transition metal clusters. The different vapour phase production routes investigated show that the technique lends itself to the formation of metallic clusters of the appropriate size while reactions of the reactive Ni atoms with the growing Teflon AF matrix, contrary to common belief, do not take place. In addition to other results, a promising route of vapour phase tandem evaporation to produce nanoclusters of reactive Ni protected between the capping layers of Teflon AF is particularly presented. Independent control over homogeneously distributed particle size ( similar to 3 - 10 nm) is discussed, while increasing a cluster volume filling from similar to 1 to 20 % by following co-deposition to many sequential thermal evaporation of the two components. TEM electron diffraction investigations have shown that crystal structure of such nanoclusters to be fee, confirming the bulk Ni crystal parameters.

Arrays of wirelike microstructures of Ag with visible wavelength transparent plasmonic response at near-ultraviolet and midinfrared regions

We present a simple masked thermal evaporation technique to fabricate arrays of wirelike Ag microstructures of width 8μm with an extremely high aspect ratio on either silicon or glass substrates. In accordance with the theory of periodic arrays of thin wires, the electromagnetic response of Ag microstructures has shown a characteristic low-frequency plasmonic behavior with a transparent visible region. Plasmon absorption is observed to be splitted largely into transverse and predominating longitudinal bands at near-ultraviolet (415nm) and midinfrared wavelengths (2867nm), corresponding to the oscillation of the free electrons perpendicular to and along the long axis of the wires.