J.C. Pivin

Synthesis of metal-polymer nanocomposite for optical applications

Thin films of Ag‐PET nanocomposite were synthesized by a novel route of atom beam co-sputtering. The nanocomposites were characterized by UV‐visible and IR absorption spectroscopy, Rutherford backscattering spectroscopy and transmission electron microscopy. The absorption spectra exhibit features suitable for applications as (i) absorber extending from the visible region to about 2400 nm in the infrared region and (ii) bandpass filter at 320 nm, useful for HeCd laser. The transmission electron microscopy observations indicate that the metal fraction is in the form of fractals. (Some figures in this article are in colour only in the electronic version)

Synthesis and characterization of ZnO thin film grown by electron beam evaporation

Highly transparent, conducting, highly oriented, and almost single phase ZnO films have been deposited by simple e-beam evaporation method, and the deposition parameters were optimized. The films were prepared by (a) evaporation of ZnO at different substrate temperatures and (b) evaporation of ZnO at room temperature and subsequent annealing of the films in oxygen ambient at different temperatures. The characterizations of the film were performed by optical absorption spectroscopy (UV-visible), Fourier transform infrared spectroscopy, resistivity measurement, transmission electron microscopy (TEM), photoluminescence, and x-ray diffraction measurement. Absorption spectra revealed that the films were highly transparent and the band gap of the pre- and postannealed films was in good agreement with the reported values. The band gap of the films increases on increasing the substrate temperature as well as annealing temperature, whereas the resistivity of the film decreases with substrate temperature and increa...

Synthesis of elongated Au nanoparticles in silica matrix by ion irradiation

The present work reports the synthesis of elongated Au nanoparticles (NPs) parallel to each other, embedded in silica matrix. Au NPs in silica, prepared using rf magnetron sputtering, were irradiated by 120MeV Au ions at different fluences to induce elongation. Optical absorption study of irradiated film showed a clear splitting of surface plasmon bands corresponding to transverse and longitudinal modes. Transmission electron microscopy investigations of pristine and irradiated samples revealed an elongation (aspect ratio of ∼3.5) in Au NPs occurred as a result of irradiation. The results are discussed in the framework of thermal spike model.

Controlled growth of gold nanoparticles induced by ion irradiation: An in situ x-ray diffraction study

Thin silica films containing Au nanoparticles were prepared by cosputtering. The kinetics of the growth of nanoparticles under 90MeV Ni ion irradiation was studied by in situ x-ray diffraction. The growth of nanoparticles from 4 (for pristine) to 9nm at a fluence of 1×1014ions∕cm2 was observed, in accordance with the observations made by transmission electron microscopy analyses. The present study shows that the ion irradiation is an effective tool for tailoring the size of nanoparticles. The results are discussed in the framework of thermal spike model.

Mesoporous silica thin films for alcohol sensors

Silica mesoporous films using cetyltrimethylammonium bromide surfactant as a template have been prepared. The films have been deposited on silicon and alumina substrates by dip-coating and calcined at 250 and 450 � C. The films were characterized by Xray diffraction analysis, Fourier transform infrared spectroscopy and Rutherford backscattering spectrometry. The films have been shown to maintain the mesophase after calcination, at 250 � C the presence of residual surfactant has been observed. A density of 1.46 and 1.65 g cm � 3 has been measured by Rutherford backscattering spectrometry in the 250 and 450 � C calcined samples, respectively. These densities are much lower than the value (2.07 g cm � 3 ) measured in a reference silica film obtained via sol–gel and with the same thermal history. The electrical response of the silica mesoporous films has been investigated with different concentrations of alcohols. The sensitivity of the material to changes in the atmospheres of ethanol, methanol, 2-propanol, butanol-1 and exane has been tested. The results have shown a large sensitivity to the alcohols at room temperature and the possibility to discriminate between the different alcoholic species. # 2001 Elsevier Science Ltd. All rights reserved.

Gold-silica nanocomposites for the detection of human ovarian cancer cells : a preliminary study

We report the structural and optical properties of Au nanoparticles embedded in a silica matrix synthesized by atom beam co-sputtering. The presence of surface plasmon resonant absorption indicates the formation of Au nanoparticles. Transmission electron microscopy (TEM) studies show the presence of Au nanoparticles with an average size ranging from ~1.8 to 5.4 nm with narrow size distributions depending on the relative areas of Au and SiO2. We discuss the process of nucleation and growth of Au nanoparticles in the nanocomposite films formed by co-sputtering. The present method of nanoparticle synthesis is compared with other ion beam based techniques such as ion implantation and ion beam mixing. Preliminary experiments for the detection of human ovarian cancer cells using these Au nanoparticles are described.

Ordering of fullerene and carbon nanotube thin films under energetic ion impact

We report the ordering of carbon nanostructures under energetic ion irradiation at low fluence (<5×1011ions∕cm2). Fullerene thin films and multiwalled carbon nanotube (MWCNT) films were irradiated with 200MeV Au and 60MeV Ni ions at different ion fluences, respectively. The changes in the irradiated films have been investigated by means of Fourier transform infrared (FTIR) spectroscopy, x-ray diffraction, and Raman spectroscopy. FTIR and Raman spectroscopy show the improvement of vibration strength in low fluence irradiated fullerene and MWCNT films. X-ray diffraction analysis on low fluence irradiated fullerene films revealed the structural order along the (220) atomic planes.

The bonding of protective films of amorphic diamond to titanium

Films of amorphic diamond can be deposited from laser plasma ions without the use of catalysts such as hydrogen or fluorine. Prepared without columnar patterns of growth, the layers of this material have been reported to have ‘‘bulk’’ values of mechanical properties that have suggested their usage as protective coatings for metals. Described here is a study of the bonding and properties realized in one such example, the deposition of amorphic diamond on titanium. Measurements with Rutherford backscattering spectrometry and transmission electron microscopy showed that the diamond coatings deposited from laser plasmas were chemically bonded to Ti substrates in 100–200‐A‐thick interfacial layers containing some crystalline precipitates of TiC. Resistance to wear was estimated with a modified sand blaster and in all cases the coating was worn away without any rupture or deterioration of the bonding layer. Such wear was greatly reduced and lifetimes of the coated samples were increased by a factor of better th...

Electronic excitation induced tuning of surface plasmon resonance of Ag nanoparticles in fullerene C70 matrix

We report the electronic excitation induced controlled tuning of the surface plasmon resonance (SPR) wavelength of Ag nanoparticles (NPs) in fullerene C70 matrix. The transformation of fullerene C70 into amorphous carbon (a:C) under ion irradiation is used to tune the SPR wavelength of C70–Ag nanocomposite thin films. A 100 nm blue shift was recorded for irradiation at a fluence of 3 × 1013 ions cm−2 by 120 MeV Ag ions. A growth of Ag NPs from 7.0 ± 0.8 to 11.0 ± 0.4 nm with increasing fluence was observed by transmission electron microscopy and it is explained in the framework of thermal spike model. The transformation of fullerene C70 into amorphous carbon with ion irradiation was confirmed by Raman spectroscopy. This work demonstrates the possibility to locally excite the SPR at a desired wavelength and therefore, acquiring multiple SPR bands at a single substrate which could be useful in developing more efficient optical sensors.

Synthesis and characterizations of silver-fullerene C70 nanocomposite

Films of C70 fullerene containing silver nanoparticles were synthesized by thermal codeposition. Optical absorption studies revealed that surface plasmon resonance of Ag nanoparticles occurs at unusually large wavelength, which showed a regular redshift from 521 to 581 nm with increase in metal content from 4.5% to 28%. It is explained by the Maxwell–Garnett theory considering the absorbing nature of fullerene matrix. Rutherford backscattering and transmission electron microscopy were performed to quantify metal content and the particle size, respectively. A better detection of low intensity vibrational modes of C70 in Raman scattering is observed due to surface enhanced Raman scattering.