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

Structural and chemical investigation for the laser ablated Poly (Phenylene Sulfide) (PPS) films upon 100 keV H+ implantation is reported here for the first time. PPS thin films were fabricated by laser ablation with a Nd: YAG laser as a source of visible photons (532 nm). The laser ablated thin films showed strong polymer breakdown resistance upto a total fluence of 1015 ions/cm2. Bulk properties of the as-deposited and the implanted samples were investigated using FTIR and UV-VIS spectroscopy. Drastic reduction in the intensity of all characteristic vibrational frequencies in the FTIR spectrum at higher doses revealed the transformation of the polymer to a conjugated carbonaceous material. UV-VIS studies showed a positive shift in the absorption edge value for the as-deposited polymer towards higher wavelengths and destruction of phenyl ring due to the H+ bombardment. X-ray Photoelectron Spectroscopic (XPS) investigation indicated the sulfur depletion as a prominent phenomenon whereas carbon content remained almost the same. XPS studies of the implanted sample also revealed a minor change in the oxidized species of carbon and more prominent change in oxidized species of sulfur which were present in the as-deposited samples. A peak at 283.4 eV attributed to 'surface reconstruction' in the XPS analysis for the as-deposited PPS film disappeared after proton implantation. © 1998 Elsevier Science B.V.

GENERAL

Department Of Chemistry

Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms

Physical and chemical implications of 100 keV H+ implantation of laser ablated PPS thin films

Thin films of poly(p-phenylene sulfide) [PPS], were deposited by pulsed laser deposition with a doubled Nd: YAG laser (λ = 532 nm) on Si (100) and quartz substrates at temperatures above and below the glass transition temperature (T g ) of the polymer. SEM micrographs of the films showed a decrease of particulate size with increasing substrate temperature. An absorption band edge at 3.4 eV in the UV-VIS spectrum of the deposited film indicated that they were polymeric as well as insulating. FTIR spectra of films deposited at various substrate temperatures mimicked all characteristic vibrational frequencies observed in pristine bulk samples. Low-angle X-ray diffraction patterns and FTIR spectral analysis of the deposited PPS films confirmed that the crystallinity was enhanced when the substrate temperature during deposition exceeded T g . X-ray photoelectron spectroscopic (XPS) investigations of the C 1s spectra of the as-deposited film on Si (100) revealed oxidation of the surface with the formation of sulfone, sulfoxide, C-O and C=O. Ar + ion sputtering with a 4 keV beam at 1 μA beam current removed ∼ 2 nm of the surface film and completely eliminated the sulfone peak from the XPS spectra, retaining a very negligible oxide component. © 1998 Elsevier Science B.V. All rights reserved.

Applied Surface Science

Deposition and characterization of laser ablated poly(p-phenylene sulfide) thin films

The interfacial interactions between in situ thermally evaporated Au and polycarbonate (PC) film, a technologically important polymeric material, is studied by x-ray photoelectron spectroscopy (XPS). Angle resolved XPS is performed to investigate the Au reactivity if any, in forming the metal-polymer interface. The spectral evidence from the above suggests that the metal interacts predominantly with the carbonyl carbon of the monomeric unit with only minor interactions with the phenyl carbons without any complex formation. In contrast to previous findings of Au to be inert at the M-polymer interfaces, this work emphasizes the salient charge transfer type interactions of Au (as electron injector) at the C=O as the primary interaction site, distributing a net charge density to C=O with the formation of a Au-CO π-back bond. The conclusions are supported by the observed new C 1s feature at 282.6 eV and the O 1s and Au 4f7/2 XPS spectral changes. The growth mode of Au on PC was proceeded by the metal monolayer deposition with cluster growth on the already weakly bonded Au onto the C=O carbon of the polymeric backbone. © 1998 American Institute of Physics.

Fulltext

Journal of Applied Physics

Evidence for metal interaction in gold metallized polycarbonate films: An x-ray photoelectron spectroscopy investigation

Binary and ternary gas mixtures of H2O, CO2, NH3 and CH4 were condensed at 10−6 mbar onto a KBr cold finger at 10 K. The composition of the few micrometre thick layers has been determined by infrared spectroscopy in transmission mode. The condensation dynamics together with the predominant matrix effect studied as a function of gas composition, deposition time and ice layer thickness reveal a lower condensation probability for the more volatile components CH4 and CO2 in mixtures of H2ONH3CH4 and H2ONH3CO2, respectively, with varying composition. The phenomena explain representative cases of early condensation and accretion processes of icy layers on interstellar grains.

World University root node

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy

Condensation dynamics of cometary ice analogs in view of primordial accretion of volatiles on grain surfaces: A study through infrared spectroscopy

Organic heteropolymers that we call here ice tholin II have been produced by plasma discharge irradiation of water/ methanol/carbon dioxide/ethane cocondensed ices in a rough simulation of cometary chemistry. The radiation yield of these organic heteropolymers is approximately 10-26 g/eV. Intermediate products including polyalcohols, ethers, esters, carboxylic acids, and hydrocarbons are also produced. No detectable polyoxymethylene is generated in this experiment. Preliminary chemical analyses of ice tholin using spectroscopic and chromatographic techniques lead to the conclusion that ice tholin contains a significant degree of polyalcohol functionality, as well as aliphatic hydrocarbon groups and carbonyl-containing groups such as ketones and esters. Ice tholin II shows some spectroscopic similarities to 1 : 6 ethane/water ice tholin (ice tholin I), but overall the two are chemically distinct. Ice tholins may be difficult to detect in comets due to their low volatility, but nevertheless may have been delivered to the early Earth by cometary impacts and interplanetary dust particles. These polyalcohol-containing molecules would then have been available to participate in prebiotic chemistry, such as the synthesis of acyclic nucleic acid analogues which have been suggested as the first biomacromolecules. © 1996 Academic Press, Inc.

Icarus

Production and chemical analysis of cometary ice tholins

The single comparator method for achieving multielement analysis of airborne particulates is adopted after being modified with the incorporation of infinite resonance integrals and the ratio of thermal to epithermal neutron flux at the activation site. Dust samples from ferro alloy and lime kiln emission sources upon analysis indicated the major elements to be Fe, Cr, Cu, Zn, Ba, Sr, Rb, Ag, Hg, Th, amongst others. Inorganic soluble sulphates, nitrates and ammonium and the organics extractable in benzene were estimated. Most of the aerosol mass seems to comprise organic carbon.The single comparator method for achieving multielement analysis of airborne particulates is adopted after being modified with the incorporation of infinite resonance integrals and the ratio of thermal to epithermal neutron flux at the activation site. Dust samples from ferro alloy and lime kiln emission sources upon analysis indicated the major elements to be Fe, Cr, Cu, Zn, Ba, Sr, Rb, Ag, Hg, Th, amongst others. Inorganic soluble sulphates, nitrates and ammonium and the organics extractable in benzene were estimated. Most of the aerosol mass seems to comprise organic carbon.

Applied Radiation and Isotopes

Use of the single comparator method in aerosol composition analysis by delayed photon spectroscopy

The formation of complex organic compounds in space by high energy and radiation chemical reactions was simulated in the laboratory using solid methane as a model substance for primordial organic solids. The reactions were induced by energetic carbon atoms formed via the 12C(3He, 4He) 11C nuclear process (high energy chemistry) and the accompanying radiolysis by the 3He-cyclotron particles (radiation chemistry). Gaschromatographic analysis of the target showed the formation of many new carbon compounds ranging from acetylene and ethylene to molecules containing up to eight carbon atoms including probably cyclic and aromatic compounds. Formation of this kind of products can only be explained by insertion of hot carbon atoms into CH bonds and bridging reactions between CH4 molecules. The mechanisms can be responsible for the formation of organic polymers, refractories and crusts on objects in space such as interplanetary dust grains, comets and asteroids hit by particle radiation (e.g. solar wind). It may constitute a general pathway for the build-up of complex molecules in prebiotic chemical evolution. © 1989.

Advances in Space Research

Modification of simple organic solids in space: Energetic carbon interactions with solid methane

An attempt js made to study the behaviour of recoil128I atoms in neutron irradiated I2O5 at ambient temperature. The initial retention is found to be 44±2%. However, a substantial increase /57±2%/ in the value is observed upon heating the sample at 473 K for 1 h prior to irradiation. A kinetic study of post-recoil thermal annealing of neutron irradiated material is also presented. Effect of pre-heat treatment results in a decrease of rate constants and saturation retention values at respective temperatures while the Eact for the overall process remains almost unaltered. © 1986 Akadémiai Kiadó.

Department of Mathematics

Journal of Radioanalytical and Nuclear Chemistry Letters

Recoil128I atoms in iodine pentoxide under /n, γ/ process

The thermal annealing of the damage caused by /n,γ/ reaction has been investigated for anhydrous copper iodate in crystalline phase. Solvent extraction and fractional precipitation methods were employed to distinguish the recoil species containing recoil iodine-128 atoms. The role of reaction intermediates have been discussed. © 1985 Akadémiai Kiadó.

Recoil iodine-128 in anhydrous copper iodate

The effect of pre-heat treatment on the (n, γ) reaction of LiIO3 and Cu(IO3)2 targets is an increase in the initial retention in Cu(IO3)2 and decrease in LiIO3. This has been ascribed to the competitive participation of oxidizing and reducing inherent crystal defects. Annealing kinetic studies reveal two apparent first-order processes for both the pre-heated and untreated iodates. An exciton mechanism is proposed to explain the higher plateau values and annealing kinetics in pre-heated Cu(IO3)2 and LiIO3.