Biopolymer Thin Films Synthesized by Advanced Pulsed Laser Techniques

This chapter provides an overview of recent advances in the field of laser-based synthesis of biopolymer thin films for biomedical applications. The introduction addresses the importance of biopolymer thin films with respect to several applications like tissue engineering, cell instructive environments, and drug delivery systems. The next section is devoted to applications of the fabrication of organic and hybrid organic–inorganic coatings. Matrix-assisted pulsed laser evaporation (MAPLE) and Combinatorial-MAPLE are introduced and compared with other conventional methods of thin films assembling on solid substrates. Advantages and limitations of the methods are pointed out by focusing on the delicate transfer of bio-macromolecules, preservation of properties and on the prospect of combinatorial libraries’ synthesis in a single-step process. The following section provides a brief description of fundamental processes involved in the molecular transfer of delicate materials by MAPLE. Then, the chapter focuses on the laser synthesis of two polysaccharide thin films, namely Dextran doped with iron oxide nanoparticles and Levan, followed by an overview on the MAPLE synthesis of other biopolymers. The chapter ends with summary and perspectives of this fast-expanding research field, and a rich bibliographic database

INVESTIGATIONS OF THIN TITANIUM OXIDE FILMS GROWN BY REACTIVE PULSED LASER DEPOSITION

Titanium oxide thin films were deposited on Si monocrystalline substrate using the pulsed laser ablation technique in a reactive oxygen atmosphere. The films were obtained starting from Ti and TiO2 targets which were ablated using a KrF* excimer laser (λ = 248 nm). During the deposition, the Si substrates were heated at 300 °C under various high purity oxygen atmosphere of 1.0, 0.5 and 0.1 mbar. Grazing incidence X-ray diffraction investigations revealed the presence of a nanostructured film consisting of a mixture of several titanium oxides, with crystalline grains size of few nm to 10 nm. Only the film deposited from the Ti target at a pressure of 1.0 mbar exhibited crystalline grains of 30-40 nm. Thin films surface morphology and topography, studied using atomic force and scanning electron microscopy, revealed a relatively smooth surface with the presence of some submicron droplets, typical for laser ablation technique. Films deposited at 0.5 mbar pressure from both targets were significantly rougher than the other deposited film

Nanoparticle generation by double pulse laser ablation

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Investigation of plumes produced by material ablation with two time-delayed femtosecond laser pulses

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Local thermodynamic equilibrium in a laser-induced plasma evidenced by blackbody radiation

International audienceWe show that the plasma produced by laser ablation of solid materials in specific conditions has an emission spectrum that is characterized by the saturation of the most intense spectral lines at the blackbody radiance. The blackbody temperature equals the excitation temperature of atoms and ions, proving directly and unambiguously a plasma in local thermodynamic equilibrium. The present investigations take benefit from the very rich and intense emission spectrum generated by ablation of a nickel-chromium-molybdenum alloy. This alternative and direct proof of the plasma equilibrium state reopens the perspectives of quantitative material analyses via calibration-free laser-induced breakdown spectroscopy. Moreover, the unique properties of this laser-produced plasma promote its use as radiation standard for intensity calibration of spectroscopic instruments

Comparative investigation of laser ablation plumes in air and argon by analysis of spectral line shapes: Insights on calibration-free laser-induced breakdown spectroscopy

International audienceWe investigate the characteristic features of plume expansion in air and argon resulting from ultraviolet laser ablation of solid matter in conditions typically applied in material analysis via laser-induced breakdown spectroscopy (LIES). Barite crown glass is chosen as a target material for the characteristic emission spectrum suitable for plasma diagnostics. The space-integrated plasma emission spectrum recorded with an echelle spectrometer coupled to a gated detector is compared to the computed spectral radiance of a nonuniform plasma in local thermodynamic equilibrium. In particular, resonance lines of neutral sodium atoms and barium ions are observed to probe gradients of temperature and density within the plume. It is shown that laser ablation in argon leads to an almost uniform plasma whereas gradients of temperature and density are evidenced in ambient air. The discrepancy is attributed to the different physical properties of both gases leading to a stronger vapor-gas energy exchange in the case of air. However, strong gradients occur only in a thin peripheral zone, close to the vaporgas contact front. The larger plasma core appears almost uniform. The peripheral zone of low temperature mostly contributes to the plasma emission spectrum by absorption and material analysis via calibration-free LIBS in air may ignore the nonuniform character of the plasma if only transitions of small optical thickness are considered. (C) 2014 Elsevier ay. All rights reserved

Analysis of Multi-elemental Thin Films via Calibration-Free Laser-Induced Breakdown Spectroscopy

International audienceElemental analyses of thin films with complex composition are challenging as the standard analytical techniques based on measurement calibration are difficult to apply. We show that calibration-free laser-induced breakdown spectroscopy (LIBS) presents a powerful solution , enabling quantitative analyses of multiele-mental thin films with analytical performances better than those obtained with other techniques. The demonstration is given for a nickel-chromium-molybdenum alloy film of 150 nm thickness that was produced by pulsed laser de-position. The LIBS spectra were recorded in experimental conditions that enable simple and accurate modeling of plasma emission. Thus, a calibration-free approach based on the calculation of the spectral radiance of a uniform plasma in local thermodynamic equilibrium was applied to deduce the elemental composition. Supported by analyses via Rutherford backscat-tering spectrometry and energy-dispersive X-ray spectroscopy, the LIBS measurements evidence nonstoichiometric mass transfer of the alloy during the thin film deposition process. This technique could be used even for thinner films provided that the film-composing elements are not present in the substrate