Les matériaux lorsqu'ils sont rendus nanométriques montrent des propriétés optiques qui peuvent différer fortement des celles des matériaux à l'état massif. C'est l'étude de ces modifications des propriétés qui a motivé les travaux qui sont présentés dans ce document. Dans une première partie je décris les propriétés de luminescence particulière des nanocristaux de silicium en mettant en évidence un décalage de la luminescence vers le bleu lorsque la taille des nanocristaux diminue et je montre qu'il s'agit d'un phénomène de confinement quantique. Dans le même temps l'importance de la passivation de surface est démontrée. Ces résultats sont ensuite appliqués à la compréhension d'une signature spectrale détectée dans les nuages de poussières inter- et circumstellaires et la fabrication de microcavités luminescente à base de nanocristaux de silicium. Dans une deuxième partie je présente les résultats des études que je mène depuis mon arrivée au sein du LPCML sur les propriétés de luminescence de nanoparticules d'oxydes dopés terres rares. Nous avons ainsi pu montrer que le confinement quantique peut aussi être mis en évidence pour ces matériaux fortement ionique même si l'effet est bien moindre que pour les semi conducteurs. De même on montre que la surface joue un rôle essentiel soit en donnant lieu à de nouvelles émissions soit en créant des défauts tueurs de la luminescence. La taille des nanoparticules modifie aussi la densité d'états de phonons ce qui modifie les populations dans les différents niveaux d'énergie des ions dopants et donc les rapports d'intensité entre les transitions optiques. Enfin le comportement sous excitation à haute énergie (UV dur et X) montre que les rendements sont fortement affectés pour les petites tailles traduisant l‘impossibilité pour les toutes petites particules de supporter une trop grande densité d'excitation. La dernière partie présente les deux axes que je souhaite développer dans les années à venir à savoir la microscopie confocale jusque dans l'UV dur et l'ablation laser en solution pour la synthèse de nanomatériaux originaux.

This paper reports the surface morphologies and ablation of crystalline silicon wafers irradiated by infra-red 775 nm Ti:sapphire femtosecond laser. The effects of energy fluences (below and above single-pulse modification) with different number of pulses were studied. New morphological features such as pits, cracks formation, Laser-Induced Periodic Surface Structures (LIPSS) and ablation were observed. The investigation indicated that there are two distinct mechanisms under femtosecond laser irradiation: low fluence regime with different morphological features and high fluence regime with high material removal and without complex morphological features. / Singapore-MIT Alliance (SMA)

Laser Induced Breakdown Spectroscopy LIBS is a fast non-contact technique for the analysis of the elemental composition using spectral information of the emission from a laser-induced plasma. For the LIBS studies in this thesis the focus has been in using very low energy, microjoule pulses in order to give high spatial resolution and minimize the laser system requirements. This is a regime that we refer to as microLIBS. Under such conditions it is important to maximize the signal detected to give the lowest limit of detection LOD possible. One technique to improve the signal to noise ratios is by coupling LIBS with Laser Induced Fluorescence. This is a technique where the _rst pulse creates a vapor plume and the second pulse tuned to a resonant absorption line of the species of interest re-excites the plume. We term this technique as Laser ablation Laser Induced Fluorescence LA-LIF. We have been investigating the performance of LA-LIF at low pulse energies (_ 1 mJ for both pulses) for the detection of elemental contaminants in water. This technique allows reasonable performance compared to high energy singlepulse LIBS, but at a much reduced total energy expenditure. This allows LODs in the parts per billion range ppb range which typically cannot be obtained with low energy single pulse probing of the systems. This approach or exceeds the sensitivities which can be obtained with many shots using much larger energy systems. In this thesis we investigated the performance of LIBS at low pulse energies for the detection of Pb as a contaminant in water. An LOD of 70 ppb was obtained for an accumulation of 100 shots with the ablation laser pulse energy of 250 _J and an excitation laser pulse energy of 8 _J. A systematic study of the detector conditions was made for the system for the detection of Pb. Scaling laws for the LOD in terms of the pump and probe energies were measured and also the e_ect of detector gain, the gate delay and the gate width were studied. In this thesis LIBS and LA-LIF were also used to analyze ultralow volumes of analyte in liquids in microuidic geometries. LIBS was applied for the detection of Na in liquid droplets in a microuidic system. The detection of Na as low as 360 femtograms was demonstrated for 100 shots integrated in this system. An LOD of 7 ppm for Pb for 100 shot accumulation was demonstrated using the LA-LIF technique on an 18 _m diameter microdroplet. To study the laser interaction with the water targets the MEDUSA one dimensional hydrocode was used. The propagation of the shockwave and plume dynamics were studied using this modeling code. The expansion of the plume was studied and compared to experimentally measured values and to physical models for blast wave expansion and stagnation. Two preconcentration techniques were also studied, one of which used a wood-chip as a substrate to absorb the analyte liquid and wick the salt on to the surface for analysis and the other used an electroplating technique to plate the analyte metal as a thin _lm on a substrate metal used as a cathode. The electroplating method for preconcentration was also studied using a microchip laser and a LOD of 6.4 ppb for Pb in water was obtained for an accumalation of 200,000 shots. / Photonics and Plasmas

This dissertation presents the design, fabrication, and testing of a microfluidic system to be used for whole-cell analysis. The study of cellular function and structure is essential for disease diagnosis and treatment. Microsystems developed to perform these bioanalyses add benefits such as requiring smaller samples and reagents, testing multiple samples in parallel, and supporting point-of-care testing, all of which increases throughput and reduces cost-per-analysis. Traditional methods for designing a microsystem use standard materials and techniques such as silicon, glass, photolithography, and wet and dry etching. This research is focused on utilizing materials and techniques that require less infrastructure, allow for a faster design-to-prototype cycle, and can integrate electrical and fluidic functionality to address a variety of possible applications. The microfluidic system presented in this thesis is comprised of multiple layers of Kapton, a polyimide available from DuPont. Kapton provides a biocompatible substrate that is flexible while maintaining structural stability and can be used in high temperature and other harsh environments. Microchannels with widths of 400 m and thru-hole fluidic vias less than 5 m in diameter are laser ablated through the flexible polyimide sheets using excimer and CO2 lasers. Electrical traces and contact pads are defined on the substrate by vapor deposition through reusable microstencils rather than with photolithography. The patterned layers are bonded using heat staking and then packaged with the addition of wires and a fluidic interface. Validation of the system for whole-cell analysis was first performed with impedance spectroscopy measurements collected on air, DI water, phosphate buffered saline, clusters of human cancer cells, and human cancer tissue samples. This was followed by testing the ability to use the device to control the movement and position of 10 m diameter microbeads and dissociated cells. As a whole, this research demonstrates the realization of a microfluidic system for whole-cell analysis based on non-standard fabrication materials and techniques.

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This thesis is about the phase transformation, shape, size distribution and coalescence of TiO2 (part I) and ZrO2 (part II) nanopartilces produced by Nd-YAG laser ablation on metal targets under oxygen background gas, and characterized by analytical electron microscopy. The optimum laser ablation condition that satisfactory and routinely yield high-pressure phases of TiO2 (i.e. £\-PbO2-type and fluorite-related structures) and ZrO2 with high residual stress were reported. Part I-1 focuses on physical coagulation, by Van der Waals force, of the TiO2 condensates at temperatures up to about 1000 K as a result of post-condensation radiant heating. In part I-2, imperfect oriented attachment of nanoparticles over specific surfaces is rationalized to cause accretion and defects for the rutile condensates. Brownian motion may proceed above a critical temperature for anchorage release at the interface of imperfect attached nanoparticles until an epitaxial relationship is reached. Part I-3 deals with further the Brownian-type rotation of the imperfectly impinged £\-PbO2-type TiO2 and rutile nanocondensates until interfacial-energy cusp was reached. In part I-4 laser ablation condensation synthesis of dense TiO2 polymorphs and their phase transformations were documented. Part II-1 is about dense tetragonal (t)-ZrO2 and cubic (c-) nanocondensates which were synthesized under very rapid heating and cooling by pulsed Nd-YAG laser ablation with oxygen background gas. The t-ZrO2 nanoparticles were found to form deformation twins/faults and followed unique transformation path upon local electron dosage. Electron diffraction indicated that the dense c- and t- phase with specific size and residual stress were allowed to relax and/or kinetically phase change into lower-energy state as constrained by the intersections of the internal energy vs. cell volume plots calculated for the two polymorphs (Part II-2).

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Laser ablation inductively coupled plasma mass spectrometry¡]LA- ICP-MS¡^has been applied to the determination of V¡ACr¡ACu¡AZn¡ACd¡ATl and Pb in soil and sediment samples. The powder were pressed into a pellet for LA-ICP-MS analysis,Triron X-100 was used as the modifier to enhance the ion signals.The influences of instrument operating conditions ¡]laser ablation and ICP-MS¡^and pellet preparation on the ion signals were reported. For Cr determination, the ICP-MS was operated under the DRC mode which alleviated the mass overlap interference significantly. Standard addition method and isotope dilution method were used for the quantitation work. The powder sample was spiked with suitable amount of element standard and/or enriched isotope, well mixed, dried, well mixed and then pressed into a pellet for LA-ICP-MS analysis.This method has been applied to the determination of V¡ACr¡ACu¡AZn¡ACd¡ATl and Pb in NIST SRM 2709 San Joaquin soil reference materials and NIST SRM 2711 Montana soil reference materials. The analysis results were agreed with the certified values. The precision between sample replicates was better than 10% with LA-ICP-MS method. Detection limits estimated from standard addition curves were about 260-620,3-5,0.3-1 and 9-20 ng g-1 for Cr¡ACu¡AZn¡ACd¡ATl and Pb, respectively, in different samples.

Introduction: Most literatures researched radiofrequency ablation (RFA) for early hepatocellular carcinoma (HCC) defined the early tumor size as 3cm or less. However, detection rate of HCC smaller than 2 cm became increasing since high risk patients had received regular screening and the imaging techniques has been much improved. Whether RFA or percutaneous ethanol injection (PEI) is better for a patient with such a small HCC is still controversial. Methods: We retrospectively obtained patients with single HCC 2 cm in diameter or smaller from the computerized medical records database in a local teaching hospital located at southern Taiwan, diagnosed during January 1, 2002 to April 30, 2008. Those patients received RFA (RFA group) or PEI (PEI group) as the first-line nonsurgical treatments were enrolled for further analysis. We compared baseline characteristics of RFA and PEI groups, including gender, age, possible risk factors of recurrence, and prognostic factors. Then, we analyzed recurrent rate, time to recurrence, survival rate, complication rate, mean cost of each treatment, and hospital stay of RFA and PEI groups. Results: There were 32 patients qualified for the study design, including 22 in PEI group¡G13 males and 9 females with mean age was 63.73 years; and 10 in RFA group¡G7 males and 3 females with mea age was 58.30 years¡CNo statistically significant differences between RFA and PEI groups were observed with respect to baseline characteristics. Nevertheless, there was significant difference between these two groups with respect to mean hospital stay (p=0.007) and mean cost (p¡Õ0.001): mean cost of PEI was NTD $16934.7; mean cost of RFA was NTD $51677.6, the difference was NTD $34732.9. There was no difference respect to complication rate, recurrent rate, time to recurrence and overall survival rate between RFA and PEI groups. Conclusion: For patients with single HCC 2 cm in diameter or smaller (i.e. very early HCC), we concluded that: if under similar basic background, the cost of RFA was much higher than that of PEI, but no difference in the complication rate, recurrent rate, time to recurrence and overall survival rate between these two treatment.