The properties of a Rydberg atom immersed in an ultracold environment were investigated. Two scenarios were considered, one of which involves the neighbouring ground-state atoms arranged in a spatially structured configuration, while the other involves them distributed randomly in space. To calculate the influence of the multiple ground-state atoms on the Rydberg atom, Fermi-pseudopotential was used, which simplified greatly the numerical effort. In many cases, the few-body interaction can be written down analytically which reveals the symmetry properties of the system. In the structured case, we report the first prediction of the formation of ``Rydberg Borromean trimers''. The few-body interactions and the dynamics of the linear A-B-A trimer, where A is the ground-state atom and B is the Rydberg atom, were investigated in the framework of normal mode analysis. This exotic ultralong-range triatomic bound state exists despite that the Rydberg-ground-state interaction is repulsive. Their lifetimes were estimated using both quantum scattering calculations and semi-classical approximations which are found to be typically sub-microseconds. In the disordered case, the Rydberg-excitation spectra of a frozen-gas were simulated, where the nuclear degrees of freedom can be ignored. The systematic change of the spectral shape with respect to the density of the gas and the excitation of the Rydberg atom were found and studied. Some parts of the spectral shape can be described by simple scaling laws with exponents given by the basic properties of the atomic species such as the polarizability and the zero-energy electron-atom scattering length.

We have developed an analytical technique for single molecule force spectroscopy (SMFS) data that avoids filtering prior to analysis and performs pattern recognition to identify distinct SMFS events. The technique characterizes the signal similarity between all curves in a data set and generates a hierarchical clustering tree, from which clusters can be identified, aligned, and examined to identify key patterns. This procedure was applied to alpha-lactalbumin (aLA) on polystyrene substrates with flat and nanoscale curvature, and bacteriorhodopsin (bR) adsorbed on mica substrates. Cluster patterns identified for the aLA data sets were associated with different higher-order protein-protein interactions. Changes in the frequency of the patterns showed an increase in the monomeric signal from flat to curved substrates. Analysis of the bR data showed a high level of multiple protein SMFS events and allowed for the identification of a set of characteristic three-peak unfolding events.

Dans ce manuscrit, nous présentons d'abord le bloc de construction moléculaire ultime pour les dispositifs de spintronique, les aimants à molécule unique (Chapitre 2). En particulier, nous nous concentrerons sur une molecule de TbPc2 et différentes approches pour sonder son aimantation à l'aide de détecteurs a base de nanotubes de carbone et de mécanismes de couplage différents (flux magnétique, couplage électronique et mécanique). Dans le but de construire un detecteur de torque supramoléculaire capable de sonder le moment magnétique d'un aimant moléculaire, nous allons décrire dans le chapitre 3 un candidat très prometteur, un système nanoélectromécanique (NEMS) à base d'un nanotube de carbone. Nous décrirons d'abord les avantages de NEMS à base de carbone par rapport aux résonateurs classiques à base de silicium. Par la suite, nous présenterons l'état de l'art des NEMS à base de nanotubes de carbone, en nous focalisant en particulier sur deux différents mouvements nanomécaniques, un mode de flexion transverse et un mode de compression longitudinal. Dans le chapitre 4, nous présenterons la mise en oeuvre expérimentale d'un detecteur de torque supramoléculaire basé sur NEMS à nanotubes de carbone et des aimants à molécule unique. Nous décrirons d'abord le processus de fabrication ultra propre et les étapes de la caractérisation d'un NEMS à nanotubes de carbone à températures ambiante et cryogénique. Nous allons ensuite démontrer un procédé de greffage d'une molécule aimants de TbPc2 sur un tel NEMS à nanotube de carbone, qui conserve à la fois les propriétés magnétiques de la molécule et les propriétés mécaniques du résonateur. Dans le chapitre 5, nous allons ensuite procéder à une étude systématique du mode de flexion transverse dans un NEMS à nanotube de carbone. Nous montrerons, que la dissipation de ce mode de vibration induit par l'effet tunnel d'électron unique à travers le nanotube de carbone (considére comme point quantique) dépend essentiellement de l'environnement électronique du nanotube, c'est à dire de la capacité, du couplage entre le nanotube de carbone et les electrodes métalliqes, du courant et de la température. Les résultats indiquent que l'on pourrait atteindre des facteurs de qualité de 10^6 ou plus en choisissant un diélectrique de grille appropriées et/ou en améliorant le couplage entre le nanotube de carbone et les electrodes, ce qui permettrait notamment d'augmenter la sensibilité du NEMS nanotubes de carbone par rapport à un torque magnétique générer par le retournement d'un aimant moléculaire. Dans le chapitre 6, nous démontrons la présence d'un mode de vibration longitudinal quantique dans un NEMS à base de nanotube de carbon fonctionnalisé avec des aimants moléculaires de TbPc2. Nous allons en particulier montrer que la nature quantique des deux systèmes, se traduit par un fort couplage entre le mode de compression longitudinal et l'aimantation d'un aimant moléculaire TbPc2 unique greffé sur la parois du nanotube de carbone. Ce fort couplage permet par la suite de détecter les états de spin nucléaire dans la molécule de TbPc2. Enfin, nous présenterons dans la conclusion de ce manuscrit quelques perspectives pour la détection et la manipulation (coherente) d'un seul spin (nucléaire) à l'aide d'un système mécanique quantique. / In this manuscript, we will first present the ultimate molecular building block for spintronic devices, so called single-molecule magnets (Chapter 2). In particular we will focus on a TbPc2 complex and various approaches of probing its magnetization using carbon nanotube detectors and different coupling mechanisms (magnetic flux, electronic and mechanical coupling). With the aim of building a supramolecular torque magnetometer capable of probing the magnetic moment of a molecular magnet, we will describe in Chapter 3 a promising candidate, a carbon nanotube nanoelectromechanical system (NEMS). We will first describe the advantages of carbon based NEMS over classical Si based resonators. Subsequently we will present the state of art of carbon nanotube NEMS and focus in particular on two different nanomechanical motions, a transverse bending mode and a longitudinal stretching mode. In Chapter 4, we present the experimental implementation of a supramolecular torque magnetometer based on carbon nanotube NEMS and single molecule magnets. We first describe the ultraclean bottom-up fabrication process and the extensive characterisation steps of carbon nanotube NEMS at room and cryogenic temperatures. We will finally demonstrate a method of grafting a TbPc2 single molecules magnet on such a carbon nanotube NEMS, that conserves both the magnetic properties of the molecule and the mechanical properties of the resonator. In Chapter 5, we will then perform a systematic study of the transverse bending mode vibration in a carbon nanotube NEMS. We demonstrate for instance, that the dissipation of a carbon nanotube's bending mode vibration to single electron tunneling through the carbon nanotube NEMS-quantum dot critically depends on the dot's electronic environment, i.e. the capacitance, the tunnel coupling to the metal leads, the current and temperature. The findings suggest that one could achieve quality factors of 10^6 or higher by choosing appropriate gate dielectrics and/or by improving the tunnel coupling to the leads, which would notably increase the sensitivity of the carbon nanotube NEMS with respect to a magnetic torque generate by a rotating molecular magnet. In Chapter 6, we demonstrate the presence of a quantized longitudinal stretching mode vibration in a carbon nanotube NEMS functionnalized with TbPc2 single molecule quantum magnets. We will in particular demonstrate that the quantum mechanical nature of both systems, results in a strong coupling between the longitudinal stretching mode and the magnetization of an individual TbPc2 single molecule magnet grafted to the carbon nanotube's sidewall. The strong coupling in fact enables the detection of the nuclear spin states in the TbPc2 molecule. Finally, we present in the conclusion of this manuscript some future prospects for the detection and (coherent) manipulation of a single (nuclear) spin using a mechanical quantum system.

Neste trabalho foi sintetizado o corante (E)-2-[3-[4-(difenilamina)-fenil]-1-(p-tolil)- alilideno]-malononitrila (DFTAM), a partir da reação de condensação entre 4- (difenilamino)-benzaldeído e 2- [1- (4- metilfenil)-etilideno]-malononitrila, com catálise básica de piperidina. O produto obtido foi purificado por cromatografia líquida de alta eficiência (HPLC) e caracterizado pelas técnicas de espectrometria de massas, ressonância magnética nuclear de 13C e 1H e espectroscopia no infravermelho com transformada de Fourier. Para estudar suas propriedades fotofísicas, espectros de absorção e emissão de fluorescência, decaimento de fluorescência e espectro de absorção de transientes foram feitos em diferentes solventes, variando-se a polaridade e viscosidade do meio. Duas bandas de absorção foram observadas, uma em 303 nm e outra em cerca de 490 nm, a qual apresentou deslocamento batocrômico com o aumento da polaridade do solvente. Para essa região de excitação a banda de emissão variou entre 517 e 630 nm, com o aumento da polaridade do meio. Os decaimentos de fluorescência mostraram duas componentes, uma na ordem de picossegundos e a outra de nanossegundos. Os experimentos de absorção de transientes apresentaram três espécies, uma mais longa (maior que 10 ms) e duas outras de cerca 2 e 22 μs. Surfactantes catiônicos, não iônico, e aniônico também foram usados para produzir micelas e fazer os experimentos já citados. Pôde-se observar que o corante interagiu com as micelas, melhorando sua fluorescência e aumentando o tempo de vida do estado singleto. Por fim, acompanhou-se in situ, através da técnica de microscopia TIRF, a reação de formação de DFTAM a nível single molecule com catalise básica de nanopartículas de MgO e lamínulas de vidro funcionalizadas com piperazina. Através da intermitência de fluorescência dos filmes feitos de ambas as amostras, observou-se a formação de moléculas do corante através de ciclos de catálise da piperazina. / In this project the synthesis of (E) -2- [3- [4- (diphenylamine) phenyl] -1- (p-tolyl) - allylidene] -malononitrile (DFTAM) dye, from the condensation reaction between 4- (diphenylamino) benzaldehyde and 2- [1- (4-methylphenyl) ethylidene]-malononitrile using piperidine basic catalysis has been achieved. The dye was purified by high-performance liquid chromatography (HPLC) and characterized by mass spectrometry, nuclear magnetic resonance 13C and 1H and Fourier Transform infrared spectroscopy techniques. To study DFTAM photophysical properties, absorption and fluorescence emission spectra, fluorescence decay and transient absorption spectrum were recorded in solvents with different polarity and viscosity. Two absorption bands of DFTAM were observed, the first one at 303 nm was solvent independent while the second one at about 490 nm, had bathochromic shift with increasing polarity of the medium. In the visible region of excitation the maximum of the dye emission band observed varied between 517 and 630 nm, upon increasing solvent polarity. Fluorescence decays showed two distinct components, a fast one in picosecond time scale and a slow one in nanoseconds. Transient absorption experiments indicated the presence of three species with different lifetimes, one longer than 10 ms and the other two with lifetimes about 2 and 22 μs. Cationic, nonionic, anionic surfactants were also used to produce micelles for easy solubilization of DFTAM. It was observed that the dye interacted with the micelles, improving its fluorescence yield and lifetime. Finally, the DFTAM formation reaction was monitored in situby TIRF wide field microscopy technique at single molecule level. The basic catalysis was tested for MgO nanoparticles and glass surface functionalized with bound piperazine. Through the fluorescence intermittency time trace obtained from TIRF movies, the discrete formation of dye molecules was only observed in the case of piperazine catalytic cycles.

Click chemistry is a molecular synthesis strategy based on reliable, highly selective reactions with thermodynamic driving forces typically in excess of 20 kcal mol-1. The 1,3-dipolar cycloaddition of azides and alkynes developed by Rolf Huisgen saw dramatic rate acceleration using Cu(I) as a catalyst in 2002 reports by Barry Sharpless and Morten Meldal enabling its click chemistry eligibility. Since these seminal reports, the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) has become the quintessential click reaction finding diverse utility. The popularity of the CuAAC has naturally led to interest in new catalyst systems with improved efficiency, robustness, and reusability with particular focus on nanomaterial catalysts, a common trend across the field of catalysis. The high surface area of nanomaterials lends to their efficacy as colloidal and heterogeneous nanocatalysts, but the latter boasts the added benefit of easy separation and recyclability. With any heterogeneous catalyst, a common question arises as to whether the active catalyst species is truly heterogeneous or rather homogeneous through metal ion leaching. Differentiating these processes is critical, as the latter would result in reduced efficiency, higher cost, and inevitable environmental and heath side effects. This thesis explores the CuAAC from an interdisciplary approach. First as a synthetic tool, applying CuAAC-formed triazoles as functional, modular building blocks in the synthesis of optical cation sensors by combining azide and alkyne modified components to create a series of sensors selective for different metal cations. Next, single-molecule spectroscopy techniques are employed to observe the CuNP-catalyzed CuAAC in real time. Combining bench-top techniques with single-molecule microscopy to monitor single-catalytically generated products proves to be an effective method to establish catalysis occurs directly at the surface of copper nanoparticles, ruling out catalysis by ions leached into solution. This methodology is extended to mapping the catalytic activity of a commercial heterogeneous catalyst by applying super-localization analysis of single-catalytic events. The approach detailed herein is a general one that can be applied to any catalytic system through the development of appropriate probes. This thesis demonstrates single-molecule microscopy as an accessible, effective, and unparalleled tool for exploring the catalytic activity of nanomaterials by monitoring single-catalytic events as they occur.

The properties of a Rydberg atom immersed in an ultracold environment were investigated. Two scenarios were considered, one of which involves the neighbouring ground-state atoms arranged in a spatially structured configuration, while the other involves them distributed randomly in space. To calculate the influence of the multiple ground-state atoms on the Rydberg atom, Fermi-pseudopotential was used, which simplified greatly the numerical effort. In many cases, the few-body interaction can be written down analytically which reveals the symmetry properties of the system. In the structured case, we report the first prediction of the formation of ``Rydberg Borromean trimers''. The few-body interactions and the dynamics of the linear A-B-A trimer, where A is the ground-state atom and B is the Rydberg atom, were investigated in the framework of normal mode analysis. This exotic ultralong-range triatomic bound state exists despite that the Rydberg-ground-state interaction is repulsive. Their lifetimes were estimated using both quantum scattering calculations and semi-classical approximations which are found to be typically sub-microseconds. In the disordered case, the Rydberg-excitation spectra of a frozen-gas were simulated, where the nuclear degrees of freedom can be ignored. The systematic change of the spectral shape with respect to the density of the gas and the excitation of the Rydberg atom were found and studied. Some parts of the spectral shape can be described by simple scaling laws with exponents given by the basic properties of the atomic species such as the polarizability and the zero-energy electron-atom scattering length.

No description available.

No description available.

Yes / Alterations of Endothelial cells (ECs) play a critical role in different pathogenesis of many serious human diseases, and dysfunction of the vascular endothelium is an indicator for human disorders. Endothelial dysfunction is considered to be an early indicator for atherosclerosis, which is characterised by overexpression of adhesion molecules, including intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1). Hydrogen peroxide (H2O2) released via neutrophils is an important mediator of endothelial cell function. Ambient production of superoxide anion (O2−) and subsequently H2O2 at low levels is critical for regulating endothelial cell functions and proliferation. In this study, we investigated the effects of H2O2 on the expression of adhesion molecules VCAM-1 and ICAM-1 in cultured human umbilical vein endothelial cells (HUVECs). Intracellular superoxide anion production was detected by using p-Nitro Blue Tetrazolium (NBT) assay. Our results showed that administration of 100μM of H2O2 on HUVECs for 2, 6, 12 and 24 h induced a time-dependent increase in ICAM-1 and VCAM-1 mRNA and protein expression levels with a significant increase observed from 6 h. HUVECs exposed to H2O2 exhibit increased O2−, suggesting that H2O2 induced oxidative stress may be a reasonable for atherosclerosis. This increase can be reduced by the flavonoid, N-acetyl cysteine (NAC). The modulation of endothelial cell function through this mechanism may underlie the contribution of H2O2 to the development of vascular disease.

Doctor of Philosophy / Department of Physics / Itzhak Ben-Itzhak / Lasers are being used widely for the study and manipulation of the dynamics of atomic and molecular targets, and advances in laser technology makes it possible to explore new areas of research — for example attosecond physics. In order to probe the fragmentation dynamics of molecular ions, we have developed a coincidence three-dimensional momentum imaging method that allows the kinematically complete study of all fragments except electrons. Recent upgrades to this method allow the measurement of slow dissociation fragments, down to nearly zero velocity, in intense ultrafast laser fields. Evidences for the low energy breakup are presented using the benchmark molecules diatomic H[subscript]2[superscript]+ and polyatomic H[subscript]3[superscript]+ . The low energy fragments in H[subscript]2[superscript]+ dissociation are due to the intriguing zero-photon dissociation phenomenon. This first experimental evidence for the zero-photon dissociation is further supported by sophisticated theoretical treatment. We have explored the laser pulse length, intensity, wavelength, and chirp dependence of zero-photon dissociation of H[subscript]2[superscript]+, and the results are well described by a two-photon process based on stimulated Raman scattering. Similar studies of the slow dissociation of H[subscript]3[superscript]+ reveal that two-body dissociation is dominant over three-body dissociation. The most likely pathways leading to low-energy breakup into H[superscript]++H[subscript]2, in contradiction to the assessments of the channels in at least one previous study, are explored by varying the laser pulse duration and the wavelength. In addition, we have investigated the dissociation and single ionization of N[subscript]2[superscript]+ , and an interesting high energy feature in addition to the low energy has been observed at higher intensities. Such high energy results from the breakup of molecules in excited states are accessible at higher intensities where their potential energy is changing rapidly with the internuclear distance. We have extended the intense field ionization studies to other molecular ions N[subscript]2[superscript]+ , CO[superscript]+, NO[superscript]+, and O[subscript]2[superscript]+ . The dissociative ionization of these molecules follow a general mechanism, a stairstep ionization mechanism. Utilizing the capability of the upgraded experimental method we have measured the non-dissociative and dissociative ionization of CO[superscript]+ using different pulse lengths. The results suggest that dissociative ionization can be manipulated by suppressing some ionization paths.