Search results for "Microscope"
showing 10 items of 1412 documents
Orbiting Orbitals: Visualization of Vi-Bronic Motion at a Conical Intersection
2013
The Jahn-Teller (JT) active unpaired electron of single metalloporphyrin radical anions is imaged through scanning tunneling microscopy. It is demonstrated that the electron is delocalized over the porphyrin macrocycle and its topographic image is determined by vibronic motion: the orbital of the electron adiabatically follows the zero-point pseudorotation of skeletal deformations. Transformation of the polar graphs of the observed images allows visualization of the adiabatic vibrational density to which the electron is coupled. The vibronic potential at the conical intersection is visualized and the half-integer angular momentum characteristic of the Berry phase is revealed in the radial f…
Voltammetry of microparticles, scanning electrochemical microscopy and scanning tunneling microscopy applied to the study of dsDNA binding and damage…
2014
Abstract Microparticulate deposits of scorpiand-like azamacrocyclic receptors (L1–L4) attached to graphite electrodes provide distinctive voltammetric features in contact with aqueous DNA solutions at biological pH, denoting the formation of DNA surface complexes. This voltammetry allows for screening dsDNA, ssDNA and G-Quadruplex DNA using L4-modified electrodes. Scanning electrochemical microscopy and scanning tunneling microscopy examination of dsDNA fibers attached to the substrate electrode in contact with DMSO solutions containing ferrocene and receptor indicate that a synergic effect is exerted between electrochemically generated ferrocenium ion and the receptors so that they increas…
Three-dimensional orientational colocalization of individual donor--acceptor pairs.
2004
We report on the determination of the three-dimensional orientation of the donor and acceptor transition dipoles in individual fluorescence resonance energy transfer (FRET) pairs by means of scanning optical microscopy with annular illumination. Knowledge of the mutual orientation of the donor and acceptor dipole is mandatory for reliable distance determination based on FRET efficiency measurements. In our model system perylenediimide as the donor and terryelenediimide as the acceptor are coupled via a stiff p-terphenyl linker. The absorption dipoles of the donor and acceptor are selectively addressed by the 488 nm and 647 line of an Ar/Kr mixed gas laser, respectively. A clear deviation fr…
Tuning the Magnetic Properties of Carbon by Nitrogen Doping of Its Graphene Domains
2015
Here we present the formation of predominantly sp-coordinate carbon with magnetic- and heteroatom-induced structural defects in a graphene lattice by a stoichiometric dehalogenation of perchlorinated (hetero)aromatic precursors [hexachlorobenzene, CCl (HCB), and pentachloropyridine, NCCl (PCP)] with transition metals such as copper in a combustion synthesis. This route allows the build-up of a carbon lattice by a chemistry free of hydrogen and oxygen compared to other pyrolytic approaches and yields either nitrogen-doped or -undoped graphene domains depending on the precursor. The resulting carbon was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM…
In vivo molecular and morphological imaging by real time confocal mini-microscopy
2006
We evaluated a newly developed miniaturized confocal laser microscopy probe for real-time in vivo molecular and morphological imaging of normal, inflammatory, and malignant tissue in rodents. In the rigid mini-microscopy probe (diameter 7 mm), a single line laser delivers an excitation wavelength of 488 nm. Optical slice thickness is 7 μm, lateral resolution 0.7 μm. The range of the z-axis is 0 - 250 μm below the tissue surface. Organ systems were examined in vivo in rodent models of human diseases. FITC-labeled Lycopersion esculentum lectin was injected or selected cell populations stained for molecular targeting. Morphological imaging was performed using fluorescein sodium, FITC-labeled d…
Template induced crystallization of biominerals on self-assembled monolayers of alkylthiols
1998
Abstract We have studied the templated crystallization of the three polymorphs of calcium carbonate on self-assembled monolayers of ω -substituted alkylthiols on gold surfaces. Our interest has been to model biomineralization processes by examining the effect of structured organic templates on heterogeneous nucleation at the inorganic–organic interphase. The crystallization of the three polymorphs was carried out from solution at two different temperatures. The crystals that were formed on the surface were examined using scanning electron microscopy. Phase quantification was achieved through Rietveld analysis of the X-ray diffraction profiles. This study provides significant clues on factor…
Preparation and photoactivity of nanocrystalline TiO2 powders obtained by thermohydrolysis of TiOSO4
2013
Nanocrystalline TiO2 photocatalysts were synthesized in mild conditions by thermohydrolysis of TiOSO4 in water at 100 °C and post-calcination treatment at various temperatures. The TiO2 powders were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, specific surface area determinations, scanning electron microscopy and electron paramagnetic resonance measurements. The photoactivity of the samples was tested employing the photodegradation of 4-nitrophenol in liquid–solid regimen and the photooxidation of gaseous 2-propanol. The best results were obtained with the powder calcined at 600 °C for 10 h. Surprisingly, the not calcined sample was the most active for the abatement…
MOCVD growth of CdTe on glass: analysis of in situ post-growth annealing
2004
Abstract In this paper, we analyse the growth by MOCVD of CdTe on glass substrates using in situ post-growth annealing. First, in order to perform a systematic study, polycrystalline layers of CdTe were deposited by MOCVD on glass substrates. The structure and morphology of the layers was investigated as a function of different growth parameters, temperature, VI/II precursor molar ratio and substrate position on the susceptor. An activation energy of Ek=20.7 kcal/mol was obtained from the experimental data. In order to better understand the process and the effects of different growth parameters, a numerical model that simulated the gas flow in the reactor, was developed. Secondly we analyse…
Characterization of MCM-48 Materials
2000
Mesoporous molecular sieves of MCM-48 type were prepared by conventional hydrothermal and novel room temperature syntheses. Scanning electron microscopy (SEM) studies have shown that nonagglomerate...