23 research outputs found
Spectroscopic and microscopic investigations of tautomerization in porphycenes: condensed phases, supersonic jets, and single molecule studies
We describe various experimental approaches that have been used to obtain a detailed understanding of double hydrogen transfer in porphycene, a model system for intramolecular hydrogen bonding and tautomerism. The emerging picture is that of a multidimensional tautomerization coordinate, with several vibrational modes acting as reaction-promoters or inhibitors through anharmonic intermode coupling. Tunnelling processes, coherent in the case of isolated molecules and incoherent in condensed phases, are found to play a major role even at elevated temperatures. Single-molecule spectroscopy studies reveal large fluctuations in hydrogen transfer rates observed over time for the same chromophore. Scanning probe microscopy is employed to directly observe the structure and tautomerization dynamics of single molecules adsorbed on metal surfaces and demonstrates how the interactions of the molecules with atoms of the supporting surface affect their static and dynamic properties: different tautomeric forms are stabilized for molecules depending on the surface structure and the reaction mechanism can also change, from a concerted to a stepwise transfer. The scanning probe microscopy studies prove that tautomerization in single molecules can be induced by different stimuli: heat, electron attachment, light, and force exerted by the microscope’s tip. Possible applications utilizing tautomerism are discussed in combination with molecular architectures on surfaces, which could pave the way for the development of single-molecule electronics
Structural analysis and corrosion studies on an ISO 5832-9 biomedical alloy with TiO2 sol–gel layers
The aim of this study was to demonstrate the
relationship between the structural and corrosion properties
of an ISO 5832-9 biomedical alloy modified with titanium
dioxide (TiO2) layers. These layers were obtained via the
sol–gel method by acid-catalyzed hydrolysis of titanium
isopropoxide in isopropanol solution. To obtain TiO2 layers
with different structural properties, the coated samples
were annealed at temperatures of 200, 300, 400, 450, 500,
600 and 800 C for 2 h. For all the prepared samples,
accelerated corrosion measurements were performed in
Tyrode’s physiological solution using electrochemical
methods. The most important corrosion parameters were
determined: corrosion potential, polarization resistance,
corrosion rate, breakdown and repassivation potentials.
Corrosion damage was analyzed using scanning electron
microscopy. Structural analysis was carried out for selected
TiO2 coatings annealed at 200, 400, 600 and 800 C. In
addition, the morphology, chemical composition, crystallinity,
thickness and density of the deposited TiO2 layers
were determined using suitable electron and X-ray measurement
methods. It was shown that the structure and
character of interactions between substrate and deposited
TiO2 layers depended on annealing temperature. All the
obtained TiO2 coatings exhibit anticorrosion properties, but
these properties are related to the crystalline structure and
character of substrate–layer interaction. From the point of
view of corrosion, the best TiO2 sol–gel coatings for stainless steel intended for biomedical applications seem to
be those obtained at 400 C.This study was supported by Grant No. N N507
501339 of the National Science Centre. The authors wish to express
their thanks to J. Borowski (MEDGAL, Poland) for the Rex 734 alloy
Superfícies fotocatalíticas de titânia em substratos cerâmicos: Parte I: Síntese, estrutura e fotoatividade
Construction of a tunnel crossing under the Martwa Wisła river in Gdańsk
Artykuł, dotyczący projektu przeprawy tunelowej pod Martwą Wisłą, wskazuje na szeroki zakres podejmowanego przedsięwzięcia. Budowa tunelu w trudnych warunkach geotechnicznych metodą drążenia maszyną TBM, tak pod korytem Martwej Wisły, jak i w pobliżu istniejących i czynnych elementów infrastruktury drogowej, portowej i przemysłowej, stanowi śmiałe i unikatowe wyzwanie z punktu widzenia organizacyjnego i inżynierskiego. Jest to pierwsza drogowa tunelowa przeprawa podwodna w Polsce, realizowana metodą drążenia przy użyciu maszyny TBM o tak dużej średnicy tarczy. Rozmach tego przedsięwzięcia jest znaczący także w skali międzynarodowej.This article concerns the project to build a tunnel under the Martwa Wisła, and indicates the extensive scope of the project being undertaken. The building of a tunnel in difficult geotechnical conditions by a method of boring using a TBM, both under the river itself and in the vicinity of existing and operational elements of road, port and industrial infrastructure, is a bold and unique challenge from an organizational and engineering point of view. It is the first underwater road tunnel to be built in Poland using a TBM with such a large shield diameter. The ambition of this project is significant even on an international scale
Spectroscopic and microscopic investigations of tautomerization in porphycenes: condensed phases, supersonic jets, and single molecule studies
Arresting Tautomerization in a Single Molecule by the Surrounding Polymer: 2,7,12,17-Tetraphenyl Porphycene
Independent association of FTO rs9939609 polymorphism with overweight and obesity in Polish adults. Results from the representative population-based WOBASZ study
Awareness of hypertension and depressive symptoms: a cross-sectional study in a primary care population
Influence of local microenvironment on the double hydrogen transfer in porphycene
We performed time-resolved transient absorption and fluorescence anisotropy measurements in order to study tautomerization of porphycene in rigid polymer matrices at cryogenic temperatures. Studies were carried out in poly(methyl methacrylate) (PMMA), poly(vinyl butyral) (PVB), and poly(vinyl alcohol) (PVA). The results prove that in all studied media hydrogen tunnelling plays a significant role in the double hydrogen transfer which becomes very sensitive to properties of the environment below approx. 150 K. We also demonstrate that there exist two populations of porphycene molecules in rigid media: “hydrogen-transferring” molecules, in which tautomerization occurs on time scales below 1 ns and “frozen” molecules in which double hydrogen transfer is too slow to be monitored with nanosecond techniques. The number of “frozen” molecules increases when the sample is cooled. We explain this effect by interactions of guest molecules with a rigid host matrix which disturbs symmetry of porphycene and hinders tunnelling. Temperature dependence of the number of hydrogen-transferring molecules suggests that the factor which restores the symmetry of the double-minimum potential well in porphycene are intermolecular vibrations localized in separated regions of the amorphous polymer