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339 results on '"Waluk J"'

5. Porphycene Films Grown on Highly Oriented Pyrolytic Graphite: Unveiling Structure–Property Relationship through Combined Reflectance Anisotropy Spectroscopy and Atomic Force Microscopy Investigations

Author

Penconi, M, Ferraro, L, Waluk, J, Duò, L, Ciccacci, F, Bossi, A, Campione, M, Bussetti, G, Penconi, Marta, Ferraro, Lorenzo, Waluk, Jacek, Duò, Lamberto, Ciccacci, Franco, Bossi, Alberto, Campione, Marcello, Bussetti, Gianlorenzo, Penconi, M, Ferraro, L, Waluk, J, Duò, L, Ciccacci, F, Bossi, A, Campione, M, Bussetti, G, Penconi, Marta, Ferraro, Lorenzo, Waluk, Jacek, Duò, Lamberto, Ciccacci, Franco, Bossi, Alberto, Campione, Marcello, and Bussetti, Gianlorenzo

Abstract

Thin organic films are widely used in sensors, solar cells, and optical devices due to their intense absorption in the visible/near-infrared (IR) region. Shifting, quenching, or reshaping of some spectral features can be achieved by chemical functionalization of the molecules, whereas an anisotropic fingerprint due to preferential molecular alignment can be induced via a proper design and/or preparation of the substrate. Recently, we investigated the optical response of thin films of porphycene to acidification. With respect to the well-known and closely related tetraphenyl porphyrin, porphycene has the clear advantage of being optically active in the full visible range, and this makes visible by naked eye the immediate change of the film from brilliant blue-turquoise to green when exposed to HCl vapors. In this work, by exploiting a homemade reflectance anisotropy spectroscopy (RAS) apparatus, we explore possible optical anisotropies in the visible spectral range of porphycene films and relate them to the film morphology analyzed by atomic force microscopy (AFM).

Published
2021

6. Porphycene protonation: a fast and reversible reaction enabling optical transduction for acid sensing

Author

Bossi, A, Waluk, J, Yivlialin, R, Penconi, M, Campione, M, Bussetti, G, Bossi, Alberto, Waluk, Jacek, Yivlialin, Rossella, Penconi, Marta, Campione, Marcello, Bussetti, Gianlorenzo, Bossi, A, Waluk, J, Yivlialin, R, Penconi, M, Campione, M, Bussetti, G, Bossi, Alberto, Waluk, Jacek, Yivlialin, Rossella, Penconi, Marta, Campione, Marcello, and Bussetti, Gianlorenzo

Abstract

Nano‐sensor materials, especially if they target biological purposes, require a fine control and tooling of the properties at the molecular scale when intra‐molecular properties have to be exploited, e. g., in optical sensors. By means of optical spectroscopies (namely, spectrophotometry, spectrofluorimetry, and surface differential reflectivity), we unveil that thin films of porphycene show a spectacular chromatic change when exposed to acid vapors (namely, to hydrochloric acid). After the exposure, the original optical properties of porphycene films are recovered in few seconds and without any thermal annealing. In addition, since clear spectroscopic signatures are observed both in absorption and in reflectivity, the porphycene reveals to be suitable even for deposition of films onto opaque substrates. These findings are of significant interest in view of a potential engineering of the molecules and an implementation in devices.

Published
2020

9. Electronic states of a novel smaragdyrin isomer: polarized spectroscopy and theoretical studies

Author

Gorski, A., Lament, B., Davis, J.M., Sessler, J., and Waluk, J.

Subjects
Isomerism -- Structure, Isomerism -- Spectra, Pyrrole -- Structure, Pyrrole -- Spectra, Chemicals, plastics and rubber industries
Abstract

The electronic structure and spectra of two novel pentapyrrolic macrocycles compounds and the isomers of smaragdyrin are examined using spectral and theoretical techniques. The results from spectral pattern that four lowest excited electronic singlet states of both compounds are in good agreement with a four-orbital model was widely used to describe the spectral analysis of such similar compounds.

Published
2001

11. Molecular dynamics and DFT studies of intermolecular hydrogen bonds between bifunctional heteroazaaromatic molecules and hydroxylic solvents

Author

Kyrychenko A., Stepanenko Y., and Waluk J.

Subjects
Density functionals -- Usage, Hydrogen bonding -- Research, Molecular dynamics -- Research, Chemicals, plastics and rubber industries
Abstract

Molecular dynamics and DFT studies of intermolecular hydrogen bonds between bifunctional heteroazaaromatic molecules and hydrolic solvents are carried out. The experiment indicates that these molecules form different types of intermolecular complexes with hydroxylic solvents in the ground electronic state.

Published
2000

14. Excited state energy degradation paths in the case of porphycene and dibenzoporphycene isolated in low temperature matrices

Author

Dobkowski, J., Galievski, V., Gawinkowski, S., Gil, M., Kijak, M., Lobko, Y., Starukhin, A., and Waluk, J.

Subjects
picosecond spectroscopy, дибензопорфицены, порфицены, флуоресценция, макрогетероциклические соединения, fluorescence, transient absorption spectra, porphycenes, dibenzoporphycenes, спектры переходного поглощения, пикосекундная спектроскопия
Published
2018

17. Electronic states of cyclophanes with small bridges.

Author

Dodziuk, H., Vetokhina, V., Hopf, H., Luboradzki, R., Gaweł, P., and Waluk, J.

Subjects
CYCLOPHANES, MAGNETIC circular dichroism, STRUCTURAL analysis (Science), DENSITY functionals, SCIENTIFIC observation, ABSORPTION, ELECTRIC properties of materials, GROUND state (Quantum mechanics)
Abstract

Electronic absorption and magnetic circular dichroism were recorded for five cyclophanes with ethano bridges: [2.2]paracyclophane, (1,2,4)[2.2.2]cyclophane, (1,2,4;1,2,5)[2.2.2]cyclophane, (1,2,3,4,5,6)(1,2,3,4,5,6)cyclophane, and trans-[2.2]metacyclophane. Spectral and structural analyses were based on geometry optimization and calculations of transition energies, carried out using density functional theory methods. The assignments have been proposed for several electronic transitions observed in the region below 52 000 cm-1. The observation of transitions which should be forbidden in the high D2h symmetry [2.2]paracyclophane suggests a twisted ground state structure of D2 symmetry, although the former structure with large amplitude vibrations at room temperature cannot be excluded. The PBE0 functional turned out to appropriately reproduce the inter-ring distances and electronic transition energies. [ABSTRACT FROM AUTHOR]

Published
2012
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18. Excited-state proton transfer through water bridges and structure of hydrogen-bonded complexes in 1H-pyrrolo[3,2-h] quinoline: Adiabatic time-dependent density functional theory study

Author

Kyrychenko, A. and Waluk, J.

Subjects
Quinoline -- Chemical properties, Density functionals -- Usage, Hydrogen bonding -- Chemical properties, Chemicals, plastics and rubber industries
Abstract

Proton transfer reaction is studied for 1H-pyrrolo[3,2-h]quinoline-water complexes [(PQ-([H.sub.2]O).sub.n], n=0-2) in the ground and the lowest excited singlet states at the density functional theory (DFT) level. The excited-state acid-base changes introduce a driving force for the proton transfer reaction, large relaxation and reorganization of the hydrogen bonded water bridge in [(PQ-([H.sub.2]O).sub.2] are required during the proton translocation from the pyrrole NH group to the quinoline nitrogen blocking the complete tautomerization in this type of solvate.

Published
2006

22. (Sub)picosecond fluorescence upconversion studies of intermolecular proton transfer of dipyrido[2,3-a:3',2'-i]carbazole and related compounds

Author

Marks, D., Zhang, H., Borowicz, P., Waluk, J., and Glasbeek M.

Subjects
Chemistry, Physical and theoretical -- Research, Fluorescence -- Usage, Solution (Chemistry) -- Electric properties, Charge transfer -- Research, Chemicals, plastics and rubber industries
Abstract

A study is conducted to examine few carbazole-related compounds in alcoholic solution, photoinduced solute--solvent proton-transfer dynamics, by means of femto- and picosecond fluorescence transient measurements. The results are suggestive of a thermally averaged deuteron tunneling process in the cyclic solute--solvent complex.

Published
2000

27. Structure and photophysics of 2-(2'-pyridyl)benzindoles: The role of intermolecular hydrogen bonds

Author

Petkova, I., Mudadu, M.S., Singh, A.K., Thummel, R.P., van Stokkum, I.H.M., Buma, W.J., Waluk, J., Petkova, I., Mudadu, M.S., Singh, A.K., Thummel, R.P., van Stokkum, I.H.M., Buma, W.J., and Waluk, J.

Abstract

The photophysical properties of two isomeric 2-(2′-pyridyl) benzindoles depend on the environment. Strong fluorescence is detected in nonpolar and polar aprotic solvents. In the presence of alcohols, the emission reveals an unusual behavior. Upon titration of n-hexane solutions with ethanol, the fluorescence intensity goes through a minimum and then increases with rising alcohol concentration. Transient absorption and time-resolved emission studies combined with ground- and excited-state geometry optimizations lead to the conclusion that two rotameric forms, syn and anti, coexist in alcohols, whereas in nonpolar and aprotic polar media, only the syn conformation is present. The latter can form cyclic complexes with alcohols, which are rapidly depopulated in the excited state. In the presence of excess alcohol, syn → anti rotamerization occurs in the ground state, promoted by the cooperative action of nonspecific and specific effects such as solvent polarity increase and the formation of hydrogen bonds to both donor and acceptor sites of the bifunctional compounds. © 2007 American Chemical Society.

Published
2007
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39. PHOTOLUMINESCENCE OF POROUS SILICON WITH INSERTED CdSe/ZnS QUANTUM DOTS.

Author

Jarimaviciute-Zvalioniene, R., Kamińska, A., Waluk, J., and Prosycevas, I.

Subjects
NANOPARTICLES, POROUS silicon, LIGHT emitting diodes, QUANTUM dots, SPECTRUM analysis, PHOTOLUMINESCENCE
Abstract

Combining basic materials, such as porous silicon, with nanoparticles we can produce low-cost light emitting materials, what is economically useful and important nowadays. In this work we have produced visible light emitting quantum dots (QD) of CdSe/ZnS and precipitated them onto the surface of porous silicon structure. The porous silicon (PS) structures were prepared by chemical etching at room temperature in HF:HNO3 solution. The structures of PS-QD were investigated by SEM and UV-VIS spectroscopy. Absorption and photoluminescence of the structures, dependent on excitation wavelength, were measured in the visible spectral region. [ABSTRACT FROM AUTHOR]

Published
2010

43. Solvent-induced syn-anti rotamerization of 2-(2'-pyridyl)indole and the structure of its alcohol complexes

Author

Kyrychenko, A., Herbich, J., Wu, F., Thummel, R. P., and Waluk, J.

Subjects
Alcohol -- Research, Molecular structure -- Research, Solution (Chemistry) -- Research, Chemistry
Abstract

Issues concerning the examination of 2-(2'-pyridyl)indole and its compounds and the structural changes which occur when it is interacted with protic solvents are discussed. The formation of syn and anti rotameric versions are possible and their relative stabilities in alcohol and aprotic solvents are presented.

Published
2000

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