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Chromophores based on push-pull substituted stilbenes
Ševčíková, Veronika ; Kratochvíl, Matouš (referee) ; Vala, Martin (advisor)
This bachelor thesis deals with the examination of the relationship between the structure and optical properties of organic luminophores based on push-pull substituted stilbene and the determination of their emission in the solid state and in solution - dual state emission (DSE). Four newly synthesized luminophores based on push-pull substituted diphenylaminodibromostilbene and diphenylaminodi(2,6-xylil)stilbene containing different electron acceptor groups were selected for measurements. Due to the limited amount of samples, only solutions of the luminophores in dichloromethane were prepared. Emission spectra, quantum yields and fluorescence lifetime were measured for these luminophores in solid state. For solutions of these luminophores in DCM, all described optical properties were measured along with the absorption spectra. Determined optical properties were related to the structure of the luminophores. For the diphenylamine-dibromostilbene-based luminophores, fluorescence of the NIR radiation was detected, while the fluorescence of these luminophores was found to be weakened due to the presence of Br substituents. The investigated diphenylaminodi(2,6-xylil)stilbene-based luminophores show relatively weak push-pull effect. The fluorescence of these luminophores was found to be intense in solution, but weakened in the solid phase, which was attributed to the weak push-pull effect. According to the measured results, it was concluded that the investigated luminophores based on diphenylaminodi(2,6-xylil)stilbene are suitable candidates for further research and potential applications considering their properties.
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Host-guest systems for efficient infrared solid-state emission
Rottenberg, Vojtěch ; Smolka, Rastislav (referee) ; Kratochvíl, Matouš (advisor)
The goal of this bachelor thesis is to compile a brief research on solid-phase fluorescence, to find suitable molecules for the preparation of host-guest systems that exhibit high quantum yields of solidphase fluorescence in the infrared region and to analyze them. These systems consist of a predominant molecule (host) that exhibits high quantum yields of fluorescence and a quantitatively less abundant molecule (guest) that exhibits fluorescence in the infrared part of the electromagnetic spectrum. The following molecules were chosen: (E)-N,N-diphenyl-4-(2-(5'-vinyl-[1,1':4',1''-terphenyl]-2'- yl)vinyl)aniline (–V) and (E)-5'-(4-(diphenylamino)styryl)-[1,1': 4',1''-terphenyl]-2'-carbonitrile (–CN) as a guest molecule and (E)-2-((5'-(4-(diphenylamino)styryl)-[1,1':4',1''-terphenyl]-2'- yl)methylene)malononitrile (–DCV) as a guest molecule. For sample analysis, emission and excitation spectra were measured using a fluorophore, quantum yields using an integrating sphere, and fluorescence lifetimes using the time-correlated single photon counting (TCSPC) method. From the spectral analyses and quantum yields, it was determined that the molecule (E)-5'-(4- (diphenylamino)styryl)-[1,1':4',1''-terphenyl]-2'-carbonitrile (–CN) is a suitable guest molecule, (E)-2- ((5'-(4-(diphenylamino)styryl)-[1,1': 4',1''-terphenyl]-2'-yl)methylene)malononitrile (–DCV) is not a suitable guest molecule and the suitability of using (E)-N,N-diphenyl-4-(2-(5'-vinyl-[1,1':4',1''- terphenyl]-2'-yl)vinyl)aniline (–V) as a guest molecule is inconclusive.
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Determination of absolute quantum yield of luminescence
Smísitel, Petr ; Valenta, Jan (advisor) ; Herynková, Kateřina (referee)
In this bachelor thesis we will study the determination of absolute quantum yields (efficiency) of photoluminiscence, which is equal to the ratio of number of emitted photons and number of absorbed photons. The common approach is to compare the absorption and luminescence spectrum. The main experimental problem is to eliminate the influence of angular dependence of reflection, emission and scattering. Therefore it is convenient to use the integrating sphere which eliminate most of the problems of relative measurements of quantum yield. In detail we will describe the method to determine the quantum yields of luminescence using the integrating sphere including the description of the experimental equipment and the procedure of processing data and estimation of uncertainty. Finally, we apply the procedure to solid and liquid samples containing silicon nanocrystals. We will measure the dependence of quantum yields on the applied excitation wavelength. 1
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Methods of Study of Photosensitizer-Photophysics with Application on Thiazolyl-porphyrins
Scholz, Marek ; Dědic, Roman (advisor) ; Hála, Jan (referee)
Title: Methods of Study of Photosensitizer-photophysics with Application on Thiazolyl-porphyrins Author: Marek Scholz Department: Department of Chemical Physics and Optics Supervisor: RNDr. Roman Dědic, Ph.D. Supervisor's e-mail address: Roman.Dedic@mff.cuni.cz Abstract: Photodynamic therapy for oncologic and various chronic diseases is a rapidly emerging method of treatment. It is based on the production of highly reactive singlet oxygen and free radicals by excitation energy transfer from the molecules of photosensitizers. Photosensitizers are preferentially accumulated in the target tissues and locally illuminated. This way produced reactive species cause apoptosis or necrosis of the cells leading to the desired therapeutic effect. Synthesis and subsequent photophysical characterization of photosensitizing dyes is a fundamental part of the development of photodynamic methods. The main aim of the work is to explain the most widely used methods of photophysical study of photosensitizers and apply them to new synthesized photosensitizers: thiazolyl-porphyrins. Methods of absorption and fluorescence spectroscopy, flash- photolysis, time- and spectral-resolved detection of luminescence, optoacoustic spectroscopy and other spectroscopic methods were used. Thiazolyl-porphyrins proved to be promising new...
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Advanced spectroscopic characterization of quantum dot ensembles
Greben, Michael ; Valenta, Jan (advisor) ; Linnros, Jan (referee) ; Vácha, Martin (referee)
Title: Advanced spectroscopic characterization of quantum dot ensembles Author: Michael Greben Department: Department of Chemical Physics and Optics Supervisor of the doctoral thesis: Prof. Jan Valenta, Ph.D. Abstract: Semiconductor quantum dots (QDs) are small crystallites whose sizes (of the order of nm) cause spatial confinement of carriers in all 3 dimensions. As result, QDs often reveal very different physical properties in comparison with their bulk counterparts. From the optical point of view, the broadening of bandgap with QD-size shrinking is particularly interesting. It is a purely quantum mechanical effect that results from quantum confinement (QC), i.e. dimensional limitations of excitons. A strong spatial confinement leads to a relaxation of momentum (Heisenberg uncertainty principle), consequently, larger overlap of the wave-functions of carriers results in significant increase of probability of radiative recombination. Therefore ensembles of QDs are promising candidates for new generations of photonic and photovoltaic devices. This PhD thesis is primary focused on detailed spectroscopic characterization of ensembles of direct (PbS) and indirect (Si) semiconductor QDs in both colloidal (toluene) and matrix-embedded (oxide or oxinitrides multilayers) forms. The oleic- acid capped PbS QDs were...
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Methods of Study of Photosensitizer-Photophysics with Application on Thiazolyl-porphyrins
Scholz, Marek
Title: Methods of Study of Photosensitizer-photophysics with Application on Thiazolyl-porphyrins Author: Marek Scholz Department: Department of Chemical Physics and Optics Supervisor: RNDr. Roman Dědic, Ph.D. Supervisor's e-mail address: Roman.Dedic@mff.cuni.cz Abstract: Photodynamic therapy for oncologic and various chronic diseases is a rapidly emerging method of treatment. It is based on the production of highly reactive singlet oxygen and free radicals by excitation energy transfer from the molecules of photosensitizers. Photosensitizers are preferentially accumulated in the target tissues and locally illuminated. This way produced reactive species cause apoptosis or necrosis of the cells leading to the desired therapeutic effect. Synthesis and subsequent photophysical characterization of photosensitizing dyes is a fundamental part of the development of photodynamic methods. The main aim of the work is to explain the most widely used methods of photophysical study of photosensitizers and apply them to new synthesized photosensitizers: thiazolyl-porphyrins. Methods of absorption and fluorescence spectroscopy, flash- photolysis, time- and spectral-resolved detection of luminescence, optoacoustic spectroscopy and other spectroscopic methods were used. Thiazolyl-porphyrins proved to be promising new...
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Advanced spectroscopic characterization of quantum dot ensembles
Greben, Michael ; Valenta, Jan (advisor)
Title: Advanced spectroscopic characterization of quantum dot ensembles Author: Michael Greben Department: Department of Chemical Physics and Optics Supervisor of the doctoral thesis: Prof. Jan Valenta, Ph.D. Abstract: Semiconductor quantum dots (QDs) are small crystallites whose sizes (of the order of nm) cause spatial confinement of carriers in all 3 dimensions. As result, QDs often reveal very different physical properties in comparison with their bulk counterparts. From the optical point of view, the broadening of bandgap with QD-size shrinking is particularly interesting. It is a purely quantum mechanical effect that results from quantum confinement (QC), i.e. dimensional limitations of excitons. A strong spatial confinement leads to a relaxation of momentum (Heisenberg uncertainty principle), consequently, larger overlap of the wave-functions of carriers results in significant increase of probability of radiative recombination. Therefore ensembles of QDs are promising candidates for new generations of photonic and photovoltaic devices. This PhD thesis is primary focused on detailed spectroscopic characterization of ensembles of direct (PbS) and indirect (Si) semiconductor QDs in both colloidal (toluene) and matrix-embedded (oxide or oxinitrides multilayers) forms. The oleic- acid capped PbS QDs were...
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Determination of absolute quantum yield of luminescence
Smísitel, Petr ; Valenta, Jan (advisor) ; Herynková, Kateřina (referee)
In this bachelor thesis we will study the determination of absolute quantum yields (efficiency) of photoluminiscence, which is equal to the ratio of number of emitted photons and number of absorbed photons. The common approach is to compare the absorption and luminescence spectrum. The main experimental problem is to eliminate the influence of angular dependence of reflection, emission and scattering. Therefore it is convenient to use the integrating sphere which eliminate most of the problems of relative measurements of quantum yield. In detail we will describe the method to determine the quantum yields of luminescence using the integrating sphere including the description of the experimental equipment and the procedure of processing data and estimation of uncertainty. Finally, we apply the procedure to solid and liquid samples containing silicon nanocrystals. We will measure the dependence of quantum yields on the applied excitation wavelength. 1
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Advanced spectroscopic characterization of quantum dot ensembles
Greben, Michael ; Valenta, Jan (advisor) ; Linnros, Jan (referee) ; Vácha, Martin (referee)
Title: Advanced spectroscopic characterization of quantum dot ensembles Author: Michael Greben Department: Department of Chemical Physics and Optics Supervisor of the doctoral thesis: Prof. Jan Valenta, Ph.D. Abstract: Semiconductor quantum dots (QDs) are small crystallites whose sizes (of the order of nm) cause spatial confinement of carriers in all 3 dimensions. As result, QDs often reveal very different physical properties in comparison with their bulk counterparts. From the optical point of view, the broadening of bandgap with QD-size shrinking is particularly interesting. It is a purely quantum mechanical effect that results from quantum confinement (QC), i.e. dimensional limitations of excitons. A strong spatial confinement leads to a relaxation of momentum (Heisenberg uncertainty principle), consequently, larger overlap of the wave-functions of carriers results in significant increase of probability of radiative recombination. Therefore ensembles of QDs are promising candidates for new generations of photonic and photovoltaic devices. This PhD thesis is primary focused on detailed spectroscopic characterization of ensembles of direct (PbS) and indirect (Si) semiconductor QDs in both colloidal (toluene) and matrix-embedded (oxide or oxinitrides multilayers) forms. The oleic- acid capped PbS QDs were...
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