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1

Właściwości spektralne i fotofizyczne wybranych cząsteczek aromatycznych i indywiduów przejściowych w krótkożyjących stanach wzbudzonych

Maciejewski A., Burdziński G., Dobek K., Grabowska A., Karolczak J., Krystkowiak E., Kubicki J., Łukaszewicz A., Naskręcki R., Ziołek M.

Wiadomości Chemiczne

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2007

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[Z] 61, 3-4

137-165

EN

The paper presents results of spectral and photophysical studies obtained for molecules representing three different classes of compounds: • Schiff bases with strong intramolecular hydrogen bond, occurring in a few phototautomers, • Aminophtalimides with LE and ICT type electronic excited states forming exciplexes through hydrogen bonds with the solvent molecules, • Thioketones with a thiocarbonyl group becoming exceptionally reactive in the S2 state, quenched by molecules of solvent of different properties. It should be emphasized that for all compounds, irrespective of the complex mechanisms of their deactivation characterised by different dynamics, the dominant final process is the reproduction of the chemically unchanged substrate in the ground state. The necessary condition of the correct interpretation of the complex properties of the compounds studied in electronic excited states is the proper choice of solvents of specific properties. Through this proper choice of solvents it becomes possible to study the role of nonspecific and specific (hydrogen bonds) interactions with the solvent and to observe the intramolecular and intermolecular processes of deactivation. The results presented could be obtained thanks to the use of the steady-state and time-resolved laser methods of absorption and emission spectroscopy with a pico- and femtosecond resolution. The results obtained can be helpful in the study of compounds of similar properties and more complex systems including biological systems.

2

Infrared-to-visible upconversion: spontaneous emission and amplified spontaneous emission in a ZBLAN:Er3+ optical fiber

Kaczmarek F., Karolczak J.

Optica Applicata

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2007

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Vol. 37, nr 1-2

101-106

EN

Careful, intensity and spectral examinations of fluorescence in the process of infrared-to-visible upconversion, observed perpendicularly to the excited ZBLAN:Er3+ optical fiber (side fluorescence), and at the fiber end, point to the existence of amplified spontaneous emission (ASE), when the fiber is long enough. We have observed the narrowing of the fluorescence band centered at 544 nm (4S3/2 - 4I15/2 transition) and an increase in the ASE intensity, when the fiber is pumped at 809 nm with a laser diode.

3

Optical pumping of an infrared-to-visible upconversion fiber laser

Kaczmarek F., Karolczak J.

Optica Applicata

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2005

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Vol. 35, nr 4

913-918

EN

In the previous article (see Optica Applicata 31(2), 2001, pp. 373-6) on laser diode pumping of an infrared-to-visible upconversion fiber laser emitting at 544 nm, special attention was paid to the role of focusing of the incident pumping power. This paper discusses the role of the wavelength dependence of the pumping beam, in particular, the appearance of undesired side fluorescences at 660 and 850 nm, and also the distribution of the pumping power along the fiber length.

4

Infrared-to-visible upconversion in erbium fluoride (ZBLAN:Er³⁺) optical fiber: competition between the parasitic 850-nm fluorescence and the green laser emission at 544 nm

Kaczmarek F., Karolczak J.

Opto-Electronics Review

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2004

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Vol. 12, No. 2

247-248

EN

The role of 850-nm fluorescence, amplification, and laser emission in ZBLAN:Er³⁺ optical fiber was first investigated by Whitley et al. [1,2] and Allain et al. [3]. In the case of a green upconversion fiber laser at 544 nm, the 850-nm fluorescence is a parasitic component, so it should be minimized or eliminated. Two pumping wavelengths are usually applied to excite the green upconversion laser: 970 nm or 800 nm. It has been already observed that 800-nm pumping favours, to some extend, the 850-parasitic emission, and the 970-nm one makes this emission negligible [1–3]. We have studied the role of 800-nm pumping in more detail and observed a dependence of the pumping wavelength ~800 nm on the intensity of the 850-nm parasitic fluorescence.

5

Upconversion fluorescence and laser emission in the visible under Ti:sapphire laser pumping at 800 nm in the ZBLAN:Er3+ optical fiber

Kaczmarek F., Karolczak J.

Optica Applicata

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2004

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Vol. 34, nr 3

313-317

EN

Infrared-to-visible upconversion in rare-earth doped optical fibers is a very interesting phenome-non, but its application in building a practically useful laser requires much more experimental work. In this paper, infrared-to-visible upconversion fluorescence observed perpendicularly to the fiber and laser emission in ZBLAN:Er3+ fiber under 800 nm excitation from a Ti:sapphire laser are described. Absorption at the pump wavelength, threshold power pumping density, and output power dependence vs. fiber length have been measured. The output power in the green (544 nm) amounts to 22 mW. Important technical details of the experiment are described.

6

What affects the rate of free radical polymerization of a multifunctional acrylate photoinitiated by cyanine borate salts? Part II. Application of electron transfer theory

Kabatc J., Pączkowski J., Karolczak J.

Polimery

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2003

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T. 48, nr 6

425-433

EN

On the basis of Schuster's investigation, a mechanism of the processes going on during radical polymerization, photoinitiated by cyanine borate salts, has been proposed. As well the possibility of Marcus theory application to describe the kinetics of such polymerization, photoinitiated via electron transfer process, has been presented. It required the determination of the value of free energy of activation of electron transfer process (DeltaG(el)), using Rehm-Weller equation. Using cyclic voltammetry the reduction potentials of the dyes and oxidation potentials of borate salts were determined. Parabolic dependence between polymerization rate (R-p) and DeltaG value has been obtained for all the salts tested. The lifetimes of excited singlet state of cyanine dye with and without quenching were determined and let calculate the rate constants of primary process of polymerization investigated, i.e. electron transfer from borate anion to excited state of the dye (k(cl)). According to the Scheme A, the effect of competitive process, i.e. cyanine and butyl radicals recombination on the photoinitiated polymerization rate was also determined. This process, which does not influence R-p value, leads to the dye bleaching what strongly depends on the structure of both dye cation and borate anion. There was stated that initiation rate of polymerization depends on the photoinitiator concentration and R-p value - on the co- initiator concentration.

PL

Na podstawie badań Schustera [9,10] zaproponowano mechanizm procesów przebiegających podczas fotoinicjowanej solami boranowymi barwników cyjaninowych polimeryzacji rodnikowej (schemat A). Przedstawiono również możliwość zastosowania teorii Marcusa [11 do opisu kinetyki takiej polimeryzacji fotoinicjowanej via proces przeniesienia elektronu. Wymagało to wyznaczenia z równania Rehma-Wellera [równanie (1)] wartości energii swobodnej aktywacji procesu przeniesienia elektronu (AGe; - tabela 1). W tym celu metodą cyklowoltoamperornetryczną wyznaczono potencjały utleniania boranu (rys. 2) i redukcji barwników (rys. 1). W odniesieniu do wszystkich badanych soli otrzymano paraboliczną zależność pomiędzy szybkością polimeryzacji (\i\Rp) a wartością AG. W seriach zawierających jako donor elektronu anion sec- lub ferł-butylotrifenyloboranowy zaobserwowano wzrost szybkości polimeryzacji wraz ze wzrostem siły napędowej procesu przeniesienia elektronu (czyli przesunięcia AG,.; w kierunku bardziej ujemnych wartości) (rys. 7), natomiast w serii zawierającej anion tetra-n-butyloboranowy w zakresie AGe/ od -0,6-0,3 eV występuje spadek Rp wraz ze wzrostem wartości AGt.; (rys. 8). Wyznaczone czasy życia wzbudzonego stanu singletowego barwnika cyjaninowego bez wygaszacza i w obecności wygaszacza (rys. 9 i 10) pozwoliły na obliczenie stałych szybkości procesu pierwotnego w badanej polimeryzacji, czyli przeniesienia elektronu z anionu boranowego do stanu wzbudzonego barwnika (fc; - tabela 2). W przypadku barwników niezawierających podstawni-ka alkilowego w położeniu mezo łańcucha polimetinowego otrzymano klasyczne paraboliczne zależności pomiędzy In kei a AGL./ (rys. 11 i 12). Zgodnie ze schematem A określono również wpływ procesu konkurencyjnego, tj. rekombinacji rodnika cyjaninowego i rodnika butylowego, na szybkość fotoinicjowanej-polimeryzacji. Proces ten prowadzi do wybielenia barwnika, które silnie zależy od struktury zarówno kationu barwnika (rys. 5), jak i anionu boranowego (rys. 6). Jednak niewielkie wydajności kwantowe tego procesu pozwalają sądzić, że nie wywiera on wpływu na wartość Rp. Stwierdzono również, że szybkość inicjowania polimeryzacji zależy od stężenia fotoinicjatora (rys. 3), którego optymalne stężenie w danych warunkach pomiarowych wynosi 1 Ś 10 M. Zwiększenie stężenia koinicjatora (anionu boranowego) powoduje przesunięcie równowagi kation barwnika cyjaninowego/anion bora-nowy w kierunku tworzenia pary jonowej, a tym samym zwiększa szybkość procesu przeniesienia elektronu, co w rezultacie powoduje wzrost Rp (rys. 4).

7

Investigation of photo-physical properties of selected diaminoacid protoporphyrin derivatives (PP(AA)2Arg2). I. Determination of quantum yield of fluorescence

Ye S., Czuba M., Romiszewska A., Karolczak J., Graczyk A.

Optica Applicata

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2003

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Vol. 33, nr 2-3

489-503

EN

An new generation of photosensitizers for photodynamic therapy (PDT) has been investigated. Different amino acids (Ala, Ser, Thr, Phe and Trp) were bound to protoporphyrin (PP). The quantum yield of fluorescence of porphyrin solutions was investigated. Fluorescence spectra and lifetimes of excited porphyrins were determined, too. The purpose of this work was to evaluate the quantum yield of fluorescence of different PP(AA)2Arg2 derivatives, since it is crucial for choosing proper ingredients of photosensitizer for diagnosis and therapy in PDT

8

Excited State Intramolecular Proton Transfer in 9-Oxo-9,10-dihydro-acridine-4-carboxylic Acid. photophysical and Computational studies

Sobczyk M., Szymańska A., Wiczk W., Łankiewicz L., Karolczak J., Rak J.

Polish Journal of Chemistry

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2002

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Vol. 76 / nr 9

1263-1269

EN

9-Oxo-9,10-dihydro-acridine-4-carboxylic acid in both methanol and acetonitrile possesses a dual fluorescence and complex fluorescence intensity decay, whereas 9-oxo- 9,10-dihydro-acridine-2-carboxylic acid shows only one emission band and monoexponential fluorescence intensity decay. Theoretical calculations, using a semiempirical PM3 method, confirm, in the case of 9-oxo-9,10-dihydro-acridine-4-carboxylic acid, the excited state intramolecular proton transfer process from nitrogen atom to the oxygen of carbonyl of the carboxylic group.

9

Transient absorption experimental set-up with femtosecond time resolution

Naskręcki R., Lorenc M., Ziółek M., Karolczak J., Kubicki J., Maciejewski A., Szymański M.

Bulletin of the Polish Academy of Sciences. Chemistry

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1999

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Vol. 47, No. 4

333-346

EN

Experimental set-up for time dependent transient absorption/gain measure-ments with femtosecond time resolution is presented. The pump-probe spectroscopy tech-nique with femtosecond pulses from Ti: Sapphire laser system (Spectra Physics) allowed measurements of the optical density of transient absorption and transient gain in the spectral range of 330-700 nm, time resolution of 120 fs, and the accuracy of up to 0.005. The real time resolution and "zero time" dispersion of the system were found in two-photon absorption experiment.

10

Fluorescence dynamics spectrometer of single-picosecond resolution: optimisation of experimental performance

Karolczak J., Komar D., Kubicki J., Szymański M., Wróżowa T., Maciejewski A.

Bulletin of the Polish Academy of Sciences. Chemistry

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1999

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Vol. 47, No. 4

361-380

EN

Design and construction of a new spectrometer for picosecond fluorescence decay measurements by time-correlated single-photon counting is described. The use of pico/femtosecond excitation pulses from a tunable Ti: Sapphire laser in combination with a fast microchannel plate photodetector and ultrafast timing electronics resulted in an excellent temporal resolution and stability of the instrument response function (IRF) of the spectrometer which enabled successful analysis of fluorescence decay signals of single picoseconds. Results of optimisation of experimental characteristics of the system concerning the effect of the geometry of the excited region of the sample, optimum optical imaging and performance of photodetectors are presented. Test measurements of fluores-cence decay of xanthione in various solvents characterised by different S(2) state lifetimes 5-38 ps proved the excellent experimental performance of the spectrometer .