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Krystyna Rotkiewicz

Bio: Krystyna Rotkiewicz is an academic researcher from Polish Academy of Sciences. The author has contributed to research in topics: Excited state & Ground state. The author has an hindex of 21, co-authored 43 publications receiving 3895 citations. Previous affiliations of Krystyna Rotkiewicz include Technical University of Berlin & Pedagogical University.

Papers
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Journal ArticleDOI
TL;DR: The Rehybridization of the Acceptor (RICT) and Planarization ofThe Molecule (PICT) III is presented, with a comparison of the effects on yield and radiationless deactivation processes.
Abstract: 6. Rehybridization of the Acceptor (RICT) 3908 7. Planarization of the Molecule (PICT) 3909 III. Fluorescence Spectroscopy 3909 A. Solvent Effects and the Model Compounds 3909 1. Solvent Effects on the Spectra 3909 2. Steric Effects and Model Compounds 3911 3. Bandwidths 3913 4. Isoemissive Points 3914 B. Dipole Moments 3915 C. Radiative Rates and Transition Moments 3916 1. Quantum Yields and Radiationless Deactivation Processes 3916

2,924 citations

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TL;DR: In this paper, the ground and excited-state dipole moments extracted from electro-optical emission and solvatochromic measurements of dual-fluorescing dimethylaminobenzonitrile (DMABN) derivatives are compared.
Abstract: Several derivatives of dual-fluorescing dimethylaminobenzonitrile (DMABN) are compared regarding their ground and excited-state dipole moments extracted from electro-optical emission and solvatochromic measurements. The comparison includes bridged model compounds as well as compounds with different degrees of steric hindrance to planarity, as well as ester and carbazolyl derivatives. The results are discussed on the basis of the twisted intramolecular charge transfer (TICT) model, the most widely accepted model. They show that (i) the dipole moment of the A (TICT) state (long-wavelength band) shows only little solvent sensitivity (polarizability), (ii) this observed small dependence of the dipole moment on solvent polarity can be considered as the result of overlap of two fluorescence bands or of solvent-induced changes in the mean deviation from the ideal TICT geometry (“atomic polarizability”), (iii) the dipole moment of the B state (short-wavelength band) is considerably smaller than that of the A band, (iv) the order of the dipole moment values obtained from solvatochromy is the same as from theoretical calculations: μgp <μep (1Lb) <μep(1La) <μeT, (v) ester derivatives show a reduced dipole moment with respect to the corresponding nitriles and (vi) sterically crowded compounds seem to possess a reduced dipole moment. The possible reasons are discussed. The agreement and the differences between the two methods are discussed and compared with results from dielectric loss measurements and from quantum-chemical calculations.

124 citations

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TL;DR: In this article, the dual fluorescence hypothesis assigned to the formation of a twisted internal charge transfer (TICT) state was proved for p-cyano-and p-(9-anthryl)-dialkylanilines.

115 citations

Journal ArticleDOI
TL;DR: In this paper, the energies of the low lying electronic states of p -cyano-N,N-dimethylaniline (CDMA) in its planar and in 90° twisted conformation have been calculated using the modified INDO method.

92 citations

Journal ArticleDOI
TL;DR: The photophysical properties of naphthalene were studied in aqueous solution (H2O and D2O), in some organic solvents (ethanol, hexane, and acetonitrile), and in complexes with the cyclodextrins (CDs) α-CD and β-CD, by means of absorption, steady-state and time-resolved fluorescence, circular dichroism, and triplet−triplet absorption spectroscopies.
Abstract: The photophysical properties of naphthalene were studied in aqueous solution (H2O and D2O), in some organic solvents (ethanol, hexane, and acetonitrile), and in complexes with the cyclodextrins (CDs) α-CD and β-CD, by means of absorption, steady-state and time-resolved fluorescence, circular dichroism, and triplet−triplet absorption spectroscopies. The structures of the CD inclusion complexes were computed using a dynamic Monte Carlo method. The main difference of the photophysics in the pure aqueous with respect to the organic media consists in a reduction of the fluorescence lifetime, τF, by a factor of about 2.5. Consideration of the triplet properties in aqueous and organic media led to the conclusion that this effect is most probably due to a corresponding increase of the intersystem crossing rate, induced by H2O or D2O. Inclusion of naphthalene in the CD hosts has the effect, at high CD concentration (>0.01 M), of increasing τF with respect to the aqueous medium, the value in α-CD being near to that...

80 citations


Cited by
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Journal ArticleDOI
TL;DR: This paper presents a meta-analysis of the chiral stationary phase transition of Na6(CO3)(SO4)2, a major component of the response of the immune system to Na2CO3.
Abstract: Ju Mei,†,‡,∥ Nelson L. C. Leung,†,‡,∥ Ryan T. K. Kwok,†,‡ Jacky W. Y. Lam,†,‡ and Ben Zhong Tang*,†,‡,§ †HKUST-Shenzhen Research Institute, Hi-Tech Park, Nanshan, Shenzhen 518057, China ‡Department of Chemistry, HKUST Jockey Club Institute for Advanced Study, Institute of Molecular Functional Materials, Division of Biomedical Engineering, State Key Laboratory of Molecular Neuroscience, Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China Guangdong Innovative Research Team, SCUT-HKUST Joint Research Laboratory, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China

5,658 citations

Journal ArticleDOI
TL;DR: The restriction of intramolecular rotation is identified as a main cause for the AIE effect and a series of new fluorescent and phosphorescent AIE systems with emission colours covering the entire visible spectral region and luminescence quantum yields up to unity are developed.

3,324 citations

Journal ArticleDOI
TL;DR: The Rehybridization of the Acceptor (RICT) and Planarization ofThe Molecule (PICT) III is presented, with a comparison of the effects on yield and radiationless deactivation processes.
Abstract: 6. Rehybridization of the Acceptor (RICT) 3908 7. Planarization of the Molecule (PICT) 3909 III. Fluorescence Spectroscopy 3909 A. Solvent Effects and the Model Compounds 3909 1. Solvent Effects on the Spectra 3909 2. Steric Effects and Model Compounds 3911 3. Bandwidths 3913 4. Isoemissive Points 3914 B. Dipole Moments 3915 C. Radiative Rates and Transition Moments 3916 1. Quantum Yields and Radiationless Deactivation Processes 3916

2,924 citations

Journal ArticleDOI
TL;DR: In this article, a blue organic light-emitting diodes that harness thermally activated delayed fluorescence was realized with an external quantum efficiency of 19.5% and reduced roll-off at high luminance.
Abstract: Blue organic light-emitting diodes that harness thermally activated delayed fluorescence are realized with an external quantum efficiency of 19.5% and reduced roll-off at high luminance.

1,909 citations

Journal ArticleDOI
TL;DR: An overview of the quick development in TADF mechanisms, materials, and applications is presented, with a particular emphasis on their different types of metal-organic complexes, D-A molecules, and fullerenes.
Abstract: The design and characterization of thermally activated delayed fluorescence (TADF) materials for optoelectronic applications represents an active area of recent research in organoelectronics. Noble metal-free TADF molecules offer unique optical and electronic properties arising from the efficient transition and interconversion between the lowest singlet (S1) and triplet (T1) excited states. Their ability to harvest triplet excitons for fluorescence through facilitated reverse intersystem crossing (T1→S1) could directly impact their properties and performances, which is attractive for a wide variety of low-cost optoelectronic devices. TADF-based organic light-emitting diodes, oxygen, and temperature sensors show significantly upgraded device performances that are comparable to the ones of traditional rare-metal complexes. Here we present an overview of the quick development in TADF mechanisms, materials, and applications. Fundamental principles on design strategies of TADF materials and the common relationship between the molecular structures and optoelectronic properties for diverse research topics and a survey of recent progress in the development of TADF materials, with a particular emphasis on their different types of metal-organic complexes, D-A molecules, and fullerenes, are highlighted. The success in the breakthrough of the theoretical and technical challenges that arise in developing high-performance TADF materials may pave the way to shape the future of organoelectronics.

1,473 citations