Photoluminescence properties of self-assembled chitosan-based composites containing semiconductor nanocrystals

The photoluminescence (PL) properties of composites obtained by embedding green-emitting semiconductor nanocrystals (NCs) of two different types (thiol-capped CdTe and CdSe/ZnS) into chitosan-based biopolymer particles were investigated. The synthesis of self-assembled particles from oppositely charged polysaccharides involved a preliminary electrostatic binding of positively charged chitosan chains by negatively charged functional groups of NC stabilizing ligands. The amount of NCs and the acidity of the solution were found to be important parameters influencing the PL. The PL properties were mainly discussed in terms of the colloidal stability of the particles and changes in energy gap of NCs. Generally, the obtained biocompatible composites with NCs randomly distributed within a biopolymer particle demonstrated a higher PL resistance to the solution acidity that expands the applicability range of thiol-capped NCs

Raman spectroscopy studies of the terahertz vibrational modes of a DUT-8 (Ni) metal-organic framework

Low-frequency lattice vibration modes have been discussed to play a crucial role in phase transformation process of switchable metal–organic frameworks (MOFs). Therefore, Raman spectroscopy was applied to study lattice dynamics of the pillared layer DUT-8(Ni) framework (DUT – Dresden University of Technology), existing in rigid and flexible form. The open pore phase and the close pore phase could be unanimously identified by breathing modes in the corresponding Raman character of low-frequency vibrations. The flexible version of DUT-8 could be distinguished by orientation dependent Raman spectroscopy experimen

Laser-induced Interaction of Multilevel Quantum Dots

A theoretical model is developed for describing the laser-induced interaction of a pair of multilevel semi- conductor quantum dots. Spectral dependencies of interaction energy are calculated in dipole-dipole ap- proximation for a pair of CdSe quantum dots in a quasi-resonant laser field, for cases of two identical quantum dots and those with differing transition wavelengths. Interaction energy of pair of multilevel quantum dots in the long-wavelength potential well is much higher than that of pair of two-level quan- tum dots. The increase of difference of resonance wavelengths of two interacting quantum dots leads to decrease of the potential well depth

Laser-induced Interaction of Multilevel Quantum Dots

A theoretical model is developed for describing the laser-induced interaction of a pair of multilevel semi- conductor quantum dots. Spectral dependencies of interaction energy are calculated in dipole-dipole ap- proximation for a pair of CdSe quantum dots in a quasi-resonant laser field, for cases of two identical quantum dots and those with differing transition wavelengths. Interaction energy of pair of multilevel quantum dots in the long-wavelength potential well is much higher than that of pair of two-level quan- tum dots. The increase of difference of resonance wavelengths of two interacting quantum dots leads to decrease of the potential well depth

Single particle Raman spectroscopy analysis of the metal-organic framework DUT-8(Ni) switching transition under hydrostatic pressure

Experimental in situ observations of phase coexistence in switchable metal-organic frameworks are reported to provide a fundamental understanding of dynamic adsorbents that can change their pore structure in response to external stimuli. A prototypical flexible pillared layer framework DUT-8(Ni) (DUT = Dresden University of Technology) was studied under hydrostatic pressure by in situ Raman spectroscopy on single crystals. The closing transition of the open pore phase (op) containing DMF in the pores in silicon oil as a pressure transmitting fluid, as well as the closed pore phase (cp) to op transition under pressure in methanol, were studied. Phase coexistences during both transitions were observed

Fluorescence and photoinduced proton transfer in the protolytic forms of fluorescein:Experimental and computational study

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Effect of Spatial Distribution of Laser Radiation Intensity on Photobleaching Kinetics of Dye in Polymer Matrix

Выполнено моделирование кинетики лазероиндуцированного обесцвечивания эозина в рамках че- тырехуровневой схемы (S0, S1, T1, Tn) с учетом распределения интенсивности в TEM00 моде. По- казано, что при учете гауссова распределения интенсивности лазерного излучения зависимость оптической плотности образцов от времени облучения отличается от моноэкспоненциальной функции, характерной для химической реакции первого порядка. Сформулированы рекомендации для проведения эксперимента, позволяющего корректно определять кинетические характеристи- ки системы.The modeling of light-induced bleaching of eosin in polymer in the frame of four-level energy scheme (S0, S1, T1, Tn) was made taking the distribution of intensiviti in TEM00 mode into account. It was shown that the time dependence of optical dentisty of the samples differs from the exponential relationship inherent for first order chemical reaction in the case of taking the normal intensity distribution into consideration. The conditions of experemental realization of correct definition kinetic paremeters of system were revealed

Effect of Spatial Distribution of Laser Radiation Intensity on Photobleaching Kinetics of Dye in Polymer Matrix

Выполнено моделирование кинетики лазероиндуцированного обесцвечивания эозина в рамках че- тырехуровневой схемы (S0, S1, T1, Tn) с учетом распределения интенсивности в TEM00 моде. По- казано, что при учете гауссова распределения интенсивности лазерного излучения зависимость оптической плотности образцов от времени облучения отличается от моноэкспоненциальной функции, характерной для химической реакции первого порядка. Сформулированы рекомендации для проведения эксперимента, позволяющего корректно определять кинетические характеристи- ки системы.The modeling of light-induced bleaching of eosin in polymer in the frame of four-level energy scheme (S0, S1, T1, Tn) was made taking the distribution of intensiviti in TEM00 mode into account. It was shown that the time dependence of optical dentisty of the samples differs from the exponential relationship inherent for first order chemical reaction in the case of taking the normal intensity distribution into consideration. The conditions of experemental realization of correct definition kinetic paremeters of system were revealed