The synthesis of a new symmetric bis(spiropyran) of the indoline series existing as an equilibrium mixture of isomeric forms in various organic solvents is described. This equilibrium was in detail studied by dynamic NMR spectroscopy. In particular, the equilibrium constants were found at various temperatures, and the thermal effects of isomerization processes were calculated. The thermal transformations were studied by quantum chemical modeling. As a result, possible isomerization pathways were proposed and the observed ratio of the forms in the NMR spectra was explained. Photo- and thermochromic transformations were studied by UV spectroscopy, which revealed positive photochromic properties of the target compound. The observed changes in the absorption spectra with increasing temperature are completely consistent with the results of NMR studies. The nature of the absorption bands observed in the spectra was explained using time-dependent density functional theory (TD-DFT) calculations. The surface-enhanced Raman scattering (SERS) spectra of the synthesized compound on the surface of silver nanoparticles were detected and analyzed before and after UV irradiation to determine prospects for using similar bis(spiropyrans) as SERS markers and probes.

An analysis of the results of complex experimental and theoretical studies of photoinduced changes in the spectral properties of photochromic diarylethene in various nanostructured systems is presented. The properties of diarylethene were studied in solutions in the presence of colloidal metal and semiconductor nanoparticles, as well as in the form of solid-phase composite nanostructured core-shell systems based on colloidal nanoparticles with a shell of diarylethene molecules (including in a polymer matrix). A photoinduced reversible change in the electronic and vibrational spectra of diarylethene in various studied matrices was found. The results can be used to create optoelectronic photo-switchable elements for ultra-high-capacity memory devices, photo-controlled molecular switches and sensors. Keywords: photochromism, diarylethenes, nanocomposites, quantum dots, electronic spectra, vibrational spectra, fluorescence, Ferster resonance energy transfer, quantum chemical calculations.

The results of studies of the spectral-kinetic (absorption and fluorescent) characteristics of the polymer nanospheres created by us (containing luminescent inorganic CdSe/ZnS quantum dots and photochromic diarylethene molecules) incorporated into a polymer film are presented. A reversible modulation of the fluorescence intensity of quantum dots, caused by the photoisomerization of diarylethene molecules, was found. It is shown that nanospheres in polymer matrices exhibit higher efficiencies of both photoinduced modulation of QD radiation and Forster resonance energy transfer (FRET) from QDs to the cyclic isomer of DAE as compared to solutions. The results can be used, for example, to create luminescent photocontrolled panels based on films containing fluorescent nanoparticles. Keywords: photochromism, fluorescence, quantum dot, Forster resonance energy transfer, polymer nanospheres, polymer films

A study was carried out and a comparative analysis of the spectral-kinetic (absorption and fluorescent) characteristics of nanospheres containing luminescent inorganic quantum dots (QDs) CdSe/ZnS, covered with an amphiphilic polymer shell, which ensures the stability of nanospheres in aqueous colloidal solutions and the possibility of introducing into them hydrophobic photochromic diarylethene molecules with different structure. Photoinduced reversible isomerization of diarylethene molecules causes modulation of the photoluminescence signal of quantum dots, including through the control of the efficiency of resonant energy transfer (FRET) from quantum dots to the cyclic isomer of diarylethene. The FRET efficiency turned out to be the highest in nanospheres with DAE2 and DAE4. The value of the quality index (QF) of the FRET photomodulator (which shows the efficiency of modulation of the quantum yield of QD photoluminescence), introduced in this work, varies for samples with different diarylethenes from 0.003 (for DAE1) to 0.09 (for DAE2). Nanospheres containing luminescent nanoparticles of various shapes can be used in the development of luminescent photocontrolled panels, fluorescent markers, etc.

An analysis of theoretical model studies of photochromic systems with reversible fluorescence modulation based on polymer nanospheres containing CdSe/ZnS semiconductor quantum dots (QDs), and photochromic diarylethene DAE2 molecules is presented. Based on the known relations of the theory of Förster resonance energy transfer (FRET), a model is constructed for the efficiency of modulation of QD fluorescence E(r) caused by photochromic transformations of DAE2 molecules located near them due to the FRET mechanism. The boundaries of the optimal values of the parameters that affect the efficiency of the fluorescence modulation due to FRET are determined. The efficiency of FRET E(r) is given for some boundary values of the influencing factors. It is shown that E(r) ~ 0.7 can be achieved at distances between donors and acceptors r = 4.5 nm, if one QD with a fluorescence quantum yield Q = 0.4 accounts for at least n = 16 DAE2 molecules (or at Q = 0.8 and n = 8), as well as at distances r = 3 nm (Q = 0.1 and n = 6; Q = 0.4 and n = 2; Q = 0.8 and n = 1). The results obtained can be used to optimize the structure and technology for the synthesis of photochromic luminescent nanospheres.

The results of studies of the spectral-kinetic (absorption and fluorescent) characteristics of the polymer nanospheres created by us (containing luminescent inorganic CdSe/ZnS quantum dots and photochromic diarylethene molecules) incorporated into a polymer film are presented. A reversible modulation of the fluorescence intensity of quantum dots, caused by the photoisomerization of diarylethene molecules, was found. It is shown that nanospheres in polymer matrices exhibit higher efficiencies of both photoinduced modulation of QD radiation and Förster resonance energy transfer (FRET) from QDs to the cyclic isomer of DAE as compared to solutions. The results can be used, for example, to create luminescent photocontrolled panels based on films containing fluorescent nanoparticles.

A study was carried out and a comparative analysis of the spectral-kinetic (absorption and fluorescent) characteristics of nanospheres containing luminescent inorganic quantum dots (QDs) CdSe/ZnS, covered with an amphiphilic polymer shell, which ensures the stability of nanospheres in aqueous colloidal solutions and the possibility of introducing into them hydrophobic photochromic diarylethene molecules with different structure. Photoinduced reversible isomerization of diarylethene molecules causes modulation of the photoluminescence signal of quantum dots, including through the control of the efficiency of resonant energy transfer (FRET) from quantum dots to the cyclic isomer of diarylethene. The FRET efficiency turned out to be the highest in nanospheres with DAE2 and DAE4. The value of the quality index (QF) of the FRET photomodulator (which shows the efficiency of modulation of the quantum yield of QD photoluminescence), introduced in this work, varies for samples with different diarylethenes from 0.003 (for DAE1) to 0.09 (for DAE2). Nanospheres containing luminescent nanoparticles of various shapes can be used in the development of luminescent photocontrolled panels, fluorescent markers, etc. Keywords: quantum dots, fluorescence, Forster resonance energy transfer, nanocomposites, photochromism, diarylethenes.

An analysis of the results of complex experimental and theoretical studies of photoinduced changes in the spectral properties of photochromic diarylethene in various nanostructured systems is presented. The properties of diarylethene were studied in solutions in the presence of colloidal metal and semiconductor nanoparticles, as well as in the form of solid-phase composite nanostructured core-shell systems based on colloidal nanoparticles with a shell of diarylethene molecules (including in a polymer matrix). A photoinduced reversible change in the electronic and vibrational spectra of diarylethene in various studied matrices was found. The results can be used to create optoelectronic photo-switchable elements for ultra-high-capacity memory devices, photo-controlled molecular switches and sensors.

Steady-state absorption and fluorescence spectra, fluorescence decay kinetics of CdSe/ZnS quantum dots (QD) with photochromic diarylethenes (DAE) in toluene have been studied. Two kinds of QDs emitting at 525 and 600 nm were investigated and DAE were selected to ensure good overlap of their photoinduced absorption band with QDs emission spectra. It has been found that photochromic molecules form complexes with QD which results in partial fluorescence quenching. A reversible modulation of QDs emission intensity which correlates with magnitude of transient photoinduced absorption band of the diarylethenes during photochromic transformations has been demonstrated.