Polystyrene sulfonate (PSS)-doped calcium carbonate microparticles (CaCO 3 @PSS) were synthesized... more Polystyrene sulfonate (PSS)-doped calcium carbonate microparticles (CaCO 3 @PSS) were synthesized and used for the encapsulation of Methylene Blue (MB). SEM and TEM images suggest the formation of spherical particles with about 2 mm diameters and raspberry-like structure. BrunauereEmmetteTeller method was used to analyze the specific surface area and the pore size distribution of the CaCO 3 @PSS microparticles. The sorption of MB from aqueous solution onto CaCO 3 @PSS microspheres was studied and equilibrium isotherm determined. A physisorption process was indicated by the values of sorption energy (B D) 2.39 Â 10 À7 mol 2 /J 2 , mean free energy (E D) 1.5 kJ/mol and heat of sorption (B) 28.8 J/mol estimated from the Dubinin-Radushkevich and Temkin isotherms. The Langmuir model precisely describes the isotherm and the maximum adsorption capacity was 149.3 mg/g indicating homogeneous nature of adsorption sites and monolayer coverage of MB on the CaCO 3 @PSS microparticle inner and outer surfaces. The pseudo-second-order model can better describe the adsorption kinetics with a maximum adsorption attained within 5 h. The intra-particle diffusion process was identified as the main mechanism controlling the rate of the dye sorption. The MB release from CaCO 3 @PSS microspheres was found to be pH-responsive. The presence of negatively charged PSS À groups in pores of CaCO 3 @PSS microparticles prevents the initial burst release of MB, decreasing the release rate of MB. The experimental results indicate high potential of CaCO 3 @PSS microspheres as carriers for encapsulation and controlled release of cationic dye molecules, such as photosensitizer MB, used in photodynamic therapy.
We present thoroughly analyzed experimental results that demonstrate the anomalous manifestation ... more We present thoroughly analyzed experimental results that demonstrate the anomalous manifestation of the exciton self-trapping effect, which is already well-known in bulk crystals, in ordered molecular nanoclusters called J-aggregates. Weakly-coupled one-dimensional (1D) molecular chains are the main structural feature of J-aggregates, wherein the electron excitations are manifested as 1D Frenkel excitons. According to the continuum theory of Rashba-Toyozawa, J-aggregates can have only self-trapped excitons, because 1D excitons must adhere to barrier-free self-trapping at any exciton-phonon coupling constant g ¼ e LR /2b, wherein e LR is the lattice relaxation energy, and 2b is the half-width of the exciton band. In contrast, very often only the luminescence of free, mobile excitons would manifest in experiments involving J-aggregates. Using the Urbach rule in order to analyze the low-frequency region of the low-temperature exciton absorption spectra has shown that J-aggregates can have both a weak (g < 1) and a strong (g > 1) exciton-phonon coupling. Moreover, it is experimentally demonstrated that under certain conditions, the J-aggregate excited state can have both free and self-trapped excitons, i.e., we establish the existence of a self-trapping barrier for 1D Frenkel excitons. We demonstrate and analyze the reasons behind the anomalous existence of both free and self-trapped excitons in J-aggregates, and demonstrate how exciton-self trapping efficiency can be managed in J-aggregates by varying the values of g, which is fundamentally impossible in bulk crystals. We discuss how the exciton-self trapping phenomenon can be used as an alternate interpretation of the wide band emission of some J-aggregates, which has thus far been explained by the strongly localized exciton model. Published by AIP Publishing. [http://dx.
The effect of cyanine dye 3,3 0-dioctadecyloxacarbocyanine perchlorate (DiO) and benzimidazole dy... more The effect of cyanine dye 3,3 0-dioctadecyloxacarbocyanine perchlorate (DiO) and benzimidazole dye 4-dimethylamino-1,8-naphthoylene-1 0 ,2 0-benzimidazole (DNBI) accumulation in nanoporous silica matrices on the dyes luminescence properties has been studied. For both dyes, ground state dimer formation with perpendicular transition dipoles at high dye concentrations has been considered as a result of restricted geometry of the nanoscale pores. The dimer excitation leads to excimer formation revealing by appearance of new long-wavelength luminescence band and shortening the dye luminescence lifetime. In the excimer luminescence excitation spectra two additional bands have been observed, one of which is bathochromically shifted relatively to the absorption band and another one is hypsocromically shifted. Using the Kasha exciton model it was shown that the excimers possess oblique transition dipoles configuration .
The kinetic and thermodynamic stability of organic (sodium dodecylsulfate micelles and egg-yolk p... more The kinetic and thermodynamic stability of organic (sodium dodecylsulfate micelles and egg-yolk phosphatidylcholine zwitterionic liposomes) and inorganic (based on GdYVO 4 :Eu 3+ nanoparticles) nanocarriers (NCs) was studied by the λ-ratiometric method (analysis of fl uorescence intensity at two wavelengths) using non-radiative transfer of electronic excitation energy. The kinetic and thermodynamic parameters of the redistribution of dyes DiO and DiI between NCs that was associated with the destruction of NC/DiO and NC/DiI complexes and the formation of new NC/(DiO + DiI) complexes were evaluated. Rate constants for the destruction of the complexes (K), lifetimes of the complexes (τ 1/2), the activation energy for the destruction (E a), the equilibrium constant (K eq), and the change of free energy (ΔG 0), enthalpy (ΔH 0), and entropy (ΔS 0) of the process were calculated. The obtained kinetic parameters pointed to high kinetic stability for all investigated complexes whereas the thermodynamic ones indicated that dye redistribution required high temperatures. Keywords: micelle, liposome, nanoparticle, non-radiative transfer of electronic excitation energy, kinetic and thermodynamic stability. Introduction. The development of pharmacological dosage forms that are based on the inclusion of drugs in one container or another is a promising approach to solving the problem of drug delivery to a biological target with the desired pharmacokinetic and therapeutic properties. The use of special nanosized carriers or containers provides an effective solution for issues related to high drug toxicity, poor solubility in biological fl uids, the need to use high doses to achieve a therapeutic effect, non-specifi c accumulation in vivo, rapid degradation, and short biological half-lives in the circulation [1–7]. Liposomal vesicles, polymeric micelles, nanoparticles (NP) based on proteins, and various conjugates of polymers are under intense scrutiny and possess the most suitable characteristics with respect to the encapsulation of drugs, genes, diagnostic agents, etc. among currently existing nanocarriers (NC) [2, 4, 7]. Stability, i.e., reliable encapsulation of an active ingredient, is the most important of many factors that are considered during construction of a NC/active-ingredient complex. Undesirable loss of active ingredient and; conversely, contamination by foreign molecules in the environment can occur during storage before use and also during circulation in vivo. NC should be predictably stable and provide controlled release of the active ingredient in order to effectively fulfi ll their functions [6–9]. Understanding of the exchange dynamics of the active ingredient between the solvent and NC and/or between NC is signifi cant for decision making. It was shown [10] that complexes of the dye JC-1 with inorganic GdYVO 4 :Eu 3+ NP were capable of accumulating in the nucleus of a living cell with the NP acting as delivery agents. This made inorganic GdYVO 4 :Eu 3+ NP and their complexes attractive for further research. Herein the kinetic and thermodynamic stability of NC/dye complexes was studied by λ-ratiometry (analysis of the fl uorescence intensity at two or more wavelengths) using Förster resonance energy transfer (FRET). Micelles of sodium dodecylsulfate (SDS), liposomes of egg-yolk phosphatidylcholine (PC), and inorganic GdYVO 4 :Eu 3+ NP were used as the NC. Experimental. Dyes 3,3′-dioctadecyloxacarbocyanine (DiO) and 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbo-cyanine perchlorate (DiI), SDS, and PC (Sigma Aldrich) were used without further purifi cation (dye purity 97%):
Formation of thiacyanine dye J-aggregates in layered polymer films has been studied. This process... more Formation of thiacyanine dye J-aggregates in layered polymer films has been studied. This process leads to the J-aggregates spectral bands widening as a result of static disorder increasing. To enhance the J-aggregate luminescence the effect of their interaction with plasmon resonances of silver nanoparticles has been used. It was found that about 4-fold luminescence enhancement for thiacyanine J-aggregates in the polymer films could be obtained at 15 nm distance from silver nanoparticles.
Using fluorescence microspectoscopy and FRET-labeling of various nano-scale carriers (NCs) the ef... more Using fluorescence microspectoscopy and FRET-labeling of various nano-scale carriers (NCs) the efficiency and kinetics of NCs/dye molecules complexes accumulation in living cells and dye release have been studied. Organic liposome vesicles and inorganic nanoparticles (Ce02 and GdYV04:Eu3+) were used as NCs. NCs/dyes complexes formed in aqueous solutions have been characterized. It has been shown that NCs based on GdYV04:Eu3+ nanoparticles exhibit the most effective accumulation in cells and provide very fast release of the lipophilic cargo (dyes molecules). Lipophilic compound (cholesterol) embedded into the NCs/dyes complexes decreases noticeably the rate of lipophilic dyes release and reduces the affinity of the complex interaction with hepatocytes. GdYV04:Eu3+ NPs could be used as a nano-scale platform for controlled intracellular delivering of hydrophobic agents.
Adsorption of cyanine dye Dil in a nanopous Si02 matrix has been studied. It was shown that the i... more Adsorption of cyanine dye Dil in a nanopous Si02 matrix has been studied. It was shown that the increase of the dye concentration in the Si02 matrix provokes the appearance of an additional red-shifted band of excimer nature in the dye fluorescence spectrum without any changes in the absorption one. Static character of the dye excimer formation was revealed. Enhanced dye concentration due to spatial confinement in a nanopore volume has been supposed as a reason of the effective excimer formation.
The metal enhanced fluorescence of thiacyanine dye monomers in polymer films has been studied. To... more The metal enhanced fluorescence of thiacyanine dye monomers in polymer films has been studied. To control the distance between dye molecules and silver nanoparticles a polymer spacer has been used. The spacer thickness has been varied using a layer-by-layer assembly method of polyelectrolytes. The best 4.5 times fluorescence enhancement has been observed for the 20 nm thick polymer spacer. The result has been confirmed both by steady-state and time resolved fluorescence spectroscopies.
Features of J-aggregates formation in highly structured pores of anodic aluminum oxide (AAO) have... more Features of J-aggregates formation in highly structured pores of anodic aluminum oxide (AAO) have been studied using steady-state absorption and luminescence spectroscopy and time-resolved luminescence spectroscopy, J-aggregates with different structures (spherical and thread-like) were chosen for the studying. Spectroscopic investigations show the presence of both types of the «/-aggregates in the AAO pores. It leads to a static disorder increasing in the J-aggregates. Besides, in the case of the thread-like J-aggregates changes in the structure have been supposed also.
In the present study, we analyze the efficiency of Electronic Excitation Energy Transfer (EEET) b... more In the present study, we analyze the efficiency of Electronic Excitation Energy Transfer (EEET) between two dyes, an energy donor (D) and acceptor (A), concentrated in structurally heterogeneous media (surfactant micelles, liposomes, and porous SiO2 matrices). In all three cases, highly effective EEET in pairs of dyes has been found and cannot be explained by Standard Fo¨rster-type theory for homogeneous solutions. Two independent approaches based on the analysis of either the D relative quantum yield (FDA=FD) or the D fluorescence decay have been used to study the deviation of experimental results from the theoretical description of EEET process. The observed deviation is quantified by the apparent fractal distribution of molecules parameter d. We conclude that the highly effective EEET observed in the nano-scale media under study can be explained by both forced concentration of the hydrophobic dyes within nano-volumes and non-uniform cluster-like character of the distribution of D and A dye molecules within nano-volumes.
The efficiency of Foerster resonance energy transfer (FRET) between pairs of different dyes in th... more The efficiency of Foerster resonance energy transfer (FRET) between pairs of different dyes in the nano-volumes of surfactant micelles and liposomes was studied using optical spectroscopy methods. More efficient FRET with the same solution concentrations of the dyes was observed in liposomes despite the greater diameter of liposomes compared with micelles (100 and 5 nm). Calculations showed that the observed effect was explained by the smaller amount of liposomes in the solution and, consequently, the larger local concentration of the dyes in the liposome lipid bilayer. It was shown that not only the spectral overlap integral and the Foerster distance but also specific interactions between molecules in the nanovolume (electrostatic, van-der-Waals, and steric) that were governed by structural features of the molecules affected the FRET efficiency.
Novel red-shifted band has been observed in luminescence spectra of a cyanine dye embedded into n... more Novel red-shifted band has been observed in luminescence spectra of a cyanine dye embedded into nanoporous SiO2 matrix. That band is concentration dependent and disappears at cooling to low temperature. It has been associated with the dye excimer formation due to strong interaction with the pores surface.
In this study we demonstrate that the electron–lattice interaction (ELI) could be controlled by c... more In this study we demonstrate that the electron–lattice interaction (ELI) could be controlled by changing exciton delocalization length in ordered organic nanoclusters called J-aggregates. Particularly it could be done via the J-aggregates solvate shell manipulation using surfactants. The strong correlation between the J-aggregates luminescence quantum yield and the ELI strength has been reviled that allows us to consider the exciton self-trapping as the main mechanism of the J-aggregates luminescence losses.
J-aggregates of amphi-PIC dye have been successfully formed in polymer films by layer-by-layer a... more J-aggregates of amphi-PIC dye have been successfully formed in polymer films by layer-by-layer assembly method. Another dye embedded into J-aggregate layer has revealed itself as efficient exciton trap, which trapped about 80% of excitons. Analyzing J-aggregate luminescence quenching using modified Stern–Volmer equation it has been found that 1 DiD molecule quenches 50% luminescence of 60 amphi-PIC molecules forming the J-aggregate. That is half as much compared to the solution case. The reason for such difference discussed.
The way to manipulate by spectral properties of cyanine dye luminescent ordered nanoclusters (J-a... more The way to manipulate by spectral properties of cyanine dye luminescent ordered nanoclusters (J-aggregates) has been demonstrated. It has been observed a surfactant shell formation around the J-aggregates of four different dyes. This leads to exciton delocalization length increasing which causes an exciton self-trapping suppression. The latter results in spectral changes observed.
The influence of anionic sodium dodecyl sulphate (SDS) on aggregation behavior of squaraine dye S... more The influence of anionic sodium dodecyl sulphate (SDS) on aggregation behavior of squaraine dye Sq-2Me has been studied in dimethylformamide–water (95%) (DMF–W) binary solutions by optical spectroscopy. The addition of surfactants at concentrations above the critical micelle concentration into a DMF–W (95%) solution is found to promote the dye ordered aggregation. The structure of Sq-2Me aggregates formed is analyzed using the exciton theory. In solutions with SDS micelles, formation of Sq-2Me J-type dimers of co-planar inclined geometry with an angle between the chromophore long axes and chromophore center-to-center line (θ) of 47 ° and center-to-center distance (R) of 5 Å has been revealed. The interaction of Sq-2Me with other hydrophobic molecules (carbocyanine dye DiI) solubilized at equal concentrations in SDS micelles is revealed to prevent the Sq-2Me dimer formation. In such a solution, fluorescent resonance energy transfer between donor dye DiI and acceptor Sq-2Me is observed.
Features of BIC J-aggregate formation in AOT reverse micelles have been studied using steady-stat... more Features of BIC J-aggregate formation in AOT reverse micelles have been studied using steady-state absorption and luminescence spectroscopy and time resolved luminescence spectroscopy. BIC J aggregates reveal spherical structure with diameter ~ 20 nm and significant thermal stability. KM diameter decrease results in strong static disorder increase leading to J-aggregate band (J band) widening and luminescence quenching. Due to high thermal stability BIC «/ aggregates are embedded into KM as a whole at any temperatures of stock water solution. Decrease of stock water solution temperature leads to J band narrowing and intensity increasing due to static disorder decreasing.
Polystyrene sulfonate (PSS)-doped calcium carbonate microparticles (CaCO 3 @PSS) were synthesized... more Polystyrene sulfonate (PSS)-doped calcium carbonate microparticles (CaCO 3 @PSS) were synthesized and used for the encapsulation of Methylene Blue (MB). SEM and TEM images suggest the formation of spherical particles with about 2 mm diameters and raspberry-like structure. BrunauereEmmetteTeller method was used to analyze the specific surface area and the pore size distribution of the CaCO 3 @PSS microparticles. The sorption of MB from aqueous solution onto CaCO 3 @PSS microspheres was studied and equilibrium isotherm determined. A physisorption process was indicated by the values of sorption energy (B D) 2.39 Â 10 À7 mol 2 /J 2 , mean free energy (E D) 1.5 kJ/mol and heat of sorption (B) 28.8 J/mol estimated from the Dubinin-Radushkevich and Temkin isotherms. The Langmuir model precisely describes the isotherm and the maximum adsorption capacity was 149.3 mg/g indicating homogeneous nature of adsorption sites and monolayer coverage of MB on the CaCO 3 @PSS microparticle inner and outer surfaces. The pseudo-second-order model can better describe the adsorption kinetics with a maximum adsorption attained within 5 h. The intra-particle diffusion process was identified as the main mechanism controlling the rate of the dye sorption. The MB release from CaCO 3 @PSS microspheres was found to be pH-responsive. The presence of negatively charged PSS À groups in pores of CaCO 3 @PSS microparticles prevents the initial burst release of MB, decreasing the release rate of MB. The experimental results indicate high potential of CaCO 3 @PSS microspheres as carriers for encapsulation and controlled release of cationic dye molecules, such as photosensitizer MB, used in photodynamic therapy.
We present thoroughly analyzed experimental results that demonstrate the anomalous manifestation ... more We present thoroughly analyzed experimental results that demonstrate the anomalous manifestation of the exciton self-trapping effect, which is already well-known in bulk crystals, in ordered molecular nanoclusters called J-aggregates. Weakly-coupled one-dimensional (1D) molecular chains are the main structural feature of J-aggregates, wherein the electron excitations are manifested as 1D Frenkel excitons. According to the continuum theory of Rashba-Toyozawa, J-aggregates can have only self-trapped excitons, because 1D excitons must adhere to barrier-free self-trapping at any exciton-phonon coupling constant g ¼ e LR /2b, wherein e LR is the lattice relaxation energy, and 2b is the half-width of the exciton band. In contrast, very often only the luminescence of free, mobile excitons would manifest in experiments involving J-aggregates. Using the Urbach rule in order to analyze the low-frequency region of the low-temperature exciton absorption spectra has shown that J-aggregates can have both a weak (g < 1) and a strong (g > 1) exciton-phonon coupling. Moreover, it is experimentally demonstrated that under certain conditions, the J-aggregate excited state can have both free and self-trapped excitons, i.e., we establish the existence of a self-trapping barrier for 1D Frenkel excitons. We demonstrate and analyze the reasons behind the anomalous existence of both free and self-trapped excitons in J-aggregates, and demonstrate how exciton-self trapping efficiency can be managed in J-aggregates by varying the values of g, which is fundamentally impossible in bulk crystals. We discuss how the exciton-self trapping phenomenon can be used as an alternate interpretation of the wide band emission of some J-aggregates, which has thus far been explained by the strongly localized exciton model. Published by AIP Publishing. [http://dx.
The effect of cyanine dye 3,3 0-dioctadecyloxacarbocyanine perchlorate (DiO) and benzimidazole dy... more The effect of cyanine dye 3,3 0-dioctadecyloxacarbocyanine perchlorate (DiO) and benzimidazole dye 4-dimethylamino-1,8-naphthoylene-1 0 ,2 0-benzimidazole (DNBI) accumulation in nanoporous silica matrices on the dyes luminescence properties has been studied. For both dyes, ground state dimer formation with perpendicular transition dipoles at high dye concentrations has been considered as a result of restricted geometry of the nanoscale pores. The dimer excitation leads to excimer formation revealing by appearance of new long-wavelength luminescence band and shortening the dye luminescence lifetime. In the excimer luminescence excitation spectra two additional bands have been observed, one of which is bathochromically shifted relatively to the absorption band and another one is hypsocromically shifted. Using the Kasha exciton model it was shown that the excimers possess oblique transition dipoles configuration .
The kinetic and thermodynamic stability of organic (sodium dodecylsulfate micelles and egg-yolk p... more The kinetic and thermodynamic stability of organic (sodium dodecylsulfate micelles and egg-yolk phosphatidylcholine zwitterionic liposomes) and inorganic (based on GdYVO 4 :Eu 3+ nanoparticles) nanocarriers (NCs) was studied by the λ-ratiometric method (analysis of fl uorescence intensity at two wavelengths) using non-radiative transfer of electronic excitation energy. The kinetic and thermodynamic parameters of the redistribution of dyes DiO and DiI between NCs that was associated with the destruction of NC/DiO and NC/DiI complexes and the formation of new NC/(DiO + DiI) complexes were evaluated. Rate constants for the destruction of the complexes (K), lifetimes of the complexes (τ 1/2), the activation energy for the destruction (E a), the equilibrium constant (K eq), and the change of free energy (ΔG 0), enthalpy (ΔH 0), and entropy (ΔS 0) of the process were calculated. The obtained kinetic parameters pointed to high kinetic stability for all investigated complexes whereas the thermodynamic ones indicated that dye redistribution required high temperatures. Keywords: micelle, liposome, nanoparticle, non-radiative transfer of electronic excitation energy, kinetic and thermodynamic stability. Introduction. The development of pharmacological dosage forms that are based on the inclusion of drugs in one container or another is a promising approach to solving the problem of drug delivery to a biological target with the desired pharmacokinetic and therapeutic properties. The use of special nanosized carriers or containers provides an effective solution for issues related to high drug toxicity, poor solubility in biological fl uids, the need to use high doses to achieve a therapeutic effect, non-specifi c accumulation in vivo, rapid degradation, and short biological half-lives in the circulation [1–7]. Liposomal vesicles, polymeric micelles, nanoparticles (NP) based on proteins, and various conjugates of polymers are under intense scrutiny and possess the most suitable characteristics with respect to the encapsulation of drugs, genes, diagnostic agents, etc. among currently existing nanocarriers (NC) [2, 4, 7]. Stability, i.e., reliable encapsulation of an active ingredient, is the most important of many factors that are considered during construction of a NC/active-ingredient complex. Undesirable loss of active ingredient and; conversely, contamination by foreign molecules in the environment can occur during storage before use and also during circulation in vivo. NC should be predictably stable and provide controlled release of the active ingredient in order to effectively fulfi ll their functions [6–9]. Understanding of the exchange dynamics of the active ingredient between the solvent and NC and/or between NC is signifi cant for decision making. It was shown [10] that complexes of the dye JC-1 with inorganic GdYVO 4 :Eu 3+ NP were capable of accumulating in the nucleus of a living cell with the NP acting as delivery agents. This made inorganic GdYVO 4 :Eu 3+ NP and their complexes attractive for further research. Herein the kinetic and thermodynamic stability of NC/dye complexes was studied by λ-ratiometry (analysis of the fl uorescence intensity at two or more wavelengths) using Förster resonance energy transfer (FRET). Micelles of sodium dodecylsulfate (SDS), liposomes of egg-yolk phosphatidylcholine (PC), and inorganic GdYVO 4 :Eu 3+ NP were used as the NC. Experimental. Dyes 3,3′-dioctadecyloxacarbocyanine (DiO) and 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbo-cyanine perchlorate (DiI), SDS, and PC (Sigma Aldrich) were used without further purifi cation (dye purity 97%):
Formation of thiacyanine dye J-aggregates in layered polymer films has been studied. This process... more Formation of thiacyanine dye J-aggregates in layered polymer films has been studied. This process leads to the J-aggregates spectral bands widening as a result of static disorder increasing. To enhance the J-aggregate luminescence the effect of their interaction with plasmon resonances of silver nanoparticles has been used. It was found that about 4-fold luminescence enhancement for thiacyanine J-aggregates in the polymer films could be obtained at 15 nm distance from silver nanoparticles.
Using fluorescence microspectoscopy and FRET-labeling of various nano-scale carriers (NCs) the ef... more Using fluorescence microspectoscopy and FRET-labeling of various nano-scale carriers (NCs) the efficiency and kinetics of NCs/dye molecules complexes accumulation in living cells and dye release have been studied. Organic liposome vesicles and inorganic nanoparticles (Ce02 and GdYV04:Eu3+) were used as NCs. NCs/dyes complexes formed in aqueous solutions have been characterized. It has been shown that NCs based on GdYV04:Eu3+ nanoparticles exhibit the most effective accumulation in cells and provide very fast release of the lipophilic cargo (dyes molecules). Lipophilic compound (cholesterol) embedded into the NCs/dyes complexes decreases noticeably the rate of lipophilic dyes release and reduces the affinity of the complex interaction with hepatocytes. GdYV04:Eu3+ NPs could be used as a nano-scale platform for controlled intracellular delivering of hydrophobic agents.
Adsorption of cyanine dye Dil in a nanopous Si02 matrix has been studied. It was shown that the i... more Adsorption of cyanine dye Dil in a nanopous Si02 matrix has been studied. It was shown that the increase of the dye concentration in the Si02 matrix provokes the appearance of an additional red-shifted band of excimer nature in the dye fluorescence spectrum without any changes in the absorption one. Static character of the dye excimer formation was revealed. Enhanced dye concentration due to spatial confinement in a nanopore volume has been supposed as a reason of the effective excimer formation.
The metal enhanced fluorescence of thiacyanine dye monomers in polymer films has been studied. To... more The metal enhanced fluorescence of thiacyanine dye monomers in polymer films has been studied. To control the distance between dye molecules and silver nanoparticles a polymer spacer has been used. The spacer thickness has been varied using a layer-by-layer assembly method of polyelectrolytes. The best 4.5 times fluorescence enhancement has been observed for the 20 nm thick polymer spacer. The result has been confirmed both by steady-state and time resolved fluorescence spectroscopies.
Features of J-aggregates formation in highly structured pores of anodic aluminum oxide (AAO) have... more Features of J-aggregates formation in highly structured pores of anodic aluminum oxide (AAO) have been studied using steady-state absorption and luminescence spectroscopy and time-resolved luminescence spectroscopy, J-aggregates with different structures (spherical and thread-like) were chosen for the studying. Spectroscopic investigations show the presence of both types of the «/-aggregates in the AAO pores. It leads to a static disorder increasing in the J-aggregates. Besides, in the case of the thread-like J-aggregates changes in the structure have been supposed also.
In the present study, we analyze the efficiency of Electronic Excitation Energy Transfer (EEET) b... more In the present study, we analyze the efficiency of Electronic Excitation Energy Transfer (EEET) between two dyes, an energy donor (D) and acceptor (A), concentrated in structurally heterogeneous media (surfactant micelles, liposomes, and porous SiO2 matrices). In all three cases, highly effective EEET in pairs of dyes has been found and cannot be explained by Standard Fo¨rster-type theory for homogeneous solutions. Two independent approaches based on the analysis of either the D relative quantum yield (FDA=FD) or the D fluorescence decay have been used to study the deviation of experimental results from the theoretical description of EEET process. The observed deviation is quantified by the apparent fractal distribution of molecules parameter d. We conclude that the highly effective EEET observed in the nano-scale media under study can be explained by both forced concentration of the hydrophobic dyes within nano-volumes and non-uniform cluster-like character of the distribution of D and A dye molecules within nano-volumes.
The efficiency of Foerster resonance energy transfer (FRET) between pairs of different dyes in th... more The efficiency of Foerster resonance energy transfer (FRET) between pairs of different dyes in the nano-volumes of surfactant micelles and liposomes was studied using optical spectroscopy methods. More efficient FRET with the same solution concentrations of the dyes was observed in liposomes despite the greater diameter of liposomes compared with micelles (100 and 5 nm). Calculations showed that the observed effect was explained by the smaller amount of liposomes in the solution and, consequently, the larger local concentration of the dyes in the liposome lipid bilayer. It was shown that not only the spectral overlap integral and the Foerster distance but also specific interactions between molecules in the nanovolume (electrostatic, van-der-Waals, and steric) that were governed by structural features of the molecules affected the FRET efficiency.
Novel red-shifted band has been observed in luminescence spectra of a cyanine dye embedded into n... more Novel red-shifted band has been observed in luminescence spectra of a cyanine dye embedded into nanoporous SiO2 matrix. That band is concentration dependent and disappears at cooling to low temperature. It has been associated with the dye excimer formation due to strong interaction with the pores surface.
In this study we demonstrate that the electron–lattice interaction (ELI) could be controlled by c... more In this study we demonstrate that the electron–lattice interaction (ELI) could be controlled by changing exciton delocalization length in ordered organic nanoclusters called J-aggregates. Particularly it could be done via the J-aggregates solvate shell manipulation using surfactants. The strong correlation between the J-aggregates luminescence quantum yield and the ELI strength has been reviled that allows us to consider the exciton self-trapping as the main mechanism of the J-aggregates luminescence losses.
J-aggregates of amphi-PIC dye have been successfully formed in polymer films by layer-by-layer a... more J-aggregates of amphi-PIC dye have been successfully formed in polymer films by layer-by-layer assembly method. Another dye embedded into J-aggregate layer has revealed itself as efficient exciton trap, which trapped about 80% of excitons. Analyzing J-aggregate luminescence quenching using modified Stern–Volmer equation it has been found that 1 DiD molecule quenches 50% luminescence of 60 amphi-PIC molecules forming the J-aggregate. That is half as much compared to the solution case. The reason for such difference discussed.
The way to manipulate by spectral properties of cyanine dye luminescent ordered nanoclusters (J-a... more The way to manipulate by spectral properties of cyanine dye luminescent ordered nanoclusters (J-aggregates) has been demonstrated. It has been observed a surfactant shell formation around the J-aggregates of four different dyes. This leads to exciton delocalization length increasing which causes an exciton self-trapping suppression. The latter results in spectral changes observed.
The influence of anionic sodium dodecyl sulphate (SDS) on aggregation behavior of squaraine dye S... more The influence of anionic sodium dodecyl sulphate (SDS) on aggregation behavior of squaraine dye Sq-2Me has been studied in dimethylformamide–water (95%) (DMF–W) binary solutions by optical spectroscopy. The addition of surfactants at concentrations above the critical micelle concentration into a DMF–W (95%) solution is found to promote the dye ordered aggregation. The structure of Sq-2Me aggregates formed is analyzed using the exciton theory. In solutions with SDS micelles, formation of Sq-2Me J-type dimers of co-planar inclined geometry with an angle between the chromophore long axes and chromophore center-to-center line (θ) of 47 ° and center-to-center distance (R) of 5 Å has been revealed. The interaction of Sq-2Me with other hydrophobic molecules (carbocyanine dye DiI) solubilized at equal concentrations in SDS micelles is revealed to prevent the Sq-2Me dimer formation. In such a solution, fluorescent resonance energy transfer between donor dye DiI and acceptor Sq-2Me is observed.
Features of BIC J-aggregate formation in AOT reverse micelles have been studied using steady-stat... more Features of BIC J-aggregate formation in AOT reverse micelles have been studied using steady-state absorption and luminescence spectroscopy and time resolved luminescence spectroscopy. BIC J aggregates reveal spherical structure with diameter ~ 20 nm and significant thermal stability. KM diameter decrease results in strong static disorder increase leading to J-aggregate band (J band) widening and luminescence quenching. Due to high thermal stability BIC «/ aggregates are embedded into KM as a whole at any temperatures of stock water solution. Decrease of stock water solution temperature leads to J band narrowing and intensity increasing due to static disorder decreasing.
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Papers by Alexander Sorokin
cases, highly effective EEET in pairs of dyes has been found and cannot be explained by Standard Fo¨rster-type theory for homogeneous solutions. Two independent approaches based on the analysis of either the D relative quantum yield (FDA=FD) or the D fluorescence decay have been used to study the deviation of experimental results from the theoretical description of EEET process. The
observed deviation is quantified by the apparent fractal distribution of molecules parameter d. We conclude that the highly effective EEET observed in the nano-scale
media under study can be explained by both forced concentration
of the hydrophobic dyes within nano-volumes
and non-uniform cluster-like character of the distribution
of D and A dye molecules within nano-volumes.
cases, highly effective EEET in pairs of dyes has been found and cannot be explained by Standard Fo¨rster-type theory for homogeneous solutions. Two independent approaches based on the analysis of either the D relative quantum yield (FDA=FD) or the D fluorescence decay have been used to study the deviation of experimental results from the theoretical description of EEET process. The
observed deviation is quantified by the apparent fractal distribution of molecules parameter d. We conclude that the highly effective EEET observed in the nano-scale
media under study can be explained by both forced concentration
of the hydrophobic dyes within nano-volumes
and non-uniform cluster-like character of the distribution
of D and A dye molecules within nano-volumes.