Singlet Oxygen Molecules Research Articles

Photochemical upconversion of near-infrared light from below the silicon bandgap

Photochemical upconversion is a strategy for converting infrared light into more energetic, visible light, with potential applications ranging from biological imaging and drug delivery to photovoltaics and photocatalysis. Although systems have been developed for upconverting light from photon energies in the near-infrared, upconversion from below the silicon bandgap has been out of reach. Here, we demonstrate an upconversion composition using PbS semiconductor nanocrystal sensitizers that absorb photons below the bandgap of silicon and populate violanthrone triplet states below the singlet oxygen energy. The triplet-state violanthrone chromophores luminesce in the visible spectrum following energy delivery from two singlet oxygen molecules. By incorporating organic chromophores as ligands onto the PbS nanocrystals to improve energy transfer, we demonstrate that violanthrone upconverts in the absence of oxygen by the triplet–triplet annihilation mechanism. The change in mechanism is shown by exploiting the magnetic field effect on triplet–triplet interactions. Photochemical upconversion of light with photon energy below the silicon bandgap has remained elusive, but the feat has now been demonstrated using PbS semiconductor nanocrystals and violanthrone.

Dynamics of Singlet Oxygen Molecule Trapped in Silica Glass Studied by Luminescence Polarization Anisotropy and Density Functional Theory

The lowest excited electronic state of the O2 molecule, a1Δg, the “singlet oxygen”, is of utmost importance for photochemistry and photobiology. For O2 trapped in silica glass, the lifetime of this...

A powerful combination of copper-cysteamine nanoparticles with potassium iodide for bacterial destruction.

Herein, for the first time, we demonstrate that the combination of copper-cysteamine (Cu-Cy) nanoparticles (NPs) and potassium iodide (KI) can significantly inactivate both Gram-positive MRSA and Gram-negative E. coli. To uncover the mystery of the killing, the interaction of KI with Cu-Cy NPs was investigated systematically and the products from their interaction were identified. No copper ions were released after adding KI to Cu-Cy NPs in cell-free medium and, therefore, it is reasonable to conclude that the Fenton reaction induced by copper ions is not responsible for the bacterial killing. Based on the observations, we propose that the major killing mechanism involves the generation of toxic species, such as hydrogen peroxide, triiodide ions, iodide ions, singlet oxygen, and iodine molecules. Overall, the powerful combination of Cu-Cy NPs and KI has good potential as an independent treatment or a complementary antibiotic treatment to infectious diseases.

X-ray induced photodynamic therapy with copper-cysteamine nanoparticles in mice tumors

Photodynamic therapy (PDT), a treatment that uses a photosensitizer, molecular oxygen, and light to kill target cells, is a promising cancer treatment method. However, a limitation of PDT is its dependence on light that is not highly penetrating, precluding the treatment of tumors located deep in the body. Copper-cysteamine nanoparticles are a new type of photosensitizer that can generate cytotoxic singlet oxygen molecules upon activation by X-rays. In this paper, we report on the use of copper-cysteamine nanoparticles, designed to be targeted to tumors, for X-ray-induced PDT. In an in vivo study, results show a statistically significant reduction in tumor size under X-ray activation of pH-low insertion peptide-conjugated, copper-cysteamine nanoparticles in mouse tumors. This work confirms the effectiveness of copper-cysteamine nanoparticles as a photosensitizer when activated by radiation and suggests that these Cu-Cy nanoparticles may be good candidates for PDT in deeply seated tumors when combined with X-rays and conjugated to a tumor-targeting molecule.

New techniques for retrieving the [O(3P)], [O3] and [CO2] altitude profiles from dayglow oxygen emissions: Uncertainty analysis by the Monte Carlo method

This study presents methods for retrieving the altitude profiles of atomic oxygen, [O(3P)], ozone, [O3], and carbon dioxide, [CO2], concentrations in the daytime mesosphere and lower thermosphere (MLT) in the framework of the YM2011 model of the electronic-vibrational oxygen kinetics. The emissions of singlet oxygen molecules O2(b1Σ+g, v ≤ 2), O2(a1Δg, v = 0) and the O(1D) atom are used as proxy of the [O(3P)], [O3] and [CO2]. For all the proposed techniques, we compare the uncertainty values of the retrieved [O(3P)], [O3] and [CO2], obtained by the Monte Carlo method, with estimations obtained by the sensitivity analysis method in the earlier works. For all the above mentioned methods for retrieving the [O(3P)], [O3] and [CO2] profiles, we obtained analytical expressions that include the concentrations of excited substances considered as proxies. In addition, the optimal altitude ranges for using these remote sensing methods were determined based on the results of numerical experiments by the Monte Carlo method.

Two single-reference approaches to singlet biradicaloid problems: Complex, restricted orbitals and approximate spin-projection combined with regularized orbital-optimized Møller-Plesset perturbation theory.

We present a comprehensive study of two single-reference approaches to singlet biradicaloids. These two approaches are based on the recently developed regularized orbital-optimized Møller-Plesset method (κ-OOMP2). The first approach is to combine Yamaguchi's approximate projection (AP) scheme and κ-OOMP2 with unrestricted (U) orbitals (κ-UOOMP2). By capturing only essential symmetry breaking, κ-UOOMP2 can serve as a suitable basis for AP. The second approach is κ-OOMP2 with complex, restricted (cR) orbitals (κ-cROOMP2). Although its applicability is more limited due to the comparative rarity of cR solutions, κ-cROOMP2 offers a simple framework for describing singlet biradicaloids with complex polarization while removing artificial spatial symmetry breaking. We compare the scope of these two methods with numerical studies. We show that AP+κ-UOOMP2 and κ-cROOMP2 can perform similarly well in the TS12 set, a dataset that includes 12 data points for triplet-singlet gaps of several atoms and diatomic molecules with a triplet ground state. This was also found to be true for the barrier height of a reaction involving attack on a cysteine ion by a singlet oxygen molecule. However, we also demonstrate that in highly symmetric systems like C30 (D5h), κ-cROOMP2 is more suitable as it conserves spatial symmetry. Finally, we present an organic biradicaloid that does not have a κ-cROOMP2 solution in which case only AP+κ-UOOMP2 is applicable. We recommend κ-cROOMP2 whenever complex polarization is essential and AP+κ-UOOMP2 for biradicaloids without essential complex polarization but with essential spin-polarization.

Mass Spectrometric Study of Acoustically Levitated Droplets Illuminates Molecular‐Level Mechanism of Photodynamic Therapy for Cancer involving Lipid Oxidation

AbstractEven though the general mechanism of photodynamic cancer therapy is known, the details and consequences of the reactions between the photosensitizer‐generated singlet oxygen and substrate molecules remain elusive at the molecular level. Using temoporfin as the photosensitizer, here we combine field‐induced droplet ionization mass spectrometry and acoustic levitation techniques to study the “wall‐less” oxidation reactions of 18:1 cardiolipin and 1‐palmitoyl‐2‐oleoyl‐sn‐glycero‐3‐phospho‐(1′‐rac‐glycerol) (POPG) mediated by singlet oxygen at the air–water interface of levitated water droplets. For both cardiolipin and POPG, every unsaturated oleyl chain is oxidized to an allyl hydroperoxide, which surprisingly is immune to further oxidation. This is attributed to the increased hydrophilicity of the oxidized chain, which attracts it toward the water phase, thereby increasing membrane permeability and eventually triggering cell death.

Mass Spectrometric Study of Acoustically Levitated Droplets Illuminates Molecular-Level Mechanism of Photodynamic Therapy for Cancer involving Lipid Oxidation.

Even though the general mechanism of photodynamic cancer therapy is known, the details and consequences of the reactions between the photosensitizer-generated singlet oxygen and substrate molecules remain elusive at the molecular level. Using temoporfin as the photosensitizer, here we combine field-induced droplet ionization mass spectrometry and acoustic levitation techniques to study the "wall-less" oxidation reactions of 18:1 cardiolipin and 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (POPG) mediated by singlet oxygen at the air-water interface of levitated water droplets. For both cardiolipin and POPG, every unsaturated oleyl chain is oxidized to an allyl hydroperoxide, which surprisingly is immune to further oxidation. This is attributed to the increased hydrophilicity of the oxidized chain, which attracts it toward the water phase, thereby increasing membrane permeability and eventually triggering cell death.

Surface oxidation model in plasma enhanced atomic layer deposition for silicon oxide films including various aminosilane precursors

In this study, a surface oxidation model for the plasma enhanced atomic layer deposition process for silicon oxide films formed by the combination of aminosilane with Ar/O2 plasma is proposed. After the discussion of the dominant oxidation pathways involving both reactive species generation and reaction energy barriers, the authors develop a surface oxidation model and compare it with experimental deposition results. From plasma simulation results, they confirmed two dominant species generated by Ar/O2 plasma; triplet oxygen atom (3O) and singlet oxygen molecule (1O2). The authors then compared the reaction energy barrier along the oxidation pathways for these oxidation species and the corresponding surface terminations by using density functional theory calculations. The calculated activation barriers were negligible in the oxidation paths with 3O, but not in the ones with 1O2. These results support that oxidation by 3O was dominant, especially at low substrate temperatures. The authors suggest a surface oxidation model having two kinds of surface terminations; hydrogen terminations (Si–H) and amino ligand terminations (Si–R). This model can explain the experimental saturation curve for surface oxidation against plasma irradiation time as a function of substrate temperature. The authors confirmed that saturation trends observed with various aminosilane precursors can successfully be explained by their differing ratios of Si–H and Si–R bonds present prior to oxidation.In this study, a surface oxidation model for the plasma enhanced atomic layer deposition process for silicon oxide films formed by the combination of aminosilane with Ar/O2 plasma is proposed. After the discussion of the dominant oxidation pathways involving both reactive species generation and reaction energy barriers, the authors develop a surface oxidation model and compare it with experimental deposition results. From plasma simulation results, they confirmed two dominant species generated by Ar/O2 plasma; triplet oxygen atom (3O) and singlet oxygen molecule (1O2). The authors then compared the reaction energy barrier along the oxidation pathways for these oxidation species and the corresponding surface terminations by using density functional theory calculations. The calculated activation barriers were negligible in the oxidation paths with 3O, but not in the ones with 1O2. These results support that oxidation by 3O was dominant, especially at low substrate temperatures. The authors suggest a surface...

Surface oxidation model in plasma enhanced atomic layer deposition for silicon oxide films including various aminosilane precursors

In this study, a surface oxidation model for the plasma enhanced atomic layer deposition process for silicon oxide films formed by the combination of aminosilane with Ar/O2 plasma is proposed. After the discussion of the dominant oxidation pathways involving both reactive species generation and reaction energy barriers, the authors develop a surface oxidation model and compare it with experimental deposition results. From plasma simulation results, they confirmed two dominant species generated by Ar/O2 plasma; triplet oxygen atom (3O) and singlet oxygen molecule (1O2). The authors then compared the reaction energy barrier along the oxidation pathways for these oxidation species and the corresponding surface terminations by using density functional theory calculations. The calculated activation barriers were negligible in the oxidation paths with 3O, but not in the ones with 1O2. These results support that oxidation by 3O was dominant, especially at low substrate temperatures. The authors suggest a surface oxidation model having two kinds of surface terminations; hydrogen terminations (Si–H) and amino ligand terminations (Si–R). This model can explain the experimental saturation curve for surface oxidation against plasma irradiation time as a function of substrate temperature. The authors confirmed that saturation trends observed with various aminosilane precursors can successfully be explained by their differing ratios of Si–H and Si–R bonds present prior to oxidation.

Changes of Intracellular Porphyrin, Reactive Oxygen Species, and Fatty Acids Profiles During Inactivation of Methicillin-Resistant Staphylococcus aureus by Antimicrobial Blue Light.

Antimicrobial blue light (aBL) has attracted increasing interest for its antimicrobial properties. However, the underlying bactericidal mechanism has not yet been verified. One hypothesis is that aBL causes the excitation of intracellular chromophores; leading to the generation of reactive oxygen species (ROS) and the resultant oxidization of various biomolecules. Thus, monitoring the levels of redox-sensitive intracellular biomolecules such as coproporphyrins, as well as singlet oxygen and various ROS may help to uncover the physiological changes induced by aBL and aid in establishing the underlying mechanism of action. Furthermore, the identification of novel targets of ROS, such as fatty acids, is of potential significance from a therapeutic perspective. In this study, we sought to investigate the molecular impact of aBL treatment on methicillin-resistant Staphylococcus aureus (MRSA). The results showed that aBL (5–80 J/cm2) exhibited a bactericidal effect on MRSA, and almost no bacteria survived when 80 J/cm2 had been delivered. Further studies revealed that the concentrations of certain intracellular molecules varied in response to aBL irradiation. Coproporphyrin levels were found to decrease gradually, while ROS levels increased rapidly. Moreover, imaging revealed the emergence and increase of singlet oxygen molecules. Concomitantly, the lipid peroxidation product malondialdehyde (MDA) increased in abundance and intracellular K+ leakage was observed, indicating permeability of the cell membrane. Atomic force microscopy showed that the cell surface exhibited a coarse appearance. Finally, fatty acid profiles at different illumination levels were monitored by GC-MS. The relative amounts of three unsaturated fatty acids (C16:1, C20:1, and C20:4) were decreased in response to aBL irradiation, which likely played a key role in the aforementioned membrane injuries. Collectively, these data suggest that the cell membrane is a major target of ROS during aBL irradiation, causing alterations to membrane lipid profiles, and in particular to the unsaturated fatty acid component.

Disaggregation of Magnesium Octa[(4'-Benzo-15-Crown-5)Oxy]Phthalocyaninate in Aqueous Micellar Solutions of Alkyltriphenylphosphonium Bromide

The behavior of magnesium octa[(4'-benzo-15-crown-5)oxy]phthalocyaninate (Mgcr8Pc) in aqueous micellar solutions of alkyltriphenylphosphonium bromides (CnTPPBs), where n = 8, 12, 14, and 16, has been studied by means of electronic absorption spectroscopy and measurements of fluorescence photophysical characteristics. Intense bands of absorption (λmax = 683 nm) and fluorescence (λmax = 694 nm) of Mgcr8Pc in CnTPPB micellar solutions are characterized by monoexponential decay of intensity (lifetime of 5.98–6.29 ns) and indicate that magnesium phthalocyaninate has the monomeric form. The disaggregation of Mgcr8Pc in the presence of CnTPPBs provides an opportunity to use aqueous micellar solutions containing this metallophthalocyane in photodynamic therapy, because it is the monomeric form of Mgcr8Pc that generates singlet oxygen molecules, which kill tumor cells.

Photosensitized Membrane Permeabilization Requires Contact-Dependent Reactions between Photosensitizer and Lipids.

Although the general mechanisms of lipid oxidation are known, the chemical steps through which photosensitizers and light permeabilize lipid membranes are still poorly understood. Herein we characterized the products of lipid photooxidation and their effects on lipid bilayers, also giving insight into their formation pathways. Our experimental system was designed to allow two phenothiazinium-based photosensitizers (methylene blue, MB, and DO15) to deliver the same amount of singlet oxygen molecules per second to 1-palmitoyl-2-oleoyl- sn-glycero-3-phosphocholine liposome membranes, but with a substantial difference in terms of the extent of direct physical contact with lipid double bonds; that is, DO15 has a 27-times higher colocalization with ω-9 lipid double bonds than MB. Under this condition, DO15 permeabilizes membranes at least 1 order of magnitude more efficiently than MB, a result that was also valid for liposomes made of polyunsaturated lipids. Quantification of reaction products uncovered a mixture of phospholipid hydroperoxides, alcohols, ketones, and aldehydes. Although both photosensitizers allowed the formation of hydroperoxides, the oxidized products that require direct reactions between photosensitizer and lipids were more prevalent in liposomes oxidized by DO15. Membrane permeabilization was always connected with the presence of lipid aldehydes, which cause a substantial decrease in the Gibbs free energy barrier for water permeation. Processes depending on direct contact between photosensitizers and lipids were revealed to be essential for the progress of lipid oxidation and consequently for aldehyde formation, providing a molecular-level explanation of why membrane binding correlates so well with the cell-killing efficiency of photosensitizers.

Novel synthetic route for low-cost carbon-modified TiO2 with enhanced visible light photocatalytic activity: carbon content and calcination effects

The aim of this study was the development of low-cost tannin-formaldehyde xerogel/TiO2 (XTi-w) and carbon xerogel/TiO2 (XTiC-w) photocatalysts. The materials used as precursors were recycled titanium scraps and black wattle tannin extract, highlighting the low-cost approach employed in the synthesis. The materials were characterized by diffuse reflectance spectroscopy, scanning electron microscopy, dispersive energy spectrophotometry, X-ray diffractometry, infrared and Raman spectroscopy. X-ray diffractometry showed that the XTiC-w have tetragonal crystalline structure (anatase), whereas the XTi-w has an amorphous structure. The Raman and infrared analysis also showed the presence of titanium dioxide in the composition of both XTi-w and XTiC-w. XTi-w and XTiC-w showed photocatalytic activity at the visible wavelength. Titanium dioxide displayed no photocatalytic activity at the visible wavelength. The XTi-60 composite displayed the highest efficiency in the removal of the methylene blue from the system, as well as good reusability properties. The radicals with higher influence in the photocatalytic reaction mechanism are the photo generated electron and the singlet oxygen molecule. The effect of the heat treatment is negative on the photocatalytic properties of the hybrids produced, due to the removal of acid sites, adsorbed water and OH surface groups.

Degradation of LiTfO/TEGME and LiTfO/DME Electrolytes in Li-O2 Batteries

In this work we discuss the degradation chemistry on carbon-free electrodes of two ether based electrolytes for Li-O2 batteries, i.e. tetraethylene glycol dimethyl ether (TEGDME) and dimethoxy ethane (DME) with lithium trifluoromethane sulfonate (LiTfO) as salt. To this aim we developed an all-metallic positive electrode by electrodeposition of a gold dendritic film on a nickel foam (Au@Ni). These carbon-free electro-catalytic electrodes have been used to investigate the degradation chemistry of the electrolytes in Li-O2 cells by eliminating the parallel parasitic reactions due to the commonly used carbon electro-catalysts. In particular the composition and morphological evolutions of the Au@Ni electrodes after discharge and cycling have been characterized ex situ by Raman Spectroscopy, X-ray Photoemission Spectroscopy and Scanning Electron Microscopy. We also couple this experimental study with thermodynamic predictions about the onset degradation of the DME molecule based on density functional theory calculations. In summary in both DME/LiTfO and TEGDME/LiTfO electrolytes, the degradation involves the oxidation of the ether solvent to a mixture of carbonates and carboxylates/formate/oxalate. DME is apparently more strongly degraded compared to TEGDME whereas the LiTfO anion is highly stable. Calculations suggest the key role played by the singlet oxygen molecule as initiator of the degradation path.

Quantum-Chemical Simulation of the Solvent Effect on Spontaneous Emission of Singlet Oxygen

A molecular simulation of the solvent effect on radiative rate constant k r of singlet oxygen is carried out. This study included a search for the most probable conformations of the complexes of molecules of singlet oxygen and ten solvents and calculation of dipole moments M of transitions a1Δ g –b1Σ + (M a–b ) and a1Δ g –X3Σ - (M a–X ) of the oxygen molecule for them. Averaging of M a–b by conformations, taking into account the probability of their formation for complexes without atoms with a large atomic number (Cl, S), yields values that, as a rule, correlate well with the behavior of k r in the experiment. Taking into account the possibility of decreasing the distance (compared to equilibrium) between molecules in a collision complex at room temperature made it possible to achieve satisfactory agreement of the calculated and experimental data also for complexes with CCl4, C2Cl4, and CS2. The obtained data indicate that a number of factors affect k r . The correlation of k r with molecular polarizability in a number of cases is due, on the one hand, to its effect on the strength of dispersion interactions in the complex and, on the other hand, to the fact that it to some extent reflects the position of the upper filled orbitals of the solvent molecule. Both factors affect the degree of mixing of the π orbitals of the singlet oxygen molecule with the orbitals of the solvent molecule, which, as was found earlier, facilitates the activation of the a1Δ g –b1Σ + transition and the borrowing of its intensity by the a1Δ g –X3Σ - transition.

Effect of reactive oxygen species generated with ultraviolet lamp and plasma on polyimide surface modification

Understanding the effect of reactive oxygen species (ROS), such as singlet oxygen molecule and atomic oxygen, on polyimide (PI) film properties, such as wettability, morphology, and chemical bonding state, is essential for further development of PI‐based surfaces. We investigated the effect of different ROS generated during ultraviolet (UV) and plasma treatment in oxygen gas on surface modification of Kapton PI. Different surface modification techniques, UV and plasma treatment, are known to generate different ROS. In this work, we demonstrate the effect of different ROS on PI surface modification. From the diagnostics of ROS by means of electron spin resonance and optical emission spectroscopy, we confirmed that during UV treatment, excited singlet oxygen molecules are the main ROS, while plasma treatment mainly generated atomic oxygen. The wettability of PI surface treated by UV and plasma resulted in hydrophilic PI surfaces. XPS results show that the wettability of PI samples is mainly determined by their surface O/C ratio. However, chemical bonding states were different: while UV treatment tended to generate C=O bonds, while plasma treatment tended to generate both C―O and C=O bonds. Singlet oxygen molecules are concluded to be the main oxidant during UV treatment, and their main reaction with PI was concluded to be of the addition type, leading to an increase of C=O groups on the surface of PI film. Meanwhile, atomic oxygen species were the main oxidant during plasma treatment, reacting with the PI surface through both etching and addition reaction, resulting in a wider variety of bonds, including both C―O and C=O groups.

Structure and Physicochemical Properties of Water Treated w ith Low-Temperature Low-Frequency Glow Plasma

Physical and selected physicochemical properties of distilled water treated with low-temperature low-frequency glow plasma (LPGP) for 5, 15, 30, 45, 60 and 90 min are given. Particular properties of PTW non-linearly vary with the time of exposure to plasma. PTW is characterized as declusterized solution of normal water consisting of clathrates of excited, probably singlet oxygen molecules, inside the clathrates. PWT is free of hydrogen peroxide and ozone. Raman spectroscopy is the best tool for diagnostic assessment of PTW. Keywords: Clathrate hydrates, singlet oxygen, water stretching modes, glow plasma, PTW, distilled water.

Degradation of N-Nitrosodimethylamine by UV-Based Advanced Oxidation Processes for Potable Reuse: a Short Review

The ultraviolet (UV)-based advanced oxidation process (AOP) is a powerful technology commonly utilised in recent potable water reuse (PR) schemes. The AOP involves the generation of highly reactive free radicals (e.g. hydroxyl, HO•) and is primarily applied for the removal of two target trace organic chemicals—N-nitrosodimethylamine (NDMA) and 1,4-dioxane — in the PR schemes. Both of these organics are not well removed by the reverse osmosis (RO) process. NDMA is a probable carcinogen and is often present in reclaimed water at concentrations higher than the guidelines established for PR. This review aimed to provide an understanding of the current UV-based advanced oxidation technologies for NDMA removal in PR, their limitations and the future of advanced technologies for their removal. NDMA is readily photolysed by direct UV irradiation, while an AOP such as UV/H2O2 process is necessary for the destruction of 1,4-dioxane. Unfortunately, the generation of hydroxyl radicals through UV photolysis of H2O2 is largely inefficient with conversion on the order of 20% under normal plant operations and the addition of H2O2 (e.g. 3 mg/L) provides only a negligible improvement in NDMA destruction. However, AOP can also be achieved without continuous chemical addition through the application of UV irradiation to heterogeneous photocatalysts (e.g. TiO2). The UV/TiO2 process generates hydroxyl radicals and singlet oxygen molecules, both of which degrade NDMA into by-products (e.g. methylamine or dimethylamine). Recent studies revealed that modification of the surface morphology of TiO2 can not only enhance NDMA destruction but also alter the composition of the degradation by-products.

Time-resolved spectral analysis of Radachlorin luminescence in water

We report results of spectral- and time-resolved study of Radachlorin photosensitizer luminescence in water in the spectral range of 950–1350nm and for determination of the photosensitizer triplet state and the singlet oxygen lifetimes responsible for singlet oxygen generation and degradation. At any wavelength within the explored spectral range the luminescence decay contained two major contributions: a fast decay at the ns time scale and a slow evolution at the μs time scale. The fast decay was attributed to electric dipole fluorescence transitions in photosensitizer molecules and the slow evolution to intercombination phosphorescence transitions in singlet oxygen and photosensitizer molecules. Relatively high-amplitude ns peak observed at all wavelengths suggests that singlet oxygen monitoring with spectral isolation methods alone, without additional temporal resolution can be controversial. In the applied experimental conditions the total phosphorescence signal at any wavelength contained a contribution from the photosensitizer triplet state decay, while at 1274nm the singlet oxygen phosphorescence dominated. The results obtained can be used for optimization of the methods of singlet oxygen monitoring and imaging.