Кафедра биофизики

A new diarylethene derivative containing a hydrazinylpyridine unit has been synthesized. The diarylethene derivative was highly selective and sensitive to Cd²⁺ and Zn²⁺ with significant fluorescence emission and color changes. Moreover, its multi-controllable photochromism and fluorescent switching characters were studied systematically with various stimuli (UV/vis lights and chemicals) in methanol solution. Based on the multi-addressable fluorescent switching characters, a combinational logic circuit was constructed by using the fluorescence emission intensity at 480 nm as output signal, the UV/vis lights, Cd²⁺, and EDTA as input signals.

A novel fluorescent sensor for Cd²⁺ and Zn²⁺ based on diarylethene derivative with a hydrazinylpyridine unit was developed. It could also be used to build a logic circuit with the emission intensity as the output signal, and UV/vis lights, Cd²⁺/EDTA as input signals.

Polyphenolic substances synthesized by plants are generally involved in protection against UV radiation and the attack of pathogenic microorganisms. Resveratrol (3,5,4′-trihydroxystilbene, RSV) is synthesized in its trans-form (trans-RSV) in plants under stress conditions like infections or UV exposure and has attracted attention as an antioxidant agent. Trans-RSV was irradiated with both UV-A (λ_MAX = 365 nm) and UV-B (λ_MAX = 300 nm) radiation in aqueous and ethanolic solutions at room temperature. The reactions were followed by UV–Vis spectrophotometry, HPLC with UV and fluorescence detection, and UPLC coupled to mass spectrometry detection. In both solvents the irradiation caused the fast isomerization of trans-RSV to cis-RSV. In ethanolic solutions, a strong fluorescent compound, identified as resveratrone (RSVT) was detected independently on the irradiation wavelength. In aqueous solutions, RSVT was not detected in both irradiation conditions. However, in aqueous/ethanol mixtures the amount RSVT was found to be proportional to the amount of ethanol in the solution. Under UV-B irradiation, both in ethanolic or water solutions other products were detected. Our results demonstrated that RSV is photosensitive and its photochemistry depends on the solvent nature and on the irradiation wavelength.

In this report, we observed that YOYO-1 immobilized on a glass surface is much brighter when dried (quantum yield 16 ± 4% in the ambient air) or in hexane than in water (quantum yield ∼0%). YOYO-1 is a typical cyanine dye that has a photo-isomerization reaction upon light illumination. In order to understand this quenching mechanism, we use femtosecond transient absorption spectroscopy to measure YOYO-1's electron dynamics after excitation directly. By deconvoluting the hot-ground-state absorption and the stimulated emission, the dynamics of electronic relaxation and balance are revealed. The results support the intermolecular charge transfer mechanism better than the intramolecular relaxation mechanism that has been widely believed before. We believe that the first step of the relaxation involves a Dexter charge transfer between the photo-excited YOYO-1 molecule and another guest molecule that is directly bound to the YOYO-1 giving two radicals with opposite signs of charges. The charges are recombined either directly between these two molecules, or both molecules start to rotate and separate from each other. Eventually, the two charges recombined non-radiatively via various pathways. These pathways are reflected on the complicated multi-exponential decay curves of YOYO-1 fluorescence lifetime measurements. This charge transfer mechanism suggests that (1) electrical insulation may help improve the quantum yield of YOYO-1 in polar solutions significantly and (2) a steric hindrance for the intramolecular rotation may have a less significant effect.

Charge transfer (right) has been considered in the literature to be a minor mechanism for YOYO-1's fluorescence quenching, but the new evidence suggests that it is a significant pathway.

Ba_3–xEu_xMgSi₂O₈ (0 < x≤ 0.20) showed Eu³⁺-derived orange emission under near-ultraviolet light. After the photostimulation using a Xe-arc lamp, the emission color turned purple because blue-emission centers arose within it. The following heat treatment reverted the emission color back to the original. From the excitation spectrum, the blue emission was assigned to Eu²⁺ ions those had not been identified before the photostimulation, which indicates that the photoreduction of Eu³⁺ caused the observed emission-color change. When x = 0.01, the most intense blue emission was induced by the photostimulation. Further addition of Eu ions lead to a decrease in the induced blue-emission intensity.

Here we focused on the fundamental study of self-cleaning properties of zirconium dioxide films, including photoinduced alteration of surface hydrophilicity, photocatalytic and photoinduced bactericidal activities. The accent was made on the factors influencing the photoinduced hydrophilic conversion such as surface acidity and spectral composition of light for the surface photoexcitation. The studies on photoinduced hydrophilic conversion of the ZrO₂ thin film were carried out using the contact angle measurements and XPS method. The experimental data demonstrate the very different hydrophilic behavior of the hydrated surface depending on the spectral region of photoexcitation corresponding to intrinsic or extrinsic ZrO₂ absorption. This is explained by the difference in the concentration of photoelectrons and photoholes which participate in the photo-induced surface processes. It is suggested that hole-trapping species such as surface hydroxyl groups and adsorbed water molecules play a crucial role in the photoinduced superhydrophilic transition. The effect of the electron-acceptor and electron-donor gas atmospheres on the aging of the surface superhydrophilicity is found to be in agreement with this conclusion. The photochemical activity of ZrO₂ coatings was tested by photodegradation of stearic acid. The antibacterial properties are investigated against Escherichia coli. The ZrO₂ thin films reveal self-cleaning properties and can be successfully used as biomedical or construction material.

Bismuth Ferrite, BiFeO₃, was synthesized using the solid state reaction and the Pechini method. The materials obtained were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), visible ultraviolet spectroscopy (UV-Vis) and field emission scanning electron microscopy (FEG). The microscopy showed that there are differences in morphology between the two synthesis and also the formation of pores obtained by the synthesis of the Pechini method. When using diffuse reflectance, a low bandgap value was obtained for the samples by both synthesis, 1.7 eV for the solid state reaction and 1.1 eV for the Pechini method. The materials synthesized through the two methods were effective for the degradation of the tartrazine dye reaching around 99% degradation, which was performed under optimized conditions and without the addition of H₂O₂. Lastly, it was found that there 3.5% of the dye was adsorbed in the solid state pellet.

In this study, a novel metal-organic hybrid material (MO1) was designed and synthesized for the detection of CN⁻ ions. The spectral analyses by FT-IR, ¹H NMR, ¹³C NMR, CHN and TGA satisfactorily confirmed the structure of MO1. The sensor MO1 was applied as colorimetric probe for sensing of cyanide ions in aqueous solutions of dimethyl sulfoxide. MO1 with electron withdrawing group at organic ligand showed high selectivity for detection of cyanide over other interfering anions. Interaction of MO1 with cyanide provides obvious colorimetric change from red to violet, enabling easy detect with the naked eye. In addition, the sensing details were evaluated using UV–vis spectroscopy. Furthermore, the detection limit of chemosensor toward CN‾ ions was found to be 5.52 μM. Moreover, probe MO1 can be used for selective sensing of cyanide based on the obvious color changes in real samples.

The novel basic bismuth (III) nitrate (BBN)/Bi_0.5O_0.5Cl_xBr_0.5-x heterostructure photocatalyts were first prepared by using a simple one-pot hydrothermal route. The samples were characterized by using SEM, TEM, XRD, XPS, BET, PL and UV–vis diffuse methods. And the photocatalytic performance of BBN/Bi_0.5O_0.5Cl_xBr_0.5-x was evaluated with the decoloration of Rhodamine B (RhB) aqueous solution. Compared with pure BBN and Bi_0.5O_0.5Cl_xBr_0.5-x, the BBN/Bi_0.5O_0.5Cl_xBr_0.5-x composites possessed the higher photocatalytic activity under simulated sunlight irradiation. The results indicated that the BBN-BiOCl_0.6Br_0.4 composite exhibited the highest photocatalytic property under the simulated solar light irradiation. The improvement of photocatalytic activity could be ascribed to the increased visible light absorption and the improved electron-hole pairs effective separation. Moreover, the holes (h⁺) and the superoxide radical (O₂⁻) were considered as the main active substances in the process of photodegradation. Last, the reasonable photocatalytic mechanism was discussed to explain the process.

Trifluoroacetic acid (TFA) is released in the atmosphere through its use in the chemical industry and as degradation product of chlorofluorocarbon (CFC) alternatives like hydrofluorocarbons and hydrochlorofluorocarbons. In the present study, we have investigated the OH formation dynamics in the photodissociation of TFA at 193 nm by Laser Photolysis-Laser Induced Fluorescence (LP-LIF) method, as well as stable product formation by GCMS and FTIR. It was found that, ∼26% of the available energy is partitioned into the relative translation of the photoproducts (f(T) = 0.26), which could be explained by presence of an exit barrier of ∼13 kcal/mol in OH formation channel. This result is very similar to OH formation from acetic acid (AA) and difluoroacetic acid (DFA), indicating fluorination at the side chain of aliphatic carboxylic acids does not significantly change the mechanism of COH bond scission. Our experimental results tallied with the theoretical studies, which suggested that the major OH formation channel in acetic acid and fluoroacetic acid is direct dissociation from the optically excited S₁ state through an exit barrier, with some competition from the T₁ state. However, quantum yield of OH formation from TFA (0.4) was found to be much smaller than AA (0.8), which is probably caused by higher reaction barrier in T₁ state of TFA, compared to AA. CHF₃, C₂F₄, C₂F₆, CO₂, CO, CF₃CFO, CF₂O and hexafluoropropylene oxide (HFPO) were detected as the stable products of the photolysis of TFA. The theoretically optimized ground state dissociation channels showed significant difference between TFA and AA.

In this study, N-doped TiO₂ (TiON) coated coal fly ash cenospheres (CFACs) was synthesized for photocatalytic disinfection against Escherichia coli (E. coli). Based on the physi-chemical evaluation of the TiON coated CFACs (TiON-CFACs), the disinfection efficiencies of E. coli under three different light sources, namely, ultraviolet A (UVA), visible light (VL), and the light emitting diodes with a wavelength of 420 nm (LED-420), were investigated. Then, a three-factor, four-level orthogonal experiment was designed to evaluate the influences of dosage, pH, and light intensity on its disinfection efficiency. The TiON-CFACs were effective under UVA, LED-420, and VL irradiation, with disinfection efficiencies of 5.78 log (45 min UVA), 5.84 log (180 min LED-420) and 5.97 log (300 min VL), respectively. The optimal disinfection efficiency was achieved at an initial pH of 6 under LED-420 irradiation at 40 mW/cm² with a dosage of 4 g/L TiON-CFACs. The mechanism of disinfection was further investigated using a range of free radical scavengers. Findings indicated that H₂O₂ appeared to play an indispensable role in E. coli disinfection. Moreover, the TiON-CFACs showed a stable disinfection efficiency of 5 log, even when the substance was recycled for four times, indicating the reliability and stability of the material. The results showed that the TiON-CFACs are promising in water treatment for photocatalytic disinfection of E. coli.

The disinfection efficiency of E. coli under three different light sources, namely, ultraviolet A (UVA), visible light (VL), and light emitting diodes with a wavelength of 420 nm (LED-420), were investigated. The TiON-CFACs were effective under UVA, LED-420, and VL irradiation, with disinfection efficiencies of 5.78 log (45 min UVA), 5.84 log (180 min LED-420) and 5.97 log (300 min VL), respectively.