Кафедра биофизики

Two donor-acceptor fluorophores were prepared and tested for quantitative determination of HSA in aqueous samples. Fluorophores were non-emissive in polar solvents due to energy loss via non-radiative decays. Complexation of the fluorophores with HSA resulted multi-fold enhancement of emission in the red-near infrared (NIR) region. The emission intensity was linearly correlated to the amount of protein in the solution, which enabled us to develop calibration graphs for quantitative estimation of HSA in synthetic urine samples. Between the two fluorophores, the methoxy substituted fluorophore 1 selectively recognized HSA. It exhibited remarkable fluorescence enhancement with HSA over bovine serum albumin (BSA) and other globular proteins. The selective sensing aptitude of 1 was attributed to its restricted motions in the protein’s microenvironment due to multiple non-covalent interactions, preventing energy loss by radiationless decay. The different recognition properties of the fluorophores were estimated by the steady-state fluorescence and molecular docking studies. These findings indicate that this class of fluorophores can be useful for quantitative estimation of HSA in biological urine and blood samples in clinical practice.

A series of Ce³⁺ and/or Mn²⁺ doped Ba₉Lu₂Si₆O₂₄ phosphors were prepared by the solid state reaction. The phase and luminescent properties of the synthesized phosphors were investigated. The single phase of the synthesized phosphors indicates that Ce³⁺/Mn²⁺ ions doped into Ba₉Lu₂Si₆O₂₄ hosts entirely and formed solid state compounds. Mn²⁺ ions substitute Lu³⁺ sites in Ba₉Lu₂Si₆O₂₄ but Ce³⁺ ions substitute both Lu³⁺ and Ba²⁺ sites in Ba₉Lu₂Si₆O₂₄. The emission bands of Ba₉Lu₂Si₆O₂₄:Ce³⁺ phosphors show dependence on excitation wavelength and Ce³⁺ concentration. Upon the excitation at 400 and 350 nm, Ba₉Lu₂Si₆O₂₄:Ce³⁺ phosphors show emission bands peaking at 495 and 422 nm, respectively. Upon the excitation at 350 nm, Ba₉Lu₂Si₆O₂₄:Ce³⁺/Mn²⁺ phosphors show emission bands corresponding to Ce³⁺ and Mn²⁺ ions. Due to energy transfer from Ce³⁺ to Mn²⁺, tunable luminescence is obtained in Ba₉Lu₂Si₆O₂₄:Ce³⁺/Mn²⁺ phosphors.

This article reports a new method for preparing mixed valence tin oxide (Sn₃O₄) flower-like nanostructures using a microwave-assisted route. Thin-film Sn₃O₄/TiO₂/Ti electrodes demonstrated highly efficient visible light driven photocatalytic degradation of monoazo acid yellow 17 (AY17) dye, reaching 95% color removal after 60 min at pH 2. Moreover, under low bias potential (0.5 V), the photoelectrocatalytic efficiency increased to 97% color removal and 83% removal of total organic carbon at a kinetic rate almost 3-fold higher than in photocatalysis. Liquid chromatography mass spectrometry was used to identify intermediate formation, and oxidation performance was proposed for photocatalytic and photoelectrocatalytic degradation with no organics identified after 120 min of treatment. The results indicate that Sn₃O₄/TiO₂/Ti photoelectrodes offer a simple, green method for wastewater treatment employing visible light source.

A novel diarylethene derivative containing a purine unit has been successfully synthesized. It not only exhibited multiple controllable fluorescent switching properties with the stimuli of metal ions, and UV/vis lights, but also showed high selectivity and sensitivity to Zn²⁺ and Al³⁺ in THF and methanol, respectively. In THF, its fluorescence intensity increased by 18-fold and the fluorescent color changed from dark orange to green with the addition of Zn²⁺. Nevertheless, its fluorescent intensity enhanced 98-fold and the fluorescent color changed from dark orange to bright green in methanol with the addition of Al³⁺. Based on the fluorescent behaviors, a logic gate was constructed with the emission intensity at 545 nm as output signal, the UV/vis lights and Zn²⁺/EDTA as input signals. Furthermore, this sensor could also be used to detect Zn²⁺ and Al³⁺ in practical samples with high accuracy.

A dual-functional fluorescent sensor based on diarylethene has been synthesized successfully. The sensor could be used to detect Zn²⁺ and Al³⁺ in practical samples with high accuracy.

The pharmaceutical wastewater of different organic loads i.e. high (HSW) and low strength wastewater (LSW) were collected from the bulk pharmaceutical industry and subjected to different applications of Fenton’s treatment followed by subsequent biological treatment. For both the HSW and LSW, applications of Fenton such as, dark-Fenton (DF), solar driven photo-Fenton (PF) and electro-Fenton (EF) were utilized as pre-treatment technologies to improve the biodegradability and reduce the organic load of wastewater by combine oxidation and coagulation. The operational parameters like pH, hydrogen peroxide dosage and iron concentration were optimized in case of DF and PF processes, whereas in case of EF process, applied voltage and hydrogen peroxide dosage were optimized to make water biocompatible for subsequent biological degradation. The use of Fenton applications as a pre-treatment resulted in a significant enhancement in the BOD₅/COD ratio validating the production of easily degradable metabolites or secondary products. Overall results indicated that among the utilized Fenton technologies, pre-treatment of pharmaceutical wastewater with PF lead to better COD and TOC removal efficiency with subsequent biological degradation when compared to DF and EF pre-treatment. Overall COD removal efficiency of the combined PF and biological treatment was around 84% for LSW and 82% for HSW. Conclusively, it can be established that combined Fenton applications as pretreatment technology and biological treatment is more effective approach in comparison to single stage oxidation either by Fenton or biological treatment. Cytotoxicity assessment revealed that complete detoxification of wastewaters were achieved indicating that hybrid treatment technology of Fenton’s and biological treatment did not exhibited any toxicity against the selected microbes.

Acetaminophen (APAP), a non-steroidal anti-inflammatory drug, is the most commonly detected wastewater contaminant together with caffeine (CAF), that is used both in beverages and food but also in medicine. The presence of pharmaceuticals in the wastewater effluent have confirmed that nowadays existing wastewater treatment methods are not effective enough in pharmaceuticals removal. The aim of presented studies was the determination of the photocatalytic efficiency of TiO₂ based nanocomposites in the removal of APAP and CAF from water under visible light irradiation. The process of photocatalytic removal of APAP from water in the presence of CAF was performed using TiO₂-SiO₂ photocatalysts containing multiwalled carbon nanotubes (MWCNT) characterized by high surface area (up to 420.8 ± 12.6 m² g⁻¹), narrow pore diameter (3–4 nm) and uniform anatase TiO₂ crystallites (5–6 nm) with reduced band gap energy (up to 2.82 eV). The high resistance of CAF to photocatalytic decomposition under visible light irradiation was noted. Slight removal of CAF (29.4 ± 2.7%) was observed after 60 min of irradiation using nanocomposite with lowest MWCNT addition (0.15 wt%). The presence of CAF hindered APAP photocatalytic oxidation. CNT10, nanocomposite that was the most effective in APAP removal (81.6 ± 0.6%) enabled to remove APAP in the presence of CAF only by 48.0 ± 4.3% during visible light irradiation. The best results of APAP removal in the presence of CAF were obtained over CNT1 (47.6 ± 2.4%), that contained 0.15 wt% of MWCNT. The kinetics of APAP, CAF and APAP with CAF photocatalytic degradation and mineralization proceeded according to a pseudo-first-order reaction model and APAP k_DOC was significantly reduced in the CAF presence (up to almost 4 times). The photocatalytic APAP removal in the presence of CAF over MWCNT-TiO₂-SiO₂ proceeded via photo generated holes and, in lower extend, OH radicals. Photocatalytically treated model water containing APAP and CAF revealed no toxicity to Vibrio fischeri.

Two unsymmetrical squaraines (SQ-OH and SQ-OPA) have been synthesized. SQ-OPA was gained by esterification of acryloyl chloride and hydroxyl group on SQ-OH. Based on the investigation of the UV–vis, fluorescent, time-dependent ¹H NMR and mass spectra, SQ-OPA was demonstrated to have two response sites to biothiols: the central four-member ring and acryloyl group. SQ-OPA is the first “turn-on” fluorescent squaraine thiol probe, and can probe the biothiols (Cys, Hcy, and GSH) simultaneously by naked-eye. However, SQ-OH bearing similar squaraine molecular framework with SQ-OPA, showed good chemical stability during the addition of biothiols. Therefore, for unsymmetrical squaraines, the substituent attached in benzene ring, far away from the central four-member ring, can signficantly affect the stability of squaraine central four-member ring against the nucleophilic attack, which could provide a new strategy for designing “turn-on” fluorescent SQ probes.

Unsymmetrical squaraine dyes SQ-OPA can effectively identify Cys, Hcy and GSH through two response processes.

The photochemical generation of uranous ions U(IV) in the aqueous solution containing 40 mM uranyl nitrate, 1% (v/v) 2-propanol and/or 1% (v/v) acetone, in the presence of different concentrations of nitric acid has been investigated. The formation of U(IV) was investigated in six different light irradiations, (i) 350 nm uv lamps, (ii) 395 nm LED lamps, (iii) 300 nm uv lamps, (iv) fluorescent lamps visible light, (v) 100 W tungsten lamp and (vi) Sunlight. The formation kinetics of U(IV) was followed by monitoring the absorbance at 648 nm from the absorption spectra of the solution recorded at different photo-irradiation time intervals. It was observed that the maximum conversion of U(VI) to U(IV) was about 72% in the case of solution containing 40 mM UO₂(NO₃)₂, 1% 2-propanol and 1 N HNO₃ under 350 nm uv light and it was stable for several days in de-aerated condition.

Detection of hydrogen sulfate from an aqueous organic solvent systems medium attracts to lots of interest because of could be in most environmental and biological systems. In this study, the simple receptors 5 and 6 containing oxindole core were synthesized, and the anion sensing properties were studied using colorimetric, fluorometric detection and ¹H-NMR spectroscopy. The research indicated that the specific ligand affinity for hydrogen sulfate ions results in drastic color and spectral changes. According to the data obtained, a new peak at 371 nm in the absorption spectrum of 5 and an increase in fluorescence intensity of 5 were observed in the presence of HSO₄^¯ ions. The binding ratio of 5 to HSO₄¯ was calculated to be 1:1 according to Job's plot experiments. The Ks value was found to be 1.21×10⁵ M⁻¹ using the Benesi-Hildebrand equation. The LOD value was calculated with value as low as 8.9 μM for HSO₄^¯. Moreover, DFT calculations confirmed the nonplanar structures or propeller structures. As a result of all these studies, it can be said that 5 which is non-toxic, may be a useful and selective candidate turn-on sensor for HSO₄¯ sensing in the industrial wastewaters.

Cyclic voltammetry, UV/Vis/NIR spectroscopy, EPR spectroscopy and theoretical calculations were used to study the mixed valence radical anions of 4,4″-dinitro-p-therphenyl (2), of 3,6-bis(4-nitrophenyl)-1,2-diazine (3) and of 2,5-bis(4-nitrophenyl)-1,4-diazine (4) as models to understand the effect of the structural changes on the conductivity of poly-p-phenylene polymers. All the results show an increase of the electronic communication between nitro groups in the order 2 < 3 < 4. Substitution of CH units by nitrogen atoms in the central aromatic ring lowers the reduction potential of the bridge, increasing the electronic coupling through the triaryl bridge and the rate of intramolecular electron transfer in the same order. Additionally, calculations show that the 1,2-diazine ring of 3, and specially the 1,4-diazine ring of 4, allow a higher planarity of the molecule by decreasing the steric strain between rings, which also increases the conjugation through the bridge. The results suggest that incorporating pyrazine (1,4-diazine) and pyridazine (1,2-diazine) units in poly-p-phenylene polymers should enhance the electronic properties of these conducting polymers.