Кафедра биофизики

The perovskite BaSnO₃, prepared by chemical route crystallizes in a cubic structure with an average crystallite size of 63 ± 2 nm. The oxide is characterized by scanning electron microscopy, granulometry, optical properties and electrochemistry. The optical properties indicate a direct transition at 3.13 eV. The electrical conductivity follows an exponential law: σ_o exp (-E_a/kT) due to electronic hopping through mixed valences Sn^4+/2+ in agreement with a semi conducting behavior. The intensity potential J(E) curve shows a small hysteresis and exhibits n-type behavior, indicating the presence of oxygen vacancies. The capacitance measurement at pH ∼ 5.5 gives a flat band potential of -0.37 V_NHE. As application, the ibuprofen is eliminated by electrocatalysis on BaSnO₃ with a conversion rate of 55% under a current of 150 mA. An increase up to 68% has been reached by electro-photocatalysis under UV illumination; the ibuprofen disappearance obeys to a first order kinetic with a rate constant of 3 × 10⁻³ mn⁻¹ and a reaction mechanism is proposed.

The energy diagram of BaSnO₃ in ibuprofen solution (pH ∼ 5).

The kinetic of ibuprofen mineralization by electrocatalysis (■), electro-photocatalysis () under UV light in Na₂SO₄ solution (3.5 g/L), pH ∼ 5, [Ibuprofen] = 20 mg/L.

Pyrochlore structured Gd₂Ti₂O₇ was supported on HZSM-5 zeolite by sol-gel method to prepare composite χGd₂Ti₂O₇/HZSM-5. Crystal growth of Gd₂Ti₂O₇ is constrained after loading on the surface of HZSM-5 zeolite. The band gap energies are 3.77, 3.75, 3.72, 3.60 and 3.37 eV for the χGd₂Ti₂O₇/HZSM-5 composites containing 30%, 50%, 70% and 90% Gd₂Ti₂O₇, respectively. The micropores in the χGd₂Ti₂O₇/HZSM-5 mainly come from the HZSM-5 zeolite, and the supported Gd₂Ti₂O₇ provides the majority of the mesopores. Besides the contribution of HZSM-5, the extra enlargements in BET surface area and total pore volume after supporting are due to the enhanced porosity in the Gd₂Ti₂O₇ layer. Photocatalytic degradation efficiency greatly depends on the variation of Gd₂Ti₂O₇ loading content in χGd₂Ti₂O₇/HZSM-5. The degradation process obeys the first order reaction law, and the reaction rate constants are 1.05 × 10⁻² and 3.52 × 10⁻² min^-1 on the pure Gd₂Ti₂O₇ and 90%Gd₂Ti₂O₇/HZSM, respectively.

For the first time the nonlinear optical (NLO) activity of indolizine-based push-pull chromophores with different acceptor moieties was studied and compared. All the chromophores demonstrate strong absorption band in the visible (orange-red) part of the spectrum, with ε of ca. 10⁵ L∙cm⁻¹∙M⁻¹ notably dependent on medium polarity. Replacement of Ph-TCF acceptor by Hex-TCP one results in twofold increase of the first hyperpolarizability value. Energy gaps estimated by electrochemical methods decrease in the series ΔE_1a,b>ΔE_3a,b>ΔE_2a,b for compounds with Ph-TCF, DCM and Hex-TCP acceptors, respectively, good agreement with DFT estimations is obtained. The nonlinear optical coefficient for poled PMMA-based films, containing 20 wt% of isomeric indolizine chromophores with weaker dicyanomethylene (DCM) acceptor and with π- bridge expanded by isophorone moiety, achieves 36 pm/V, thus exceeding those for materials containing chromophores with stronger Ph-TCF or Hex-TCP acceptors and with short vinylene π-bridge.

A new monoterpenoid based fluorescent receptor (E)-2-(5-allyl-2-hydroxy-3-methoxybenzylidene)-N-phenylhydrazinecarbothioamide (1) was synthesized and applied as a fluorescent chemosensor for the selective detection of bioactive Zn²⁺ and Mg²⁺ ions over other tested cations and anions. The selective complexation with the receptor 1 provides a fluorescence enhancement that is highly specific for the determination of Zn²⁺ and Mg²⁺ ions. Under optimal conditions, the limit of detection was estimated down to 59.4 nM and 89.1 nM for Zn²⁺ and Mg²⁺ ions, respectively. Furthermore, the receptor 1 showed good cell permeability and was successfully applied for the monitoring of Zn²⁺ and Mg²⁺ ions in live cells.

A hydroxyphenylquinazolinone-based fluorescent probe DAP-1 with a large Stokes shift (162 nm) was firstly developed for detection of cysteine. The probe DAP-1 with two acrylate as highly Cys-selective sites was designed based on the combination of excited state intramolecular proton transfer (ESIPT) and aggregation-induced emission (AIE) mechanism. Upon the treatment with cysteine, DAP-1 displayed a strong fluorescence enhancement (65-fold). The limit of detection obtained from fluorescent titration was as low as 0.03 μM. DAP-1 could detect cysteine with high selectivity and sensitivity. Significantly, DAP-1 could be used to detect cysteine in living cells.

Different morphologies of titania with different dimensions (0, 1 and 2 D) were prepared using hydrothermal technique and Au nanoparticles were deposited on its surface using photoreduction method. The obtained materials were characterized using X-ray diffraction, HRTEM and FESEM. The optical properties were studied for all morphologies before and after depositing of Au nanoparticles, a clear shift toward visible light absorption was confirmed after Au loading. Moreover, the surface area, pore size and pore volume were discussed and revealed that BET surface area was decreased after Au nanoparticles deposition on all morphologies. The prepared materials were applied as a photoanode for water splitting in alkaline media and the effect of titania dimension and Au deposition on the photocurrent were investigated. Au deposition on the surfaceof titania dramatically improves the performance of photocurrent generation during photoelectochemical electrolysis of water under simulated solar light irradiation. The titania dimension played a significant role on the value of photocurrent. Au modified nanotubes (1D) exhibit the highest photocurrent with high stability. The maximum photocurrent densities were 1.16, 0.63, 1.45, 2.97, 3.28, and 5.23 mA cm⁻² at an applied potential of 1 V with 4.98, 2.01, 2.50, 3.47, 4.05, and 5.19 times increment for particles (0D), sheets (2D), tubes (1D), particles@Au, sheets@Au, and tubes@Au compared to its corresponding current density in dark respectively. Depositing of Au nanoparticles on titania, decreases the charge transfer resistance due to the surface plasmon resonance effect of Au nanoparticles leading to enhancement in the photoelectrochemical activity. TNT@Au photoanode had the longest electron pass due to the tubular form (1D) which help in charge separation.

Based on the concept of dynamic membrane and photocatalytic membrane reactor (PMR), the dynamic photocatalytic membrane reactor is developed via deposition of ZnIn₂S₄ suspension on polyvinylidene fluoride (PVDF) membrane. Operating with effluent circulating to the photocatalytic membrane reactor, the highest total organic carbon (TOC) removal efficiency of 57% is obtained after 3 h reaction with 1.88 mg cm⁻² photocatalyst under the flux of 84.06 L m⁻² h⁻¹ and light intensity of 50 mW cm⁻². Operating with continuous influent and effluent mode under the flux of 26.09 L m⁻² h⁻¹ and light intensity of 50 mW cm⁻², an average of 50% removal efficiency can be maintained during the 24 h photocatalytic reaction with photocatalyst loading of 1.88 mg cm⁻² when the initial concentration of tetracycline is 10 mg L⁻¹. Under the same operating conditions, more than 92% removal efficiency can be maintained during 36 h photocatalytic reaction when lower initial concentration of 100 μg L⁻¹ is applied. After this reaction, the characterizations show that the surface and structure of PVDF basement membrane are not affected.

In this work, mesoporous titanium dioxide sphere Mp-TiO₂/SnS₂ composites have been synthesized for the photodegradation of formaldehyde with fluorescent lamp. SnS₂ nanosheets/nanoparticles were deposited on the surface of Mp-TiO₂ sphere uniformly through an in-situ method. The morphology of SnS₂ can be modulated through adjusting the Sn/Ti molar ratio. SnS₂ nanosheet turned into nanoparticle when the Sn/Ti molar ratio changed from 0.05 and 0.10 to 0.15 and 0.20. The physical and chemical properties of as-prepared composite catalysts were thoroughly studied by X-ray diffraction (XRD), Raman, scanning electron microscope (SEM), Brunauer Emmett Teller (BET), energy-dispersive X-ray spectroscopy (EDS), photoluminescence (PL) and UV–vis spectrophotometer. The photocatalytic performance of Mp-TiO₂/SnS₂ in the degradation of HCHO was assessed in a smog chamber with the irradiation of fluorescent light. A degradation efficiency of about 63% was achieved when the molar ratio of SnS₂/TiO₂ was 0.10. Through extending the light absorption range and hindering the recombination of photo-generated electron-hole pairs, the combination with SnS₂ enabled the fabrication of hybrid photocatalysts with high photocatalytic activity and long-term stability.

The morphology of SnS₂ can be modulated through adjusting Sn/Ti molar ratio, SnS₂ nanosheet turned into nanoparticle when the Sn/Ti molar ratio charged from 0.05 and 0.10 to 0.15 and 0.20.

An extremely sensitive colorimetric sensor has been developed for selective determination of Hg²⁺ in aqueous solution based on magnetic nanocomposite (Fe₃O₄@ZIF-67), which results in an effective intrinsic peroxidase mimicking activities and makes the composites oxidize the 3, 3′, 5, 5′- tetramethyl benzidine (TMB) in the presence of hydrogen peroxide (H₂O₂) to produce a blue coloured solution. Significantly, the oxidation of TMB was retarded or prevented in the presence of antiradical biomolecules Glutathione (GSH) because of its strong cation restoration property. When Hg²⁺ is added, the strong affinity of mercury ions with thiol groups of GSH provokes the oxidation of the substrates, which helps the solution turn into blue colour. The absorbance intensity was proportional to the concentration of Hg²⁺ in the wide range of 0–30 nM and detection limit was successfully as low as 0.36 nM. The resultant nanocomposite based peroxidase mimicking activity applied as a versatile platform in the colorimetric detection of Hg²⁺ was established the other co-existing metal ions in aqueous solutions. Finally the sensor was applied to detect Hg²⁺ in real water sample with satisfactory recovery results. Interestingly, the proposed colorimetric sensing platform held great potential in the application of mercury contamination in industrial sewage.

This communication reports the effect of micelles on the molecular organisation of an anionic fluorescent dye Fluorescein Sodium salt (FSS) in Langmuir-Blodgett (LB) film. FSS forms non-fluorescent H-aggregates in LB film when interact with Cetyltrimethylammonium Bromide (CTAB) molecules below critical micellar concentration (CMC). While above CMC, LB films of FSS adsorbed on the micellar surface of CTAB, show predominant J-aggregated sites. Complex LB films of FSS are also prepared by allowing it to adsorb onto a preformed Langmuir monolayer of cationic amphiphile octadecylamine (ODA) at the air-water interface and then depositing it onto the solid substrate. Complex ODA-FSS LB films are also investigated and a comparison is made with the SA-CTAB-FSS complex films. Unlike SA-CTAB-FSS complex LB films, ODA-FSS LB films can not effectively control the non-fluorescent H-aggregated sites. The films are characterised by UV–vis absorption and fluorescence spectroscopic studies and in-situ Brewster Angle Microscopic (BAM) studies. Thus CTAB micelles play an important role to decrease the H-aggregated sites in the SA-CTAB-FSS complex LB films. This complex LB film can act as efficient fluorescence probe for several biological systems due to the absence of non-fluorescent H-aggregated sites.

In-situ BAM images of SA-CTAB-FSS complex Langmuir monolayer at the air-water interface when CTAB concentration in the aqueous sub-phase is (a) below CTAB CMC, (b) above CTAB CMC. Distinct changes in the two BAM images give visual evidence of different types of molecular organisations.