Quantum chemical simulation of MoO3 dispergation on hydroxylated SiO2 surface

Метою даної роботи є оцінка енергетичної сприятливості утворення різних молібдатних груп (≡Si‑O‑)2Mo(=O)2 та =Si(‑O‑)2Mo(=O)2 під час термічно ініційованого диспергування MoO3 на гідроксильованій поверхні SiO2. Для цього було здійснено квантовохімічне моделювання реакції O12Si10(OH)16 + MoO3 = O12Si10(OH)14O2MoO2 + H2O в температурному інтервалі 300–1100 K із використанням обмеженого методу Хартрі-Фока (наближення ЛКАО) з валентним базисом SBKJC (Stevens-Basch-Krauss-Jasien-Cundari). Кластер O12Si10(OH)16, який являє собою структурний фрагмент кристала β‑кристобаліту, був використаний як модель високогідроксильованої поверхні кремнезему. Ми розглянули дві структури молібдатних груп (≡Si‑O‑)2Mo(=O)2, прикріплених до кремнеземного кластера O12Si10(OH)16 через силанольні групи. Молібдатні групи (Etot ‑584.60147 Hartree), прикріплені до кремнеземного кластера через віддалені силанольні групи, виявляються більш енергетично вигідними, ніж молібдатні групи (Etot ‑584.56565 Hartree), прикріплені до кремнеземного кластера через сусідні силанольні групи. Енергія молібдатних груп =Si(‑O‑)2Mo(=O)2 (Etot ‑584.48399 Hartree), прикріплених до кремнеземного кластера O12Si10(OH)16 через силандіольні групи, менш енергетично вигідні в порівнянні з подібними групами, прикріпленими через силанольні групи, через більше напруження кута між зв’язками. Знайдено, що реакція O12Si10(OH)16 + MoO3 = O12Si10(OH)14O2MoO2 + H2O в температурному інтервалі 300–1100 K, змодельована шляхом квантовохімічних розрахунків, свідчить, що процес диспергування MoO3 на гідроксильованій поверхні SiO2 є енергетично вигідним. Експ The aim of the present work is to evaluate the energetic favourability of the formation of different molybdate species (≡Si‑O‑)2Mo(=O)2 and =Si(‑O‑)2Mo(=O)2 during the thermally induced MoO3 dispergation on hydroxylated SiO2 surface. In order to do this a quantum chemical modelling of the reaction O12Si10(OH)16 + MoO3 = O12Si10(OH)14O2MoO2 + H2O within the temperature interval of 300–1100 K was undertaken using the Restricted Hartree-Fock method (the LCAO approximation) with the SBKJC (Stevens-Basch-Krauss-Jasien-Cundari) valence basis set. The cluster O12Si10(OH)16 which represents a structural fragment of a β‑cristobalite crystal was used in this work as a model of highly hydroxylated silica surface. We considered two structures of molybdate (≡Si‑O‑)2Mo(=O)2 species attached to O12Si10(OH)16 silica cluster via silanol groups. Molybdate species (Etot ‑584.60147 Hartree) attached to silica cluster via distant silanols appeared more energetically favourable than molybdate species (Etot ‑584.56565 Hartree) attached to silica cluster via nearby silanols. The energy of molybdate =Si(‑O‑)2Mo(=O)2 species (Etot ‑584.48399 Hartree) attached to O12Si10(OH)16 silica cluster via silanediol group is less favourable energetically in comparison with those attached via silanol groups because of higher bond angle straining. The reaction O12Si10(OH)16 + MoO3 = O12Si10(OH)14O2MoO2 + H2O in the temperature interval of 300–1100 K which simulates by quantum chemical calculations the dispergation of MoO3 on hydroxylated SiO2 surface was found to be energetically favourable. The experimentally optimised temperature of ca. 800 K required for dispergation of MoO3 on hydroxylated SiO2 surface is determined by MoO3 evaporation and transportation via the gas phase. ериментальна оптимальна температура (близько 800 K), потрібна для диспергування MoO3 на гідроксильованій поверхні SiO2, визначається випаровуванням та перенесенням MoO3 в газовій фазі.

Quantum-chemical modeling of cortisone-fullerenol agents of cancer therapy

In order to therapeutically destroy oncological neoplasms, chemotherapy or radiotherapy is usually applied, and in isotope medicine – short-lived radio nuclides are injected into the tumor (59Fe, 90Y, 95Zr, 99mTc, 106Ru, 114*In, 147Eu, 148Eu, 155Eu, 170Tm, 188Re, 210Po, 222Rn, 230U, 237Pu, 240Cm, 241Cm, 253Es). Binary (or neutron capture) therapy is a technology developed for the selective effect on malignant tumors using drugs that are tropic to tumors and contain non-radioactive nuclides (10B, 113Cd, 157Gd at al.). Triadic therapy involves the sequential introduction into the body of a combination of two or more separately inactive and harmless components, which are tropic to tumor tissues and capable of selectively accumulating in them or chemically interacting with each other and destroying tumor neoplasms under the action of certain sensitizing external influences. The aim of this work is quantum-chemical simulation of the electronic structure and analysis of the thermodynamic stability of new cortisone-fullerenol agents for the treatment of tumor neoplasms. The need for preliminary studies of modeling such objects is due to the very high labor intensity, cost and complexity of their practical production.

Energy transfer in luminescence composite materials based on mesogenic europium (III) complexes and some semiconducting polymers according to quantum-chemical simulation

A TDDFT study of energy transfer processes in luminescence composite materials based on mesogenic europium (III) complexes with substituted β-diketones and Lewis bases and some semiconducting polymers is presented. The calculated energies of the lowest singlet and triplet excited states of ligands and polymers were used to construct the energy level diagrams and indentify the main channels of intramolecular energy transfer. A system of a complex and a polymer, which is most preferable for practical application in optoelectronics, was selected. The simulated data agree well with the experiment.

PROSPECTS FOR CREATING RADON CONTAINING AGENTS IN RADIONUCLIDE THERAPY

One of the methods for treating oncological diseases is application of short-lived radionuclides. Existing risks of intoxication and radioactive contamination can be eliminated by introduction of a short-lived radon isotope into a hard strong fullerene coat. To increase the effectiveness of these drugs it is promising to introduce structural fragments of amino acids, peptides, steroid hormones, nucleic bases or heterocyclic compounds being able to accumulate exactly in tumoral but not in healthy tissues of the body. The article presents data on quantum-chemical simulation of electronic structure and thermodynamic stability of fullerenol radon-containing agents of radionuclide therapy on the example of a model cortisonefullerenol bioconjugate.

Aggregate Formation of Boron-Containing Molecules in Thermal Vacuum Deposited Films

The spectral properties of new boron-containing dyes were studied. One-component (pure dyes) and composite “Alq3+dye” thin films were fabricated using the thermal vacuum deposition method. The positions of the transmission spectra maxima in a one-component film are different for different film thicknesses. The best correlation of the maxima positions of the dye transmission spectra in solid and liquid solutions was observed for thicknesses of films close to a few (up to 10) monolayers. On the other hand, the absorption spectra maxima positions of one-component dye films (upper 10 nm) and composite films with high concentration, did not match the corresponding positions of absorption spectra maxima recorded in solutions. Comparison of the absorption spectra in one-component dye films and in solutions indicates the presence of both monomers and their aggregates in one-component films (contrary to solutions where such processes of aggregation do not take place, even at very high concentrations). Simultaneously with aggregation manifestation in the absorption spectra, the intensity of fluorescence of one-component dye films dramatically decreases. A quantum chemical simulation of the possible relative arrangement of two dye molecules indicates that the most possible of the simplest types of aggregates are physical dimers. Films of practical importance (due to efficient energy transfer from host to guest molecules when all singlet excitons are captured) possess a high quantum yield of fluorescence when reaching an impurity concentration of a few percent (aggregation does not take place yet).

Fluorination vs. Chlorination: Effect on the Sensor Response of Tetrasubstituted Zinc Phthalocyanine Films to Ammonia

In this work, the effect of fluorine and chlorine substituents in tetrasubstituted zinc phthalocyanines, introduced into the non-peripheral (ZnPcR4-np, R = F, Cl) and peripheral (ZnPcR4-p, R = F, Cl) positions of macrocycle, on their structure and chemiresistive sensor response to low concentration of ammonia is studied. The structure and morphology of the zinc phthalocyanines films (ZnPcR4) were investigated by X-ray diffraction and atomic force microscopy methods. To understand different effects of chlorine and fluorine substituents, the strength and nature of the bonding of ammonia and ZnPcHal4 molecules were studied by quantum chemical simulation. It was shown on the basis of comparative analysis that the sensor response to ammonia was found to increase in the order ZnPcCl4-np < ZnPcF4-np < ZnPcF4-p < ZnPcCl4-p, which is in good agreement with the values of bonding energy between hydrogen atoms of NH3 and halogen substituents in the phthalocyanine rings. ZnPcCl4-p films demonstrate the maximal sensor response to ammonia with the calculated detection limit of 0.01 ppm; however, they are more sensitive to humidity than ZnPcF4-p films. It was shown that both ZnPcF4-p and ZnPcCl4-p and can be used for the selective detection of NH3 in the presence of carbon dioxide, dichloromethane, acetone, toluene, and ethanol.

APPLICATION OF PIEZOSENSORS BASED ON THE MOLECULARLY IMPRINTED POLYIMIDE FOR DETERMI-NATION OF CAFFEINE IN TEA

In this article the molecularly imprinted polymers (MIPs) have been synthesized on the surface of piezosensors. The starting polymer for MIPs production was polyamic acid, which is a copolymer of 1,2,4,5-benzenetetracarboxylic acid and 4,4′-diaminodiphenyl ether. The caffeine served as the template. The quantum-chemical simulation was performed by the Gaussian 09 software using the DFT method at the B3LYP/6-31G(d,p) level with the basis set superposition error (BSSE) at the preliminary stage of the synthesis of the MIP for caffeine. The prepolymerization complexes were calculated to establish intermolecular interactions and obtain the optimum molar ratio between the template and polyamiс acid. It is shown that the constitutional repeating units of polyamic acid interact with the caffeine by forming H-bonds via carboxyl groups. The interaction energy first increases and then decreases with increasing the molar ratio of imprinting. Based on the quantum-chemical calculations, the optimal ratio of the reagents in prepolymerization mixture was set to 1 : 3 with the highest interaction energy (96.7 kJ/mol). Applying thermal imidization of solution of polyamic acid in the presence of a template, the molecularly imprinted polyimide has been synthesized by the non-covalent imprinting method. The ability of the obtained piezosensors to recognize the tempalte in model mixtures was experimentally evaluated. It was found that the range of detectable concentrations of caffeine is 3.1.10-6-10-1 mol/dm3 and the detection limit is 10-6 mol/dm3. Correctness of the caffeine determination in model solutions was verified in the spike/recovery tests. Piezosensors based on MIP were approved for the determination of the caffeine in tea varieties. It is shown that the concentration of caffeine in the aqueous solution increases with increasing brewing time. The relative standard deviation is less than 8%.