41 research outputs found
Modeling and analysis of fundamental properties of sumanene
U disertaciji je sprovedeno teorijsko istraživanje fizičko-hemijskih svojstava elektronskog podsistema molekula sumanena. Proračuni su sprovedeni u okvirima DFT i TDDFT teorije sa B3LYP funkcionalom i 6-31Gd, 6-31Gdp i 6-31++Gdp bazisom. Za sve proračune u okvirima navedenog nivoa teorije, korišćen je softverski paket Gaussian03. Ispitana su: strukturna i optička (zajedno sa nelinearnim) svojstva sumanena i njegovih derivata dobijenih modifikovanjem sa atomima bora iazota, aromatična i inverziona svojstva svojstva sumanena i njegovih derivata, adsorpciona svojstva sumanena prema molekulima H2, CO, CO2 i NH3 i uticaj spoljašnjeg električnog polja na svojstva sumanena. Prema dobijenim rezultatima, fundamentalna fizičko-hemijska svojstva molekula sumanena mogu se efikasno i fino podešavati supstitucijom i disupstitucijom hetero-atomima bora i azota. Dubina i inverziona barijera sumanena se na ovaj način može menjati u oba smera. Pokazalo se da su ova dva parametra u korelaciji, s obzirom da inverziona barijera skoro potpuno zavisi od dubine sumanena. Slično je i sa aromatičnim svojstvima prstenova, koja se u zavisnosti od broja uvedenih hetero-atomamenja od aromatične preko nearomatične do antiaromatične prirode. Optička svojstva su, pomenutim modifikacijama, takođe značajno poboljšana: apsorpcioni pikovi kod UV/Vis spektra se pomeraju ka vidljivoj oblasti, dok je hiperpolarizibilnost sumanena i derivata sa jednim atomom bora viša od referentnog molekula uree, respektivno, 9 i 49 puta. Prema dobijenim rezultatima, adsorpciona svojstva sumanena su veoma kompetitivna sa ostalim organskim molekulima kao što su ugljenične nanotube i fuleren C60, usled postojanja značajnog dipolnog momenta zbog specifične geometrije. Posebno se ističu pozitivna adsorpciona svojstva prema molekulima H2 i CO. Dok je prvo pomenuti bitan sa energetskog aspekta, specifičnost drugog molekula se ogleda u činjenici da ne može biti adsorbovan od strane ugljeničnih nanotuba. Potencijal sumanena, posebno u oblasti organske elektronike, dodatno ističu i rezultati ispitivanja uticaja spoljašnjeg električnog polja. Naime, dobijeni rezultati ukazuju da se specifična (posebno adsorpciona) svojstva sumanena mogu dodatno poboljšati primenom slabog, i eksperimentalno lako ostvarljivog, električnog polja, jer se intenzivira razdvajanje naelektrisanja.Theoretical investigation of physicochemical properties of electron subsystem of sumanene molecule has been conducted in this doctoral work. Calculations are performed within DFT and TD-DFT with B3LYP functional and 6-31Gd, 6-31Gdp i 6-31++Gdp basis sets. For all calculations, on the mentioned level of theory, Gaussian03software package was used. Investigation encompassed: structural and optical (including nonlinear) properties of sumanene and its derivatives obtained by modification with boron and nitrogen atoms, aromatic and bowl to bowl inversion properties of sumanene and its derivatives, adsorption properties of sumanene towards H2, CO, CO2 i NH3 molecules and the influence of external electric field to the properties of sumanene. According to obtained results, fundamental physicochemical properties of sumanene molecule could be efficiently and finely adjusted with the monosubstitution and disubstitution with hetero-atoms of boron and nitrogen. Bowl depth and bowl to bowl inversion barrier could be tuned in both directions. It was demonstrated that these two parameters are correlated, since bowl to bowl inversion barrier principally depends on the fourth power of bowl depth. Similar situation is with aromatic nature of sumanene rings, which change, depending on the number of introduced boron and nitrogen atoms, from aromatic through non-aromatic towards anti-aromatic nature. Thanks to mentioned modifications, optical properties are improved as well: absorption peaks in UV/Vis spectra shift towards visible area, while hyperpolarizabilities of sumanene and its derivative containing one boron atom are higher than hyperpolarizability of referent molecule of urea, respectively, 9 and 49 times. Thanks to significant dipole moment due to the specific geometry, nvestigated adsorption properties of sumanene are very competitive to the other organic molecules such as carbon nanotubes and fullerene C60. Positive adsorption properties of sumanene towards H2 and CO molecules are distinguished. While the H2 molecule is important from the energetic aspects, specificity of CO molecules is that it can’t be adsorbed by carbon nanotubes. Potential of sumanene, especially in the field of organic electronics, is emphasized through the obtained results related to the investigation of the influence of external electric field. Obtained results indicate that specific (especially adsorption) properties of sumanene could be additionally improved by application of weak, and experimentally easily achievable, external electric field, due to the higher charge separation.
Computational study of amiloride – a WADA banned molecule
Amiloride (AMI) is a representative of diuretics. Among other purposes, it is utilized for high blood pressure or swelling induced by heart failure. While it is identified as one of the safest medicines available, it is also listed in the World Anti-doping Agency’s list of substances banned in sport, because it is considered a masking agent. Since it has been abused in sports, methods have been developed to be able to detect it during doping controls. We have computationally investigated selected structural and reactive properties of the AMI molecule in this work, employing density functional theory calculations
Structural and computational study of quinoline-based chalcogensemicarbazones
Chalcogensemicarbazones are condensation products between semicarbazide and its sulphur and selenium isosters with carbonyl compounds with a broad spectrum of biological activities [1-3]. In this work the X-ray structural investigation of library of six chalcogensemicarbazones has been complemented with computational study of their global and local reactive properties, within the framework of density functional theory (DFT). Among other information, DFT calculations helped us to locate the most reactive sites of studied molecules and to identify their sensitivity towards the oxidation. Investigated compounds have been also checked for their optoelectronic properties, due to the fact that they share certain structural similarity with molecules that have exhibited potentially important properties for the area of organic electronics. Pharmacokinetic properties have been assessed by the analysis of frequently employed drug likeness parameters
Titanium Dioxide as the Most Used Photocatalyst for Water Purification: An Overview
Titanium dioxide (TiO2), one of the most frequently used materials in general, has emerged as an excellent photocatalytic material for environmental applications. In this review, principles and mechanisms of the photocatalytic activity of TiO2 have been analyzed. Structural and physical specificities of TiO2 nanoparticles, such as morphology, crystal structure, and electronic and optical properties, have been considered in the context of photocatalytic applications. A review of the influence of several factors, such as the type and dimensions of photocatalyst particles, pH of the solution, the influence of oxidants/electron acceptors, and light intensity on photocatalytic properties of TiO2, has been provided. Superhydrophilicity as an intrinsic property of the TiO2 surface was discussed through surface reconstruction on TiO2 during the reversible hydrophilic changes. Additionally, attention was paid to improving the photocatalytic properties of TiO2 particles through aggregation and agglomeration
TRANSPORT PROPERTIES OF PENTACENE, HEXACENE AND THEIR BN ANALOGUES
We have investigated transport properties of higher acenes pentacene and hexacene and compared it with the transport properties of their BN analogues. Charge hopping from one structure to another was investigated through calculations of reorganization energies based on DFT and Marcus semiempiric approach, while the investigation of charge transport along the investigated structures was based on DFT calculations and non-equilibrium Green's function (NEGF) method. Attention was also paid to the energy separation between the lowest excited singlet (S1) and triplet (T1) state, which is quantity that is important for the field of thermally activated delayed fluorescence (TADF). The obtained results indicate that both groups of investigated structures have certain advantages and drawbacks. According to the reorganization energies and I-V characteristics, pentacene and hexacene have better properties, while from the aspect of TADF, BN analogues of pentacene and hexacene have better properties
Sumanene and its adsorption properties towards CO, CO2 and NH3 molecules
Density functional theory calculations were used in the theoretical investigation of the adsorption properties of sumanene towards molecules considered as common air pollutants: CO, CO2 and NH3. The insignificant perturbation of sumanene after adsorption and the adsorption energies obtained indicate a physisorption mechanism. It was shown that, contrary to carbon nanotubes, sumanene is able to adsorb CO molecules, and that adsorption of CO2 by sumanene is stronger than adsorption of CO2 by C-60. To better understand the adsorption characteristics of sumanene, density of states and natural bond order analyses were performed, which showed that chemical interactions exist and that these are more important mostly on the convex side. Better adsorption properties were obtained for the concave side as adsorption is dictated by physisorption mechanisms due to the specific bowl-shaped geometry of sumanene, because of which more negative charge is located precisely on the concave side. Molecular electrostatic potential surfaces were also used in order to better locate the adsorption sites and gain additional details about adsorption
Remarkable Sensing Behavior of Pyrazole-based Chemosensor Towards Cu(II) Ion Detection: Synthesis, Characterization and Theoretical Investigations
We report the synthesis of a new imine based
ligand, 3-((3-methoxybenzylidene)amino)-1H-pyrazol-5-ol (HL) and its Cu(II) complexes in 2:1 (HL:metal) and 1:1:1 (HL:metal:HQ) stoichiometric ratio using
8-hyroxyquinoline (HQ) as an
additional bidentate ligand. The synthesized ligand (HL) and its Cu(II) complexes (1
and 2) are structurally
characterized using FT-IR, electronic absorption and emission, NMR, MS and TGA
techniques. Furthermore, the complexation of Cu2+ with HL leads to the immediate formation of
brown colored solution which indicates that HL can act as simple colorimetric sensor for Cu2+ ions.
We further investigated that the sensor could selectively bind to the Cu2+
ions even in the presence of competitive ions such as Mn2+, Fe2+,
Co2+, Ni2+, Zn2+, Ag+ and Na+ ions
in aqueous solutions which was studied by electronic absorption spectroscopy.
The HL ligand and corresponding
Cu(II) complexes have been investigated for their reactive properties by
density functional theory (DFT) calculations. Quantum molecular descriptors
describing local reactive properties have been calculated in order to identify
the most reactive molecule sites of title compounds. DFT calculations
encompassed molecular electrostatic potential (MEP), local average ionization
energies (ALIE), Fukui functions and bond dissociation energies for hydrogen
abstraction (H-BDE)
Particularities in physical characteristics of molecular crystalline nanofilms
In this paper, the alterations and changes in dielectrical properties of different nanofilm molecular crystals, caused by the presence of boundaries were theoretically investigated and analyzed. By combined analytical and numerical calculations, allowed exciton states were found, and their spatial distribution along the axis limit (by layers of film) and the surface localization was examined. The relative permittivity of the observed ultrathin film was determined, and the impact of (five) boundary parameters on resonant absorption phenomenon: discrete (by frequencies) and selective (by layers of film) was examined. The conditions for the emergence of single-resonant absorption lines were found
Zeolites as Adsorbents and Photocatalysts for Removal of Dyes from the Aqueous Environment
This study investigated the potential of zeolites (NH4BETA, NH4ZSM-5, and NaY) to remove two frequently used dyes, methylene blue (MB) and rhodamine B (RB), from an aqueous environment. The removal of dyes with zeolites was performed via two mechanisms: adsorption and photocatalysis. Removal of dyes through adsorption was achieved by studying the Freundlich adsorption isotherms, while photocatalytic removal of dyes was performed under UV irradiation. In both cases, the removal experiments were conducted for 180 min at two temperatures (283 K and 293 K), and dye concentrations were determined spectrophotometrically. Additionally, after photodegradation, mineralization was analyzed as chemical oxygen demand. A computational analysis of the structures of MB and RB was performed to gain a deeper understanding of the obtained results. The computational analysis encompassed density functional theory (DFT) calculations and analysis of two quantum-molecular descriptors addressing the local reactivity of molecules. Experimental results have indicated that the considered zeolites effectively remove both dyes through both mechanisms, especially NH4BETA and NH4ZSM-5, due to the presence of active acidic centers on the outer and inner surfaces of the zeolite. The lowest efficiency of dye removal was achieved in the presence of NaY zeolite, which has a lower SiO2/Al2O3 ratio. A more efficient reduction was completed for RB dye, which agrees with the computationally obtained information about reactivity