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Interakcije mikroplastike i organskih onečišćivala u vodi
No full textNowadays, microplastics (MPs), plastic particles smaller than 5 mm, are a hot topic in the field of environmental science due to their abundance and widespread in the environment and the food chain, including the human organism. The greatest concern is the potential harmful and toxic effect MPs can have on both the environment and human health. Additionally, MPs can adsorb and transport other pollutants, possibly increasing overall toxicity compared to the toxicity of isolated MPs and pollutants. Hence, it is important to understand the adsorption process to properly assess the potential risk of MPs. Experimental results show that adsorption is mainly governed by weak hydrophobic, electrostatic, van der Waals and π-π interactions, and hydrogen bonds. However, due to system complexity and many influencing factors, the results often lack consistency and reproducibility, which makes it impossible to draw clear conclusions and build a predictive model for MPs adsorption. The computational chemistry studies on the adsorption of MPs are still at the early stages, but they are believed to provide further insights into the adsorption mechanism. In this thesis, polyethylene terephthalate (PET) MPs was chosen as one of the most frequently found types of MPs in the environment. Adsorption was studied using quantum mechanical (QM) and molecular dynamics (MD) methods. QM study revealed that the interactions are weak and local, mainly dependent on the pollutants ability to form multiple contacts with MPs. Further quantitative structure activity/property relationship (QSA/PR) modelling showed that the key pollutant properties governing the adsorption can be correlated to the size of pollutants and the number of proton donor/acceptor functional groups. On the other hand, MD study showed that, when the explicit water molecules are included, the adsorption is mainly controlled by the pollutant relative affinity for water and MPs. Additionally, the affinity also depends on the structure of MPs, as the aggregated PET model, made of thirty 5-mer, showed stronger capacity compared to the PET model made of one 150- mer chain. MD results showed similar trend as the experimental results. However, the difference in calculated interaction energies could not be quantitatively correlated with the difference in adsorption capacities. Overall, computational studies showed a great potential as a tool to help to understand adsorption mechanism, although more work is needed to further develop the model’s accuracy.Mikroplastika (MP) su čestice polimera manje od 5 mm koje su danas vrlo popularna tema u istraživanju okoliša zbog velike količine i rasprostranjenosti u okolišu i hranidbenom lancu, čak i u ljudskom organizmu. MP može imati štetne i toksične učinke na okoliš i ljudsko zdravlje. Osim toga, MP može adsorbirati i prenositi druga štetna onečišćivala što može dovesti do povećanja njihove ukupne toksičnosti u odnosu na toksičnost same MP i onečišćivala. Upravo iz tog razloga, važno je detaljno proučiti proces adsorpcije kako bi se moglo preciznije procijeniti potencijalne rizike povezane s MP. Dosadašnja eksperimentalna istraživanja pokazala su da adsorpciju organskih onečišćivala na MP kontroliraju slabe interakcije poput hidrofobnih, elektrostatskih, van der Waalsovih, π-π interakcija i vodikovih veza. S obzirom na složenost sustava i veliki broj čimbenika koji utječu na adsorpciju, rezultati iz literature često su nedosljedni te nisu reproducibilni. To otežava donošenje zaključaka i izradu pouzdanih predikcijskih modela za adsorpciju organskih onečišćivala na MP. Metode računalne kemije omogućuju dublje razumijevanje mehanizma adsorpcije te se sve više počinju koristiti u ovom području istraživanja. U okviru ovog rada, odabran je poli(etilen-tereftalat) (PET), kao jedan od najčešćih tipova MP u okolišu. Za istraživanje su korištene kvantno-mehaničke (QM, engl. quantum mechanics) i metode molekulske dinamike (MD, engl. molecular dynamics). QM proračuni pokazali su da su interakcije između MP i onečišćivala slabe, lokalne interakcije te da adsorpcija ovisi o broju interakcija koje onečišćivalo može uspostaviti s MP. Modeliranjem odnosa strukture i aktivnosti/svojstva (QSA/PR, engl. quantitative structure activity/property relationship) utvrđeno je da su ključna svojstva onečišćivala koja kontroliraju adsorpciju povezana s veličinom molekule i brojem proton donora/akceptora. MD simulacije koje uključuju eksplicitne molekule vode pokazale su da adsorpcija značajno ovisi o razlici između afiniteta onečišćivala za molekule vode i za MP. Također, pokazale su da struktura MP ima značajnu ulogu s obzirom na to da je model PET-a sačinjen od 30 lanaca koji sadržavaju 5 monomera pokazao veću sposobnost adsorpcije od modela jednog lanca koji sadržava 150 monomera. Rezultati MD simulacija u skladu su s eksperimentalnim opažanjima, iako razlike u izračunatim energijama interakcije nisu bile u izravnoj kvantitativnoj korelaciji s razlikama u adsorpcijskom kapacitetu. Zaključno, računalne metode pokazuju velik potencijal u istraživanju adsorpcijskih mehanizama MP, no potrebna su dodatna istraživanja i razvoj modela kako bi se povećala njihova točnost i primjenjivost
Interakcije mikroplastike i organskih onečišćivala u vodi
No full textNowadays, microplastics (MPs), plastic particles smaller than 5 mm, are a hot topic in the field of environmental science due to their abundance and widespread in the environment and the food chain, including the human organism. The greatest concern is the potential harmful and toxic effect MPs can have on both the environment and human health. Additionally, MPs can adsorb and transport other pollutants, possibly increasing overall toxicity compared to the toxicity of isolated MPs and pollutants. Hence, it is important to understand the adsorption process to properly assess the potential risk of MPs. Experimental results show that adsorption is mainly governed by weak hydrophobic, electrostatic, van der Waals and π-π interactions, and hydrogen bonds. However, due to system complexity and many influencing factors, the results often lack consistency and reproducibility, which makes it impossible to draw clear conclusions and build a predictive model for MPs adsorption. The computational chemistry studies on the adsorption of MPs are still at the early stages, but they are believed to provide further insights into the adsorption mechanism. In this thesis, polyethylene terephthalate (PET) MPs was chosen as one of the most frequently found types of MPs in the environment. Adsorption was studied using quantum mechanical (QM) and molecular dynamics (MD) methods. QM study revealed that the interactions are weak and local, mainly dependent on the pollutants ability to form multiple contacts with MPs. Further quantitative structure activity/property relationship (QSA/PR) modelling showed that the key pollutant properties governing the adsorption can be correlated to the size of pollutants and the number of proton donor/acceptor functional groups. On the other hand, MD study showed that, when the explicit water molecules are included, the adsorption is mainly controlled by the pollutant relative affinity for water and MPs. Additionally, the affinity also depends on the structure of MPs, as the aggregated PET model, made of thirty 5-mer, showed stronger capacity compared to the PET model made of one 150- mer chain. MD results showed similar trend as the experimental results. However, the difference in calculated interaction energies could not be quantitatively correlated with the difference in adsorption capacities. Overall, computational studies showed a great potential as a tool to help to understand adsorption mechanism, although more work is needed to further develop the model’s accuracy.Mikroplastika (MP) su čestice polimera manje od 5 mm koje su danas vrlo popularna tema u istraživanju okoliša zbog velike količine i rasprostranjenosti u okolišu i hranidbenom lancu, čak i u ljudskom organizmu. MP može imati štetne i toksične učinke na okoliš i ljudsko zdravlje. Osim toga, MP može adsorbirati i prenositi druga štetna onečišćivala što može dovesti do povećanja njihove ukupne toksičnosti u odnosu na toksičnost same MP i onečišćivala. Upravo iz tog razloga, važno je detaljno proučiti proces adsorpcije kako bi se moglo preciznije procijeniti potencijalne rizike povezane s MP. Dosadašnja eksperimentalna istraživanja pokazala su da adsorpciju organskih onečišćivala na MP kontroliraju slabe interakcije poput hidrofobnih, elektrostatskih, van der Waalsovih, π-π interakcija i vodikovih veza. S obzirom na složenost sustava i veliki broj čimbenika koji utječu na adsorpciju, rezultati iz literature često su nedosljedni te nisu reproducibilni. To otežava donošenje zaključaka i izradu pouzdanih predikcijskih modela za adsorpciju organskih onečišćivala na MP. Metode računalne kemije omogućuju dublje razumijevanje mehanizma adsorpcije te se sve više počinju koristiti u ovom području istraživanja. U okviru ovog rada, odabran je poli(etilen-tereftalat) (PET), kao jedan od najčešćih tipova MP u okolišu. Za istraživanje su korištene kvantno-mehaničke (QM, engl. quantum mechanics) i metode molekulske dinamike (MD, engl. molecular dynamics). QM proračuni pokazali su da su interakcije između MP i onečišćivala slabe, lokalne interakcije te da adsorpcija ovisi o broju interakcija koje onečišćivalo može uspostaviti s MP. Modeliranjem odnosa strukture i aktivnosti/svojstva (QSA/PR, engl. quantitative structure activity/property relationship) utvrđeno je da su ključna svojstva onečišćivala koja kontroliraju adsorpciju povezana s veličinom molekule i brojem proton donora/akceptora. MD simulacije koje uključuju eksplicitne molekule vode pokazale su da adsorpcija značajno ovisi o razlici između afiniteta onečišćivala za molekule vode i za MP. Također, pokazale su da struktura MP ima značajnu ulogu s obzirom na to da je model PET-a sačinjen od 30 lanaca koji sadržavaju 5 monomera pokazao veću sposobnost adsorpcije od modela jednog lanca koji sadržava 150 monomera. Rezultati MD simulacija u skladu su s eksperimentalnim opažanjima, iako razlike u izračunatim energijama interakcije nisu bile u izravnoj kvantitativnoj korelaciji s razlikama u adsorpcijskom kapacitetu. Zaključno, računalne metode pokazuju velik potencijal u istraživanju adsorpcijskih mehanizama MP, no potrebna su dodatna istraživanja i razvoj modela kako bi se povećala njihova točnost i primjenjivost
Synthesis, characterization, and electronic structure calculations of select families of BN doped polycyclic aromatic hydrocarbons
No full textDans mon projet de thèse, je me concentre principalement sur les hydrocarbures aromatiques polycycliques dopés BN. Au cours des trois dernières années, j'ai terminé trois œuvres. Tout d'abord, j'ai fait le calcul théorique de l'isostérime BN/CC sur les propriétés photophysiques, et j'ai obtenu une tendance générale pour décrire comment la position de l'unité BN sur les HAP affecte les propriétés photophysiques. Deuxièmement, j'ai développé la stratégie D-BN-A pour la conception de molécules fonctionnelles qui pourraient être potentielles dans les matériaux avancés. Troisièmement, j'ai synthétisé le BN--2,1-Naphtalène et ses dérivés. Cette méthode de synthèse de base peut être appliquée à la synthèse de grands HAP contenant du BN.In my thesis project, I mainly focus on the BN doped polycyclic aromatic hydrocarbons. In the past of three years, I have finished three works. Firstly, I did the theoretical calculation of the BN/CC isosterim on the photophysical properties, and obtained a general trend to describe how the position of BN unit on PAHs affects the photophysical properties. Secondly, I developed D-BN-A strategy to the design of functional molecules which could be potential in advanced materials. Thirdly, I synthesized the BN--2,1-Naphthalene and its derivatives. This basic synthetic method can be appiled in the synthesis of large BN-containing PAHs
Vers la synthèse et la caractérisation des dérivés d'azulène dopés au bore et à l'azote en tant que matériaux potentiels de fission singulet.
No full textL'énergie solaire a le potentiel de répondre à la demande croissante d'un système énergétique mondial, neutre en carbone. Les cellules solaires à jonction unique approchent de la limite d'efficacité dans la conversion de l'énergie solaire. En conséquence, la conception et le développement de matériaux capables de contourner la limite de conversion photoélectrique, dite de Shockley-Queisser, ont reçu une attention particulière. Les matériaux de fission singulet (SF) ont la capacité potentielle de générer deux excitons triplets à partir d'un exciton singulet, doublant ainsi le nombre de porteurs de charge et augmentant l'efficacité d'un dispositif photovoltaïque. Selon les études théoriques préliminaires les composés organiques conjugués dopés au bore-azote (BN) présentent les propriétés favorables requises pour la fission singulet. Dans cette thèse, nous avons d'abord exploré de manière systématique à l'aide de la chimie computationnelle l'effet du dopage BN sur les paramètres clés critiques pour le comportement de fission singulet dans le cas de l'azulène. Nos résultats de calcul ont permis d'identifier une cible appropriée pour l'exploration synthétique. Dans la deuxième partie de la thèse, la conception synthétique et les progrès réalisés en vue d'obtenir un BN-azulène et ses dérivés sont décrits. L'approche synthétique proposée s'appuie sur la richesse des connaissances existantes sur les dérivés de 1,2-azaborine (isostères BN du benzène), développées par le groupe du Pr Liu. Les connaissances fondamentales acquises grâce aux études computationnelles et synthétiques des BN-azulènes jetteront les bases du développement d'une nouvelle famille de BN-hétérocycles.Solar energy has the potential to meet the growing demand for a carbon-neutral global energy system. Single-junction solar cells are approaching the limit of efficiency in the conversion of solar energy. As a result, the design and development of materials capable of circumventing the so-called Shockley-Queisser photoelectric conversion limit has received significant attention. Singlet fission (SF) materials have the potential capability of generating two triplet excitons from a singlet exciton, and therefore doubling the number of charge carriers and increase the efficiency in a photovoltaic device. Boron-nitrogen (BN) doped conjugated organic compounds have been predicted to exhibit favourable properties required for singlet fission. In this thesis, we first computationally explored in a systematic fashion the effect of BN doping on key parameters critical for singlet fission behaviour in the context of the azulene framework. Our computational results informed about a suitable target for synthetic exploration. In the second part of the thesis the synthetic design and progress toward a BN azulene and its derivatives are described. The proposed synthetic approach builds on the wealth of existing knowledge of 1,2-azaborine derivatives (BN isosteres of benzene) developed by the Liu group. The fundamental insight gained from the computational and synthetic studies of BN azulenes will lay the foundation for the development of a new family of BN-heterocycles
How many shades of grey? On the proximity of density functional approximation to ab initio method via calculations of electric multipole moments
No full textInternational audienceThe wide spreading of the application of Density Functional Approximation via its represtnatives, i.e. the Density Functionals (DFs), in almost all the fields of computational chemistry is globally witnessed. Therefore, it is believed that an evaluation of their performance in tedious calculations will offer useful insights to both users and developers. As such calculations we chose the prediction of electric multipole moments of first to fourth order, namely dipole (µα/ea0), quadrupole (Θαβ/ea0^2), octupole (Ωαβγ/ea0^3) and hexadecapole (Φαβγδ/ea0^4). Values at both ab initio up to the highly accurate couple cluster with singles and doubles (reference values) as well as different flavors of DFs: hybrid, GGA, double hybrid , long range corrected, including dispersion correction, both hybrid and long range corrected and some from the Minessota family. The target set is a group of 10 molecules of C2v symmetry. The results were further analyzed with the root mean square deviation (RMSD) method as to find the method that is the most proximal to reference CCSD. The functionals PBE1PBE, CAM-B3LYP and B2PLYP seem to survive the proximity test, whereas B97D, M05, M06 and M08 provide results that are the least proximal to CCSD ones
How large are the microscopic electronic dipole (hyper)polarizabilities of CdnTen bare clusters compared to those of CdnSn and CdnSen? A systematic ab initio study
No full textcited By 15International audienceThe static mean dipole polarizabilities, the polarizability anisotropies and the second hyperpolarizabilities of the ground state structures of stoichiometric CdnTen (n = 2, 3, 4, 5, 9) clusters are presented for the first time and they are compared with those of selected CdnSn and CdnSen clusters. Our ab initio results suggest that the CdTe clusters are significantly more hyperpolarizable than clusters constituted by CdS, and CdSe, in accordance to earlier experimental measurements. Also, it is demonstrated that the second hyperpolarizability magnitudes computed at different theoretical equilibrium geometries of the same cluster, determined by geometry optimization at different levels of theory, are significantly sensitive to the obtained equilibrium inter-atomic distances among the electropositive Cd atoms. © 2009 Elsevier B.V. All rights reserved
Structures and Electric Properties of Semiconductor clusters
No full textInternational audienceMaterials that exhibit an electrical resistivity between that of conductor and insulator are called semiconductors. Devices based on semiconductor materials, such as transistors, solar cells, light-emitting diodes, digital integrated circuits, solar photovoltaics, and much more, are the base of modern electronics. Silicon is used in most of the semiconductor devices while other materials such as germanium, gallium arsenide, and silicon carbide are used for specialized applications. The obvious theoretical and technological importance of semiconductor materials has led to phenomenal success in making semiconductors with near-atomic precision such as quantum wells, wires, and dots. As a result, there is a lot of undergoing research in semiconductor clusters of small and medium sizes both experimentally and by means of computational chemistry since the miniaturization of devices still continues. In the next pages, we are going to learn which the most studied semiconductor clusters are, we will explore their basic structural features and visit some of the most representative ab initio studies that are considered as works of reference in this research realm. Also, we are going to be introduced to the theory of the electric properties applied in the case of clusters by visiting some of the most illustrative studies into this research area. It is one of the purposes of this presentation to underscore the strong connection between the electric properties of clusters and their structure
Dipole Polarizability of C28 and its Counterparts Nb4B18 and Ta4B18. Insights from a Density Functional Theory (DFT) Endeavour
No full textInternational audienceWe report on a preliminary investigation of the non linear optical (NLO) properties and in particular dipole polarizability. The target species are two perfect tetrahedral nanoclusters NbB and TaB, along with their nanofullerene counterpart that is C. Our study based on density functionals (DFs) that have gained popularity among the scientific community. In addition we performed Hartree-Fock calculations known for not including dynamic electron correlation. The DF obtained values are characterized by some dispersion, with maximal differences to be around 5 \%, in all three cases. Given that the DFT introduces a fuzzy percentage of electron correlation sets the observed convergence of HF values to DFT ones is at least surprising. Furthermore, it should be said that though the values can be characterized as accurate their reliability should not be taken for granted. Last, we note the smooth convergence of LC-BLYP, LC-BP86, LC-BPW91 to LC-hPBE
Fullerene-C 60 in contact with alkali metal clusters: Prototype nano-objects of enhanced first hyperpolarizabilities
No full textcited By 43International audienceThe electric first hyperpolarizabilities (β) of a representative set of alkali metal droplets in contact with fullerene (C 60) have been explored at the static limit via ab initio and density functional theory methods for the first time. We find that, when alkali metal droplets are adsorbed on the surface of C 60, systems of enhanced static dipolar and/or octupolar hyperpolarizabilities are delivered. Both the type and the magnitudes of the first hyperpolarizabilities in such systems are dictated by the way the sodium atoms adsorb on the surface of fullerenes. One large metallic droplet of sodium atoms results to species with large hyperpolarizabilities of dipolar character. Smaller droplets adsorbed on the surface of C 60 deliver systems of large octupolar contributions. In both cases two synergic polarization mechanisms have been detected by means of the classical version of configuration interaction singles (CIS) sum-over-states approach and a natural transition orbital analysis. The first comprises charge transport from the fullerene to the adsorbed droplets and resembles the polarization process met in simple diatomic molecules. In this case, C 60 unconventionally functions as an electron donor at the excited states. The second, local in character, is related to the easily polarizable excess electrons maintained in the framework of the adsorbed clusters. From a certain point of view, such systems can be considered as hybrids that combine the basic characteristics of a classical donor/acceptor superstructure and systems with easily polarizable excess electrons. © 2012 American Chemical Society
Comment on "How the number and location of lithium atoms affect the first hyperpolarizability of graphene"
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