AuS and SH bond formation/breaking during the formation of alkanethiol SAMs on Au(111): A theoretical study

The bonding of propanethiol molecules on a Au(111) surface is investigated using period DFT calculations within the framework of our model for chemical bond breaking that was recently proposed. The S-H bond breaking and the Au-S bond formation are analyzed through the evolution of the density of states. The energetics confirms the complexity of the reaction emerging from the interthiol chain interaction. The formation of a self-assembled monolayer is explained through a two-step mechanism, S-H bond breaking and Au-S bond formation. The production of H2 is found to be more favorable than the formation of Au-H species. The bonding and antibonding electronic states of the S-H bond have been identified and their evolutions during the process of bond breaking carefully analyzed. The corresponding bonding and antibonding states for the C-S bond are practically not affected during this process, indicating that the bond is preserved. The s orbital of the hydrogen atom strongly interacts with the gold surface and finally a Au-H bond is formed.Fil: Tielens, Frederik. Sorbonne University. Campus Pierre Et Marie Curie; Francia. Centre National de la Recherche Scientifique; FranciaFil: Santos, Elizabeth del Carmen. Universitat Ulm; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentin

Peculiar opportunities given by XPS spectroscopy for the clinician

X-ray Photoelectron Spectroscopy (XPS) constitutes an elegant way to describe the chemical characteristics of the surface of biological materials. It is thus a unique approach to decipher the interaction between biological materials and tissues. In the case of medical implants, it is thus possible to understand its biocompatibility as well as its integration in the body which can be wanted in the case of prothesis or avoided in the case of JJ-stents. More precisely, XPS can bring valuable information of the interaction between physiological calcification (here bone) and the prosthesis as well as the interaction between pathological calcifications (lithiasis) and the JJ-stent. This mini overview is dedicated to two communities, the physical chemists and the clinicians. In the first part of this overview, after an introduction on the basic principles of XPS, we focus on the theoretical techniques adopted for the computation of XPS spectra of materials.The second part, dedicated to clinicians, describes the use of XPS for the characterization of biological materials. We report which kind of chemical information can be gained by this surface-sensitive technique and how this information has a relevant impact on medical applications.Through different examples, we show that XPS is a strong and very useful tool, and thus receiving a crucial place in medical research

Peculiar opportunities given by XPS spectroscopy for the clinician

X-ray Photoelectron Spectroscopy (XPS) constitutes an elegant way to describe the chemical characteristics of the surface of biological materials. It is thus a unique approach to decipher the interaction between biological materials and tissues. In the case of medical implants, it is thus possible to understand its biocompatibility as well as its integration in the body which can be wanted in the case of prothesis or avoided in the case of JJ-stents. More precisely, XPS can bring valuable information of the interaction between physiological calcification (here bone) and the prosthesis as well as the interaction between pathological calcifications (lithiasis) and the JJ-stent. This mini overview is dedicated to two communities, the physical chemists and the clinicians. In the first part of this overview, after an introduction on the basic principles of XPS, we focus on the theoretical techniques adopted for the computation of XPS spectra of materials.The second part, dedicated to clinicians, describes the use of XPS for the characterization of biological materials. We report which kind of chemical information can be gained by this surface-sensitive technique and how this information has a relevant impact on medical applications.Through different examples, we show that XPS is a strong and very useful tool, and thus receiving a crucial place in medical research

Unravelling the enhanced reactivity of bulk CeO 2 doped with gallium: A periodic DFT study

Doping CeO2 with gallium leads to promising materials with application in hydrogen purification processes for fuel cells. The bulk ceria?gallia is investigated by ab initio calculations. The outstanding reactivity is explained by important relaxations induced by gallium in the ceria host, having a strong impact in the electronic structure. As a result, the mixed oxide is found to be more reducible than the pure oxides in agreement with experimental data. It is thus possible to correlate structure and reactivity of the doped system on the molecular level, representing a step forward to the rational design of materials with selected properties.Fil: Quaino, Paola Monica. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada e Ingeniería Electroquímica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe; ArgentinaFil: Syzgantseva, Olga. Université Pierre et Marie Curie; FranciaFil: Siffert, Luca. Université Pierre et Marie Curie; FranciaFil: Tielens, Frederik. Université Pierre et Marie Curie; FranciaFil: Minot, Christian. Université Pierre et Marie Curie; FranciaFil: Calatayud, Monica. Universite de Paris; Franci

Opportunities given by density functional theory in pathological calcifications

International audienc

A Molecular Picture of the Adsorption of Glycine in Mesoporous Silica through NMR Experiments Combined with DFT‑D Calculations

International audienceThe adsorption behavior of the amino acid glycine in mesoporous silica has been investigated using a combination of quantum chemical calculations and NMR spectroscopy experiments. Glycine adsorption on two representative sites of an amorphous silica surface, vicinal silanols and a silanol nest, was investigated by DFT-D. The effect of water coadsorption on the energetics of adsorption and NMR shifts was characterized. It was found that the silanol nest is a more favorable site for glycine adsorption due to a local increased H-bond density. Co-adsorption with water is also favored, especially a water molecule between a SiOH and the ammonium moiety. NMR chemical shifts computed on these models fall into the observed 13C and 15N experimental range, suggesting that the presence of different energetically comparable adsorption configurations cannot be excluded

Análisis estructural y energético de nanotubos de carbono modificados con platino

El platino es ampliamente conocido por su alta actividad catalítica en reacciones de interés tecnológico y científico como HER, OER, water splitting, water-gas shift, entre otras. Sin embargo, se trata de un material precioso y sumamente caro, por lo cual es imperante reducir su utilización. Una de las maneras de lograrlo es mediante la síntesis de nuevos compuestos con bajas proporciones de Pt que mantengan lascaracterísticas deseables del mismo. En este sentido, los nanotubos de carbono (CNT) han mostrado interesantes y únicas propiedades físicas y químicas (estructura tubular, alta estabilidad química, baja resistividad, alta conductividad térmica y eléctrica, y una enorme área superficial) que les permiten ser considerados excelentes materiales de electrodo, tanto individualmente como modificados con otro tipo de átomos, moléculas o iones conformando nuevos compuestos híbridos. Aunque la modificación de CNTs con Pt ha sido estudiada en diversos trabajos teóricos, ninguno presenta un análisis de la inserción gradual y sistemática de pocos átomos de platino sobre el nanotubo. En elpresente trabajo fueron utilizados métodos computacionales ab-initio para modelar la adsorción de átomos, dímeros y trímeros de Pt sobre la superficie externa de nanotubos de carbono de quiralidad (5,5), con el objeto de estudiar la estabilidad energética, geometría y magnetización total de estos sistemas híbridos.Nuestros resultados indican que la adsorción de átomos, dímeros y trímeros de Pt sobre la superficie del CNT (5,5) es energéticamente favorable en todos los casos analizados, produciéndose una respuesta magnética considerable en algunos de estos sistemas. Adicionalmente, la aglomeración de átomos de Pt se ve favorecida frente a su dispersión sobre la superficie carbonosa.De acuerdo con los resultados obtenidos, la adsorción de Pt sobre CNT es factible y genera estructuras interesantes para un posterior análisis riguroso de los centros o zonas reactivas, y posteriormente de la reactividad química de estos sistemas híbridos en reacciones de interés tanto académico como tecnológico.Fil: Nuñez, José. Universidad Nacional del Litoral. Instituto de Química Aplicada del Litoral. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Química Aplicada del Litoral.; ArgentinaFil: Belletti, Gustavo Daniel. Universidad Nacional del Litoral. Instituto de Química Aplicada del Litoral. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Química Aplicada del Litoral.; ArgentinaFil: Tielens, Frederik. No especifíca;Fil: Quaino, Paola Monica. Universidad Nacional del Litoral. Instituto de Química Aplicada del Litoral. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Química Aplicada del Litoral.; ArgentinaXXII Congreso Argentino de Fisicoquímica y Química InorgánicaArgentinaAsociación Argentina de Investigación FisicoquímicaUniversidad Nacional de la Plata. Facultad de Ingenierí

Trapping of Ag+, Cu2+, and Co2+ by faujasite zeolite Y: new interpretations of the adsorption mechanism via DFT and statistical modeling investigation

This work evaluated the potential of a synthesized faujasite-type zeolite Y as an adsorbent for the removal of relevant heavy metals such as silver (Ag+), copper (Cu2+), and cobalt (Co2+). The adsorption data of Ag+, Cu2+, and Co2+ ions were determined experimentally at pH 6 and temperatures of 298, 308, and 318 K. Two theoretical approaches have been applied based on statistical physics modeling and density functional theory (DFT) to understand and characterize the ion exchanges involved in the removal of all metals. Results showed that this zeolite was more efficient for the adsorption of Ag+ via cation-exchange. Based on the physical modelling, the removal of heavy metals on this zeolite was mono and multi-ionic (simple and multi-interactions), where the ions interacted via one and two adsorption sites. It was also noted that the temperature increment generated more available functional groups of the zeolite, facilitating the access to the smaller cavities and the interactions with the adsorbent. Adsorption energies for removing these metals with tested zeolite were slightly endothermic and were consistent with the typical values reported for ion exchange systems of heavy metals + zeolites. DFT results demonstrated that these cationic exchange energies depend on the nature of precursor salt, but with the same ranking. Both statistical and DFT approaches agreed that exchange Ag+ in zeolite Y was easier than Cu2+ and Co2+. Overall, the application of both theoretical approaches provided a reliable interpretation of the adsorption mechanism

Understanding the Reactivity of Supported Late Transition Metals on a Bare Anatase (101) Surface: A Periodic Conceptual DFT Investigation

The rapidly growing interest for new heterogeneous catalytic systems providing high atomic efficiency along with high stability and reactivity triggered an impressive progress in the field of single-atom catalysis. Nevertheless, unravelling the factors governing the interaction strength between the support and the adsorbed metal atoms remains a major challenge. Based on periodic density functional theory (DFT) calculations, this paper provides insight into the adsorption of single late transition metals on a defect-free anatase surface. The obtained adsorption energies fluctuate, with the exception of Pd, between -3.11 and -3.80 eV and are indicative of a strong interaction. Depending on the considered transition metal, we could attribute the strength of this interaction with the support to i) an electron transfer towards anatase (Ru, Rh, Ni), ii) s-d orbital hybridisation effects (Pt), or iii) a synergistic effect between both factors (Fe, Co, Os, Ir). The driving forces behind the adsorption were also found to be strongly related to Klechkowsky's rule for orbital filling. In contrast, the deviating behaviour of Pd is most likely associated with the lower dissociation enthalpy of the Pd-O bond. Additionally, the reactivity of these systems was evaluated using the Fermi weighted density of states approach. The resulting softness values can be clearly related to the electron configuration of the catalytic systems as well as with the net charge on the transition metal. Finally, these indices were used to construct a model that predicts the adsorption strength of CO on these anatase-supported d-metal atoms. The values obtained from this regression model show, within a 95 % probability interval, a correlation of 84 % with the explicitly calculated CO adsorption energies