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Calcium oxalate precipitation is a common pathological calcification in the human body, whereby crystallite morphology is influenced by the chelating properties of biological ions such as citrate.

Since its first use several decades ago, scanning electron microscopy has been used in numerous investigations dedicated to biological systems. This contribution focuses on observations on pathological calcifications in order to review several major applications of primary importance to the clinician. Among these, we highlight such observations as medical diagnostic tools in pathologies arising from primary hyperoxaluria and urinary infections.

Titania-based materials are abundant in technological applications, as well as everyday products; however, many of its structure–property relationships are still unclear. In particular, its surface reactivity on the nanoscale has important consequences for fields such as nanotoxicity or (photo)catalysis. Raman spectroscopy has been used to characterize titania-based (nano)material surfaces, mainly based on empirical peak assignments. In the present work, we address the structural features responsible for the Raman spectra of pure, stoichiometric TiO2 materials from a theoretical characterization. We determine a computational protocol to obtain accurate Raman response in a series of anatase TiO2 models, namely, the bulk and three low-index terminations by periodic ab initio approaches. The origin of the Raman peaks is thoroughly analyzed and the structure–Raman mapping is performed to account for structural distortions, laser and temperature effects, surface orientation, and size. We address the appropriateness of previous experimental use of Raman to quantify the presence of distinct TiO2 terminations, and provide guidelines to exploit the Raman spectrum based on accurate rooted calculations that could be used to characterize a variety of titania systems (e.g., single crystals, commercial catalysts, thin layered materials, facetted nanoparticles, etc.).

Efficient energy storage devices, such as batteries and capacitors play an important role in the development of renewable energy sources. C2/m space group Li2B6O13 (B = Ti4+, Sn4+, or Zr4+) compounds are expected to be materials with high potential for use as negative electrodes in high-performance batteries. The structural and electronic properties of these materials were studied in this article using density functional theory. The increase of the ionic radius of the B ions in the studied materials expands the unit cell parameters and the Li–Li distance in the channel of the Li2B6O13 (B = Ti4+, Sn4+, or Zr4+) compounds. Electronic structure calculations confirm that all structures present semiconductor characteristics. Li2Sn6O13 presents the best semiconductor properties with a band gap of 1.24 eV. The open cell voltages are found to be 2.20, 2.70 and 1.95 V per Li+/Li intercalation in Li2B6O13 structures, respectively. These predicted properties bring in new evidence to consider of these Li2B6O13 for use asan alternative battery materials.

International audience; It is assumed that genetic diseases affecting the metabolism of cysteine and the kidney function lead to two different kinds of pathologies, namely cystinuria and cystinosis whereby generate L-cystine crystals. Recently, the presence of L-cysteine crystal has been underlined in the case of cystinosis. Interestingly, it can be strikingly seen that cystine ([-S-CH2-CH-(NH2)-COOH]2) consists of two cysteine (C3H7NO2S) molecules connected by a disulfide (S-S) bond. Therefore, the study of cystine and cysteine is important for providing a better understanding of cystinuria and cystinosis. In this paper, we elucidate the discrepancy between L-cystine and L-cysteine by investigating the theoretical and experimental infrared spectra (IR), X-ray diffraction (XRD) as well as Raman spectra aiming to obtain a better characterization of abnormal deposits related to these two genetic pathologies.

The drive to develop maximal atom-efficient catalysts coupled to the continuous striving for more sustainable reactions has led to an ever-increasing interest in single-atom catalysis. Based on a periodic conceptual density functional theory (cDFT) approach, fundamental insights into the reactivity and adsorption of single late transition metal atoms supported on a fully hydroxylated amorphous silica surface have been acquired. In particular, this investigation revealed that the influence of van der Waals dispersion forces is especially significant for a silver (98 %) or gold (78 %) atom, whereas the oxophilicity of the Group 8–10 transition metals plays a major role in the interaction strength of these atoms on the irreducible SiO2 support. The adsorption energies for the less-electronegative row 4 elements (Fe, Co, Ni) ranged from −1.40 to −1.92 eV, whereas for the heavier row 5 and 6 metals, with the exception of Pd, these values are between −2.20 and −2.92 eV. The deviating behavior of Pd can be attributed to a fully filled d-shell and, hence, the absence of the hybridization effects. Through a systematic analysis of cDFT descriptors determined by using three different theoretical schemes, the Fermi weighted density of states approach was identified as the most suitable for describing the reactivity of the studied systems. The main advantage of this scheme is the fact that it is not influenced by fictitious Coulomb interactions between successive, charged reciprocal cells. Moreover, the contribution of the energy levels to the reactivity is simultaneously scaled based on their position relative to the Fermi level. Finally, the obtained Fermi weighted density of states reactivity trends show a good agreement with the chemical characteristics of the investigated metal atoms as well as the experimental data.

Copper and manganese modified zeolites play key roles in selective oxidation catalytic reactions. Combining Density Functional Perturbation Theory (DFPT) implemented in VASP, and infrared spectroscopy experiments, we have studied and elucidated the incorporation of Cu2+ and Mn2+ in the framework of SiBEA zeolite. Six isomers are investigated for both models CuSiBEA and MnSiBEA. The energy stability study identified the most stable isomer in each case, which correspond to M-O2 bent moieties in the vicinity of hydroxyl groups. The isomers are then characterized by experimental and theoretical IR spectra. Both experimental and calculated IR spectra are in good agreement highlighting the presence of active sites (Cu-OH and Mn-OH) in the obtained models. The accurate molecular description of the nature of the active sites presented in this work will be important for understanding the catalysis going on and for developing novel catalytic processes.

Much of our current understanding of catalytic activity is derived from materials with well-defined structures, either molecular (i.e., homogeneous catalysts) or extended, ordered solids (i.e., heterogenous catalysts and surface science), and active sites in real catalysts are often assumed to closely resemble structures found in such ordered materials, at least locally. Yet many real catalysts involve amorphous materials and are much more active than their well-ordered counterparts would suggest. This implies that at least some active sites in amorphous materials are intrinsically different. One of these important and versatile amorphous materials is silica. The materials properties are based in many cases on the way molecules interact with the silica surface. Since several years we investigate silica and its role as support of transition metal oxide catalysts, but also the interaction with bio-organic systems, and this at different levels: from the phenomenological description of the interaction at the interface substrate-adsorbate (adsorption and self-assembling of biomolecules) to technologic applications (catalysis, ionic liquids), pharmaceutical (controlled delivery of drug molecules) and their plausible role in different scenarios in the origin of life. For this, we use the tools of quantum chemistry combined with experimental back up with the aim to improve the understanding of the complex chemical behavior of these silica based materials.

The nature of isolated tungsten oxide (WOx) sites in the dispersed phase on the surface of a β-cristobalite (β-SiO2) support in undoped and Na- or Mn-doped WOx/SiO2 model catalysts used for the oxi...

Although silica-supported molybdenum and tungsten oxide systems are widely used in catalysis, the nature of the surface metal oxide species is still not fully recognized. In this work, comprehensive periodic and cluster density functional theory (DFT) studies of the isolated Mo(VI) and W(VI) oxide species on dehydrated amorphous silica have been performed to give insight into their heterogeneity. It is shown that the relative stabilities of the metal oxide species strongly depend on their location that influences their geometry and the strain of the dehydrated silica surface. The favorable located monooxo W(VI) species are clearly more stable than the dioxo W(VI) species, whereas no strong thermodynamic preference is predicted in the case of the Mo(VI) species. The relative stability of the monoxo species increases in the order: Cr < Mo < W. However, due to geometrical constraints on the silica surface, formation of the tetragrafted monooxo species is hampered, compared to the digrafted dioxo species and the latter are expected to be in majority. The monografted hydroxy dioxo Mo(VI) species are unstable. Based on the vibrational frequency analysis, some details regarding the structure of the experimentally observed dioxo species in the MoOx/SiO2 catalyst are proposed, while the results for the WOx/SiO2 system are somewhat ambiguous.

In this contribution, we would like to underline the peculiar chemical properties of nanome-ter scale metallic particles. To attain this goal, we select the case of DeNox catalysis (NOx reduction to nitrogen molecule) for which such nanomaterials play a crucial role. Experimental data as well as re-cent theoretical calculation through density functional theory are used to assess the relationship be-tween the adsorption mode of NO and the behaviour of nanometre scale metallic particles. Resume. Les oxydes d'azote NOx issus des gaz d'echappement des moteurs Diesel participent a la de-terioration de l'environnement, la moitie des emissions de NO leur etant imputable. Le monoxyde d'azote provient essentiellement des reactions chimiques entre l'azote de l'air et l'oxygene qui s'eta-blissent a tres haute temperature. Le defi consiste a reduire cette emission qui doit etre selective en azote (eviter la formation de N2O ou de NO2). En ce qui concerne les catalyseurs mis en & OELIG;uvre, on en distingue trois groupes : les oxydes de metaux, les metaux nobles et les zeolites. A partir de donnees ex-perimentales obtenues sur l'adsorption du NO sur des agregats monometalliques, une relation entre les modes d'adsorption de cette molzcule (adsorption molzculaire/chimisorption) et la rzponse de l'agrzgat mztallique face a cette adsorption (croissance/dissociation) a ztz proposze. Les ztudes thzo-riques baszes sur la thzorie de la fonctionnelle de la densitz confortent cette relation. Cette contri-bution przsente l'ensemble de ces rzsultats expzrimentaux et thzoriques et tache de montrer l'aspect przdictif d'une telle relation.

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 useof 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.

Most papers on kidney stones arising from infection concentrate on the mineral struvite. In this contribution, we would like to call attention to other mineral phases such as highly carbonated calcium phosphate apatite, ammonium urate, and whitlockite, by presenting clinical and chemical data. We start with epidemiological data which emphasize the increase in the prevalence of kidney stones related to infection. Then we present a statistical analysis of more than 85,000 stones which have been analysed at the Laboratoire des Lithiases of Assistance Publique-Hôpitaux de Paris which gives insights regarding the link between urinary tract infection and struvite, carbonated calcium phosphate apatite (carbapatite), and also surprisingly whitlockite. Some information regarding the pathogenesis of kidney stones linked to infection, the nature of the bacteria which have been identified, and the approach to precisely analyse infrared spectra to identify struvite, carbapatite, and whitlockite, conclude this first part. To complete this clinical description, we describe the crystallographic structure and the chemistry of three relevant compounds namely carbonated calcium phosphate, struvite, and whitlockite. To conclude this second part, the dependence of crystallite morphology of struvite on pH and on the presence, or absence, of bacteria, is described. Based on clinical and chemical data, it is becoming clear that struvite is not the only mineral intimately related to renal infectious processes, but that whitlockite and carbapatite with a high carbonation rate are strongly associated with urinary tract infection as well.

Ag-based semiconductors have attracted significant attention as promising visible-light photocatalysts for environmental purification. In this study, electronic and photocatalytic properties of AgTi2(PO4)3 NASICON-type phosphate, have been addressed in detail, combining experimental results and theoretical calculations. The as-prepared sample was characterized for its morphological, structural and optical properties by various techniques. The generalized gradient approximation by Perdew-Burke-Ernzerhof (GGA-PPE) within density functional theory (DFT) was used to investigate the electronic structure. We have applied corrective Hubbard U terms to Ti 3d orbitals in order to better reproduce the experimental band gap of 2.6 eV. The photocatalytic activity has then been performed for rhodamine B dye degradation under visible light illumination. Efficient dye degradation up to 97.2% was achieved in 120 min. In addition, the catalyst exhibited good stability over four consecutive cycles. Finally, combining experimental and theoretical findings, the origin of the photocatalytic activity was identified and a photodegradation mechanism was proposed.

Aouidat F, Boumati S, Khan M, Tielens F, Doan BT, Spadavecchia J. Int J Nanomedicine. 2019;14:9309–9324. The Editor and Publisher of International Journal of Nanomedicine wish to retract the published article. The authors raised concerns regarding errors that had been made during the calculation of the size of the nanostructures shown in Figure 2. The sizes reported in the histograms of Figure 2; a1, a2 and a3 were incorrect due to miscalculations that occurred during analysis of the gold core and polymer shells of the spherical nanostructures represented in TEM images of Figure 2A. The authors provided the editor with data from the original study and requested to remove the incorrect histograms and replace them. However, the Editor determined that this part of the article was integral to the study and the admission of these errors, because of the miscalculation, meant the data was unreliable and would not accept the correction proposed by the authors. The Editor requested for the article to be retracted and the authors were notified but do not agree with this decision. Our decision-making was informed by our policy on publishing ethics and integrity and the COPE guidelines on retraction. The retracted article will remain online to maintain the scholarly record, but it will be digitally watermarked on each page as “Retracted”.

In this work we present the development of a novel, quantitative solubility descriptor based on the non-covalent interaction index. It is presented as a more insightful alternative to Hansen's solubility parameters and the COSMO model to assess and predict polymer solubility in different solvents. To this end, we studied the solvation behaviour as a function of the chain length of a single chain of arguably the most simple polymer, polyethylene, in anisole (solvent) and methanol (poor solvent) via molecular dynamics simulations. It was found that in anisole the solute maximized its interface with the solvent, whereas in methanol the macromolecule formed rod-like structures by folding on itself once the chain length surpassed a certain barrier. We assessed this behaviour – which can be related to solubility – quantitatively and qualitatively via well-known descriptors, namely the solvation free energy, and the solvent accessible surface area. In addition, we propose the non-covalent interaction (NCI) index as a versatile descriptor, providing information on the strength, as well as the nature, of the solute–solvent interactions, the solute's intramolecular interactions and on the solute's conformation, both qualitatively and quantitatively. Finally, as a quantitative measure for solubility, defined in this context as the solute's tendency to maximize its interactions with the solvent, we propose two new NCI-based descriptors: the relative integrated NCI density and the integrated NCI difference. The former represents the quantitative difference in solute–solvent interactions between a fully extended coil and the actual conformation during simulation and the latter the quantitative difference between the intermolecular (solute–solvent) and the intramolecular (in the solute) non-covalent interactions. The easy interpretation and calculation of these novel quantities open up the possibility of fast, reliable and insightful high-throughput screening of different (anti)solvent and solute combinations.

Embedding energetically stable single metal atoms in the surface of Pt nanocatalysts exposed to varied temperature (T) and hydrogen pressure (P) could open up new possibilities in selective and dynamical engineering of alloyed Pt catalysts, particularly interesting for hydrogenation reactions. In this work, an environmental segregation energy model is developed to predict the stability and the surface composition evolution of 24 Metal M-promoted Pt surfaces (with M: Cu, Ag, Au, Ni, Pd, Co, Rh and Ir) under varied T and P. Counterintuitive to expectations, the results show that the more reactive alloy component (i.e., the one forming the strongest chemical bond with the hydrogen) is not the one that segregates to the surface. Moreover, using DFT-based Multi-Scaled Reconstruction (MSR) method and by extrapolation of M-promoted Pt nanoparticles (NPs), the shape dynamics of M-Pt are investigated under the same ranges of T and P. The results show that under low hydrogen pressure and high temperature ranges, Ag and Au—single atoms (and Cu to a less extent) are energetically stable on the surface of truncated octahedral and/or cuboctahedral shaped NPs. This indicated that coinage single-atoms might be used to tune the catalytic properties of Pt surface under hydrogen media. In contrast, bulk stability within wide range of temperature and pressure is predicted for all other M-single atoms, which might act as bulk promoters. This work provides insightful guides and understandings of M-promoted Pt NPs by predicting both the evolution of the shape and the surface compositions under reaction gas condition.

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.

The spectroscopic study of pathological calcifications (including kidney stones) is extremely rich and helps to improve the understanding of the physical and chemical processes associated with their formation. While FTIR imaging and optical/electron microscopies are routine techniques in hospitals, there has been a dearth of solid state NMR studies introduced into this area of medical research, probably due to the scarcity of this analytical technique in hospital facilities. This work introduces effective multinuclear and multi-dimensional solid state NMR methodologies to study the complex chemical and structural properties characterising kidney stone composition. As a basis for comparison three hydrates (n = 1, 2 and 3) of calcium oxalate are examined along with nine representative kidney stones. The multinuclear MAS NMR approach adopted investigates the 1H, 13C, 31P and 43Ca nuclei, with the 1H and 13C MAS NMR data able to be readily deconvoluted into the constituent elements associated with the different oxalates and organics present. For the first time, the full interpretation of highly resolved 1H NMR spectra is presented for the three hydrates, based on structure and local dynamics. The corresponding 31P MAS NMR data indicates the presence of low-level inorganic phosphate species, however the complexity of these data make the precise identification of the phases difficult to assign. This work provides physicians, urologists and nephrologists with additional avenues of spectroscopic investigation to interrogate this complex medical dilemma that requires real multi technique approaches to generate effective outcomes.

International audience; Introduction: The therapy to reduce urinary oxalate excretion in primary hyperoxaluria type 1 is still required. Case presentation: A 37-year-old hemodialyzed man suffered from systemic oxalosis secondary to primary hyperoxaluria type 1 exhibited a drastic plasma oxalate decrease from 110 to 22 µmol/L two months after adjunction of lanthanum carbonate to classical treatment (intensive hemodialysis with pyridoxine). A 34-year-old woman with normal kidney function presented 10 years of bilateral kidney stones due to primary hyperoxaluria type 1 [hyperoxaluria (109.2 mg/24 h), plasma oxalate (56.0 µmol/L)]. The oxalate level remained uncontrolled despite of low oxalate-normal calcium diet, pyridoxine and increased water intake though the lanthanum carbonate adjunction resulted in significant decrease in plasma oxalate and oxaluria. Conclusion: We report the lanthanum efficacy in reducing circulating and urinary oxalate levels in type 1 primary hyperoxaluria. Possible mechanism of observed falls in oxalate concentration would be a decrease in the intestinal absorption of oxalate.

Limiting gastrointestinal oxalate absorption is a promising approach to reduce urinary oxalate excretion in patients with idiopathic and enteric hyperoxaluria. Phosphate binders, that inhibit gastrointestinal absorption of dietary phosphate by the formation of easily excretable insoluble complexes, are commonly used as a treatment for hyperphosphatemia in patients with end-stage renal disease. Several of these commercially available phosphate binders also have affinity for oxalate. In this work, a series of metallic cations (Li+, Na+, Mg2+, Ca2+, Fe2+, Cu2+, Zn2+, Al3+, Fe3+ and La3+) is investigated on their binding affinity to phosphate and oxalate on one side and anionic species that could be used to administer the cationic species to the body on the other, e.g., acetate, carbonate, chloride, citrate, formate, hydroxide and sulphate. Through quantum chemical calculations, the aim is to understand the competition between the different complexes and propose possible new and more efficient phosphate and oxalate binders.

Density Functional Theory has made the study of biomaterials feasible in the past years leading to better understanding of causes and possible treatments of related pathologies. Although it has been successfully applied in many fields, it has not yet consistently found its way into the field of pathological calcifications. An overview will be given of the studies where this technique has been applied in order to outline the important contributions that it can bring in the field of biomineralization.More specifically, studies on DFT calcifications from calciumoxalates and calcium phosphates, with relevance to bone formation and kidney stones, will be reviewed. Finally, a short outlook on silica mineralization will be presented as well.

International audience; Dans cette contribution, nous étudions les calculs rénaux contenant la whitlockite (Wk). En premier lieu, la présence du fer dans la formule stœchiométrique de la Wk est discutée grâce à la fluorescence X. Puis, nous abordons la relation à l’infection à l’aide d’observations au Microscope électronique à balayage (MEB) aptes à mettre en évidence de possibles empreintes de bactéries. Elles montrent que le processus infectieux est établi pour des teneurs supérieures à 20%, ceux-ci ne pouvant toutefois pas être écartés en dessous de cette teneur. Finalement, l’étude de relation entre la taille des cristaux de Wk et l’infection par DRX ne permet pas de l’établir. Le message pour le clinicien est le suivant : pour un patient asymptomatique, si le calcul ne contient ni struvite, ni apatite carbonatée et moins de 20% de Wk, il convient d’observer par MEB les calculs rénaux afin de pouvoir écarter ou non un processus infectieux.

International audience; Single-atom alloys (SAAs) are emerging materials containing isolated metal atoms dispersed on host metal surfaces, exhibiting unique reactivity compared with the corresponding monometallic counterparts. However, the stability of the isolated atoms in the host metal has hardly been studied, although, metal segregation has been commonly observed in bimetallic nanoparticles under reaction conditions. In this work we focus on single-atom Pt anchored on various metallic support surfaces. Density Functional Theory (DFT) calculations coupled with environmental segregation energy analysis are performed to map the segregation trends of 22 different Pt-SAA surfaces under various hydrogen conditions. The results show the high stability of single-atom Pt in Ni, Co, Rh and Ir host metallic surfaces while no stability is predicted on Au and Ag surfaces. For Pd and Cu host supports, the single-atom Pt is found to be stable on specific surface facets and within definite temperature and pressure conditions. This work brings an important understanding of SAA systems through the prediction of of surface atomic ordering changes under operating conditions which related to the reactivity will ultimately allow the design of more efficient catalysts.

Interpreting the interaction between the amorphous silica surface and water is a key step to understand its physicochemical properties. However, due to the flexibility of the structure and the distribution of types and geometries of the silanols one can obtain a broad range of interaction energies, as was already shown in former studies. This time we were able to investigate the distribution of silanols in relation with the calculated interaction energies, and thus designate those different silanols sites. Different dispersion-correction PBE-D (PBE + D2, D3, D3-BJ, TS, TS-HI, MBD, and FI-MBD) and meta-GGA SCAN methods has been used to quantify the interactions between water and defined silanols sites of the surface. All the methods give similar interaction energies, showing equivalent performances of SCAN and PBE-D methods to describe week interactions in our system. Following various routes, we identified a protocol of calculation in order to compute the interaction energies more accurately, taking into consideration the van der Waals (vdW) forces. Once different silanols are correctly described within the calculation level, it is clear that the geometry and environment determine its chemistry. Furthermore, the possible deformation of the silica surface affected by the water interaction is studied. The quantification of the interaction energies is important in order to correctly scale the results and confront with the experiments. With this information in mind, one can think about synthesis techniques that modify the silanols distribution of the silica surface in a way to tune its hydrophobicity and acidity.

International audience; Monohydrated and dihydrated calcium oxalates have been widely studied in the literature because of their role in urolithiasis, a mammal pathology responsible for the formation of stones in the kidney. It is clear that the physicochemical environment plays a crucial role in the crystal growth and the resulting morphologies of calcium oxalates. To study these processes, reliable models for the calcium oxalates’ faces, exposed to water and potential additives, are needed. Here, we have used a total surface energy minimization approach to predict the crystal morphology of the calcium oxalate monohydrate and dihydrate phases. Surface energies were calculated at density functional theory level, taking into account surface relaxation and the effect of solvation. An excellent agreement was found between theoretically predicted morphologies and their experimental counterparts obtained by SEM, clearly demonstrating the importance of the inclusion of water in the model for the prediction of morphologies.

In this paper we present a DFT investigation on the structure and energetics of (√3 × 2√3)R30° high coverage SAMs of n-alkanethiols up to twelve carbon atoms on a clean Au(111) surface. The surface was found to be more reconstructed for longer chains, although a surface reconstruction plateau was reached for decanethiol SAMs. The geometry was suggested to be dictated by steric effects and van der Waals interactions between the adsorbates resulting in a specific adsorption configuration. Furthermore, the increasing adsorption energy per thiol molecule is due to the increasing van der Waals forces between the adsorbates. In conclusion a more stable monolayer was obtained with increasing adsorbate chain length. In other words a subtle balance between interchain interactions and surface reconstruction is at the origin of the alkylthiol/Au(111) self-assembled monolayer geometry.

The thorough understanding of the adsorption mechanism of phosphate on hydrous ferric oxides is necessary to deal with the environmental issues related to high phosphate concentrations in soils and open water. In this work, we consider three different adsorption geometries (monodentate and bidentate chemisorption and physisorption) and calculate the adsorption geometries and related adsorption energies at optPBE-vdW level. Using the Maxwell-Boltzmann distribution, it is estimated that about 83% of the phosphate molecules is in a monodentate chemisorption configuration, while 17% is physisorbed. Furthermore, theoretical infra-red spectra are obtained and compared to equivalent experimental spectra, supporting the conclusion that mainly monodentate chemisorption and physisorption occur. Most interestingly, a weighed infra-red spectrum is then calculated, using the weights from the Maxwell-Boltzmann distribution, showing a very good comparison with the experimental spectra.

Whitlockite is a calcium phosphate phase of crucial interest in various pathologies. It appears in abnormal calcification such as dental calculi, kidney stones, or dystrophic calcifications of tuberculous origin. It is a complex material which involves cation substitutions, cation vacancies, and protonation of phosphate groups. In the literature, there is a lack of theoretical characterization of such materials originating from biological calcifications. By means of DFT calculations, we were able to quantify the ability of whitlockite to hold these substitutions and vacancies in preferential sites. The impact of Ca2+/Mg2+ substitutions on characterizations (IR, RAMAN, and XRD) was also investigated in the scope of DFT. Fil: Debroise, Théau. Sorbonne University; Francia. General Chemistry (algc), Vrije Universiteit Brussel; Bélgica Fil: Colombo, Estefanía. 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.; Argentina Fil: 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.; Argentina Fil: Vekeman, Jelle. General Chemistry (algc), Vrije Universiteit Brussel; Bélgica Fil: Su, Yangyang. General Chemistry (algc), Vrije Universiteit Brussel; Bélgica Fil: Papoular, Robert. Centre D'etudes de Saclay; Francia Fil: Hwang, Nathaniel S.. Seoul National University; Corea del Sur Fil: Bazin, Dominique. Universite de Paris; Francia Fil: Daudon, Michel. Hôpital Tenon; Francia. Inserm; Francia 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.; Argentina Fil: Tielens, Frederik. General Chemistry (algc), Vrije Universiteit Brussel; Bélgica

The nature of isolated tungsten oxide (WOx) sites in the dispersed phase on the surface of a β-cristobalite (β-SiO2) support in undoped and Na-or Mn-doped WOx/SiO2 model catalysts used for the oxidative coupling of methane (OCM) has not been explored previously. This work provides a computational model for isolated surface WOx sites (doped and undoped) supported on β-cristobalite (β-SiO2) and computationally explores their molecular structure, degree of hydration, and energetics over a wide range of OCM-relevant temperatures from 500 to 1300 K. Ab initio thermodynamic analysis showed that the most stable molecular configuration of the surface sites in all cases (WOx, Na-WOx, Mn-WOx) was the digrafted, dioxo pseudotetrahedral WO4. The thermal stability of the surface WO4 sites was in the order Na-WO4 ≫ WO4 > Mn-WO4 in the OCM-relevant temperature range of 850-1300 K. A spin analysis of an Mn-WO4 isolated surface site indicates a paramagnetic high-spin Mn2+-O-W6+ electronic state, in line with literature reports. The computed frequencies for isolated surface WO4 sites agree well with the experimental in situ Raman spectra of the corresponding model catalysts, proving their existence. Finally, steady-state OCM studies showed that the C2 selectivity was highest for Na-WO4 sites, followed by Mn-WO4 and WO4, a trend mimicking the degree of distortion in the molecular geometry of each site. Na-WO4 exhibited the lowest reactivity toward CH4 and the highest degree of Wâ• O bond elongation.

Non-ferrous metallurgy slags are gaining significant interest as a resource in the production of alternative low-energy cementitious materials. Their atomistic structures, however, are still not fully understood due to their glassy nature. In the work presented herein, a comprehensive description of the nano-structure of a CaO-FeO-SiO2 slag was obtained by using molecular dynamic simulations in conjunction with previously obtained experimental data from X-ray and neutron pair distribution function studies. Iron was predominately 4- and 5-fold coordinated with oxygen, forming polyhedra in tetrahedral and pyramidal/triangular bipyramidal configuration. The [FeOx] polyhedra were corner-shared to the silica tetrahedra, while the higher coordinated fractions (x = 5 or 6) seemed to prefer to be next to each other, sharing edges. Ca was mostly surrounded by 6 or 7 oxygens in polyhedra that are predominantly edge-sharing with other units. The obtained results fit the experimental data well and as such provide an accurate and realistic picture of the iron-rich slag structure.

Silver based-nanoparticles (Ag NPs) have been recently shown to be promising catalysts for the degradation of toxic organic dyes in wastewater despite the challenges of recycling. In this paper, self-supported Ag NPs were obtained at the surface of AgTi2(PO4)3 NASICON-type phosphates through in situ chemical reduction by sodium borohydride (NaBH4). The adopted approach enables the self-growth of zero-valent Ag NPs on the NASICON matrix, and concomitantly leads to the formation of Ag1−xNaxTi2(PO4)3. The crystalline structure, morphology and phase composition of the Ag nanocomposite has been characterized by several techniques. The catalytic performance of the as-fabricated Ag NPs/Ag1−xNaxTi2(PO4)3 has then been verified in the reduction of methylene blue (MB) and methyl orange (MO) dyes, chosen as target pollutants. Our findings reveal a good catalytic activity with an efficiency and time of reaction of respectively ∼ 96.30% and 320 s in the case of the MB reduction and ∼ 94.60% and 270 s in the case of the MOreduction. Additionally, the initial AgTi2(PO4)3 phase can be regenerated via simple calcination route and recycled up to five times with no appreciable loss of catalytic activity.

The focus of this short review is directed towards investigations of the dynamics of nanostructured metallic heterogeneous catalysts and the evolution of interfaces during reaction—namely, the metal–gas, metal–liquid, and metal–support interfaces. Indeed, it is of considerable interest to know how a metal catalyst surface responds to gas or liquid adsorption under reaction conditions, and how its structure and catalytic properties evolve as a function of its interaction with the support. This short review aims to offer the reader a birds-eye view of state-of-the-art methods that enable more realistic simulation of dynamical phenomena at nanostructured interfaces by exploiting resource-efficient methods and/or the development of computational hardware and software.

International audience; The adsorption of GLY-PRO-GLU tripeptide on Au(110) is investigated within the frame of all atom classical mechanics simulations and Density Functional Theory, focusing on the surface reconstruction. It is shown that the tripeptide adsorption reorganizes and restructures the Au(110) surface. A mechanism for the surface restructuration is proposed for both the neutral and zwitterionic form of the peptide at room temperature in Ultra High Vacuum. Diverse residues may be involved in the Au atoms displacement, and in particular glutamic acid, triggering a double proton transfer and the formation of a zwitter ionic state, is found to be responsible for the triggering of the surface reconstruction.

A detailed analysis of fluorinated polyphenylthiols adsorbed on a nanostructured Au(111) is performed on the basis of first principle calculations to understand the interface at the atomic level. Our analysis is focused on the energetics, the density of states projected onto different atoms, the charge rearrangements induced by the presence of the adlayer as well as the modifications in the electrostatic potential to gain a deeper insight into the involved processes. Fil: Colombo, Estefanía. 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.; Argentina. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada e Ingeniería Electroquímica; Argentina Fil: 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.; Argentina. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada e Ingeniería Electroquímica; Argentina Fil: Tielens, Frederik. Vrije Unviversiteit Brussel; Bélgica 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.; Argentina. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Programa de Electroquímica Aplicada e Ingeniería Electroquímica; Argentina

International audience; Zinc oxide species grafted on mesostructured cellular foam (MCF) silica are investigated using a combination of experimental and theoretical techniques. MCF is modelled using a realistic amorphous silica surface model surface slab. The most energetically favorable complexes grafted on the silica surface were identified and characterized at the molecular level. The Zn metal center was found in tetrahedral coordination. Moreover, the Si-O-Zn-OH species is found to be stabilized in a 5 fold coordinated silicon with an unusual trigonal bipyramidal geometry. A mechanism for the grafting process of the metal species on the support is proposed.

International audience; Green composites based on montmorillonite (Mt) and cysteine, were prepared for heavy metal removal. A comparison between the adsorption properties of the resulting hybrid inorganic-organic materials and the pure montmorillonite was carried out for the following heavy metal cations Cd2+, Hg2+, Pb2+, Co2+ and Zn2+. It appears that the adsorption capacity is higher on the composite. Moreover, in release experiments, the heavy metal cations are more strongly retained by the hybrid material. Interactions between the hybrid clay mineral and the inorganic hosts were studied by spectroscopic methods such as solid-state NMR (Nuclear Magnetic Resonance) and FTIR (Fourier Transform Infrared). The experimental data were in agreement with the theoretical periodic DFT (Density Functional Theory) calculations where a molecular picture of the adsorption complex is proposed.

Sodium and lithium hexatitanates (A2B6O13, where A = Li or Na, B = Ti or Sn) have been considered as anode materials in batteries. In this work, the Li- and Na-ion migration energies of Li2Ti6O13, Li2Sn6O13 and Na2Ti6O13 are explored using atomistic simulations. Alkali-ion transport is explored using a validated forcefield with nudged elastic band and synchronous transition state calculations. The results show that Li-ion migration exhibits activation energies of 0.47 and 0.52 eV for Li2Ti6O13 and Li2Sn6O13, respectively. In addition, Na-ion migration in Na2Ti6O13 has the lowest activation energy of 0.17 eV. Sodium and lithium can also be accommodated into the Li2Ti6O13, Li2Sn6O13 and Na2Ti6O13 structures. Li-ion migration through the channel of Na2Ti6O13 has an activation energy of 0.39 eV, while Na-ion migration in Li2Sn6O13 and Li2Ti6O13 has values of 0.95 and 1.16 eV, respectively. The Li-ion migration barrier in Na2Ti6O13 is lower than that for Li2Sn6O13 and Li2Ti6O13 because of the lower electrostatic interactions in the NaO8 channels. The presence of quasi-transition state structures for the diffusion path impacts on the reduction of the energy barrier to reach the transition state structure, providing the low barriers for Na and Li ions in Na2Ti6O13 lattice structure. The calculated defect energetics reveal that there is a viable incorporation mechanism, without the involvement of Ti4+ to Ti3+ reduction, as reported in the literature, which describes the defect behavior and the reversible insertion of Li+ and Na+ ions in these tunnel structures.

International audience; With the aim of rationalizing the reactivity of transition-metal (TM) clusters, the model reaction of NO dissociation on TM 13 clusters was investigated on a set of seven TMs. The adsorption energy and the activation energy for NOdissociation were calculated for each TM and discussed within the findings of Boudart in his article “model catalysts: reductionism for understanding”. In this work, we focused on selected TM cluster calculations instead of surface science slab-type calculations, which have been performed for some TMs and focus on the electronic structure to investigate and rationalize the TM reactivity. Besides the electronic and spin properties of the TM, we discuss the reactivity trends using also qualitatively the chemical hardness and softness. We conclude that the combination of these reactivity parameters will be necessary to fine- tune TM clusters’ reactivity with the scope of multimetallic TM clusters.

Amorphous silica is an intrinsic challenging system to study. In the last decades, some particular chemical properties have been discovered and described, but their description and understanding at the molecular level are experimentally difficult. Therefore, theoretical quantum chemical methods and descriptors, combined with experimental input, are a very appropriate set up to tackle this topic. In this study, the acidity of silanol groups of amorphous silica in hydrated conditions is investigated. Special attention has been drawn to the chemical shift, but also Bader charges, and vibrational frequencies with their intensities. The known bimodal acidity behavior was recovered and rationalized. The findings support that the chemistry of the silica surface is not determined by a single site or a family of sites but by a broad distribution of very different geometries of silanol groups in a H-bond network that can eventually show very acidic and at the same time very basic properties.