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The unraveling of the hydrophobicity/hydrophilicity molecular signature of nanometric bidimensional confined systems represents a challenging task with repercussions in environmental transport processes. Swelling clay minerals represent an ideal model system, as hydrophobicity can be modified during material synthesis by substituting hydroxyls by fluorine in the structure, without additional surface treatment. This following work presents a combined approach, integrating experimental inelastic neutron scattering spectroscopy and ab initio molecular dynamics simulations, with the objective of advancing our understanding of the role of surface hydroxylation/fluorination and the extent of confinement on water properties. From computed structures, the analysis of molecular hydrophobicity/hydrophilicity signature was investigated in detail through water-cation-surface interactions. The results elucidate the influence of fluorination on interlayer species, thereby tracing the impact of the surface on the diminished number of water molecules in such a sample. It is notable that the strong cation-water interaction can overcome the disruptive influence of fluorine, thereby maintaining comparable water hydration shells around cations and resulting in an almost identical bidimensional confinement geometry for both hydroxylated and fluorinated specimens. The analysis of the hydrogen-bond network revealed a significant reorganization of the water molecules due to fluorination. Our results suggest that a quantitative molecular signature of hydrophobicity/hydrophilicity can be derived from the analysis of the formation of cavities in the confined fluid. This new finding represents a robust approach for generalizing the hydrophobicity/hydrophilicity character for a wide variety of bidimensional systems while proposing a framework for the design of new materials with controlled water properties.

We used THz (terahertz) and INS (inelastic neutron scattering) spectroscopies to study the interaction between an endohedral noble gas atom and the C60 molecular cage. The THz absorption spectra of powdered A@C60 samples (A = Ar, Ne, Kr) were measured in the energy range from 0.6 to 75 meV for a series of temperatures between 5 and 300 K. The INS measurements were carried out at liquid helium temperature in the energy transfer range from 0.78 to 54.6 meV. The THz spectra are dominated by one line, between 7 and 12 meV, at low temperatures for three noble gas atoms studied. The line shifts to higher energy and broadens as the temperature is increased. Using a spherical oscillator model, with a temperature-independent parameterized potential function and an atom-displacement-induced dipole moment, we show that the change of the THz spectrum shape with temperature is caused by the anharmonicity of the potential function. We find good agreement between experimentally determined potential energy functions and functions calculated with Lennard-Jones additive pair-wise potentials with parameters taken from the work of Pang and Brisse, J. Chem. Phys. 97, 8562 (1993)., (© 2023 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).)

We study the binding mechanism of CO and CO 2 in the porous spin-crossover compound Fe(pz)[Pt(CN) 4 ] by combining neutron diffraction (ND), inelastic neutron scattering (INS) and density-functional theory (DFT) calculations. Two adsorption sites are identified, above the open-metal site and between the pyrazine rings. For CO adsorption, the guest molecules are parallel to the neighboring gas molecules and perpendicular to the pyrazine planes. For CO 2 , the molecules adsorbed on-top of the open-metal site are perpendicular to the pyrazine rings and those between the pyrazines are almost parallel to them. These configurations are consistent with the INS data, which are in good agreement with the computed generalized phonon density of states. The most relevant signatures of the binding occur in the spectral region around 100 cm -1 and 400 cm -1 . The first peak blue-shifts for both CO and CO 2 adsorption, while the second red-shifts for CO and remains nearly unchanged for CO 2 . These spectral changes depend both from steric effects and the nature of the interaction. The interpretation of the INS data as supported by the computed binding energy and the molecular orbital analysis are consistent with a physisorption mechanism for both gases. This work shows the strength of the combination of neutron techniques and DFT calculations to characterize in detail the gas adsorption mechanism in this type of materials.

The interactions between atoms and molecules may be described by a potential energy function of the nuclear coordinates. Nonbonded interactions between neutral atoms or molecules are dominated by repulsive forces at a short range and attractive dispersion forces at a medium range. Experimental data on the detailed interaction potentials for nonbonded interatomic and intermolecular forces are scarce. Here, we use terahertz spectroscopy and inelastic neutron scattering to determine the potential energy function for the nonbonded interaction between single He atoms and encapsulating C 60 fullerene cages in the helium endofullerenes 3 He@C 60 and 4 He@C 60 , synthesized by molecular surgery techniques. The experimentally derived potential is compared to estimates from quantum chemistry calculations and from sums of empirical two-body potentials.

Morphological and structural properties of amorphous disaccharide lactulose (C 12 H 22 O 11 ), obtained by four different amorphization methods (milling, quenching of the melt form, spray-drying, and freeze-drying), are investigated by scanning electron microscopy, polarized neutron scattering, and molecular dynamics simulations. While major differences on the morphology of the different amorphous samples are revealed by scanning electron microscopy images, only subtle structural differences have been found by polarized neutron scattering. Microstructure of the milled sample appears slightly different from the other amorphized materials with the presence of remaining crystalline germs which are not detected by X-ray diffraction. Quantitative phase analysis shows that these remaining crystallites are present in a ratio between 1 and 4%, and their size remains between 20 and 30 nm despite a long milling time of about 8 h. The impact of the change in tautomeric concentrations on the physical properties of lactulose in the amorphous state has been investigated from molecular dynamics simulations. It is suggested that chemical differences between lactulose tautomers could be at the origin of small structural differences detected by polarized neutron scattering.

The interaction of hydrogen with platinum is enormously important in many areas of catalysis. The most significant of these are in polymer electrolyte membrane fuel cells (PEMFC), in which carbon-supported platinum is used to dissociate hydrogen gas at the anode. The nature of adsorbed hydrogen on platinum has been studied for many years on single-crystal surfaces, on high-surface area-platinum metal (Raney platinum and platinum black), and on supported catalysts. Many forms of vibrational spectroscopy have played a key role in these studies, however, there is still no clear consensus as to the assignment of the spectra. In this work, ab initio molecular dynamics (AIMD) and lattice dynamics were used to study a 1.1 nm nanoparticle, Pt 44 H 80 . The results were compared to new inelastic neutron scattering spectra of hydrogen on platinum black and of a carbon-supported platinum fuel cell catalyst and an assignment scheme that rationalises all previous data is proposed., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The relative amounts of hydrogen retained by a range of supported palladium catalysts have been investigated by a combination of electron microscopy and spectroscopic techniques, including incoherent inelastic neutron scattering. Contrary to expectation, the hydrogen capacity is not determined solely by the metal particle size, but it is a complex interaction between the particle size and its state of aggregation. The nature of the support is not only integral to the amount of hydrogen held by the catalyst, it also causes a marked difference in the rate of release of stored hydrogen from palladium. It is more difficult to fully dehydrogenate palladium on/in the porous activated carbon than on the non-porous carbon black based catalyst. The type of support also results in differences in the form of the residual hydrogen: whether it is α- or β-hydride phase, subsurface or in the threefold surface site. Our data on the supported catalysts reinforces what has only been seen previously with palladium black and our computational study provides confirmation of the empirical assignments. We also report the first vibrational spectroscopic study of hydrogen adsorbed at the surface of β-PdH and have observed for the first time hydrogen in the on-top site. This has enabled the relative proportion of bulk- to surface-H occupation in calculated model and in industrial nanoparticles to be estimated.

We describe the synthesis and characterisation of open fullerene (1) and its reduced form (2) in which CH 4 and NH 3 are encapsulated, respectively. The 1 H NMR resonance of endohedral NH 3 is broadened by scalar coupling to the quadrupolar 14 N nucleus, which relaxes rapidly. This broadening is absent for small satellite peaks, which are attributed to natural abundance 15 N. The influence of the scalar relaxation mechanism on the linewidth of the 1 H ammonia resonance is probed by variable temperature NMR. A rotational correlation time of τ c =1.5 ps. is determined for endohedral NH 3 , and of τ c =57±5 ps. for the open fullerene, indicating free rotation of the encapsulated molecule. IR spectroscopy of NH 3 @2 at 5 K identifies three vibrations of NH 3 (ν 1 , ν 3 and ν 4 ) redshifted in comparison with free NH 3 , and temperature dependence of the IR peak intensity indicates the presence of a large number of excited translational/ rotational states. Variable temperature 1 H NMR spectra indicate that endohedral CH 4 is also able to rotate freely at 223 K, on the NMR timescale. Inelastic neutron scattering (INS) spectra of CH 4 @1 show both rotational and translational modes of CH 4 . Energy of the first excited rotational state (J=1) of CH 4 @1 is significantly lower than that of free CH 4 ., (© 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

A detailed study of the thermal behaviour of atomic motions in the organic ferroelectric croconic acid is presented in the temperature range 5-300 K. Using high-resolution inelastic neutron scattering and first-principles electronic-structure calculations within the framework of density functional theory and a quasiharmonic phonon description of the material, we find that the frequencies of the well defined doublet in inelastic neutron scattering spectra associated with out-of-plane motions of hydrogen-bonded protons decrease monotonically with temperature indicating weakening of these bonding motifs and enhancement of proton motions. Theoretical mean-square displacements for these proton motions are within 5% of experimental values. A detailed analysis of this observable shows that it is unlikely that there is a facile proton transfer along the direction of ferroelectric polarization in the absence of an applied electric field. Calculations predict constrained thermal motion of proton along crystallographic lattice direction c retaining the hydrogen bond motif of the crystal at high temperature. Using the Berry-phase method, we have also calculated the spontaneous polarization of temperature dependent cell structures, and find that our computational model provides a satisfactory description of the anomalous and so far unexplained rise in bulk electric polarization with temperature. Correlating the thermal motion induced lattice strain with temperature dependent spontaneous polarizations, we conclude that increasing thermal strain with temperatures combined with constrained thermal motion along the hydrogen bond motif are responsible of this increase in ferroelectricity at high temperature.

Discrimination between different gases is an essential aspect for industrial and environmental applications involving sensing and separation. Several classes of porous materials have been used in this context, including zeolites and more recently MOFs. However, to reach high selectivities for the separation of gas mixtures is a challenging task that often requires the understanding of the specific interactions established between the porous framework and the gases. Here we propose an approach to obtain an enhanced selectivity based on the use of compartmentalized coordination polymers, named CCP-1 and CCP-2 , which are crystalline materials comprising isolated discrete cavities. These compartmentalized materials are excellent candidates for the selective separation of CO 2 from methane and nitrogen. A complete understanding of the sorption process is accomplished with the use of complementary experimental techniques including X-ray diffraction, adsorption studies, inelastic- and quasi-elastic neutron scattering, magnetic measurements and molecular dynamics calculations.

In this paper we report a methodology for calculating the inelastic neutron scattering spectrum of homonuclear diatomic molecules confined within nano-cavities of spherical symmetry. The method is based on the expansion of the confining potential into multipoles of the coupled rotational and translational angular variables. The Hamiltonian and the INS transition probabilities are evaluated analytically. The method affords a fast and computationally inexpensive way to simulate the inelastic neutron scattering spectrum of molecular hydrogen confined in fullerene cages. The potential energy surface is effectively parametrized in terms of few physical parameters comprising an harmonic term, anharmonic corrections and translation-rotation couplings. The parameters are refined by matching the simulations against the experiments and the excitation modes are identified for transfer energies up to 215 meV.

Understanding the mobility of H at the surface of carbon nanostructures is one of the essential ingredients for a deep comprehension of the catalytic formation of H 2 in interstellar clouds. In this paper, we combine neutron vibrational spectroscopy with DFT molecular dynamics simulations to study the local environment of H structures chemisorbed at the surface of disordered graphene sheets. At 5 K, the ground state is composed of large clusters of hydrogen chemisorbed at sp 2 carbon sites, on the edges and in voids of the graphene sheets. At temperatures of ∼300 K, a high degree of dispersion of the clusters is observed, involving the breaking and reforming of covalent bonds which, at low temperatures, is mediated by incoherent tunnelling of hydrogen.

A combination of electron microscopy, X-ray and neutron spectroscopies and computational methods has provided new insights into the species present on the surface of freshly prepared precious metal catalysts. The results show that in all cases, at least half of the surface is metallic or nearly so, with the remainder covered by oxygen, largely as hydroxide. Water is also present and is strongly held; weeks of pumping under high vacuum is insufficient to remove it. The hydroxyls are reactive as shown by their reaction with or displacement by CO and can be removed by hydrogenation. This clearly has implications for how precious metal catalysts are activated after preparation.

Two different organic cations (structure directing agents, SDAs) have been selected because of their ability to drive the synthesis of zeolites towards the same microporous material, RUB-13 (RTH), both being organophosphorous compounds. These P containing structure directing agents are characterized by a high concentration of positive charge on the phosphorus atom. Then, in the presence of fluoride anions used in these syntheses, a strong P(+)F(-) electrostatic contribution competes with the van der Waals short range SDAzeolite interaction that drives the zeolite formation. The rotation of the methyl groups present in the SDA is expected to be nearly free if van der Waals interactions dominate, but they will be hindered if the Coulombic P(+)F(-) term forces a closer approach to the SDA towards the zeolite framework. SDAs can be designed a priori to tune which interactions dominate. The rotational mobility of the SDAs, as well as certain related bending modes, has been well tackled by inelastic neutron scattering (INS) in order to test this hypothesis. The INS results provide valuable information for the design of specific SDAs for the synthesis of zeolites.

The different contributions to the entropy change linked to the austenite-martensitic transition in a Ni-Mn-Sn metamagnetic shape memory alloy have been determined by combining different experimental techniques. The vibrational contribution has been inferred from the vibrational density of states of both the martensitic and austenite phases. This has been accomplished by combining time-of-flight neutron scattering measurements and ab initio calculations. Further, the electronic part of the entropy change has also been calculated. Since the martensitic transformation takes place between two paramagnetic phases, the magnetic contribution can be neglected and the entropy change can be reduced to the sum of two terms: vibrational and electronic. The obtained value of the vibrational contribution ([Formula: see text]) nearly provides the total entropy change measured by calorimetry ([Formula: see text]), the difference being the electronic contribution within the experimental error.

Inelastic neutron scattering (INS) has been employed to investigate the quantum dynamics of water molecules permanently entrapped inside the cages of C60 fullerene molecules. This study of the supramolecular complex, H2O@C60, provides the unique opportunity to study isolated water molecules in a highly symmetric environment. Free from strong interactions, the water molecule has a high degree of rotational freedom enabling its nuclear spin isomers, ortho-H2O and para-H2O to be separately identified and studied. The INS technique mediates transitions between the ortho and para spin isomers and using three INS spectrometers, the rotational levels of H2O have been investigated, correlating well with the known levels in gaseous water. The slow process of nuclear spin conversion between ortho-H2O and para-H2O is revealed in the time dependence of the INS peak intensities over periods of many hours. Of particular interest to this study is the observed splitting of the ground state of ortho-H2O, raising the three-fold degeneracy into two states with degeneracy 2 and 1 respectively. This is attributed to a symmetry-breaking interaction of the water environment.

We report an inelastic neutron scattering (INS) study of a H2 molecule encapsulated inside the fullerene C60 which confirms the recently predicted selection rule, the first to be established for the INS spectroscopy of aperiodic, discrete molecular compounds. Several transitions from the ground state of para-H2 to certain excited translation-rotation states, forbidden according to the selection rule, are systematically absent from the INS spectra, thus validating the selection rule with a high degree of confidence. Its confirmation sets a precedent, as it runs counter to the widely held view that the INS spectroscopy of molecular compounds is not subject to any selection rules.

Transformation of deuterated ethanol from the plastic crystal phase into the monoclinic one is investigated by means of a singular setup combining simultaneously dielectric spectroscopy with neutron diffraction. We postulate that a dynamic transition from plastic crystal to supercooled liquid-like configuration through a deep reorganization of the hydrogen-bonding network must take place as a previous step of the crystallization process. Once these precursor regions are formed, subsequent crystalline nucleation and growth develop with time.

Collective excitations of water confined in the interlayer space of swelling clay minerals were studied by means of inelastic neutron scattering. The effect of bidimensional confinement on the dynamics of the interlayer water was investigated by using a synthetic Na-saponite sample with a general formula of Si(7.3)Al(0.7)Mg(6)O(20)(OH)(4)Na(0.7) in a bilayer hydration state. Experimental results reveal two inelastic signals, different from those described for bulk water with a clear anisotropy on the low-energy excitation of the collective dynamics of interlayer water, this difference being stronger in the perpendicular direction. Results obtained for the parallel direction follow the same trend as bulk water, and the effect of the confinement is mainly manifested from the fact that clay interlayer water is more structured than bulk water. Data obtained in the perpendicular direction display a nondispersive behavior below a cutoff wavenumber value, Q(c), indicating a nonpropagative excitation below that value. Molecular dynamics simulations results agree qualitatively with the experimental results.

Transformation of deuterated ethanol from supercooled liquid into a plastic crystal or rotator phase is investigated by means of a particular experimental setup combining simultaneously dielectric spectroscopy with neutron diffraction techniques. We demonstrate that, previous to the growth of the bcc lattice of the plastic crystal phase, the formation of a precursor or intermediate phase through a liquid-liquid phase separation takes place. Once this precursor phase is formed, subsequent (plastic) crystalline nucleation and growth is expected to develop.

An inelastic neutron scattering study of Cu2Te2O5X2 (X=Cl, Br) shows strong dispersive modes with large energy gaps persisting far above TN, notably in Cu2Te2O5Br2. The anomalous features: a coexisting unusually weak Goldstone-like mode observed in Cu2Te2O5Cl2 and the size of the energy gaps cannot be explained by existing theories, such as our mean-field or random-phase approximation. We argue that our findings represent a new general type of behavior due to intercluster quantum fluctuations and call for development of a new theoretical approach.

Venous canalization can be one of the most frequent causes of accidents due to an accidental puncture. To carry out activities which serve to lessen these misfortunes, bearing high biological risk, should become a priority for sanitary institutions and for their professionals. Inside a global strategy which deals with this aspect and with the objective of evaluating the convenience these instruments have in our center the authors made a practical evaluation on a series of them to discover their technical viability and their subjective consideration by professionals who employ them. For motives related to the practices of the ward in which this research took place, an emergency ward, the authors intentionally chose two passive instruments, available on the market, and three nurses who received 120 sample security catheters, 60 each for products A and B, to carry out habitual clinical practices, alongside a pad of paper on which to record any incidents. Regarding instrument A, 30 incidents, 52.6%, were detected while 37 sample procedures occurred. Regarding instrument B, 4 incidents, 7.01%, were detected while 47 sample procedures occurred. In absolute terms, neither of the two instruments demonstrated problems of an insecure manner; which is to say neither produced a situation related to the appearance of mis fortunate incidents associated to accidental punctures. The lower number of incidents with instrument B appears to be related to the habitual use of a conventional cathetec not a security one, produced by the same manufacturer in our center This research project was subsidized by the Sanitary Research Fund, PI 051265.