The study of hybrid systems MPA@SWNT of peapods kind involving photoactive molecules (MPA) confined in single-walled carbon nanotubes (SWNT) find its motivation in the possibility of modulating the physical properties of the nanotubes. Many experimental studies using vibrational spectroscopy in particular are interested in the physical properties of these hybrid systems. The key point of this issue is the nature of the interaction between the nanoconfinement matrix and MPAs, and the complexity of its study requires a comparison between experimental data and modelizations. In this work, we study the hybrid systems MPA@SWNT through modeling performed in different settings ranging from the use of molecular dynamics (MD) to that of the density functional theory (DFT). The limiting factor in DFT calculations is the computation time. the latter which varies in N3 (N is the number of atoms) increases drastically when N exceeds a hundred atoms for energy minimizations calculation, and even more for phonons calculations. In this context, the study of hybrid systems with organic MPAs is delicate. Indeed, the MPAs are complex molecules generally comprising side chains for the solubility of the system. For example, the smallest hybrid system studied, which consists on encapsulating a single molecule of thiophene oligomer functionalized with methyl groups at the edges inside an (11,0) nanotube contains 344 atoms. For the computation time not to be prohibitive, we tested different methods of simulation of the vibrational spectra of MPA@SWCNT: molecular dynamics, tight binding, and hybrid calculations MD/DFT. We discuss in details the results comparing models with experimental data for 1D thiophene oligomer molecules encapsulated inside nanotubes.

Purpose Polymers typically have intrinsic thermal conductivity much lower than other materials. Enhancement of this property may be obtained by the addition of conductive fillers. Nanofillers are preferred to traditional ones, due to their low percolation threshold resulting from their high aspect ratio. Beyond these considerations, it is imperative that the development of such new fillers takes place in a safe and sustainable manner. A conventional life cycle assessment (LCA) has been conducted on epoxy-based composites, filled with graphite nanoplatelets (GnP). In particular, this study focuses on energy requirements for the production of such composites, in order to stress environmental hot spots and primary energy of GnP production process (nano-wastes and nanoparticles emissions are not included). Methods A cradle-to-grave approach has been employed for this assessment, in an attributional modeling perspective. The data for the LCA have been gathered from both laboratory data and bibliographic references. A technical LCA software package, SimaPro (SimaPro 7.3), which contains Ecoinvent (2010) life cycle inventory (LCI) database, has been used for the life cycle impact assessment (LCIA), studying 13 midpoint indicators. Sensitivity and uncertainty analyses have also been performed. Results and discussion One kilogram of GnP filler requires 1,879 MJ of primary energy while the preparation of 1 kg of epoxy composite loaded with 0.058 kg of GnP 303 MJ. Besides energy consumption in the filler preparation, it is shown that the thermoset matrix material has also a nonnegligible impact on the life cycle despite the use of GnP: the primary energy required to make epoxy resin is 187 MJ, i.e., 62 % of the total energy to make 1 kg of composite. Conclusions Raw material extraction and filler and resin preparation phase exhibit the highest environmental impact while the composite production is negligible. Thermosetting resin remains the highest primary energy demand when used as matrix for GnP fillers. The result of the sensitivity analysis carried out on the electricity mix used during the GnP and the composite production processes does not affect the conclusions.

Microporous AlPO4-54·xH2O, which exhibits the largest pores among zeolites and aluminophosphates with a diameter of 12.7 Å, was investigated at high pressure by X-ray powder diffraction and Raman spectroscopy in diamond anvil cells. The material was found to begin to amorphize near 2 GPa using either a nonpenetrating pressure transmitting medium (PTM) silicone oil or no PTM. When H2O is used as a PTM, amorphization begins at a lower pressure of 0.9 GPa. In this case, superhydration effects are observed and higher relative unit cell volumes are observed prior to the beginning of pressure-induced amorphization (PIA) as compared to the experiment in silicone oil due to insertion of the H2O molecules in the pores. In all cases, in these experiments at room temperature, amorphization was irreversible. Ex situ experiments were used to investigate the local structure of pressure-amorphized AlPO4-54·xH2O by nuclear magnetic resonance and by X-ray absorption spectroscopy, which show that, upon increasing pressure, two water molecules enter in the coordination sphere of IVAl, thereby increasing the coordination number from 4 to 6, which destabilizes the structure. The present results show that the insertion of and/or reaction with guest species can be used to strongly modify the stability of microporous materials with respect to PIA.

We have investigated the phonon modes of Ag-3[Co(CN)(6)] using first-principles based methods and high-pressure infrared spectroscopy to understand the origin of its colossal thermal expansion. Griineisen parameters of its zone-center vibrational modes were obtained from the calculations and compared to the experimental ones. We found that optical phonon modes below 100 cm(-1) mainly contribute to its negative thermal expansion, and they also have a significant mixing with acoustic branches. These modes have been assigned to translational motion of the Co-CN-Ag-NC-Co linkages. We also identify a pressure-induced softening of zone-center phonon modes that could account for the experimentally observed phase transition in terms of a first-order displacive instability from the trigona1P-3-1m space group to the acentric Cm space group.

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