Conversion-type electrode materials show extremely interesting performance in terms of capacity, which is however usually associated with bad Coulombic efficiency. The latter is mainly the consequence of the relentless evolution of solid electrolyte interphase (SEI) formed and/or dissolved during conversion/back-conversion reactions on the continuously reshaping active material surface. The thorough comprehension of the dynamic processes occurring during cycling in a working electrochemical cell, such as solvation/desolvation of ionic species and formation/dissolution of the SEI at the electrode/electrolyte interface, is thus of utmost relevance in the study of electrochemical mechanism and performance of conversion-type electrode materials. Operando Fourier transform infrared (FTIR) spectroscopy, one of the methods of choice for the study of such phenomena, was applied to study the dynamic interfacial properties of NiSb2, a representative intermetallic conversion-type electrode material for Li batteries, during cycling in the presence of a commercial electrolyte based on LiPF6 dissolved in a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC). Using a specifically developed in situ ATR-IR electrochemical cell, it was possible to correlate the electrochemical processes to the ratio between solvent molecules associated with Li+ ions and free solvent molecules and thus to follow the dynamic evolution of the concentration of lithium in the electrolyte during cycling.

We report direct and unambiguous evidence of the existence of inner semiconducting tube (ISCT) photoluminescence (PL) from measurements performed on four individual freestanding index-identified double-walled carbon nanotubes (DWNTs). Based on thorough Rayleigh scattering, Raman scattering, and PL experiments, we are able to demonstrate that the ISCT PL is observed with a quantum yield estimated to be a few 10−6 independent of the semiconducting or metallic nature of the outer tube. This result is mainly attributed to ultrafast exciton transfer from the inner to outer tube. Furthermore, by carrying out PL excitation experiments on the (14,1)@(15,12) DWNT, we show that the ISCT PL can be detected through the optical excitation of the outer tube, indicating that the exciton transfer can also occur in the opposite way.

Ionic transport through single-walled carbon nanotubes (SWCNTs) is promising for many applications but remains both experimentally challenging and highly debated. Here we report ionic current measurements through microfluidic devices containing one or several SWCNTs of diameter of 1.2 to 2 nm unexpectedly showing a linear or a voltage-activated I-V dependence. Transition from an activated to a linear behavior, and stochastic fluctuations between different current levels were notably observed. For linear devices, the high conductance confirmed with different chloride salts indicates that the nanotube/water interface exhibits both a high surface charge density and flow slippage, in agreement with previous reports. In addition, the sublinear dependence of the conductance on the salt concentration points toward a charge-regulation mechanism. Theoretical modelling and computer simulations show that the voltage-activated behavior can be accounted for by the presence of local energy barriers along or at the ends of the nanotube. Raman spectroscopy reveals strain fluctuations along the tubes induced by the polymer matrix but displays insufficient doping or variations of doping to account for the apparent surface charge density and energy barriers revealed by ion transport measurements. Finally, experimental evidence points toward environment-sensitive chemical moieties at the nanotube mouths as being responsible for the energy barriers causing the activated transport of ions through SWCNTs within this diameter range.

Single-walled carbon nanotubes (SWCNTs) are functionalized with copper hexacyanoferrate (CuHCF) nanoparticles and therefore constitutes promising solid substrates for the sorption of Cs+ ions from liquid effluents. The high mechanical resistance and large electrical conductivity of SWCNTs are associated to the ability of CuHCF nanoparticles to selectively complex Cs+ ions in order to achieve membrane-like buckypapers presenting high loading capacity of cesium. The materials are thoroughly characterized using electron microscopy, Raman scattering, X-ray photoelectron spectroscopy and thermogravimetric analyses. Cs sorption isotherms are plotted after liquid phase ionic chromatography of the Cs solutions before and after exposure to the materials. It is found that the total sorption capacity of the material reaches 230 mg.g-1, and that one third of the sorbed Cs (80 mg.g-1) is selectively complexed in the CuHCF nanoparticles grafted on SWCNTs. These high values open interesting perspectives in the integration of such materials in electrically driven devices for the controlled sorption and desorption of these ions.

In this work we have carried out variable-load indentation testing on three sodium borosilicate glassesand characterized the indentation imprints using Raman spectroscopy. The resulting analysis of thespectra helps describe the relative amount of densification and shear ow appearing in each glass, as wellas the different microstructural mechanisms that take place during deformation. Additionally, we showthat the two glasses that are relatively poor in sodium exhibit enhanced mixing of the silicate and borateunits after indentation. For the indentations performed using the highest load, we also acquired spectraby focusing at various depths below the imprint, in order to characterize the deformed region of theglasses and estimate its size. Similar experiments have been also carried out for one of the three glassesafter neutron irradiation, in order to study the effects of mechanical deformation on its depolymerizedand swollen structure.

AlPO4-17, known as the oxide with the highest negative thermal expansion (NTE), was studied under high pressure by angle-dispersive X-ray diffraction (XRD), mid- and far-infrared (IR) spectroscopy. Upon increasing pressure, the closure of the (P–O–Al) angle destabilizes the porous AlPO4-17 structure, which drives the amorphization process. On the basis of the decrease in intensity of the XRD lines and broadening of the IR modes, the material was found to begin to amorphize near 1 GPa. XRD, mid- and far-IR analysis evidenced pressure-induced framework softening and complete irreversible amorphization near 2.5 GPa corresponding to the collapse of the pores. The bulk modulus and its first pressure derivative (B0 = 31.2(5) GPa and B′0 = −10.1(3)) at ambient temperature were determined by fitting a third order Birch–Murnaghan equation of state (EOS) to the pressure–volume data. The material is extremely compressible and exhibits an elastic instability. Anomalous (negative) values of B′0 are very rare and have been observed previously for cyanides and metal–organic frameworks. Such an instability appears to be characteristic of materials, which exhibit strong NTE behavior and indicates a link between NTE and anomalous compressibility behavior. Mid-IR, far-IR, nuclear magnetic resonance, and pair distribution function analysis of the new amorphous form allow an amorphization mechanism to be proposed corresponding to a collapse of the structure around its pores retaining the columns built up of cancrinite cages and hexagonal prisms, based on alternating AlO4 and PO4 tetrahedra. An increase in coordination number of 10% of the Al atoms was observed. The pressure-induced amorphization in the strong NTE material AlPO4-17 opens the door to the development of new technological applications as crystal–amorphous nanocomposites with zero or specifically selected thermal expansion coefficients.

In situ and ex situ Raman measurements were used to study the dynamics of the populations of single-walled carbon nanotubes (SWCNTs) during their catalytic growth by chemical vapor deposition. Our study reveals that the nanotube diameter distribution strongly evolves during SWCNT growth but in dissimilar ways depending on the growth conditions. We notably show that high selectivity can be obtained using short or moderate growth times. High-resolution transmission electron microscopy observations support that Ostwald ripening is the key process driving these seemingly contradictory results by regulating the size distribution and lifetime of the active catalyst particles. Ostwald ripening appears as the main termination mechanism for the smallest diameter tubes, whereas carbon poisoning dominates for the largest ones. By unveiling the key concept of dynamic competition between nanotube growth and catalyst ripening, we show that time can be used as an active parameter to control the growth selectivity of carbon nanotubes and other 1D systems.