Mössbauer spectroscopy in the investigation of new mineral–related materials

New materials based on the composition of the mineral schafarzikite, FeSb $_{2}\textit {O}_{4}$ , have been synthesised. $^{57}$ Fe- and $^{121}$ Sb- Mössbauer spectroscopy shows that iron is present as Fe $^{2+}$ and that antimony is present as Sb $^{3+}$ . The presence of Pb $^{2+}$ on the antimony sites in materials of composition FeSb $_{1.5}$ Pb $_{0.5}\textit {O}_{4}$ induces partial oxidation of Fe $^{2+}_{}$ to Fe $^{3+}$ . The quasi-one-dimensional magnetic structure of schafarzikite is retained in FeSb $_{1.5}$ Pb $_{0.5}\textit {O}_{4}$ and gives rise to weakly coupled non-magnetic Fe $^{2+}$ ions coexisting with Fe $^{3+}$ ions in a magnetically ordered state. A similar model can be applied to account for the spectra recorded from the compound Co $_{0.5}$ Fe $_{0.5}$ Sb $_{1.5}$ Pb $_{0.5}\textit {O}_{4}$ .     

Synthetic versiliaite and apuanite: investigation by <Superscript>57</Superscript>Fe Mössbauer spectroscopy

The minerals versiliaite and apuanite have been synthesised for the first time. The ⁵⁷Fe Mössbauer spectra recorded at 298 and 4 K are reported. The results are indicative of a formulation for versiliaite as \(\left (\text {Fe}_{4}^{2+}\text {Fe}_{4}^{3+}\right )^{\text {oct}}\left [\text {Fe}_{4}^{3+}\text {Sb}_{12}^{3+}\right ]^{\text {tet}}\textit {O}_{32}\textit {S}_{2}\) and of apuanite as \(\left (\text {Fe}_{4}^{2+}\text {Fe}_{8}^{3+}\right )^{\text {oct}}\left [\text {Fe}_{8}^{3+}\text {Sb}_{16}^{3+}\right ]^{\text {tet}}\textit {O}_{48}\textit {S}_{\mathrm {4.}}\) The spectra recorded at low temperature are indicative of complex magnetic interactions. The results indicate the potential for the synthesis of further new structurally-related materials with different compositions and new low dimensional physical properties.     

Classical trajectory study of the dynamics of the reaction of Cl atoms with ethane

We present an electronic-structure and dynamics study of the Cl + C2H6 --> HCl + C2H5 reaction. The stationary points of the ground-state potential energy surface have been characterized using various electronic-structure methods and basis sets. Our best calculations, CCSD(T) extrapolated to the complete basis limit, using geometries and harmonic frequencies obtained at the MP2/aug-cc-pVTZ level, are in agreement with the experimental reaction energy. Ab initio information has been used to reparameterize a semiempirical Hamiltonian so that the predictions of the improved Hamiltonian agree with the higher-level calculations in key regions of the potential energy surface. The improved semiempirical Hamiltonian is then used to propagate quasiclassical trajectories. Computed kinetic energy release and scattering angle distributions at a collision energy of approximately 5.5 kcal mol(-1) are in reasonable agreement with experiments, but no evidence was found for the low translational energy HCl products scattered in the backward hemisphere reported in recent experiments.     

Protic ionic liquids: physicochemical properties and behavior as amphiphile self-assembly solvents

The physicochemical properties of 22 protic ionic liquids (PILs) and 6 protic molten salts, and the self-assembly behavior of 3 amphiphiles in the PILs, are reported. Structure-property relationships have been explored for the PILs, including the effect of increasing the substitution of ammonium cations and the presence of methoxy and hydroxyl moieties in the cation. Anion choices included the formate, pivalate, trifluoroacetate, nitrate, and hydrogen sulfate anions. This series of PILs had a diverse range of physicochemical properties, with ionic conductivities up to 51.10 mS/cm, viscosities down to 5.4 mPa.s, surface tensions between 38.3 and 82.1 mN/m, and densities between 0.990 and 1.558 g/cm3. PILs were designed with various levels of solvent cohesiveness, as quantified by the Gordon parameter. Fourteen PILs were found to promote the self-assembly of amphiphiles. High-throughput polarized optical microscopy was used to identify lamellar, hexagonal, and bicontinuous cubic amphiphile self-assembly phases. The presence and extent of amphiphile self-assembly have been discussed in terms of the Gordon parameter.     

Plastic Antibodies for Cosmetics: Molecularly Imprinted Polymers Scavenge Precursors of Malodors

Molecularly imprinted polymers (MIPs) are synthetic antibody mimics capable of specific molecular recognition. Advantageously, they are more stable, easy to tailor for a given application and less expensive than antibodies. These plastic antibodies are raising increasing interest and one relatively unexplored domain in which they could outplay these advantages particularly well is cosmetics. Here, we present the use of a MIP as an active ingredient of a cosmetic product, for suppressing body odors. In a dermo‐cosmetic formulation, the MIP captures selectively the precursors of malodorous compounds, amidst a multitude of other molecules present in human sweat. These results pave the way to the fabrication of a novel generation of MIPs with improved selectivities in highly complex aqueous environments, and should be applicable to biotechnological and biomedical areas as well.