ABSTRACT
The most common MXene composition Ti3C2Tx (T = F, O) shows outstanding stability as anode for sodium ion batteries (100% of capacity retention after 530 cycles with charge efficiency >99.7%). However, the reversibility of the intercalation/deintercalation process is strongly affected by the synthesis parameters determining, in turn, significant differences in the material structure. This study proposes a new approach to identify the crystal features influencing the performances, using a structural model built with a multitechnique approach that allows exploring the short-range order of the lamella. The model is then used to determine the long-range order by inserting defective elements into the structure. With this strategy it is possible to fit the MXene diffraction patterns, obtain the structural parameters including the stoichiometric composition of the terminations (neutron data), and quantify the structural disorder which can be used to discriminate the phases with the best electrochemical properties.
ABSTRACT
FeNb11O29 is an intriguing and promising material that has been emerging in the last few years. It is isostructural with Nb12O29, one of the rare compounds in which Nb displays a local magnetic moment and shows both antiferromagnetic ordering and metallic conductivity at low temperatures. Both the two polymorphic monoclinic and orthorhombic forms have a mono-dimensional magnetic arrangement, but the different disposition of the structural building blocks leads to a strong frustration phenomenon of the magnetic order in the high-temperature orthorhombic form. Whereas Nb12O29 has been widely studied, barely few magnetic data can be found on its analogous FeNb11O29, for which a role of the Fe3+ localized d electrons in affecting the original magnetic behaviour can be foreseen. In this paper, we report how we synthesized undoped and, for the first time, Mn- and V-doped FeNb11O29. Both the monoclinic and orthorhombic polymorphs, stable in different temperature ranges, were then thoroughly structurally characterized. With the help of micro-Raman spectroscopy, we investigated the differences introduced into the vibrational levels by doping, while EPR data allowed us to obtain information on the transition metal ions and to point out the related peculiar structural features. Static magnetization measurements evidenced the paramagnetic character of the compounds and the high-spin configuration of Fe3+ ions.
ABSTRACT
The development of efficient strategies for drug delivery is considerably desired. Indeed, often several issues such as the drug solubility, the control of the drug release rate, the targeted delivery of drugs, the drug bioavailability, and the minimization of secondary effects still present great obstacles. Different methodologies have been proposed, but the use of nano-hybrids compounds that combine organic and inorganic substances seems particularly promising. An interesting inorganic host is the layered double hydroxide (LDH) with a sheets structure and formula [M2+1-x M3+x (OH)2](An-)x/n yH2O (M2+ = Zn, Mg; M3+ = Al; An- = nitrates, carbonates, chlorides). The possibility to exchange these counterions with drug molecules makes these systems ideal candidates for the drug delivery. In this article, we synthesize by co-precipitation method the hybrid compound Carprofen-Zn2Al-LDH. Carprofen, a poorly soluble anti-inflammatory drug, could also benefit of the association with a natural antacid such as LDH, to reduce the gastric irritation after its administration. Through X-ray diffraction and Fourier-transformed infrared spectroscopy (FT-IR), we could verify the effective drug intercalation into LDH. The dissolution tests clearly demonstrate a significant improvement of the drug release rate when carprofen is in the form of hybrid compound.
