Stefania Ferrari

Pair distribution function analysis and Mössbauer study of defects in microwave-hydrothermal LiFePO 4

Olivine-type LiFePO4 is nowadays one of the most important cathode materials of choice for high-energy lithium ion batteries. Its intrinsic defectivity, and chiefly the so-called lithium ironanti-site, is one of the most critical issues when envisaging electrochemical applications. This paper reports a combined diffractometric (Synchrotron Radiation XRD with Rietveld and PDF analyses) and spectroscopic (Mossbauer) approach able to give a thorough characterization of the material defectivity. Such analytical procedure has been applied to a sample prepared following an innovative microwave-assisted hydrothermal synthesis route that, in a few minutes, allowed us to obtain a well crystallized material. PDF analysis, which is applied for the first time to this type of battery material, reveals the presence of disorder possibly due to Li/Fe exchange or to a local symmetry lowering. A 5% amount of iron on the lithium site has been detected both by PDF as well as by Mossbauer spectroscopy, which revealed a small percentage of Fe3+ on the regular sites.

Polymorphism and magnetic properties of Li2MSiO4 (M = Fe, Mn) cathode materials

Transition metal-based lithium orthosilicates (Li2MSiO4, M = Fe, Ni, Co, Mn) are gaining a wide interest as cathode materials for lithium-ion batteries. These materials present a very complex polymorphism that could affect their physical properties. In this work, we synthesized the Li2FeSiO4 and Li2MnSiO4 compounds by a sol-gel method at different temperatures. The samples were investigated by XRPD, TEM, 7Li MAS NMR, and magnetization measurements, in order to characterize the relationships between crystal structure and magnetic properties. High-quality 7Li MAS NMR spectra were used to determine the silicate structure, which can otherwise be hard to study due to possible mixtures of different polymorphs. The magnetization study revealed that the Néel temperature does not depend on the polymorph structure for both iron and manganese lithium orthosilicates.

Preparation and characterization of carprofen co-crystals

Carprofen co-crystals with selected co-formers were prepared by solvent evaporation and wet/dry grinding methods. Their effective formation was investigated by thermal analysis, FT-IR, X-ray single crystal and powder diffraction and SEM-EDS. This last technique has been applied for the first time to co-crystals since it provides unambiguous confirmation of co-crystal formation. Among the investigated co-formers we studied, only 4,4′-dipyridyl yields co-crystals. Two different crystal structures are obtained when the molar ratio of carprofen : 4,4′-dipyridyl is 2 : 1 (triclinic cell) and 1 : 1.5 (monoclinic cell). The asymmetric triclinic cell (Z = 2) contains two carprofen and two half 4,4′-dipyridyl moieties while the monoclinic cell (Z = 4) contains a single carprofen, and one and a half 4,4′-dipyridyl moieties. Several hydrogen-bond supramolecular synthons can be identified in the solid state. For both the 2 : 1 and 1 : 1.5 co-crystals, the main hydrogen-bond interaction consists of an O–H⋯N heterosynthon involving, as a donor, the COOH group of carprofen and, as a H-acceptor, the nitrogen of a 4,4′-dipyridyl molecule. The two co-crystals have characteristic FT-IR spectra and slightly different melting temperatures. X-Ray powder diffraction patterns of the 1 : 1 and 1 : 2 compositions reveal a mixture of phases, whose amount is quantified with Rietveld analysis.

Perphenazine–fumaric acid salts with improved solubility: preparation, physico-chemical characterization and in vitro dissolution

New compounds of perphenazine and fumaric acid in 2 : 1 and 1 : 2 molar ratios have been prepared by solvent evaporation with the aim of increasing the drug solubility. Their physico-chemical properties were thoroughly characterized by differential scanning calorimetry, powder X-ray diffraction, Fourier infrared spectroscopy and scanning electron microscopy coupled with energy dispersive X-ray spectrometry. In addition, the crystal structure of the 2 : 1 salt was determined by single-crystal X-ray diffraction. The pharmaceutical characterization included solubility and dissolution studies in comparison with the commercial product Trilafon®. Perphenazine solubility is strongly pH-dependent: the binary systems show improved solubility and intrinsic dissolution rate compared with perphenazine, but only the capsule formulation containing the 1 : 2 dihydrate sample shows a quick and complete dissolution behaviour at neutral pH. This sample could represent an interesting perphenazine formulation to improve drug bioavailability and perhaps reduce in vivo variability even when the gastric fluid pH is increased by the presence of food.

Thermal, Spectroscopic, and Ab Initio Structural Characterization of Carprofen Polymorphs

Commercial and recrystallized polycrystalline samples of carprofen, a nonsteroidal anti-inflammatory drug, were studied by thermal, spectroscopic, and structural techniques. Our investigations demonstrated that recrystallized sample, stable at room temperature (RT), is a single polymorphic form of carprofen (polymorph I) that undergoes an isostructural polymorphic transformation by heating (polymorph II). Polymorph II remains then metastable at ambient conditions. Commercial sample is instead a mixture of polymorphs I and II. The thermodynamic relationships between the two polymorphs were determined through the construction of an energy/temperature diagram. The ab initio structural determination performed on synchrotron X-Ray powder diffraction patterns recorded at RT on both polymorphs allowed us to elucidate, for the first time, their crystal structure. Both crystallize in the monoclinic space group type P2(1) /c, and the unit cell similarity index and the volumetric isostructurality index indicate that the temperature-induced polymorphic transformation I → II is isostructural. Polymorphs I and II are conformational polymorphs, sharing a very similar hydrogen bond network, but with different conformation of the propanoic skeleton, which produces two different packing. The small conformational change agrees with the low value of transition enthalpy obtained by differential scanning calorimetry measurements and the small internal energy computed with density functional methods.

Characterization of nicergoline polymorphs crystallized in several organic solvents

Nicergoline (NIC), a poorly water-soluble semisynthetic ergot derivative, was crystallized from several organic solvents, obtaining two different polymorphic forms, the triclinic form I and the orthorhombic form II. NIC samples were then characterized by several techniques such as (13)C cross-polarization magic angle spinning solid-state spectroscopy, room-temperature and high-temperature X-ray powder diffraction, differential scanning calorimetry, and by analysis of weight loss, solvent content, powder density, morphology, and particle size. Solubility and intrinsic dissolution rates determined for the two polymorphic forms in water and hydrochloride solutions (HCl 0.1 N) were always higher for form II than for form I, which is actually the form used for the industrial preparation of NIC medicinal products. Preformulation studies might encourage industry for the evaluation of polymorph II, as it is more suitable for pharmaceutical applications. Results in drug delivery, as well as those obtained by the above-mentioned techniques, and the application of Burger-Rambergers rules make it possible to conclude that there is a thermodynamic relation of monotropy between the two polymorphs. This last assumption may help formulators in predicting the relative stability of the two forms.

Heteroatom Doped-Carbon Nanospheres as Anodes in Lithium Ion Batteries

Long cycle performance is a crucial requirement in energy storage devices. New formulations and/or improvement of “conventional” materials have been investigated in order to achieve this target. Here we explore the performance of a novel type of carbon nanospheres (CNSs) with three heteroatom co-doped (nitrogen, phosphorous and sulfur) and high specific surface area as anode materials for lithium ion batteries. The CNSs were obtained from carbonization of highly-crosslinked organo (phosphazene) nanospheres (OPZs) of 300 nm diameter. The OPZs were synthesized via a single and facile step of polycondensation reaction between hexachlorocyclotriphosphazene (HCCP) and 4,4′-sulphonyldiphenol (BPS). The X-ray Photoelectron Spectroscopy (XPS) analysis showed a high heteroatom-doping content in the structure of CNSs while the textural evaluation from the N2 sorption isotherms revealed the presence of micro- and mesopores and a high specific surface area of 875 m2/g. The CNSs anode showed remarkable stability and coulombic efficiency in a long charge–discharge cycling up to 1000 cycles at 1C rate, delivering about 130 mA·h·g−1. This study represents a step toward smart engineering of inexpensive materials with practical applications for energy devices.

New materials for Li-ion batteries: synthesis and spectroscopic characterization of Li2(FeMnCo)SiO4 cathode materials.

Improving cathode materials is mandatory for next-generation Li-ion batteries. Exploring polyanion compounds with high theoretical capacity such as the lithium metal orthosilicates, Li2MSiO4 is of great importance. In particular, mixed silicates represent an advancement with practical applications. Here we present results on a rapid solid state synthesis of mixed Li2(FeMnCo)SiO4 samples in a wide compositional range. The solid solution in the P21/n space group was found to be stable for high iron concentration or for a cobalt content up to about 0.3 atom per formula unit. Other compositions led to a mixture of polymorphs, namely Pmn21 and Pbn21. All the samples contained a variable amount of Fe3+ ions that was quantified by Mössbauer spectroscopy and confirmed by the TN values of the paramagnetic to antiferromagnetic transition. Preliminary characterization by cyclic voltammetry revealed the effect of Fe3+ on the electrochemical response. Further work is required to determine the impact of these electrode materials on lithium batteries.

Recent Advances in Graphene-Based Materials for Lithium Batteries

Energy production and storage have become key issues due to the ever increasing demand of electricity in modern days. Rechargeable batteries are recognized as the primary power sources for applications from portable electronic devices to electric vehicles. Recently, there has been a growing interest in investigating graphene nanocomposite materials for various energy storage applications, such as electrodes in lithium batteries. With its unique structural, mechanical, and electrical properties, graphene can be a critical component in nanostructured electrode materials with improved capacity and cyclability, enabling the development of advanced batteries and new battery technologies. This paper reviews the recent achievements in graphene utilization in negative electrodes for Li-ion batteries and introduces the latest progress of flexible graphene-based Li-ion batteries. A survey of the scientific advances achieved thanks to the use of graphene in the so called “beyond Li-ion” technologies, namely Li-sulphur and Li-O2 batteries, is also presented.

Structure and properties of domperidone and its succinate salt

This paper describes the structure and properties of the drug domperidone and a novel 1:1 domperidone succinate salt. The new salt is characterized by means of thermal, spectroscopic, microscopic and powder diffraction measurements. The crystal structures of the salt and, for the first time, of pure domperidone have been determined by means of single-crystal X-ray diffraction. In both structures, the piperidine ring of domperidone adopts the expected chair conformation, and supramolecular centrosymmetric R2(2)(8) motifs are formed by N-H...O hydrogen bonds between chlorine-substituted oxobenzimidazolyl groups. Further N-H...O hydrogen bonds occur between non-substituted oxobenzimidazolyl groups and the resulting C(4) motifs originates hydrogen-bonded chains, extending along the crystallographic b axis. In the salt, a single N-H...O hydrogen bond forms between the protonated nitrogen of the piperidine ring and the carboxylic O atom of the succinate ion. Two alternative and mutually exclusive positions for the nonsubstituted oxobenzimidazolyl group have also been observed; this disorder makes the hydrogen-bonded chains originating from the bicyclic group polar. The dissolution behaviour of the salt in dosage form is compared with two reference commercial products. The salt shows an increased solubility, a characteristic that could be of great advantage from a pharmaceutical view point.