Chiara Ferrara

Innovative high performing metal organic framework (MOF)-laden nanocomposite polymer electrolytes for all-solid-state lithium batteries

An enhancement of two orders of magnitude in the ambient temperature ionic conductivity of poly(ethylene oxide)-based nanocomposite polymer electrolyte (NCPE) membranes is here fundamentally achieved by the incorporation of specific amounts of aluminium-based metal organic framework (MOF) as the filler. Thorough characterization, particularly solid-state NMR and FT-IR studies, shed light on the specific role of the defective MOF frameworks in greatly enhancing the Li+ ion mobility inside the polymeric matrix. The prepared NCPEs are highly stable towards lithium metal even after prolonged storage time, and an excellent cycling profile is evidenced even at moderate temperatures, which has never been reported so far for an all-solid-state lithium polymer cell composed of Li/NCPE/LiFePO4.

Structural and in vitro study of cerium, gallium and zinc containing sol–gel bioactive glasses

Sol–gel derived glasses comprised of bioactive materials exhibit a high in vitro response, i.e., the capability to form a hydroxycarbonate apatite (HCA) layer that is claimed to be responsible for the bonding between the glass and the host bone. In this paper, the sol–gel bioactive glass 80% SiO2–15% CaO–5% P2O5 (B_BG) was modified by adding the biologically relevant elements cerium, gallium and zinc. Structural characterization of the glasses was performed by 29Si MAS NMR and their in vitro response was investigated by soaking them in simulated body fluid (SBF) for up to 15 days at 37 °C. The HCA formation was monitored by XRD, FTIR, SEM-EDS and ICP measurements. Ce3+, Ga3+, and Zn2+ can be classified as “intermediate ions”. However, 29Si NMR revealed that Ce3+ ions have a more marked role of “modifier ions” than Ga3+ ions, while the behavior of Zn2+ lies between those of Ce3+ and Ga3+. On the other hand, in spite of the decrease in the in vitro response of B_BG by substitution, the glasses show HCA formation after 15 days of soaking. In addition, an increase in substitution of zinc accelerated the formation of HCA along with the formation of the mixed phase CaZn2(PO4)2·2H2O (scholzite) acting as nucleating agent for HCA. Moreover, the therapeutic effect of optimum Zn released as an ionic dissolution product from Zn-glasses could be beneficial to stimulate osteogenesis.

Silica–polyethylene glycol hybrids synthesized by sol–gel: Biocompatibility improvement of titanium implants by coating

Although metallic implants are the most used in dental and orthopaedic fields, they can early fail due to low tissue tolerance or osseointegration ability. To overcome this drawback, functional coatings can be applied on the metallic surface to provide a firm fixation of the implants. The objective of the present study was twofold: to synthesize and to characterize silica/polyethylene glycol (PEG) hybrid materials using sol-gel technique and to investigate their capability to dip-coat titanium grade 4 (Ti-gr4) substrates to improve their biological properties. Various hybrid systems have been synthesized by changing the ratio between the organic and inorganic phases in order to study the influence of the polymer amount on the structure and, thus, on the properties of the coatings. Fourier transform infrared (FTIR) spectroscopy and solid state Nuclear Magnetic Resonance (NMR) allowed us to detect the formation of hydrogen bonds between the inorganic sol-gel matrix and the organic component. SEM analysis showed that high PEG content enables to obtain crack free-coating. Moreover, the effective improvement in biological properties of Ti-gr4 implants has been evaluated by performing in vitro tests. The bioactivity of the hybrid coatings has been showed by the hydroxyapatite formation on the surface of SiO2/PEG coated Ti-gr4 substrates after soaking in a simulated body fluid and the lack of cytotoxicity by the WST-8 Assay. The results showed that the coated substrates are more bioactive and biocompatible than the uncoated ones and that the bioactivity is not significantly affected by PEG amount whereas its addition makes the films more biocompatible.

Synthesis of zirconia/polyethylene glycol hybrid materials by sol–gel processing and connections between structure and release kinetic of indomethacin

Abstract Controlled and local drug delivery systems of anti-inflammatory agents are attracting an increasing attention because of their extended therapeutic effect and reduced side effects. In this work, the sol–gel process was used to synthesize zirconia/polyethylene glycol (ZrO2/PEG) hybrid materials containing indomethacin for controlled drug delivery. Different percentages of PEG were introduced in the synthesis to modulate the release kinetic and an exhaustive chemical characterization of all samples was performed to detect the relationship between their structure and release ability. Fourier transform spectroscopy and solid-state NMR show that the Zr–OH groups of the inorganic matrix bond both the ethereal oxygen atoms of the polymer and the carboxylic groups of the drug. X-ray diffraction analysis ascertains the amorphous nature of those materials. Scanning electron microscopy detects the nanostructure and the homogeneous morphology of the synthesized materials. The bioactivity was demonstrated by the formation of a hydroxyapatite layer on the surface of the samples, after soaking in a simulated body fluid. The release kinetics study, performed by HPLC UV–Vis spectroscopy, proves that the release ability depends on PEG and the drug amount and also demonstrates the indomethacin integrity after the synthetic treatment.

Preparation and Physicochemical Characterization of Acyclovir Cocrystals with Improved Dissolution Properties

Acyclovir is a well-known antiviral agent. It can be administered in very high doses (from 200 to 1000 mg even three-four times daily). It has absorption problems mainly due to its poor solubility in water (about 0.2 g/100 mL at 25°C) and its oral bioavailability is approximately 15%-20% with a half-life of about 3 h. To improve acyclovir solubility and/or its dissolution properties, two cocrystals of this drug were successfully produced with glutaric acid (AGA1:1) and fumaric acid (AFA1:1) as conformers, using a cogrinding method. Their effective formation was investigated by a broad range of techniques: thermal analysis, Fourier transform infrared spectroscopy, X-ray powder diffraction, solid state nuclear magnetic resonance, and scanning electron microscopy coupled with energy dispersive X-ray spectrometry. The water solubility of the AGA1:1 cocrystal was not improved in comparison to acyclovir, while AFA1:1 showed a slight increased solubility at equilibrium. The main difference was detected in terms of intrinsic dissolution rates (IDR). The IDR of the new phases were much faster compared with acyclovir, particularly at neutral pH. AFA1:1 showed the most rapid dissolution behavior in water; within 10 min, the drug was released completely, while just 60% of acyclovir was dissolved in 1 h.

Vacancy and interstitial oxide ion migration in heavily doped La2−xSrxCoO4±δ

La2−xSrxCoO4±δ, a K2NiF4-type structured oxide, is currently under investigation for its possible application as a cathode material in solid oxide fuel cells operating at intermediate temperature (IT-SOFCs). Here we report a combined energy minimization and molecular dynamics study of oxygen migration mechanisms in the La2−xSrxCoO4±δ material for high Sr levels (x > 0.8). In the oxygen-deficient composition La0.8Sr1.2CoO3.9 the oxide-ion transport mainly occurs through the migration of oxygen vacancies within the perovskite layer of the structure, with possible vacancy paths between adjacent layers. In the oxygen-rich composition La1.2Sr0.8CoO4.1 interstitial oxygen transport is via an interstitialcy mechanism and within the ab plane.

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.

Average versus local structure in K2NiF4-type LaSrAlO4: direct experimental evidence of local cationic ordering

The long-range ordering of a crystalline material can be accurately determined by analyzing the Bragg intensities and positions. In contrast, direct observation of short-range ordering in crystalline materials, which is increasingly considered of fundamental importance to unravel the structure–property relationships that underpin their technological applications, is a challenging task. In this study we have investigated the structure of LaSrAlO4, a representative example of compounds with the K2NiF4-type structure. By the combined use of synchrotron and neutron diffraction, pair distribution function analysis, 27Al MQMAS NMR and atomistic simulations we have highlighted differences between the average and local structure of this material, directly determining the existence of at least two distinct Al sites. The results presented in this study confirm that La and Sr are, on average, randomly distributed throughout the structure, but demonstrate that the situation is considerably more complex at the short range.

Operando electrochemical NMR microscopy of polymer fuel cells

The design of high-temperature polymer fuel cells (PEMFCs), e.g. those expected for automotive applications, requires a deep understanding of the electrochemical reactions occurring in the device during operation. Operando electrochemical nuclear magnetic resonance microscopy can constitute a powerful investigation tool to this aim. At present, however, some strong technical limitations, like low sensitivity to less mobile protons, and the limited temperature range of analysis, have bound its use to case models based on perfluorinated membranes operating at high relative humidity and low temperature. By means of a suitable design of the experimental set-up and the use of a new 3D acquisition protocol, we proved the feasibility of electrochemical NMR microscopy on low-water containing polybenzimidazole-based devices, thus allowing full operando characterization of high-temperature PEMFCs, and also paving the way for applications to other electrochemical devices, such as batteries, sensors, supercapacitors, etc.

Aqueous Processing of Na0.44MnO2 Cathode Material for the Development of Greener Na-Ion Batteries

The implementation of aqueous electrode processing of cathode materials is a key for the development of greener Na-ion batteries. Herein, the development and optimization of the aqueous electrode processing for the ecofriendly Na0.44MnO2 (NMO) cathode material, employing carboxymethyl cellulose (CMC) as binder, are reported for the first time. The characterization of such an electrode reveals that the performances are strongly affected by the employed electrolyte solution, especially, the sodium salt and the use of electrolytes additives. In particular, the best results are obtained using the 1 M solution of NaPF6 in EC/DEC (ethylene carbonate/diethyl carbonate) 3:7 (v/v) + 2 wt % FEC (fluoroethylene carbonate). With this electrolyte, the outstanding capacity of 99.7 mA h g-1 is delivered by the CMC-NMO cathode after 800 cycles at a 1C charge/discharge rate. On the basis of this excellent long-term performance, a full sodium cell, composed of a CMC-based NMO cathode and hard carbon from biowaste (corn cob), has been assembled and tested. The cell delivers excellent performances in terms of specific capacity, capacity retention, and long-term cycling stability. After 75 cycles at a C/5 rate, the capacity of the NMO in the full-cell approaches 109 mA h g-1 with a Coulombic efficiency of 99.9%.