Hexagonal manganites, RMnO3 (R = Sc, Y, Ho-Lu), can reversibly store and release large quantities of oxygen at temperatures in the range of 150–400 °C. The oxygen storage properties can be tuned by combining different R 3+ cations, aliovalent dopants, and crystallite sizes in the nanometer range. Here, we study the oxygen absorption of nanocrystalline RMn1–x Ti x O3 (R = Y, Ho, Dy; x = 0, 0.15) using thermogravimetric analysis (TGA) and high-temperature X-ray diffraction (HT-XRD) in O2 and N2 atmospheres. The maximum oxygen storage capacity increases from R = Y through Ho and Dy and even further with Ti4+ as a donor dopant. Density functional theory (DFT) calculations show that the observed trends in oxygen absorption capacity are correlated with the enthalpy of oxidation and the lattice parameters. Ti4+ also increases the thermal stability of absorbed oxygen and thereby extends the operation range to higher temperatures where the absorption and desorption kinetics are faster. Reducing the size of the crystallites improves the oxygen storage capacity as well as the absorption kinetics due to shorter diffusion distances. Finally, a thermodynamic model for the oxidation of RMnO3 is presented and fitted to TGA data and the implications for the microscopic understanding of the oxidation process are discussed.

Chemotherapy treatment usually involves the delivery of fluorouracil (5-Fu) together with other drugs through central venous catheters. Catheters and their connectors are increasingly treated with silver or argentic alloys/compounds. Complications arising from broken catheters are common, leading to additional su↵ering for patients and increased medical costs. Here, we uncover a likely cause of such failure through a study of the surface chemistry relevant to chemotherapy drug delivery, i.e. between 5-Fu and silver. We show that silver catalytically decomposes 5-Fu, compromising the e cacy of the chemotherapy treatment. Furthermore, HF is released as a product, which will be damaging to both patient and catheter. We demonstrate that graphene surfaces inhibit this undesirable reaction and would o↵er superior performance as nanoscale coatings in cancer treatment applications.

This study demonstrates the application of Al2O3 coatings for the high-voltage cathode material LiNi0.5–x Mn1.5+x O4−δ (LNMO) by atomic layer deposition. The ultrathin and uniform coatings (0.6–1.7 nm) were deposited on LNMO particles and characterized by scanning transmission electron microscopy, inductively coupled plasma mass spectrometry, and X-ray photoelectron spectroscopy. Galvanostatic charge discharge cycling in half cells revealed, in contrast to many published studies, that even coatings of a thickness of 1 nm were detrimental to the cycling performance of LNMO. The complete coverage of the LNMO particles by the Al2O3 coating can form a Li-ion diffusion barrier, which leads to high overpotentials and reduced reversible capacity. Several reports on Al2O3-coated LNMO using alternative coating methods, which would lead to a less homogeneous coating, revealed the superior electrochemical properties of the Al2O3-coated LNMO, suggesting that complete coverage of the particles might in fact be a disadvantage. We show that transition metal ion dissolution during prolonged cycling at 50 °C is not hindered by the coating, resulting in Ni and Mn deposits on the Li counter electrode. The Al2O3-coated LNMO particles showed severe signs of pitting dissolution, which may be attributed to HF attack caused by side reactions between the electrolyte and the Al2O3 coating, which can lead to additional HF formation. The pitting dissolution was most severe for the thickest coating (1.7 nm). The uniform coating coverage may lead to non-uniform conduction paths for Li, where the active sites are more susceptible to HF attack. Few benefits of applications of very thin, uniform, and amorphous Al2O3 coatings could thus be verified, and the coating is not offering long-term protection from HF attack.

TiO 2 -coating of LiNi 0.5-x Mn 1.5 + x O 4 (LNMO) by atomic layer deposition (ALD) has been studied as a strategy to stabilize the cathode/electrolyte interface and mitigate transition metal (TM) ion dissolution. The TiO 2 coatings were found to be uniform, with thicknesses estimated to 0.2, 0.3, and 0.6 nm for the LNMO powders exposed to 5, 10, and 20 ALD cycles, respectively. While electrochemical characterization in half-cells revealed little to no improvement in the capacity retention neither at 20 nor at 50 °C, improved capacity retention and coulombic efficiencies were demonstrated for the TiO 2 -coated LNMO in LNMO j j graphite full-cells at 20 °C. This improvement in cycling stability could partly be attributed to thinner cathode electrolyte interphase on the TiO 2 -coated samples. Additionally, energy-dispersive X-ray spectroscopy revealed a thinner solid electrolyte interphase on the graphite electrode cycled against TiO 2 -coated LNMO, indicating retardation of TM dissolution by the TiO 2 -coating.

The degradation of the chemotherapy drug 5-Fluorouracil by a non-pristine metal surfaces is studied. Using Density Functional Theory, X-ray Photoelectron Spectroscopy and X-ray Absorption Spectroscopy we show that the drug is entirely degraded by medicalgrade silver surfaces, already at body temperature, and that all of the fluorine has left the molecule, presumably as HF. Remarkably, this degradation is even more severe than that reported previously for 5-Fluorouracil on a pristine monocrystalline silver surface (in which case 80% of the drug reacted at body temperature)[1]. We conclude that that the observed reaction is due to a reaction pathway, driven by H to F attraction between molecules on the surface, which results in the direct formation of HF; a pathway which is favoured when competing pathways involving reactive Ag surface sites are made unavailable by environmental contamination. Our measurements indicate that realistically cleaned, non-pristine silver alloys, which are typically used in medical applications, can result in severe degradation of 5-Fluorouracil, with the release of HF-a finding which may have important implications for the handling of chemotherapy drugs.