Lithium-rich transition-metal-oxide cathodes are among the most promising materials for the next lithium-ion-batteries generation because they operate at high voltages and deliver high capacities. However, their cycle-life remains limited and individual roles of the transition-metals are still not fully understood. By bulk-sensitive X-ray absorption and emission spectroscopy on Li[Li 0.2 Ni 0.16 Mn 0.56 Co 0.08 ]O 2 we inspect the behavior of Mn, generally considered inert upon the electrochemical process. During the first charge Mn appears to be redox-active showing a partial transformation from high-spin Mn 4+ to Mn 3+ in both high and low spin configurations, where the latter is expected to favor reversible cycling. The Mn redox-state along cycling continues changing in opposition to the expected charge compensation and is correlated with Ni oxidation/reduction, also spatially. The findings suggest the strain induced on the Mn-O sublattice by the Ni oxidation to trigger the Mn reduction. These results unravel the Mn role in controlling the electrochemistry of Li-rich cathodes. The wide use of rechargeable lithium-ion batteries and the continuously growing demands of increased energy and power densities stimulate the investigation of novel high-voltage cathode materials. 1, 2 Lithiated transition-metal-oxides are under intensive investigation as cathode materials for Li-ion batteries. The best performing cathodes show an ordered layered structure, which locates the Li ions in between the metal-oxygen layers. 3, 4 Generally these materials offer the best cycle life when the layered structure is maintained during the delithiation/lithiation process. Among Mn, Co, and Ni, only Co 3+ and Ni 3+ enable 2D layered Li-based oxides. LiNiO 2 , however, has various drawbacks related to its crystal structure: difficulty to be synthesized, poor cycling performance, and poor thermal stability. 5 As a matter of fact, LiCoO 2 is the 2D layered oxide showing the best electrochemical performance and the most commonly used material in Li-ion batteries 6. The
The synthesis, characterization and assessment of the antibacterial properties of hydrophilic silver nanoparticles (AgNPs) were investigated with the aim to probe their suitability for innovative applications in the field of nanobiotechnology. First, silver nanoparticles were synthetized and functionalized with two capping agents, namely 3-mercapto-1-propansulfonate (3MPS) and 1-β-thio-d-glucose (TG). The investigation of the structural and electronic properties of the nano-systems was carried out by means of X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Spectroscopy (XAS). XPS data provided information about the system stability and the interactions between the metallic surface and the organic ligands. In addition, XPS data allowed us to achieve a deep understanding of the influence of the thiols stoichiometric ratio on the electronic properties and stability of AgNPs. In order to shed light on the structural and electronic local properties at Ag atoms sites, XAS at Ag K-Edge was successfully applied; furthermore, the combination of Dynamic Light Scattering (DLS) and XAS results allowed determining AgNPs sizes, ranging between 3 and 13 nm. Finally, preliminary studies on the antibacterial properties of AgNPs showed promising results on four of six multidrug-resistant bacteria belonging to the ESKAPE group (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter sp.).
We report the ligand-exchange-induced transformation from an icosahedral Au 25 (SR) 18 cluster (where SR = 2-phenylethanethiol (PET)) to a bitetrahedral Au 22 (SR) 4 (SR′) 14 cluster (where SR′ = 4-tert-butylbenzenethiol (TBBT)). This partial exchange of the ligands was achieved by controlling the concentration of the incoming TBBT ligand. Being a bulky and aromatic ligand, TBBT can efficiently distort the atomic structure of the Au 25 PET 18 cluster, resulting in Au 22 (PET) 4 (TBBT) 14 , which is highly stable and considered to be an intermediate with a bitetrahedral structure. Time-dependent mass spectrometry and optical spectroscopy revealed the dissociation of the parent cluster and gave a deep insight on the ligand-exchange mechanism. Theoretical calculations and extended Xray absorption fine structure studies confirm the formation of the Au 22 structure. Identifying the atomic structure of the intermediate species opens a new avenue to study the transformation of one cluster to another.
Bis(pyrazol-1-yl)- and bis(3,5-dimethylpyrazol-1-yl)-acetates were conjugated with the 2-hydroxyethylester and 2-aminoethylamide derivatives of the antineoplastic drug lonidamine to prepare Cu(I) and Cu(II) complexes that might act through synergistic mechanisms of action due to the presence of lonidamine and copper in the same chemical entity. Synchrotron radiation-based complementary techniques [X-ray photorlectron spectroscopy and near-edge X-ray absorption fine structure (NEXAFS)] were used to characterize the electronic and molecular structures of the complexes and the local structure around the copper ion (XAFS) in selected complexes. All complexes showed significant antitumor activity, proving to be more effective than the reference drug cisplatin in a panel of human tumor cell lines, and were able to overcome oxaliplatin and multidrug resistance. Noticeably, these Cu complexes appeared much more effective than cisplatin against 3D spheroids of pancreatic PSN-1 cancer cells; among these, PPh 3 -containing Cu(I) complex 15 appeared to be the most promising derivative. Mechanistic studies revealed that 15 induced cancer cell death by means of an apoptosis-alternative cell death.
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