Hydrothermal synthesis of euhedral Co3O4Co_{3}O_{4} nanocrystals via nutrient-assisted topotactic transformation of the layered Co(OH)2Co(OH)_{2} precursor under anoxic conditions : insights into intricate routes leading to spinel phase development and shape perfection

Euhedral cobalt spinel cubes, octahedra, and cuboctahedra with narrow size dispersions have been synthesized in a one-pot hydrothermal reaction, using cobalt(II) nitrate and sodium hydroxide at variable concentrations as the only reagents, while their ratio was kept constant at $c_{Co^2+}/c_{OH^–}$ = 2.7. Three main reaction stages, including parent reactive template (PRT) formation, nutrient mediated topotactic nucleation (NTN), and morphogenesis of nanocrystals (MNC), were distinguished. In the NTN step, the primary spinel grains development occurs with the [100] and [111] directions of the $Co_{3}O_{4}$ facets inheriting the [1-11] direction of the elongated PRT plates (formation of cubes) or the [001] direction of the hexagonal PRT plates (formation of octahedra). In an anoxic environment, the excess nitrate anions play a critical role as the $Co^{2+}$ to $Co^{3+}$ oxidants and oxygen donors required to attain the $Co_{3}O_{4}$ stoichiometry. The nucleated $Co_{3}O_{4}$ primary nanocrystals are spontaneously assembled into sub-micrometer spinel mesocrystals via imperfectly oriented attachments and then consolidated into euhedral bulk nanocrystals by a hydrothermal treatment (nanocubes) or via dissolution and reentrant recrystallization processes (octahedra and cuboctahedra)

Functionalization of graphenic surfaces by oxygen plasma toward enhanced wettability and cell adhesion : experiments corroborated by molecular modelling

Graphenic materials attract huge attention because of their outstanding properties, and have a wide range of applications as, i.e., components of biomaterials. Due to their hydrophobic nature, however, the surfaces need to be functionalized to improve wettability and biocompatibility. In this study, we investigate the functionalization of graphenic surfaces by oxygen plasma treatment, introducing surface functional groups in a controlled way. The AFM images and LDI-MS results clearly show that the graphenic surface exposed to plasma is decorated with -OH groups, whereas the surface topography remains intact. The measured water contact angle decreases significantly after oxygen plasma treatment from $99^{\circ}$ to ca. $5^{\circ}$, making the surface hydrophilic. It is also reflected in the surface free energy values which increase from 48.18 mJ $m^{−2}$ to 74.53 mJ $m^{−2}$ when the number of surface oxygen groups reaches 4 -OH/84 $Å^{2}$. The DFT (VASP) molecular models of unmodified and oxygen-functionalized graphenic surfaces were constructed and used for molecular interpretation of water-graphenic surface interactions. The computational models were validated by comparison of the theoretically determined water contact angle (based on the Young–Dupré equation) to the experimentally determined values. Additionally, the VASPsol (implicit water environment) results were calibrated against the explicit water models that can be used in further research. Finally, the biological role of functional groups on the graphenic surface was examined in terms of cell adhesion with the use of mouse fibroblast cell line (NIH/3T3). The obtained results illustrate the correlation between surface oxygen groups, wettability, and biocompatibility providing the guidelines for the molecular level-driven design of carbon materials for various applications

Into the Origin of Electrical Conductivity for the Metal-Semiconductor Junction at the Atomic Level

The metal-semiconductor (M-S) junction based devices are commonly used in all sorts of electronic devices. Their electrical properties are defined by the metallic phase properties with a respect to the semiconductor used. Here we make an in-depth survey on the origin of the M-S junction at the atomic scale by studying the properties of the AuIn2 nanoelectrodes formed on the InP(001) surface by the in situ electrical measurements in combination with a detailed investigation of atomically resolved structure supported by the first-principle calculations of its local electrical properties. We have found that a different crystallographic orientation of the same metallic phase with a respect to the semiconductor structure influences strongly the M-S junction rectifying properties by subtle change of the metal Fermi level and influencing the band edge moving at the interface. This ultimately changes conductivity regime between Ohmic and Schottky type. The effect of crystallographic orientation has to be taken into account in the engineering of the M-S junction-based electronic devices

Zirconium-based metal–organic frameworks as acriflavine cargos in the battle against coronaviruses : a theoretical and experimental approach

[Image: see text] In this study, we present a complementary approach for obtaining an effective drug, based on acriflavine (ACF) and zirconium-based metal–organic frameworks (MOFs), against SARS-CoV-2. The experimental results showed that acriflavine inhibits the interaction between viral receptor-binding domain (RBD) of spike protein and angiotensin converting enzyme-2 (ACE2) host receptor driving viral cell entry. The prepared ACF@MOF composites exhibited low (MOF-808 and UiO-66) and high (UiO-67 and NU-1000) ACF loadings. The drug release profiles from prepared composites showed different release kinetics depending on the local pore environment. The long-term ACF release with the effective antiviral ACF concentration was observed for all studied ACF@MOF composites. The density functional theory (DFT) calculations allowed us to determine that π–π stacking together with electrostatic interaction plays an important role in acriflavine adsorption and release from ACF@MOF composites. The molecular docking results have shown that acriflavine interacts with several possible binding sites within the RBD and binding site at the RBD/ACE2 interface. The cytotoxicity and ecotoxicity results have confirmed that the prepared ACF@MOF composites may be considered potentially safe for living organisms. The complementary experimental and theoretical results presented in this study have confirmed that the ACF@MOF composites may be considered a potential candidate for the COVID-19 treatment, which makes them good candidates for clinical trials

Spin-resolved NOCV analysis of the zeolite framework influence on the interaction of NO with Cu(I/II) sites in zeolites

In the present work the function of a zeolite framework in modifying the properties of copper sites has been studied. The [Al(OH)4CuNO]0/+ systems were studied by applying the analysis of the electron density flows – contributions to deformation density between two interacting fragments. The systems were divided in the following partition scheme: the first fragment, [Al(OH)4]− (tagged T1), and the second one, [CuNO]+/2+. The analysis allowed us to elucidate the function of the zeolite fragment in modification of the cation properties towards activating the NO molecule. For both [(T1)CuNO]0/+ systems several channels showing the role of the zeolite framework have been identified. The geometry of the adducts influences either the efficiency of the channels or spin polarization. The two most important channels, zeolites–cations, influence the flow of electrons between the copper site and the antibonding NO orbitals. One channel favors the π-backdonation in the plane perpendicular to the Cu–N–O plane while the other contribution influences the π-backdonation in the C–N–O plane. The first one is found only in the system with copper(I) and it is essential for facilitating the π-backdonation and activating the NO molecule. The second channel is spin sensitive for both copper(I) and copper(II) sites. In the case of the system with copper(I) the second channel favors the π-backdonation while in the system containing copper(II) the direction of these flows is opposite for α and β electrons