Changes to the Disordered Phase and Apatite Crystallite Morphology during Mineralization by an Acidic Mineral Binding Peptide from Osteonectin

Noncollagenous proteins regulate the formation of the mineral constituent in hard tissue. The mineral formed contains apatite crystals coated by a functional disordered calcium phosphate phase. Although the crystalline phase of bone mineral was extensively investigated, little is known about the disordered layer’s composition and structure, and less is known regarding the function of noncollagenous proteins in the context of this layer. In the current study, apatite was prepared with an acidic peptide (ON29) derived from the bone/dentin protein osteonectin. The mineral formed comprises needle-shaped hydroxyapatite crystals like in dentin and a stable disordered phase coating the apatitic crystals as shown using X-ray diffraction, transmission electron microscopy, and solid-state NMR techniques. The peptide, embedded between the mineral particles, reduces the overall phosphate content in the mineral formed as inferred from inductively coupled plasma and elemental analysis results. Magnetization transfers between disordered phase species and apatitic phase species are observed for the first time using 2D ¹H–³¹P heteronuclear correlation NMR measurements. The dynamics of phosphate magnetization transfers reveal that ON29 decreases significantly the amount of water molecules in the disordered phase and increases slightly their content at the ordered-disordered interface. The peptide decreases hydroxyl to disordered phosphate transfers within the surface layer but does not influence transfer within the bulk crystalline mineral. Overall, these results indicate that control of crystallite morphology and properties of the inorganic component in hard tissue by biomolecules is more involved than just direct interaction between protein functional groups and mineral crystal faces. Subtler mechanisms such as modulation of the disordered phase composition and structural changes at the ordered–disordered interface may be involved

Millimeter-Tall Carpets of Vertically Aligned Crystalline Carbon Nanotubes Synthesized on Copper Substrates for Electrical Applications

We synthesized millimeter-tall, dense carpets of crystalline CNTs on nonpolished copper substrates with a thin Al₂O₃ (below 10 nm) underlayer and Fe (1.2 nm) layer as a catalyst using chemical vapor deposition (CVD). Preheating of the hydrocarbon precursor gases and in-situ formation of controlled amounts of water vapor were critical process parameters. High-resolution microscopy showed that the CNTs were crystalline with lengths up to a millimeter. Electrical conduction between the CNTs and the copper substrate was demonstrated using multiple methods (probe station, electrodeposition, and hydrolysis of water). Through TEM characterizations of cross sections, we demonstrated that copper diffusion into the alumina layer during the thermal process was the key to explain the observed electrical conductivity. Additionally, the high electrical conductivity of a thermally processed sample compared to the insulating behavior of a pristine sample confirmed the mechanistic hypothesis. Adsorption isotherm measurements showed the mesoporous structure of the vertically aligned carbon nanotubes (VACNTs) with a surface area of 342 m²/g. Electrical conduction and high surface area of this nanostructure make it a promising platform to be functionalized for future battery electrodes

Electrochemical Performance of a Layered-Spinel Integrated Li[Ni_1/3Mn_2/3]O₂ as a High Capacity Cathode Material for Li-Ion Batteries

Li­[Ni_1/3Mn_2/3]­O₂ was synthesized by a self-combustion reaction (SCR), characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy, and studied as a cathode material for Li-ion batteries at 30 °C and 45 °C. The structural studies by XRD and TEM confirmed monoclinic Li­[Li_1/3Mn_2/3]­O₂ phase as the major component, and rhombohedral (LiNiO₂), spinel (LiNi_0.5Mn_1.5O₄), and rock salt Li_0.2Mn_0.2Ni_0.5O as minor components. The content of the spinel phase increases upon cycling due to the layered-to-spinel phase transition occurring at high potentials. A high discharge capacity of about 220 mAh g^–1 is obtained at low rate (C/10) with good capacity retention upon cycling. However, LiNi_0.5Mn_1.5O₄ synthesized by SCR exhibits a discharge capacity of about 190 mAh g^–1 in the potential range of 2.4–4.9 V, which decreases to a value of 150 mAh g^–1 after 100 cycles. Because of the presence of the spinel component, Li­[Ni_1/3Mn_2/3]­O₂ cathode material exhibits part of its capacity at potentials around 4.7 V. Thus, it can be considered as an interesting high-capacity and high-voltage cathode material for high-energy-density Li-ion batteries. Also, the Li­[Ni_1/3Mn_2/3]­O₂ electrodes exhibit better electrochemical stability than spinel LiNi_0.5Mn_1.5O₄ electrodes when cycled at 45 °C