Enhancing CaP Biomimetic Growth on TiO₂ Cuboids Nanoparticles via Highly Reactive Facets

Pure decahedral anatase TiO₂ particles with high content of reactive {001} facets were obtained from titanium­(IV) tetrachloride (TiCl₄) using a microemulsions droplet system at specific conditions as chemical microreactor. The product was systematically characterized by X-ray diffraction, field-emission scanning and transmission electron microscopy (FE-SEM, TEM), N₂ adsorption–desorption isotherms, FT-IR and UV–vis spectroscopy, and photoluminescence studies. The obtained cuboids around 90 nm in size have a uniform and dense surface morphology with a BET specific surface area of 11.91 m² g^–1 and a band gap energy (3.18 eV) slightly inferior to the anatase dominated by the less-reactive {101} surface (3.20 eV). The presence of reactive facets on titania anatase favors the biomimetic growth of amorphous tricalcium phosphate after the first day of immersion in simulated human plasma. The results presented here can facilitate and improve the integration of anchored implants and enhance the biological responses to the soft tissues

Effect of Ionization on the Behavior of <i>n</i>‑Eicosanephosphonic Acid Monolayers at the Air/Water Interface. Experimental Determinations and Molecular Dynamics Simulations

Monolayers of <i>n</i>-eicosanephosphonic acid, EPA, were studied using a Langmuir balance and a Brewster angle microscope at different subphase pH values to change the charge of the polar headgroups (<i>Z</i>_av) from 0 to −2. Molecular dynamics simulations (MDS) results for |<i>Z</i>_av| = 0, 1, and 2 were compared with the experimental ones. EPA monolayers behave as mixtures of mutually miscible species (C₂₀H₄₁–PO₃H₂, C₂₀H₄₁–PO₃H^–, and C₂₀H₄₁–PO₃^2–, depending on the subphase pH). The order and compactness of the monolayers decrease when increasing |<i>Z</i>_av|, while go from strongly interconnected by phosphonic–phosphonic hydrogen bonds (|<i>Z</i>_av| = 0–0.03) through an equilibrium between the total cohesive energy and the electrostatic repulsion between the charged polar groups (0.03 < |<i>Z</i>_av| < 1.6) to an entirely ionic monolayer (|<i>Z</i>_av| ≈ 2). MDS reveal for |<i>Z</i>_av| = 0 that the chains form spiralled nearly rounded structures induced by the hydrogen-bonded network. When |<i>Z</i>_av| ≈ 1 fingering domains were identified. When <i>Z</i> ≈ 2, the headgroups are more disordered and distanced, not only in the <i>xy</i> plane but also in the <i>z</i> direction, forming a rough layer and responding to compression with a large plateau in the isotherm. The monolayers collapse behavior is consistent with the structures and domains founds in the different ionization states and their consequent in-plane rigidity: there is a transition from a solid-like response at low pH subphases to a fluid-like response at high pH subphases. The film area in the close-packed state increases relatively slow when the polar headgroups are able to form hydrogen bonds but increases to near twice that this value when |<i>Z</i>_av| ≈ 2. Other nanoscopic properties of monolayers were also determined by MDS. The computational results confirm the experimental findings and offer a nanoscopic perspective on the structure and interactions in the phosphonate monolayers