Hydroxylapatite amphiphilic nano-sheets for photocatalysis

The starting point was Hydroxyapatite (Hap) nanoparticles, which were functionalized through an acid-base reaction with lauric, caprylic, oleic and stearic acids, changing the polarity by anchoring as carboxylates to the surface of the particles, but not their crystalline structure. Analysis by thermogravimetry and differential scanning calorimetry, allow reporting the degree of coverage of the surface by the carboxylates of the studied acids, and their decomposition reaction enthalpies, which are related to the length of the acid chain, and its assembly on the surface. In addition, it was found that this reaction generated an ordering, which in the case of hybrid materials based on shorter chain acids such as lauric and caprylic, indicates not only the formation of a motif of regular size, but also an ordering Newspaper. This was determined by grazing beam X-ray diffraction, and high resolution transmission microscopy. A change in the polarity of the hydrophobic material was produced, resulting from the reaction with the carboxylic acids, through re-suspension with a dispersing agent such as Tetrabutylammonium hydroxide (TBA). A higher degree of complexity is introduced, which affects the ordering for materials based on lauric and caprylic acid. Finally, a more intense treatment in TBA, destroys the hydrophobic interactions, favors the hydrophilic ones, but nevertheless in one of the cases, in the case where the hydrophobic interactions were stronger, with the functionalization with stearic acid, the order is transmitted, through a kind of template effect, to the final material. This behavior material assembled from Hap was also modified through the exchange of Ca^+₂ ions of Hap for Ag⁺₁ ions, which enhances its photocatalytic activity under UV radiation, showing how these materials could be part of complex photocatalysis systems, since they are capable of absorbing organic dyes, as well as Ag⁺ ions, due to their hybrid characteristics. (author)