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The biogenic hydroxyapatite (BHAP), obtained by proper treatment of bovine bones, was functionalized with 5-aminosalicylic acid (5-ASA). The coordination of 5-ASA to the surface of 2 BHAP leads to the charge transfer (CT) complex formation accompanied with absorption in visible spectral range. The sorption ability of surface-modified BHAP with 5-ASA (5-ASA/BHAP) for removal of Pb 2+ and Cu 2+ ions from single-and bi-component solutions was compared with unmodified BHAP. The thorough characterization of both sorbents, BHAP and 5-ASA/BHAP, was performed including X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), nitrogen adsorption-desorption isotherms, as well as diffuse reflection spectroscopy. Sorption kinetics and equilibriums for both ions (Pb 2+ and Cu 2+ ) by as-prepared BHAP and 5-ASA/BHAP are quite different. Functionalized sorbent demonstrated faster sorption kinetic and higher maximum sorption capacity for Pb 2+ ions from bi-component solutions. From equimolar Pb 2+ and Cu 2+ mixture with a total concentration of 10 -2 mol/L, 66% of Pb 2+ was recovered using BHAP, while 97% using 5-ASA/BHAP. These preliminary data indicate potential applicability of properly functionalized hydroxyapatite for selective removal of heavy metal ions from contaminated water.

Surface modification of Al 2 O 3 powders, prepared using reproducible sol-gel synthetic route with small colorless organic molecules, induces charge transfer complex formation and the appearance of absorption in the visible spectral region. Comprehensive microstructural characterization involving transmission electron microscopy, X-ray diffraction analysis, and nitrogen adsorptiondesorption isotherms, revealed that γ-crystalline alumina powders consist of mesoporous particles

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Cerium dioxide (CeO 2 ) finds applications in areas such as corrosion protection, solar cells, or catalysis, finding increasing applications in biomedicine. This work reports on surface-modified CeO 2 particles in order to tune their applicability in the biomedical field. Stable aqueous CeO 2 sol, consisting of 3−4 nm in size crystallites, was synthesized using forced hydrolysis. The coordination of catecholate-type of ligands (catechol, caffeic acid, tiron, and dopamine) to the surface-Ce atoms is followed with the appearance of absorption in the visible spectral range as a consequence of interfacial charge-transfer complex formation. The spectroscopic observations are complemented with the density functional theory calculations using a cluster model. The synthesized samples were characterized by X-ray diffraction analysis, transmission electron microscopy, and nitrogen adsorption− desorption isotherms. The ζ-potential measurements indicated that the stability of CeO 2 sol is preserved upon surface modification. The pristine CeO 2 nanoparticles (NPs) are nontoxic against pre-osteoblast cells in the entire studied concentration range (up to 1.5 mM). Hybrid CeO 2 NPs, capped with dopamine or caffeic acid, display toxic behavior for concentrations ≥0.17 and 1.5 mM, respectively. On the other hand, surface-modified CeO 2 NPs with catechol and tiron promote the proliferation of pre-osteoblast cells.