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Thermal oxidation of Na-cholate hydrate at 300 °C in air results in a carbonaceous solid (SC-30) nanomaterial bearing a steroid interior and a significant fraction of carboxylate sites. Electron Paramagnetic Resonance spectroscopy reveals that SC-30 bears a significant concentration of stable C-based radicals located at the interior of the steroid carbonaceous matrix. H-binding, determined by potentiometric acid-base titrations show that the SC-30 contains three types of H-binding sites. One type with p Ka = 4.2 corresponds to surfacial metal-binding COOH groups. A second type of sites with p Ka = 6.2 corresponds to COOH buried at the interior of the SC-30 carbon matrix, which are inactive in metal binding. A third type with p Ka = 8.5-is also inactive in metal binding-originates from aggregated stacked-states like those observed for cholate in solution. The surfacial COO carboxylate groups, confer the solid hydrophilic character, therefore it can be easily dispersed in water at high concentrations providing clear aqueous colloids. pH-edge metal uptake experiments and Surface Complexation Modelling show that SC-30 is an efficient heavy metal adsorbent in aqueous solution for Pb and Cu ions at pH 5-8. A structural/functional model is discussed based on the heterogeneous character of the SC-30 material. [ABSTRACT FROM AUTHOR]

The article discusses a study on nanodiamonds and the fabrication of fluorescent nanodiamond at C core-shell hybrids through moderate carbonization of nanodiamond sodium cholate. The study used fluorescence spectroscopy to examine the fabrication of a core-shell hybrid obtained by the wetimpregnation of NDs with sodium cholate and subsequent mild pyrolysis in air. Result shows that a novel core-shell hybrid was synthesized by the solid-state pyrolysis.

The solid-state pyrolysis of acetylenedicarboxylic acid, monopotassium salt at 300 °C in air results in bulk quantities of a micron-sized yet macroporous oxidized carbon, which inherently possesses high content of metal-binding sites, such as carboxylate groups, free radicals, and ether/hydroxyl units. Besides its high oxygen content, the solid is stable in water and does not leach or disorient, while it also exhibits an appreciable thermal stability, at temperature exceeding 200 °C in air. Several techniques including TEM/SEM, TGA, Raman/FT-IR, XPS, EPR, and potentiometric titrations were employed for the characterization of the solid. Furthermore, liquid phase adsorption experiments revealed that the material is an efficient heavy metal adsorbent due to the presence of diverse surface-accessible binding sites, showing unusually high metal uptake capacities for Pb and Cu ions (ca. 4.5 mmol g). [ABSTRACT FROM AUTHOR]

Metallic silver nanoparticles were prepared by the sol-gel method in an SiO2 matrix. The process includes complexation of silicon alkoxides with metal salts, hydrolysis, polycondensation, formation of powder, and subsequent thermal treatment first in oxidizing and second in reducing atmospheres. The sizes of metallic particles were determined both by X-ray diffraction and transmission electron microscopy. These measurements revealed sizes of metallic particles between 1 and 20 nm, depending upon processing conditions. The magnetic properties were investigated using electron paramagnetic resonance spectroscopy in the temperature range between 4 and 300 K. The spin-lattice relaxation time T1 was measured by pulsed EPR. The temperature dependence of T1 is described by the relation 1/T1 ∝ Tn, where 0.4 < n < 1. This behavior is unusual and different from any well-known relaxation processes such as Raman, Direct or the Orbach-Aminov. [ABSTRACT FROM AUTHOR]