Marc Estruga

Zirconium-doped and silicon-doped tio2 photocatalysts synthesis from ionic-liquid-like precursors

Nanocrystalline titania powders doped with either zirconium or silicon were synthesized at low temperature via destabilization of ionic-liquid-like precursors. Titania materials prepared at low temperature (85 degrees C) consisted of anatase nanocrystals of about 25 nm, according to powder X-ray diffraction and transmission electron microscopy. Dopant incorporation was evaluated using inductively coupled plasma-optical emission spectrometry, and it was found that dopant/titanium ratios in the powder (0.011 for Zr and 0.026 for Si) were lower than those in the precursor (0.11 for both). Low-temperature nitrogen adsorption-desorption isotherms displayed the characteristic hysteresis loop of mesoporous materials. Specific surface areas reached values of 130 and 155 m(2) g(-1) for Zr-doped and Si-doped TiO(2), respectively. The photocatalytic activity of the synthesized nanopowders was tested using methyl orange and 4-chlorophenol as target pollutants.

Low temperature N,N-dimethylformamide-assisted synthesis and characterization of anatase–rutile biphasic nanostructured titania

Anatase and rutile biphasic nanostructured titania (TiO(2)) has been synthesized via hydrolysis of titanium tetraisopropoxide in an aqueous solution of hydrobromic acid (HBr) and N,N-dimethylformamide (DMF) at 80 degrees C for 16 h. The presence of DMF, which was partially hydrolyzed during the process, determined the formation of a biphasic material. Powder x-ray diffraction showed the presence of both anatase and rutile titania phases in a ratio of approx. 1:1. Transmission electron microscope analysis showed that rutile was present as radial flower-like nanorods, which were surrounded by anatase spherical nanoparticles of 5 nm diameter. Low temperature nitrogen adsorption-desorption analysis showed the characteristic hysteresis loop of a mesoporous material. Specific surface area reached a value of 120 m(2) g(-1) and the average pore diameter was 50 A. X-ray photoelectron spectroscopic analysis revealed that interstitial nitrogen was incorporated (0.35 at.%) during the annealing process. According to ultraviolet (UV)-visible diffuse reflectance spectroscope characterization, the N-doping caused a bandgap reduction from 3.0 to 2.9 eV. Photocatalytic activity of the material was tested for the degradation of methylene blue, methyl orange and 4-nitrophenol under near-UV and visible light radiation.

Solution-processable ZnO nanoparticles obtained by low-temperature solventless synthesis

Carboxylate-capped zinc oxide nanoparticles are produced by a simple user-friendly solventless route. ZnO precursors are obtained by the intimate mixing of zinc acetate dihydrate and a carboxylic acid. Subsequent thermal treatment of the solid precursor at low temperature (90–120 °C) for 30–148 h leads to the elimination of the acetate as acetic acid and yields carboxylate-coated crystalline ZnO nanoparticles. The method gives excellent results with a great variety of acids, such as benzoic acid, phenylacetic acid, phenylvaleric acid or long chain carboxylic acids (f.i., lauric and 3,6,9-trioxadecanoic acids). The chemical structure of the carboxylic acid tail significantly determines several properties of the powdered nanocrystalline ZnO material, such as the morphology of the aggregates and their dispersibility in common solvents. Further, the easiness of the method to produce colloidal suspensions facilitates thin film deposition. Finally, deposited laurate-capped ZnO can be transformed into pure ZnO by short-time (15 min) UV light treatment.