Silver nanoparticles with an average size of ∼5 nm were deposited on the surface of preformed silica
submicrospheres with the aid of power ultrasound. Ultrasound irradiation of a slurry of silica
submicrospheres, silver nitrate, and ammonia in an aqueous medium for 90 min under an atmosphere
of argon to hydrogen (95:5) yielded a silver−silica nanocomposite. By controlling the atmospheric and
reaction conditions, we could achieve the deposition of metallic silver on the surface of the silica spheres.
The resulting silver-deposited silica submicrosphere samples were characterized with X-ray diffraction,
transmission electron microscopy, differential scanning calorimetry, energy-dispersive X-ray analysis,
high-resolution transmission electron microscopy, high-resolution scanning electron microscopy, photoacoustic spectroscopy, and Fourier transform infrared, UV−visible, and X-ray photoelectron spectroscopy.
Shaped silver nanoparticles with spheres, rods, and dendrites have been prepared by a pulse sonoelectrochemical technique from an aqueous solution of AgNO3 in the presence of nitrilotriacetate N(CH2COOH)3-NTA. The silver nanoparticles were characterized by using transmission electron microscopy, X-ray diffraction, and absorption spectroscopy. The effects of electrosonic time on particle shape have been discussed. It was found that the concentration of AgNO3 and NTA affects the shape of the nanoparticles.
Nanoparticles of various dimensions of II-VI binary chalcogenides CdSe, PbSe, and Cu 2-x Se, have been prepared by a very simple fast reaction between acetates or sulfates of Cd, Pb, and Cu and Na 2 SeSO 3 in the presence of complexating agents, using microwave irradiation. The nanoparticles were analyzed by X-ray diffraction (XRD), electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS).
A novel method for shortening the synthesis time of mesoporous TiO 2 to 6 h is reported. Low-angle XRD and TEM showed that mesoporous TiO 2 with short-range ordered structures was synthesized when octadecylamine was used as a structure-directing agent and when Ti(OPr i ) 4 was used as a precursor. The highest surface area (853 m 2 g 21 ) was obtained after extraction with a dilute solution of nitric acid. The material maintained a high surface area (467 m 2 g 21 ) after calcination at 350 ³C, but the short-range ordered structures collapsed. XPS showed the interaction between TiO 2 and octadecylamine, while DSC, TGA, and FT-IR spectra showed the removal of octadecylamine by extraction and calcination. A mechanism for the fast formation of mesoporous TiO 2 is proposed. It is attributed to the formation of mesoporous material at high temperatures formed in the interface between the gas and bulk solutions resulting from ultrasound irradiation. Electrodes made from the mesoporous TiO 2 were tested in a dye-sensitized solar cell. The short-circuit photocurrent, open-circuit photovoltage and ®ll factor increased with an increase in the sintering temperature, having a performance threshold at 450 ³C, showing that the more ordered structures are required for high solar cell conversion ef®ciencies.
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