Agileo Hernández-Gordillo

Photoconversion of 4-nitrophenol in the presence of hydrazine with AgNPs-TiO2 nanoparticles prepared by the sol-gel method.

The photocatalytic properties of functionalized TiO2 with silver nanoparticles (AgNPs) for the conversion of 4-nitrophenol to 4-aminophenol in the presence of hydrazine were investigated. The TiO2 semiconductor synthesized by the sol-gel method was functionalized with AgNPs at different loadings, and their structural and optical properties were characterized by several techniques. The functionalized TiO2 with 1.5wt% AgNPs presented the highest photocatalytic activity for the conversion of 4-nitrophenol with appropriate hydrazine concentrations (0.5M). The photoefficiency enhancement under UV light irradiation was attributed to the electron transfer from the TiO2 semiconductor surface to the adsorbed acceptor reactant (4-nitrophenol) through the deposited AgNPs.

Preparation of efficient cadmium sulfide nanofibers for hydrogen production using ethylenediamine (NH2CH2CH2NH2) as template.

The preparation of CdS was performed by the precipitation method using ethylenediamine as template and tetrahydrofuran, acetonitrile or butanol as organic solvents. The formation of CdS with hexagonal structure was observed by XRD due to the template effect. FTIR studies showed that the amount of the template linked to the surface of the CdS depends on the organic solvent used. TEM observations evidenced the formations of CdS nanofibers and the EDS analysis show the chemical composition of the surface. The photocatalytic activity of CdS nanofibers under blue light irradiation was strongly influenced by the amount of ethylenediamine template on the nanofiber surface. It was observed that when the amount of the template on the samples diminishes by the heat treatment, the photocatalytic activity is affected. The role of the ethylenediamine template in the mechanism for the H2 production reaction is discussed.

Synthesis of new ZnS–Bipy based hybrid organic–inorganic materials for photocatalytic reduction of 4-nitrophenol

ZnS and ZnS–Bipy (4,4-bipyridine) hybrid based organic–inorganic materials are easily synthesized using solvothermal methods, and their structural, optical and morphological properties are characterized by FTIR spectroscopy, X-ray diffraction, UV-vis spectroscopy, nitrogen physisorption and transmission electron microscopy (TEM). The newly synthesized materials are tested as catalysts in the photocatalytic reduction of 4-nitrophenol to 4-aminophenol using Na2SO3 as hole scavengers, under UV light irradiation. ZnS–Bipy hybrid organic–inorganic materials show a high performance in the photocatalytic activity. In contrast, for non-hybrid cubic ZnS, performance is lower in comparison and also is unable to complete the whole photoreduction reaction. The high bipy contents linked to cubic ZnS surface induce changes in the electronic-optical, steric and textural properties in the new resultant hybrid materials.

TiO2 xerogels prepared by modified sol–gel method with ethylenediamine are photoactive for the 4-nitrophenol photoreduction

AbstractAmorphous and nanocrystalline TiO2 xerogel semiconductors were synthesized by sol–gel using different hydrolysis pH conditions with and without ethylenediamine as structural modifier. Blue-shift of the optical-electronic properties was observed for the amorphous TiO2 xerogel samples obtained in an alkaline hydrolysis medium. Different textural properties (specific surface area, N2 adsorption–desorption isotherm and pore size distribution) were promoted by the use of ethylenediamine for the amorphous TiO2 xerogel semiconductors, as well as high photocatalytic activity for the reduction of 4-nitrophenol. These results are discussed as function of the textural properties of the samples.

Photoreduction of 4-Nitrophenol in the presence of carboxylic acid using CdS nanofibers

The photocatalytic reduction of 4-Nitrophenol was assisted with blue light irradiation using CdS semiconductor nanofiber. The kinetic study of the blue-photoreduction of 4-Nitrophenol to 4-Aminophenol was performed by using Na2SO3 as “hole scavenger” in the presence of middle carboxylic acids (acetic, oxalic and citric acid). The effect of photocatalyst load, the carboxylic acid concentration and of the pH solution (acid, neutral and alkaline media) were investigated. The maximum 4-Nitrophenol photoreduction rate was reached in neutral media and it is related to the enhanced “hole scavenging” effect caused by the SO32− or HSO32− ions in the presence of carboxylic acid. Electrochemical characterization of CdS nanofiber was made in the presence of 4-NP and citric acid. The 4-NP photoreduction reaction follows a zero order reaction and a possible mechanism to explain the fast electron transfer process is discussed as a consequence of the carboxylic acid adsorbed on the CdS surface.