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Xia K.,University of Moncton | Ferguson D.,University of Moncton | Ferguson D.,Institute de Recherche sur les Zones Cotieres Inc. | Djaoued Y.,University of Moncton | And 4 more authors.
Applied Catalysis A: General | Year: 2010

Hierarchical porous titanium dioxide is of great interest as a potential photocatalyst material because of its enhanced mass transfer capability and light capture efficiency. Tuning of these nanostructures allows for the design of new photocatalysts with improved performance. In this study, we report the synthesis of hierarchically meso-macroporous TiO2 materials through a template-free aqueous technique. Controlled porous textures and crystalline structures of TiO2 were obtained by varying the pH of the starting aqueous solution and the method of crystallization. The catalytic efficiency of these materials was investigated using photodegradation of methyl orange and the results show that specific surface area, pore volume and crystallinity play a key role in the photocatalytic performance. The hierarchical titania prepared by the hydrothermal method at a pH of 2 has the highest efficiency with an apparent reaction rate of 9.10 × 10-2 min-1, surpassing that of Degussa P25, hence showing its promising potential in environmental remediation. © 2010 Elsevier B.V. All rights reserved. Source


Xia K.,University of Moncton | Ferguson R.Z.,University of Moncton | Ferguson R.Z.,Institute de Recherche sur les Zones Cotieres Inc. | Losier M.,Institute de Recherche sur les Zones Cotieres Inc. | And 3 more authors.
Journal of Hazardous Materials | Year: 2010

Porous silica materials S8, S12, S16, and SBA with controllable pore structures and morphology were synthesized by varying the type or alkyl chain length of the surfactant. Diverse amino-functionalized organic-inorganic hybrid porous materials were then prepared by post-grafting. Depending on the relation between the pore diameter of the porous silica materials and the size and content of the moiety to be grafted, the functionalized materials exhibited varying degrees of decline of structure properties, i.e. regular arrangement of pores, specific surface area, pore size, and pore volume. The hybrid silica materials have been employed as heavy metal ions adsorbents from simulated drinking water at room temperature. The results indicated that the diverse pore structures and different amino group densities influence the heavy metal ions adsorption of functionalized silicas significantly. The best adsorbent was found to be monoamino-functionalized silica S16-1N, which could effectively remove heavy metal Cd(II), Pb(II), Fe(III), as well as Mn(II). The good performance can be attributed to the accessibility of effective amino groups in the pores, as well as the suitable pore structure with high specific surface area of 728m2/g and total pore volume of 0.34cm3/g. © 2010 Elsevier B.V. Source


Subramanian B.,University of Moncton | Subramanian B.,Institute de Recherche sur les Zones Cotieres Inc. | Tchoukanova N.,Institute de Recherche sur les Zones Cotieres Inc. | Djaoued Y.,University of Moncton | And 2 more authors.
Journal of Raman Spectroscopy | Year: 2013

Astaxanthin is a carotenoid naturally found in microbial organisms, microalgae, and many crustaceans. Its consumption has led to beneficial effects such as pigmentation of marine animals, and it favorably addresses several human health issues as a result of its high important antioxidant property. Several companies produce synthetic trans-astaxanthin for dietary purposes in aquaculture, where it is mainly used for pigmentation. It is known that trans-astaxanthin manifests itself as a monomer in organic solvents, as aggregates in aqueous solutions of organic solvents, or as crystalline solids. These forms display unique optical and structural properties, which have an impact on biological systems. In this work, we report on detailed Raman investigations, in conjunction with optical absorption spectroscopy, of monomer, aggregates, and crystalline forms of trans-astaxanthin. The Raman and optical absorption spectroscopic investigations of trans-astaxanthin aggregates were performed as a function of time, showing the formation of card-packed aggregates after 2 h, and head-to-tail aggregates after 24 h in a 10% acetone-water astaxanthin solution. For the crystalline trans-astaxanthin, a pointwise Raman mapping evidenced the presence of two distinct crystal structures. The Raman modes of these crystal structures (A and B) were correlated with the intermolecular interactions present in chloroform solvated (AXT-Cl) and unsolvated (un-AXT) trans-astaxanthin single crystals. Both crystal structure A and the card-packed aggregates have similar intermolecular π stacking interactions as AXT-Cl. The crystal structure B and the head-to-tail aggregates showed linear chain features as in un-AXT. This work also clearly demonstrates that Raman spectroscopy is a powerful tool to distinguish the crystal structures present in crystalline powder of trans-astaxanthin. Copyright © 2012 John Wiley & Sons, Ltd. Source


Subramanian B.,University of Moncton | Subramanian B.,Institute de Recherche sur les Zones Cotieres Inc. | Tchoukanova N.,Institute de Recherche sur les Zones Cotieres Inc. | Djaoued Y.,University of Moncton | And 3 more authors.
Journal of Raman Spectroscopy | Year: 2014

Recent research interests in geometrical isomers of astaxanthin (AST) are motivated by their metabolic activities in aquatic animals and human. It has been established that cis-isomers of AST are selectively absorbed in human plasma during the metabolic process; however, exact absorption mechanism is still unclear. Hence, a detailed investigation of the structural and optical properties of geometrical isomers of AST is required. Among the techniques available for the study of AST and other carotenoids, Raman spectroscopy has been much acclaimed. Raman spectra have been shown to be influenced by the electronic and mechanical confinement effects arising from the conjugated polyene chain of carotenoids. In this work, we present Raman studies of geometrical isomers of AST, along with their optical absorption characteristics. Geometrical isomers of AST were prepared by heating all trans-AST in solution form, and the isomers were separated using high performance liquid chromatography. Optical absorption spectra of cis-isomers of AST showed hypsochromic shifts in the main absorption band and formation of new bands at lower wavelengths. A detailed Raman spectral analysis performed on the cis-isomers of AST showed new modes which have not been observed and accounted for so far. In addition, we demonstrate that the electronic and mechanical confinement effects in the polyene chain of AST play an important role in the Raman spectra of geometrical isomers of AST. It is anticipated that this work will demonstrate that Raman spectroscopy is an important diagnostic tool in distinguishing and identifying the geometrical isomers of AST. Copyright © 2014 John Wiley & Sons, Ltd. Source

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