4^th International Conference and Expo on Ceramics and Composite Materials May 14-15, 2018 Holiday Inn Rome Aurelia, Rome, Italy

Biography:

Dr. David G. Calatayud received his doctorate in Chemistry from the University of Autonoma de Madrid in 2004 where he studied new asymmetric double-Schiff-bases containing a thiosemicarbazone moiety and their complexes. After completing his PhD he worked as a postdoctoral researcher in the Spanish National Research Council – CSIC, focusing on novel materials, nanotechnology, photocatalytic nanoparticles and crystal engineering. In 2014 he joined Sofia Pascu’s group at the University of Bath (UK) as a Research Associate developing on ‘smart’ all-in-one multimodal imaging probes as novel synthetic platform systems for personalised diagnosis and treatment of diseases such as cancer. In 2016 he moved to the Funceramics group at Instituto de Ceramica y Vidrio – CSIC, his current research is focused on the development of new experimental techniques to assemble functional materials for advanced micro and nanoelectronics, biosensing, molecular imaging and drug delivery applications

Abstract:

TiO₂ has become a material of great interest for photocatalytic H₂ production, environmental purification and solar energy conversion.[1] It is generally accepted that anatase is the most active photocatalyst of the three possible polymorphs of TiO₂. The properties influencing the photoactivity of anatase particles have been reported to include surface area, crystallinity, crystallite size, crystal structure;[2,3] and the morphology of the particles. Among the key parameters boosting the photocatalytic efficiency of anatase nanoparticles, an increased light absorption to extend the optical response to the visible, together with an improved charge separation of the electrons and holes generated upon photoexcitation, shall be enumerated. Conventional TiO₂ anatase nanoparticles have a bandgap of 3.20 eV which only allows the excitation of carriers by light with wavelengths smaller than 387 nm (UV region); if visible light harvesting is to be enabled, this gap should be narrowed. In this work, pure anatase nanoparticles have been obtained using a solvothermal process with reduced band-gap and/or reactive faces. Trifluoroacetic acid is used as morphological control and doping agent, and urea is employed as a reduction agent.[4,5] Through the careful choice and control of the working conditions, it is possible to control the final properties of the produced nanoparticles, e.i. morphology, size, crystallinity, crystal phase, network defects and band gap. The obtained results point out that in order to improve the photocatalytic performance, a well-designed intrinsic defective TiO₂ system for visible light driven photocatalysis should meet all three requirements simultaneously: (i) reduced band gap for visible light absorption, (ii) appropriate energy level to initiate photocatalytic reaction, and (iii) proper defect species or highly active surfaces to separate photo-generated charge-carriers (electrons and holes) for reaching high catalytic performance.

 

Biography:

Julian J. Reinosa has her expertise in dispersion of nanoparticles, in developing of nanoparticulated microparticles and in obtaining nano and micro hierarchical composites. His studies are centered in the valuation of the developed particles and composites in comparison with microparticles or nanoparticles of similar composition in several fields. Hence, he achieved new effects in ceramics materials thanks to the dispersion and protection of oxides and metallic particles into ceramic glazes; he demonstrated the increase of the yield of UV filters when are correctly dispersed at the same time that the photodegradation is lowered; and he is studying the heating process by applying microwaves energy in particles with different dispersion grade. His expertise joined to other scientist in materials field gave rise to a spin off (AD-Particles) about the dispersion of nanoparticles and the achieving of hierarchical composites for industrial applications

Abstract:

Nowadays, sunscreens are formulated by using TiO₂ and ZnO nanoparticles because they are efficient inorganic UV filters. In fact microsized TiO₂ and ZnO have been increasingly replaced by TiO₂ and ZnO nanoparticles in order to solve the cosmetic drawback of the white opaque sunscreens apart from the higher yield that nanoparticles suppose. Also the aggregation state of the particles in sunscreens is related to the solar protection factor (SPF) of the final emulsion. In this sense, dispersed nanoparticles into sunscreens increase the SPF value, but it means a possible leading to their incorporation into the stratum cornea, the outer layer of the skin. Moreover, when TiO₂ is irradiated produces free radicals which are implicated in a number of potential health issues such as skin aging because of the formation of reactive oxygen species (ROS).

In this work, composites combining TiO₂ microparticles and ZnO nanoparticles have been achieved by using several synthesis and dispersion methods. It has been demonstrated by the incorporation of the different composites into sunscreens that the presence of nanoparticles anchored over TiO₂ microparticles allows increasing the efficiency of nanoparticles but decreases the possible health problems by their absorption as nanoparticles. The aim of these new composites is to gain the advantages of inorganic nanoparticles avoiding their potential drawbacks. Hence, the combination of both oxides provokes higher SPF value and lower photodegradation, in comparison with TiO₂ microparticles. Moreover, the disposition of ZnO and TiO₂ particles means a positive synergy by the recombination of photo induced electrons holes, which decreases the formation of free radicals.