Volume 3 Issue 4
Authors: Juliana N. Schianti; Wagner Aldeia; Fernanda C.P. Ferreira; Natália N.P. Cerize; Adriano M. Oliveira
Abstract: This study describes a successful process using high pressure homogenization (HPH) and interfacial polymerization to produce nanoencapsulation of a UV-filter. Actually, this kind of agent has some limitations mainly related to photostability, degradation and toxicity, and then the process of encapsulation promises to overcome these drawbacks by protecting the active substance. Octyl-methoxycinnamate (OMC) was used as UV-filter model to develop the nanostructured particles. The nanocapsules were prepared by emulsification (using HPH) of an organic phase containing 4,4’-methylene-diphenyl-di-isocyanate (MDI) (a hydrophobic monomer), medium-chain triglycerides, Span 80 and OMC, in an aqueous solution composed of sodium lignosulfonate (stabilizing agent), Pluronic F127 and ethylene glycol (a hydrophilic monomer). In sequence, the polymerization of MDI and ethylene glycol at the water–oil droplet interface was performed at 40 °C during 4 hours. The nanocapsules dispersions were characterized with respect to their particle size (DLS), zeta potential (electrophoretic mobility), morphology (SEM-FEG), efficiency for UV absorption (UV spectrometry) and FTIR. The nanostructured particles developed here have diameter in a nanometric scale (between 251 and 661 nm), very low polydispersity index (around 0.1 to 0.3), negative zeta potential (about –46,0 mV), fluid aspect and colloidal stability during more than 2 months. The nanocapsules dispersion in a 0.005% (w/w) concentration absorbed around 70% of UV light incident, demonstrating the increase of UV-filter efficacy. In conclusion, the HPH and interfacial polymerization processes allowed producing nanostructured particles to encapsulate UV-filters, presenting a promising system to protect against UV radiation.
Keywords: Sunscreen; Nanoencapsulation; Interfacial Polymerization; High Pressure Homogenization
Authors: M.A.S. Boff; B. Canto; F. Mesquita; R. Hinrichs; L.L. Araujo; D.L. Baptista; F.P. Luce; P.F.P. Fichtner; G.L.F. Fraga; L.G. Pereira
Abstract: Three granular systems (Fe-Al2O3, Co-Al2O3, and Ti-SiO2) had their electrical properties analyzed in the low-field regime (eV<<kBT). Even though the metals and the insulators were different, a systematic non-ohmic behavior was observed in all systems when bias or injected current were varied. The temperature dependence on the resistance was best described with the Mott variable range hopping model. It is suggested that the behavior of the electrical resistance and the electronic localization length are associated with the activation of new electronic paths between more distant grains. As these new paths configure resistances in parallel, total resistance is reduced. In the low-field regime, the resistance drop and the change in localization length seem to be universal to metal/insulator granular thin films.
Keywords: Electrical Properties; Metal/Insulator Granular Film; Variable Range Hopping
Authors: Pavan Krishnama Naidu; Narasimha Vinod Pulagara; Raja Sekhar Dondapati
Abstract: Carbon nanotubes are molecular-scale tubes of graphite carbon that possess superior properties. They are the strongest and stiffest fibres with Young’s modulus 1 TPa and maximum tensile strength of 63 GPa. Carbon nanotubes are widely used in Biological, Chemical, Medical, Material Science and Engineering applications. This review outlines the engineering applications of carbon nanotubes and discusses benefits and concerns associated with their uses. Many research works have been done on this particular topic and various technologies have been proposed and applied at experimental and field levels. It is planned to identify the applica-tions of carbon nanotubes from engineering point of view.
Keywords: Nano Tubes; Nano Technology; Engineering Applications