Paper TF-ThP7
Development of Thin Film of Ferric Hydroxide Dispersed in Polymer Matrix Doped with Ethylenediamine

Thursday, October 24, 2019, 6:30 pm, Room Union Station B

The present work presents the development of a thin film based on ferric hydroxide (Fe(OH)₃) dispersed in a polymer matrix of polyvinyl acetate (PVA) containing ethylenediamine (H₂N-(CH₂)₂-NH₂) to form a membrane phosphate in solution. Ferric hydroxide was obtained from the stoichiometric reaction of iron (FeCl₃) perchloride with ammonium hydroxide (NH₄OH), and after washing, filtration and drying the Fe(OH)₃ was diluted with ethyl alcohol to add to ethylenediamine doped PVA. The thin film for the formation of the membrane was obtained by the spin-coating method. For the selectivity tests, the membrane was applied in a semiconductor insulating electrolyte (EIS) device to be used as hydrogen phosphate sensor. The EIS device is formed by the selective membrane deposited on a structure composed of a thin layer of silicon oxide on the silicon substrate, and a gold-plated tungsten micro tip as the reference electrode. The thin film composing the selective membrane was characterized structurally by elliptiometry, Raman spectroscopy, X-ray diffraction, and atomic force microscopy (AFM). In order to evaluate the selectivity of the thin film of the membrane, the electrical characterization of the EIS device was carried out, obtaining the voltage capacitance curves for the pH variation and for the variation of the hydrogen phosphate concentration in solution, which showed a result in the sensitivity of 143 mV/pH and sensibility in the measurement of the hydrogen phosphate concentration of 42 mV/mg/dL.

Keywords— ferric hydroxide; hydrogen phosphate; thin films; selective membrane