Untitled in english

Author(s)

Antonio Pereira do Nascimento Filho

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Escola Politécnica (EP/BC)
• Defense date: 2002-04-30

Examining board members

Maria Lucia Pereira da Silva; Nicole Raymonde Demarquette; Elisabete Galeazzo

• Advisor: Maria Lucia Pereira da Silva

Abstract

This work made use of cleaner technologies and environmental friendly reagents to produce polar organic compounds with adsorption capability in order to develop sensors in the environmental field. To achieve the proposed aim, the plasma deposition technique was used with 2-propanol, acetone and ethanol. Indeed, 2-propanol showed the best results. Two different deposition processes were used and their deposition rates were measured by profile meter. The films were characterized by infrared and Raman spectroscopy, contact angle measurements with different aqueous solutions, optical and atomic force microscopy. The 2-propanol films are hydrophilic and present contact angles smaller than 70´DEGREE´ for water. All the films showed affinity for 2-propanol aqueous solutions in a large concentration range (0,01 - 50 % in vol.). The 2-propanol films were obtained on silicon with good adhesion for thickness up to 2000 A. It was necessary to promote adhesion using mono and double hexamethyldisilazane layer deposition over this thickness. The films with higher adsorption capability were characterized by X-ray photoelectron spectroscopy (XPS). The C:O atomic ratio is 4:1. The adsorption was determined by Raman microscopy and aqueous acetophenon and cobalt (II) phtalocyanine solutions. It was possible to notice that the adsorption mechanism happens through the superficial OH competition. The possible uses of these films were verified through interdigited and piezoelectric quartz crystal sensor structures. It was possible to notice that there is adsorption and permeation of organic compounds. Therefore, this film can be used as selective membrane for sensors. The low current value obtained for voltage (V) x current (I) measurements suggest that capacitance (C) x voltage (V) is more adequate. (AU)