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| Author(s): |
Vanessa Cristina Gonçalves
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Carlos. |
| Institution: | Universidade de São Paulo (USP). Instituto de Física de São Carlos (IFSC/BT) |
| Defense date: | 2010-04-20 |
| Examining board members: |
Debora Terezia Balogh;
Antonio Carlos Bender Burtoloso;
Arnaldo Alves Cardoso;
Ronaldo Censi Faria;
Francisco Eduardo Gontijo Guimaraes
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| Advisor: | Debora Terezia Balogh |
| Abstract | |
The conjugated polymers, especially polythiophenes, have emerged as alternative materials to obtain chemically selective layers in gas sensors. The main advantages of these materials are the possibility of obtaining sensing devices that operate at room temperature and the diversity of materials. For example, a simple modification of the side chain of polythiophene can provide materials with different chemical affinities, which can contribute to the improvement of the selectivity of these devices. The selectivity and sensitivity are the main practical limitations of the gas sensors containing conjugated polymers as sensing layers. In this study, different polythiophene derivatives have been synthesized by oxidative polymerization with ferric chloride and characterized by FTIR, 1H NMR, HPSEC and thermal analysis (TG). Films of these polymers have been obtained by spin-coating techniques and casting, depending on their solubility in chloroform. It has been shown that the surface characteristics and the properties of absorption in the UV-vis and the emission of the films of these polythiophene derivatives are dependent on the type of side chain attached to the thiophene ring. These films have been used in the study of their optical and electrical sensing properties of VOCs and humidity, and it has been demonstrated that optical sensors are less sensitive to these analytes than the electrical ones. Their fractional sensitivities are 10-7 and 10-5 ppm-1, respectively, with some exceptions. The responses of such sensors have been qualitatively and quantitatively reproducible, however, the responses of electrical sensors showed influence of the initial electrical characteristics of the films. Different detections patterns were showed for optical and electrical detections of a particular polymer, showing that these polymers are good candidates to be used as active layers in sensing devices to detect VOCs. (AU) | |
| FAPESP's process: | 05/03137-0 - Synthesis and characterization of polythiophenes derivatives for sensor applications |
| Grantee: | Vanessa Cristina Gonçalves |
| Support Opportunities: | Scholarships in Brazil - Doctorate |