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Langmuir-Schaefer films of poly (o-anisidine) conducting polymer for sensors and displays

Sergio Paddeu, Manoj Ram, Sandro Carrara, and Claudio Nicolini*

Polo Nazionale Bioelettronica, Marciana, (LI), Italy
El.B.A. Foundation, Rome (Italy) and
Institute of Biophysics, University of Genoa (Italy)

This is an abstract for a poster to be presented at the Fifth Foresight Conference on Molecular Nanotechnology. The full paper is available here.

Ultrathin films of polyanilines play an important role for the application of this class of polymer in nanotechnology. The nature of the surface properties is critical for the function of electronics products which may be determined by the layers of nanometers thickness of polyanilines. In this regards, the Langmuir-Blodgett (LB) films of polyanilines have been fabricated at the molecular level [1]. The deposition of quasi ordered and ordered LB films of polyaniline were also reported, where emeraldine base dissolved in N-methyl 2-pyrrolidinone (NMP)/chloroform (CHCl3) could be used to cast LB films using an aqueous subphase containing neutral or acidic water [1]. The deposited LB films of polyaniline is used to give rise to an irregular surface after 10-20 monolayers due to the presence of NMP. Considering that poly (o-anisidine) (POAS) conducting polymer is directly soluble in CHCl3, the horizontal lifting technique [Langmuir-Schaefer (LS)] was employed for the manufacture of ultra-thin films of the substituted polyanilines, where each successive deposited monolayer was dried by blowing nitrogen flux [2,3]. The Langmuir-Schaefer (LS) films of POAS conducting polymer were then investigated by using UV-visible absorption, Brewster microscopy, X-ray low angle scattering ellipsometric, electrochemical and nanogravimetric techniques. The obtained results revealed a regular deposition during at least 40 monolayers of POAS LS films. The development of surface irregularities beyond 40 monolayers of LS films resulted in an electrochemical kinetics similar to the electrodeposited films. The electrochemical kinetics in fewer number of monolayers was shown to be the first electron transfer process. The influence of the doping anion concentration on the redox properties of POAS LS films were determined by cyclic voltammetry. The nature of anions caused significant changes in the redox properties of POAS LS films. An exploitation of POAS ultra-thin films as sensing elements in a sensor system or as active layer in an electrochromic display is in progress in our laboratories. Namely, the POAS films used for the detection of HCl in water by conductimmetric measurements revealed a detection limit better than 0.1 ppm of HCl.

[1] M.K.Ram, N.S. Sundaresan, and B.D. Malhotra. J. Phys. Chem. 97, 11580 (1993)
[2] M.K.Ram, S. Carrara, S. Paddeu, E. Maccioni, and C. Nicolini. Langmuir. 13, 2760 (1997).
[3] S. Paddeu, M.K. Ram, and C. Nicolini. J. Phys. Chem., in press (1997)

*Corresponding Address:
Claudio Nicolini, Fondazione EL.B.A., Via Medaglie d'Oro 305 - 00136 Rome, Italy, ph: +39 6 35410728, fax: +39 6 35451637, email:
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