Elsevier

Materials Letters

Volume 48, Issues 3–4, April 2001, Pages 144-150
Materials Letters

Electrical properties of conducting polypyrrole films functionalized with phthalocyanine

https://doi.org/10.1016/S0167-577X(00)00294-9Get rights and content

Abstract

Polypyrrole films containing phthalocyanine were deposited by direct electrochemical deposition method using mixed solvent system (NMP:H2O) with H2SO4 (0.1 M). The films obtained were characterized by conventional techniques such as FT-IR and UV–VIS, which confirmed the incorporation of phthalocyanine. The presence of Cu(2p) core level peak in the ESCA studies also confirmed the incorporation of phthalocyanine in these films. The electrical conductivity was found to increase with the increase of phthalocyanine concentration in the electrolyte. Even for a moderate increase of CuPc (from 1.0 to 2.0 mol%) in the PPy films, there is a drop in activation energy from 0.133 to 0.08 eV. Sensitivity measurements show that the CuPc containing PPy films are selectively more sensitive to the nitrogen dioxide vapours. The CV studies carried out on these films under illumination show that the photochemical response in electrochemical mode increases due to the presence of phthalocyanine. The cathodic peak at −700 mV, which is associated with the phthalocyanine, becomes prominent under illumination due to photogenerated carriers.

Introduction

Recently, a great deal of interest has been given to the electrochemical preparation of a number of polypyrroles, utilizing a variety of ionic complexes and polyelectrolytes as the electrolytes during electropolymerization which serve as charge-balancing dopant anions. This has led to a new class of multicomponent materials with controllable electrical, mechanical, electrochemical, catalytic ion-binding and ion-releasing properties. These approaches include the preparation of PPy containing Ru-bipyridine complexes, naphthoquinone and benzoquinone groups [1], complexes with metallotetraphenyl–porphyrin [2] and phthalocyanines complexes, etc. [3].

Metal phthalocyanines complexes have been widely studied for their electrochemical [4], electrocatalytic [5], photocatalytic [6], non-linear optical [7] and photo electrochemical properties [8]. Polypyrrole, containing metal phthalocyanine complexes, is thus a potential electro-switchable, multifunctional material for modified electrodes. In all these reported works on metallophthalocyanine complexes a unique feature was observed that these are all aqueous soluble complexes. Hence, in the present study, emphasis has been given on incorporation of phthalocyanines in conducting polypyrrole. This study has been focused mainly on the effect of incorporation of phthalocyanines into polypyrrole on its electrical conductivity, thermal stability, photosensitivity and chemical gas sensitivity.

Section snippets

Experimental

An electrolytic bath containing 2.15-ml (0.4 m) conc. H2SO4 in 100 ml NMP:H2O (1:1) mixture, pyrrole monomer 2.8 g (0.4 m) and desired amount of CuPc say 1%, 2%, 3% and 4% (mol% per monomer) was used for deposition of films. The electrolytic cell comprised of single compartment cell containing SCE (Saturated Calomel electrode), platinum foil as a counter electrode and gold PET/glass substrates as a working electrode. The deposition of polymeric films was carried out at 0.7 V vs. SCE for a fixed

Results and discussions

The FT-IR spectrum of pure PPy sample showed peaks at 1700, 1562, 1480, 1320, 1105, 935, 805, 750 and 690 cm−1 can be easily assignable to polypyrrole moiety. These values obtained for PPy are well matched with the reported value for PPy [13]. The polymeric films functionalized with phthalocyanine exhibit peaks at 1440, 1350, 1210, 1100, 1050 and 960 cm−1 which are assignable to the phthalocyanine skeleton, in addition to above mentioned polypyrrole peaks. The pure PPy film shows a broad

Conclusions

The incorporation of phthalocyanine into polypyrrole backbone has been successfully carried out, using both chemical as well as electrochemical method. The FT-IR and UV–VIS techniques to confirm the incorporation of phthalocyanine in them studied the synthesized polymers. The net effect of the addition of phthalocyanine in the PPy polymeric chain is the enhancement in electrical conductivity, due to delocalization of charge carriers, additional doping sites and increased conjugation level. The

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