Journal of Colloid and Interface Science 316 (2007) 292–297 www.elsevier.com/locate/jcis Study of the growth process of in situ polyaniline deposited films Silmar A. Travain a , Nara C. de Souza b,∗ , Débora T. Balogh c , José A. Giacometti d a Instituto de Ciências Exatas e Biológicas, Universidade Federal de Ouro Preto, 35400-000, Ouro Preto, MG, Brazil b Instituto Universitário do Araguaia, Universidade Federal de Mato Grosso, 78698-000, Pontal do Araguaia, MT, Brazil c Instituto de Física de São Carlos, Universidade de São Paulo, CP 369 13566-970, São Carlos, SP, Brazil d Faculdade de Ciências e Tecnologia, Universidade Estadual Paulista, CP 467 19060-900, Presidente Prudente, SP, Brazil Received 5 June 2007; accepted 7 August 2007 Available online 17 August 2007 Abstract Polyaniline (PAni) thin films were deposited onto BK7 glass substrates using the in situ deposition technique. The control of the time and the aniline concentration in the PAni polymerization reaction on the film deposition allowed us to prepare films with different thickness, down to ∼25 nm. The film growth process was monitored by measuring the UV–vis spectra and the AFM height profiles of the film surface. The curves of adsorption kinetics were analyzed with the Avrami’s model, yielding an exponent n = 3, thus indicating nucleation of spheroids at the initial stages of polymerization that grow through a diffusion process. AFM images of the surface height profiles corroborate this hypothesis, with spheroids growing with no preferred orientation during the in situ deposition.  2007 Elsevier Inc. All rights reserved. Keywords: Polyaniline; Adsorption kinetics; Surface morphology 1. Introduction Polyaniline (PAni) is a semiconducting polymer of great in- terest for technological applications as it can be easily synthe- sized and possesses good environmental stability under room conditions, redox reversibility, and an electric conductivity that can be increased by ten orders of magnitude upon doping [1,2]. The control in the fabrication of PAni thin films is also rele- vant because for many applications one may require organized molecular structures, with low roughness and high electric conductivity [3]. Thin films of PAni have been used in light- emitting diodes [4,5], biosensors [6,7], photoelectric cells [8], battery electrodes [9], and anti-static coating [10]. Deposition of a thin layer of PAni on substrates can be performed using several techniques, namely casting or spin coating [11], layer- by-layer technique (LbL) [12], Langmuir–Blodgett (LB) tech- nique [13], electrochemical deposition [14], and in situ poly- merization [15]. * Corresponding author. E-mail address: ncsouza@ufmt.br (N.C. de Souza). The simplest technique to prepare PAni films is spin-coating or casting from a PAni solution in solvents such as N -methyl- 2-pyrrolidinone (NMP) [11]. Casting allows the fabrication of films with thickness of few micrometer but the thickness, roughness, and structural organization are not well controlled. The LbL technique is a simple technique for deposition of films with thickness of the order of a few nanometers, with alternated layers of different materials, but the production of thicker films is tedious and time consuming. The Langmuir– Blodgett technique produces films with distinct properties due to its layer-by-layer nature and with thickness in the nanometric scale, but deposition is not straightforward and in some cases a monolayer-forming substance must be used in conjunction [13], such as stearic acid for example, to transfer the Langmuir films onto a substrate. McDiarmid and Epstein [15] have suggested an alternative technique to deposit high quality films onto solid substrates by immersion of a substrate in the aqueous solution during the chemical synthesis of PAni. This in situ deposition [16,17] occurs in three steps: (i) the induction period for aniline oxi- dation, (ii) an exothermic oxidative polymerization producing a protonated pernigraniline and (ii) the conversion to a green 0021-9797/$ – see front matter  2007 Elsevier Inc. All rights reserved. doi:10.1016/j.jcis.2007.08.024