Nucleation and growth mechanism of polycarbazole deposited by electrochemistry

Abstract

Neste trabalho foram estudados os mecanismos de nucleação e de crescimento (MNC) de camadas finas de policarbazol (PCz) depositadas por eletro-oxidação de carbazol em LiClO 4 + acetonitrila anidra sobre um substrato de vidro coberto com SnO 2 , usando método potenciostático. Os transientes corrente-tempo (j-t) obtidos foram ajustados usando uma equação matemática que levou em conta três contribuições: a nucleação instantânea com crescimento bidimensional (IN2D) e tridimensional (IN3D) e, também, a nucleação progressiva com crescimento tridimensional (PN3D). No começo, a contribuição IN2D predomina mas, rapidamente, o processo IN3D passa a ser o mais importante. Para tempos de deposição t ≥ 17 s, IN3D corresponde a 80% da corrente total. A visualização da morfologia da superfície das películas de PCz via microscopia eletrônica de varredura (SEM) concorda com o MNC proposto pelo método matemático. A película cobre muito rapidamente a camada de SnO 2 que está relacionada ao processo bidimensional, 2D, mesmo que se observe alguma heterogeneidade distribuída aleatoriamente na película, proveniente do processo tridimensional, 3D. Após dois minutos de deposição, a rugosidade de toda a superfície dos depósitos corrobora a predominância dos processos 3D. Conseqüentemente, a informação obtida diretamente a partir dos transientes (j-t) é uma ferramenta muito conveniente e útil para predizer as condições de trabalho com o intuito de controlar o tipo de morfologia da película preparada por eletro-polimerização.Polycarbazole (PCz) thin films have been deposited by electro-oxidation of carbazole in LiClO 4 + anhydrous acetonitrile onto SnO 2 coated glass substrates, by potentiostatic method and the nucleation and growth mechanism (NGM) were studied. The obtained current time transients (j-t) were fitted using a mathematical equation with three contributions: instantaneous nucleation with two-dimensional (IN2D) or three-dimensional (IN3D) growth, and also a progressive nucleation with three dimensional (PN3D) growth. At the beginning, the IN2D contribution is predominant but, quickly the IN3D processes become more important. At a deposition time t ≥ 17 s the IN3D corresponds to 80 % of the total current. The visualization by scanning electron microscopy of the surface morphology of the PCz films is in agreement with the NGM proposed by the mathematical method. The film covers very rapidly the SnO 2 under layer related to the 2D process, even if some heterogeneities randomly distributed in the films, issued from the 3D processes, are also visible. After two minutes of deposition, the roughness of the whole surface of the films corroborates the 3D processes domination. Therefore, the information directly obtained from the (j-t) transients is a suitable and very useful tool to predict the working conditions in order to control the type of morphology of the film prepared by electropolymerization.

Controlled Electropolymerization of 1-Pyrrolyl-10-decanephosphonic Acid: An Anion Barrier Layer

“…Deposition at 1.55 V ͑Fig. 3a͒ displays a sharp anodic peak, indicating nucleation, 30,33,34 followed by a stable current for ca. 1400 s before the current begins to slowly decrease.…”

Growth Processes and Morphological Evolution of Polyaniline Film During Potentiostatic Growth

“…One of the most important points in the electrochemical studies of conducting polymers is the understanding of nucleation/growth processes. Studies of electrochemical growth processes have been performed employing three different methods: potentiostatic (constant potential), galvanostatic (constant current), and potentiodynamic (cyclic voltammetry) . Our research group has conducted comparative studies of the effects of electrodeposition methods on the electrochemical and morphological properties of PAni films, e.g.…”

“…Studies of electrochemical growth processes have been performed employing three different methods: potentiostatic (constant potential), 5-7 galvanostatic (constant current), [8][9][10] and potentiodynamic (cyclic voltammetry). [5][6][7][8][9][10][11][12][13] However, few systematic studies have been conducted on the growth processes and morphological evolution of PAni films during potentiostatic growth. 8,14 There have been several studies conducted on the electrochemical growth processes of PAni.…”

“…, potentiodynamic vs. potentiostatic and potentiodynamic vs. galvanostatic modes . There have been several studies conducted on the electrochemical growth processes of PAni . However, few systematic studies have been conducted on the growth processes and morphological evolution of PAni films during potentiostatic growth .…”