Square wave voltammetric studies of LbL thin Films of
propylpyridiumsilsesquioxane chloride polymer and CuTsPc
for dopamine determination
C. G. de Jesus1, S. T. Fujiwara2, V. Zucolloto3, K. Wohnrath1 and C. A. Pessôa1
1
UniversidadeEstadual de Ponta Grossa, PR, Brazil
2
Departamento de Química, UNICENTRO, Guarapuava, PR, Brazil
3
IFSC, Universidade de São Paulo, São Carlos, SP, Brazil.
Dopamine (DA) is an important neurotransmitter which plays a very important role in the
function of central nervous. Extreme abnormalities of DA levels will lead to brain disorders
such as parkinsonism and schizophrenia[1]. Therefore, it is essential to develop simple and
rapid methods for DA determination. DA can be easily oxidized electrochemically at
conventional electrodes, which have been widely used to detect it by electrochemical
methods[2]. In this context, modified electrodes have been developed, especially based on
nanostructured thin films obtained by the LbL technique. This technique is widely used
because the simplicity of the experimental work and also the possibility to control the film
architecture at the molecular level, in which the synergy between different materials can be
achieved[3]. This paper reports the preparation of LbL films using a
propylpyridiumsilsesquioxane chloride polymer (SiPy+Cl-) and a CuTsPc in a FTO substrate.
The LbL films were obtained by immersing the substrates alternately into the SiPy+Cl- and
CuTsPc solutions (with a concentration of 2 mg/mL) for 5 min. After each layer deposition,
the films were rinsed in aqueous solution at the pH=8 (pH adjusted with NaOH solution) and
dried at air. The electrochemical characterization of the films was performed by cyclic
voltammetric technique. The voltammograms of the LbL films with different bilayers,
designed as (SiPy+Cl-/CuTsPc)n revealed no redox peaks. However, it was observed that the
LbL film in presence of the DA, showed an oxidation peak at Epa=1.1 V. The oxidation peak
current decreases with the number of bilayers. Morphological studies were carried out using
the AFM technique, which showed that the roughness and thickness of the films increase with
the number of bilayers. This thickness increase makes difficult for chemicals species to access
the electrode surface, hindering the charge transfer. The film containing 5 bilayers showed a
higher peak current and was employed for DA detection using square wave voltammetry
(SWV), at concentrations ranging from 4.97x10-6 to 4.76x10-5 molL-1. The SWV parameters
were studied to determine the optimal values providing the best analytical signals. The
optimized parameters encountered were: frequency (f) = 10 s-1, amplitude (a)=40 mV and step
(∆Es)=1 mV. In these conditions, a good linear response was obtained with a detection limit
(DL)= 2.49x10-6 molL-1 and a quantification limit (QL)= 8.30x10-6 molL-1. The proposed
procedure, provided a great sensitivity and specificity, besides being very simple and requires
no complex development or renewal of electrode surface, with potential applications in
pharmaceutical solutions.
Keywords: LbL films, silsesquioxane, dopamine, square wave voltammetry
Work supported by CAPES, Nanobionet/CAPES
[1] B. J. Venton, R. M. Wightman. Anal. Chem. 75, 414 (2003).
[2] M. A. Kamyabi et al. J. Electroanal. Chem. 632, 170 (2009).
[3] M. Zhang, K. Gong, H. Zhang, L. Mao. Biosens. Bioelectron. 20, 1270 (2005).
e-mail: clicianeg@gmail.com