Filmes automontados contendo nanopartículas de SiO2 : aplicação em sensores e biossensores de efeito de campo

Abstract

In this work, we study a hybrid system consisting of a glass electrode coated with gold (Au), suitably modified with nanoparticles of silicon dioxide (SiO2-Np). SiO2-Np containing films fabricated by the self-assembly technique, layer by layer (LBL), using polyallylamine hydrochloride (PAH) as counter ion. The growth of multilayer PAH/SiO2-Np was monitored by absorption spectroscopy, ultraviolet-visible (UV-Vis) and morphology of the films was analyzed by atomic force microscopy (AFM). The platform PAH/SiO2-Np was applied as a pH sensor based on the concept of field effect and as support for the immobilization of the enzyme acetylcholinesterase (AChE) seeking the potentiometric detection of the neurotransmitter acetylcholine (ACh) and the organophosphate pesticide methamidophos. Evaluated by measurements of output voltage of a field effect device, the sensors have been proven effective for the detection of pH, showing sensitivity to values close to those commonly found in bulk Si (~ 40 mV/pH). AChE modified with the enzyme system also showed promise for the potentiometric detection and quantification of acetylcholine and methamidophos. AChE acts in the degradation of ACh by altering the electrical potential of the medium due to the presence of ions H+. As the enzyme has its action inhibited in the presence of methamidophos was then possible to detect small concentrations of this pesticide by measuring the percentage of enzyme inhibition of enzymatically modified platform. As potential advantages include the simplicity in making the electrode, the possibility of building on an industrial scale and no need for qualified human resources for the device operation and its low cost processing.