Sensores de feito de campo contendo nanofilmes de grafeno CoFe2O4 aplicados em monitoramento ambiental

Abstract

The synthesis of new materials and the formation of novel structures with specific features and properties are advantageous in the development of sensors applied to detect substances for the control and environmental monitoring. This study was aimed to nanostructure graphene oxide (GO), poly(aminoamine) hydrochloride (PAH) and cobalt ferrite nanoparticles (NPs-CoFe2O4), by using the layer-by-layer (LbL) technique. The films were fabricated onto Field-Effect-Devices (FED) type ElectrolyteInsulator-Semiconductor (EIS) with p-Si-SiO2-Ta2O5 structure and used to detect hydrogen peroxide (H2O2), and heavy metals of Cd2+ and Cu2+ ions. The NPs-CoFe2O4 and GO solutions were characterized by transmission electron microscopy (TEM), and the films were characterized by scanning electron microscopy with field emission (FEG-SEM). For the preparation of the films we used three different GO concentrations: 0.1 mg/mL, 0.5 mg/mL and 1.0 mg/mL. The films were characterized by electrochemical techniques of capacitance/voltage (C/V) and constant capacitance (ConCap) to investigate an optimal number of bilayers and for detecting pH, H2O2, and Cd2+, Cu2+ ions. The results showed that the optimum number of bilayers to be deposited onto the chips were between 6 and 10 bilayers. pH detections showed that the films prepared with GO at 0.5 mg/mL were more sensitive than others prepared with concentrations at 0.1 mg/mL and 1 mg/mL. Films without the presence of NPsCoFe2O4 revealed no response signals toward H2O2, demonstrating that the detection of such substance is directly associated with the ferrites. For all films, the sensor EISPAH-CoFe2O4/GO(6bi/0,5) exhibited the best properties with stable response signal and higher sensitivity for the detection of H2O2, and Cd2+, Cu2+ ions. These results show the importance of studying optimized films with suitable architectures that lead to nanostructures that may be used as sensing units with enhanced properties for the detection of substances of interest for environmental monitoring.