Iron Oxide Nanostructured Electrodes for Detection of Copper(II) Ions

Abstract

Iron oxide nanostructured (ION) electrodes were assembled layer-by-layer onto ITO-coated glass substrates and their structure, morphology, and electrochemical properties were investigated, the latter aiming at the development of a chemical sensor for Cu 2+ . The electrodes were built by immersing the substrate alternately into an aqueous colloidal suspension of positively charged magnetite nanoparticles (np-Fe 3 O 4 , 8 nm) and an aqueous solution of anionic sodium sulfonated polystyrene (PSS). The adsorbed amount of both materials was monitored ex-situ by UV-vis spectroscopy and it was found to increase linearly with the number of deposition cycles. The resulting films feature a densely-packed structure of magnetite nanoparticles, as suggested by AFM and Raman spectroscopy, respectively. Cyclic voltammograms of electrodes immersed in acetate buffer (pH 4.6) displayed three electrochemical events that were tentatively ascribed to the reduction of Fe(III) oxy-hydroxide to magnetite, reduction of maghemite to magnetite, and finally oxidation of magnetite to maghemite. The effect of np-Fe 3 O 4 /PSS bilayers on the ION electrode performance was to increase the anodic and cathodic currents produced during electrochemical oxidationreduction of the Fe(CN) 3−/4− redox couple. With more bilayers, the ION electrode provided higher anodic/cathodic currents. Moreover, the redox couple exhibited a quasi-reversible behavior at the ION electrode as already observed with other working electrode systems. Fitting of voltammetry data provided the apparent electron transfer constants, which were found to be higher in ION electrodes for both redox couples (Fe(CN) 3−/4− and Cu 2+/0 ). By means of differential pulsed anodic stripping voltammetry, the ION electrodes were found to respond linearly to the presence of Cu 2+ in aqueous samples in the range between 1.0 and 8 0 × 10 −6 mol · L −1 and displayed a limit of detection of 0 3 × 10 −8 mol · L −1 . The sensitivity was ∼ 0.6 A/ mol · L −1 . In standard addition and recovery experiments performed with tap water the recovery was about 102%-119%. In similar experiments conducted with ground and instant coffee samples the recovery was 92.5% and 103%, respectively. Furthermore, the ION electrodes were almost insensitive to the presence of common interfering ions, such as Zn 2+ , Mn 2+ , Ni 2+ , and Fe 3+ , even at concentrations ten times higher than that of Cu 2+ .

Biocompatible superparamagnetic carriers of chondroitin sulfate

“…protocol for synthesizing the IONs is the same as the one described by Kang et al [39] and reproduced elsewhere [40,41]. In short, FeCl2•4H2O (25 mL, 0.30 molL -1 ) and FeCl3•6H2O (25 mL, 0.60 molL -1 ) aqueous solutions were mixed and slowly added to mL of NaOH (2.0 molL -1 ) and kept under mechanical stirring (2,000 rpm), at room temperature, for extra 30 min.…”

Determinação eletroanalítica de ácido salicílico em produto dermatológico com eletrodos de nanotubos de carbono e nanopartículas de óxido de ferro

“…O preparo das nanopartículas de magnetita foi realizado por co-precipitação de íons Fe(II) e Fe(III) em NaOH, segundo método descrito na literatura (Santos et al, 2014). Uma solução aquosa (20 mL) contendo íons de Fe(II) 0,1 mol L -1 e Fe(III) na concentração de 0,2 mol L -1 foi adicionada gota a gota sobre 25 mL de solução de NaOH (0,4 mol L -1 ) sob agitação magnética e a temperatura ambiente como mostrado na Figura 9 (a).…”

“…Na (Santos et al, 2014;ALCANTARA et al, 2011). Num determinado momento, esse espaço é completamente preenchido e a rugosidade da superfície não varia mais quando mais tetracamadas são depositadas.…”

“…MAG. Um efeito similar foi observado porSantos et al (2014) em filmes de np-MAG com poli(estireno sulfonato de sódio). Este último apresenta uma banda característica em 270 nm e que não foi observada nos filmes.…”

Filmes formados pelo copolímero SEBS e nanopartículas de óxidos de ferro : preparação e caracterização

“…A figura 3.2 exemplifica o fenômeno de transição eletrônica. A espectroscopia de UV-vis pode ser útil para identificar a presença de um material em outro, através da concentração [54,109,110]. A presença do material é reconhecida por sua banda caracterísitca, relacionada à transição eletrônica de alguns dos elementos constituintes da amostra.…”