Santos J G M, Souza J R, Letti C J, Soler M A G, Morais P C, Pereira-da-Silva M A, Paterno L G
J Nanosci Nanotechnol. 2014 Sep;14(9):6614-23. doi: 10.1166/jnn.2014.9379.
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 Cu2+. The electrodes were built by immersing the substrate alternately into an aqueous colloidal suspension of positively charged magnetite nanoparticles (np-Fe3O4, 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-Fe3O4/PSS bilayers on the ION electrode performance was to increase the anodic and cathodic currents produced during electrochemical oxidation-reduction 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 Cu2+ in aqueous samples in the range between 1.0 and 8.0 x 10(-6) mol x L(-1) and displayed a limit of detection of 0.3 x 10(-8) mol x L(-1). The sensitivity was - 0.6μA/μmol x 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 Zn2+, Mn2+, Ni2+, and Fe3+, even at concentrations ten times higher than that of Cu2+.
将氧化铁纳米结构（ION）电极逐层组装到涂有ITO的玻璃基板上，并对其结构、形态和电化学性质进行了研究，后者旨在开发一种用于检测Cu2+的化学传感器。通过将基板交替浸入带正电的磁铁矿纳米颗粒（np-Fe3O4，8纳米）的水胶体悬浮液和阴离子型磺化聚苯乙烯（PSS）的水溶液中来构建电极。通过紫外-可见光谱对两种材料的吸附量进行了非原位监测，发现其随沉积循环次数呈线性增加。原子力显微镜（AFM）和拉曼光谱分别表明，所得薄膜具有磁铁矿纳米颗粒的致密堆积结构。浸入醋酸盐缓冲液（pH 4.6）中的电极的循环伏安图显示了三个电化学事件，初步归因于氢氧化铁还原为磁铁矿、磁赤铁矿还原为磁铁矿，以及最后磁铁矿氧化为磁赤铁矿。np-Fe3O4/PSS双层对ION电极性能的影响是增加了Fe(CN)(3-/4-)氧化还原对电化学氧化还原过程中产生的阳极和阴极电流。双层越多，ION电极提供的阳极/阴极电流越高。此外，如在其他工作电极系统中已经观察到的那样，氧化还原对在ION电极上表现出准可逆行为。伏安数据拟合得到了表观电子转移常数，发现对于两种氧化还原对（Fe(CN)(3-/4-)和Cu(2+/0)），ION电极中的表观电子转移常数都更高。通过差分脉冲阳极溶出伏安法发现，ION电极对水样品中1.0至8.0×10(-6) mol×L(-1)范围内的Cu2+呈线性响应，检测限为0.3×10(-8) mol×L(-1)。灵敏度为-0.6μA/μmol×L(-1)。在用自来水进行的标准加入和回收率实验中，回收率约为102%-119%。在用研磨咖啡和速溶咖啡样品进行的类似实验中，回收率分别为92.5%和103%。此外，ION电极对常见干扰离子如Zn2+、Mn2+、Ni2+和Fe3+的存在几乎不敏感，即使其浓度比Cu2+高十倍。
