Abstract
In this paper, we investigated how different growth conditions (i.e., temperature, growth time, and composition) allows for trading off cost (i.e., In content) and performance of nanostructured indium tin oxide (ITO) for biosensing applications. Next, we compared the behavior of these functionalized nanostructured surfaces obtained in different growth conditions between each other and with a standard thin film as a reference, observing improvements in effective detection area up to two orders of magnitude. This enhanced the biosensor’s sensitivity, with higher detection level, better accuracy and higher reproducibility. Results show that below 150 °C, the growth of ITO over the substrate forms a homogenous layer without any kind of nanostructuration. In contrast, at temperatures higher than 150 °C, a two-phase temperature-dependent growth was observed. We concluded that (i) nanowire length grows exponentially with temperature (activation energy 356 meV) and leads to optimal conditions in terms of both electroactive surface area and sensitivity at around 300 °C, (ii) longer times of growth than 30 min lead to larger active areas and (iii) the In content in a nanostructured film can be reduced by 10%, obtaining performances equivalent to those found in commercial flat-film ITO electrodes. In summary, this work shows how to produce appropriate materials with optimized cost and performances for different applications in biosensing.
Highlights
Nanostructured materials have attracted the attention of the scientific community due to their intrinsic characteristics, like emission and signal amplification, being applicable to medicine for drug delivery and tissue engineering, energy applications, nanotechnology, sensing and biosensing, among others [1,2,3]
In this paper we have performed an in-depth structural and electrochemical study to provide a better understanding of the characteristics of nanostructured indium tin oxide (ITO)
From the ITO growth dependence with temperature we have demonstrated that it exists an activation temperature, of about 150 ◦C, from which nanowires begin to grow exponentially
Summary
Nanostructured materials have attracted the attention of the scientific community due to their intrinsic characteristics, like emission and signal amplification, being applicable to medicine for drug delivery and tissue engineering, energy applications, nanotechnology, sensing and biosensing, among others [1,2,3]. One of the first nanomaterials used for biosensing was porous silicon, in the early 1990s. Dancil et al [10] used it for highly sensitive biosensing devices. Other nanomaterials for this purpose were carbon nanowires and nanotubes [11], and silicon carbide nanostructures [12], which exhibit a range of fascinating and industrially important properties, among them the stability of interband and defect-related green-to-blue luminescence and good biocompatibility
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