Abstract
The increasing interest of attachment of gold nanoparticles (AuNPs) on titanium dioxide nanotubes (TNTs) has been devoted to obtaining tremendous properties suitable for biosensor applications. Achieving precise control of the attachment and shape of AuNPs by methods described in the literature are far from satisfactory. This work shows the comparison of physical adsorption (PA), cyclic voltammetry (CV) and chronoamperometry (CA) methods and the parameters of these methods on TNTs properties. The structural, chemical, phase and electrochemical characterizations of TNTs, Au/TNTs, AuNPs/TNTs are carried out using scanning electron microscopy (SEM), electrochemical impedance spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy. The use of PA methods does not allow the deposition of AuNPs on TNTs. CV allows easily obtaining spherical nanoparticles, for which the diameter increases from 20.3 ± 2.9 nm to 182.3 ± 51.7 nm as a concentration of tetrachloroauric acid solution increase from 0.1 mM to 10 mM. Increasing the AuNPs deposition time in the CA method increases the amount of gold, but the AuNPs diameter does not change (35.0 ± 5 nm). Importantly, the CA method also causes the dissolution of the nanotubes layer from 1000 ± 10.0 nm to 823 ± 15.3 nm. Modification of titanium dioxide nanotubes with gold nanoparticles improved the electron transfer and increased the corrosion resistance, as well as promoted the protein adsorption. Importantly, after the deposition of bovine serum albumin, an almost 5.5-fold (324%) increase in real impedance, compared to TNTs (59%) was observed. We found that the Au nanoparticles—especially those with smaller diameter—promoted the stability of bovine serum albumin binding to the TNTs platform. It confirms that the modification of TNTs with gold nanoparticles allows the development of the best platform for biosensing applications.
Highlights
The last decade has confirmed the preparation, characterization and application of various nanostructures such as nanotubes, nanoparticles, nanorods and nanowires—each with unique properties
The electrical conductivity and adsorption properties depend on the morphology of titanium dioxide nanotubes (TNTs) and their modification process
We focused on the structural, chemical, phase and electrochemical investigations of TNTs decorated with AuNPs
Summary
The last decade has confirmed the preparation, characterization and application of various nanostructures such as nanotubes, nanoparticles, nanorods and nanowires—each with unique properties. Titanium dioxide (TiO2 ) nanotubes are materials used as a biosensor platform and possess several beneficial properties in sensor construction, e.g., the ease of preparation methods, high orientation, large surface area, high uniformity and excellent biocompatibility [1,2]. The electrical conductivity and adsorption properties depend on the morphology of TNTs and their modification process. According to our previous research [2,7], the best electrochemical properties show the TNTs, for which the diameter was equal to 50 nm. TNTs adsorption and electrical properties are improved by thermal processing and doping with gold nanoparticles. The most desirable crystal phases are anatase and rutile from the three structures, which show good electrical conductivity [8]. The catalytic activity of AuNPs is a result of the quantum-scale dimension and the large surface-to-volume ratio [13]
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