Direct electrochemistry of cytochrome c at a hierarchically nanostructured TiO2 quantum electrode

Abstract

Monodisperse TiO 2 nanoparticles and urchin-like hierarchical TiO 2 nanospheres assembled with ultrathin quantum nanowires (about 2 nm) have been synthesized by a simple template-free wet chemical method. The morphology, structure, and crystallinity of the TiO 2 nanomaterials were investigated by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and high resolution transmission electron microscopy (HRTEM). Electrochemical measurements with the hierarchically nanostructured TiO 2 nanospheres as an electrode showed much better reversibility for direct electrochemistry of cytochrome c (cyt c) and much higher sensitivity than for an electrode composed of the monodisperse TiO 2 nanoparticles. The excellent performance of the hierarchical TiO 2 nanospheres may result from a quantum size effect, and their favorable nanostructure (with the presence of an abundance of both uniform macropores and mesopores), excellent structural stability and high specific surface area. The relative ionic strength had significant effect on the direct electrochemistry. Very high ionic strengths relative to cyt c concentration (I/c) induced a conformational change of cyt c on the nanostructure-coated electrode, from the native state to a partially unfolded one in 25 mmol/L phosphate buffer solution (pH 6.8).

Core-Size-Dependent Catalytic Properties of Bimetallic Au/Ag Core–Shell Nanoparticles

“…31−36 Moreover, in the presence of seed, the formation of bimetallic core/shell nanoparticle followed a seedassisted growth mechanism, which follows both homogeneous and heterogeneous nucleation of metal atoms and Ostwald ripening growth. 37 In the present work, similar type of evolution of Au/Ag NCs was observed, which was investigated by taking aliquots out of the reaction system at various stages to understand the formation mechanism of Au/Ag bimetallic core/shell nanoparticle. These are discussed in detail in the Supporting Information ( Figure S4).…”

Electrochemical and thermodynamic properties of hexacyanoferrate(II)/(III) redox system on multi-walled carbon nanotubes

“…It is noticeable that at T = 278.15 K, where the smallest k s values (k s % 3 Á 10 À3 cm Á s À1 ) were obtained on both MWCNT-based films, the impedance semicircle dominates in the high frequency region of EIS spectrum, indicating that the slow charge transfer kinetics mainly controls the electrochemical response on the film. Likewise, at T = 303.15 K, where the greatest k s values (k s % 6 Á 10 À3 cm Á s À1 ) were determined, the semicircle almost disappears and the EIS spectrum mainly consists of a linear part, which reveals that the redox process is diffusion-controlled [46]. As it was already mentioned above the Warburg impedance is created by the limited diffusion of charge carriers and depends strongly on the frequency range used for EIS experiments.…”

Convertible electron transfer pathways of cytochrome c at TiO2 quantum electrode

“…[12][13][14][15] TiO 2 quantum wires and their assemblies are ideal platforms for the investigation of the direct electrochemistry of cyt c, owing to their significant enhancement on adsorption and biocompatibility for the targeted protein based on their large specific surface area, highly organized nanostructures and mesopores, which resulted in higher bio-sensitivity and faster sensing response. 16,17 However, in contrast with the measurements made along with the increase of ionic strength in big strides reported before, [7][8][9] research on the effect of minor fluctuations in ionic microenvironment on the electron transfer process of cyt c at a nanoscale TiO 2 electrode is rather limited, although such a work may present a deeper understanding of some regional phenomena such as critical conformational fluctuations as well as electron pathways conversion. 17 New insight into the interplay of suitable strength of electrostatic attraction between cyt c and electrode (EA) and the corresponding hydrophobic interaction (HI) is only of scientific interest in the electron transfer kinetics of cyt c but also could provide real benefits such as the development of related biosensors and biomaterials.…”

“…16,17 However, in contrast with the measurements made along with the increase of ionic strength in big strides reported before, [7][8][9] research on the effect of minor fluctuations in ionic microenvironment on the electron transfer process of cyt c at a nanoscale TiO 2 electrode is rather limited, although such a work may present a deeper understanding of some regional phenomena such as critical conformational fluctuations as well as electron pathways conversion. 17 New insight into the interplay of suitable strength of electrostatic attraction between cyt c and electrode (EA) and the corresponding hydrophobic interaction (HI) is only of scientific interest in the electron transfer kinetics of cyt c but also could provide real benefits such as the development of related biosensors and biomaterials.…”