Adsorption Characteristics of Thionine on Gold Nanoparticles

Abstract

Adsorption characteristics of thionine on gold nanoparticles have been studied by using UV-vis absorption spectroscopy, fluorescence spectroscopy, transmission electron microscopy (TEM), cyclic voltammetry and Fourier transform infrared spectroscopy. With the increasing concentration of gold nanoparticles, the absorption peak intensity of H-type dimers of thionine increases continuously, whereas that of monomers of thionine first increases and then decreases. The addition of gold nanoparticles makes the equilibrium between the monomer and H-type dimer forms of thionine move toward the dimer forms. Furthermore, the adsorption behavior of thionine on gold nanoparticles is also influenced by temperature. TEM images show that the addition of thionine results in an obvious aggregation, and further support the absorption spectral results. The fluorescence intensity of adsorbed thionine is quenched by gold nanoparticles due to the electronic interaction between thionine molecules and gold nanoparticles. Cyclic voltammetric and infrared spectroscopic studies show that the nitrogen atoms of both of the NH2 moieties of thionine strongly bind to the gold nanoparticle surfaces through the electrostatic interaction of thionine with gold nanoparticles. For 15-20 nm particles, the number of adsorbed thionine molecules per gold nanoparticle is about 7.66 x 10(4). Thionine molecules can not only bind to a particle to form a compact monolayer via both of the NH2 moieties, but they can also bind to two particles via their two NH(2) moieties, respectively.

Aptamer biosensor for dopamine based on a gold electrode modified with carbon nanoparticles and thionine labeled gold nanoparticles as probe

“…Firstly, thionine was directly immobilized onto the surface of AuNPs according to methods reported previously with slightly modification [27]. A 100 μL of 1×10 −4 mol L −1 thionine solution was added into 1 mL AuNPs solution for 30 min to Scheme 1 Schematic illustration of dopamine detection based on thionine modified AuNPs and carbon nanoparticle-modified gold electrode immobilize thionine on its surface.…”

Electrochemical and in situ spectroelectrochemical studies of gold nanoparticles immobilized Nafion matrix modified electrode

“…The increase in the peak currents due to PS + redox process observed at the GC/Nf-Au Nps /PS + electrode (figure 4) when compared to the GC/Nf/PS + electrode (figure 3) clearly shows that the redox reaction of PS + at Au nanoparticles is significantly improved with fast electron transfer kinetics. The nitrogen atoms of the -NH 2 moieties of the cationic PS + bind strongly to Au Nps (Ding et al 2006) immobilized in Nf matrix and hence the electrostatic interaction plays an important role in increasing the reversibility and peak currents. Scheme 1 depicts the schematic representation of the interaction of dispersed Au Nps and their interaction with the incorporated PS + dye at the Nf-Au Nps modified electrodes.…”

Determination of carcinoembryonic antigen using a novel amperometric enzyme-electrode based on layer-by-layer assembly of gold nanoparticles and thionine

“…Till positively charged Thi and negatively charged nano-Au were assembled for 4 times, alternately, the increase of the peak currents began to level off. Figure 2(3) shows a quasi-reversible CV wave with i pa /i pc ≈ 1 at 50 mV/s, indicating a well performance of the {(nano-Au) 3 /(Thi) 4 } multilayer film [14,15] . After the modified electrode was soaked in gold colloids for the fourth time, a further increase in anodic and cathodic peaks could be seen (Figure 2 (4)).…”

“…Figure 6(1)(including curve 1 of the insert in the top right corner) is the CV of Thi/Nf modified electrode in HAc-NaAc. Figure 6(2) presents the CV of nano-Au/Thi/Nf modified electrode, the increase of the peaks can be found, as the nano-Au is able to make it easier for the electrons transfer to take place [14,15] . Curve 3 in the insert in the top right corner of Figure 6 is the CV of nano-Ag/Thi/Nf modified electrode.…”

“…Immobilization of Thi was attributed to the electrostatic force between positively charged Thi and the negatively charged sulfonic acid groups in Nf polymer, whereas immobilization of nano-Au particles was attributed to the chemisorption of the amine groups of the Thi and the opposite-charged adsorption [11][12][13] . Then the Thi and nano-Au was alternately adsorbed onto the modified electrode surface, which constructed the {nano-Au/Thi} n multilayer films by layer-by-layer (LBL) assembly, based on the electrostatic interaction between positively charged Thi and negatively charged nanoAu [14,15] . Finally, carcinoembryonic antibody (anti-CEA) was adsorbed onto the surface of the nano-Au layer and horseradish peroxidase (HRP) was used to block possible remaining active sites of the nano-Au monolayer instead of BSA and amplify the response of the antigen-antibody reaction at the same time.…”