Gold nanoparticles (GNP) induced redox modulation in organoselenium compounds: distinction between cyclic vs. linear structures

Abstract

Selenium, like other chalcogens, shows a high affinity for gold nanoparticles (GNP). The binding interactions between the selenium centre and GNP can greatly influence its important physico-chemical properties, including electron transfer ability. To know if the chemical structure has any influence on these properties, in the present paper, binding and electron transfer reactions of two simple water soluble organoselenium compounds (SeC), i.e. a linear compound, (bis(2-ethanol)selenide) (SeEOH) and a cyclic compound, DL-trans-3,4-dihydroxy-1-selenolane (DHS) with GNP have been investigated. The binding with GNP of four different sizes (5–58 nm) was characterized by UV-visible spectroscopy, dynamic light scattering (DLS), zeta (ζ) potential, transmission electron microscopy (TEM) and surface enhanced Raman spectroscopy (SERS). Although both the compounds bind GNP through selenium atoms, they differ in orientation on the GNP surface. In DHS, only the selenium atom interacts, while in SeEOH, along with selenium atoms, alkyl groups also interact with the GNP surface. Stronger Se–GNP interaction and an increase in the electrophilicity of DHS as compared to SeEOH, was confirmed by their relative electron transfer reactivity with the ABTS˙⁻ radical. Pulse radiolysis studies suggested that both the compounds on reaction with the hydroxyl (˙OH) radical produced similar selenium centered dimer radical cations (Se∴Se)⁺, either in the presence or in absence of GNP, but significantly increased the yield of selenoxide in the presence of GNP, which is known to influence their antioxidant ability. Thus our results confirm that GNP can be used to modulate the electron transfer ability of selenium compounds.