Plasmonic osmium hydrosols: Preparation, characterization, and properties

Abstract

A simple route for the synthesis of mesoporous and plasmonic chitosan supported osmium hydrosols (Os0) has been reported using osmium (III)-sodium borohydride redox reaction at room temperature. The composition and morphology of nanoparticles were determined with XRD, XPS, TEM, EDX, SEM, FTIR and N2-adsorption desorption techniques. No SPR band of Os0 at 485 nm was observed for the same redox reaction with cetyltrimethylammonium bromide (CTAB) for ca. 120 min at room temperature. The surface oxidation of Os0 into OsO2 was detected by XRD and XPS. XRD shows the presence of chitosan onto the surface of nanoparticles. The average pore size, and pore volume were found to be 7.23 nm, and 0.239 cc/g, respectively, for Os0. The persulfate activation catalytic activity was tested in situ chemical oxidation of basic red 2 (safranin) under activated and un-activated persulfate. Safranin was adsorbed onto the Os0 and complex was formed. The oxidation of dye follows pseudo-first order kinetics (kapp = 14.8 × 10-3 min−1 at [S2O82-] = 3.3 mM). The activated system showed a much higher dye oxidation rate compared to either S2O82- or Os0 alone. The activation energy (Ea = 105 kJ/mol) was calculated for the system by using Arrhenius equation. The reaction mechanism of Os0 activation of persulfate was elucidated and discussed.