Fig. 6: Interfacial catalysis with o/w SiO2NP-AgNP Pickering emulsions.
a Schematic illustrations of a modifier-free o/w SiO2NP-metal NP emulsion droplet acting as an interfacial catalyst for the reduction of 4-nitrophenol to 4-aminophenol. b Optical images of a Ag emulsion sample formed with 3-MPA modifiers before and a few minutes after being treated with NaBH4 solution. Also shown is the schematic illustrations of the 3-MPA modifiers being replaced by H- in the NaBH4 solution leading to emulsion destabilization. c Optical images of a SiO2NP-AgNP emulsion sample before and after 20 min of catalytic reaction. Also shown is the schematic illustrations of the surface-accessible AgNPs in modifier-free emulsions acting as stable catalysts. d UV–vis spectra of 4-nitrophenol measured at different stages of its catalytic reduction using SiO2NP-AgNP Pickering emulsions as the catalyst. e Semi-log plot of ln(A/A0) against time for 4-nitrophenol. The absorbance is measured for the peak at 400 nm using the data shown in d. f Plot showing the absorbance of 4-nitrophenol measured by UV–vis spectroscopy at different points of catalytic reduction using fresh SiO2NP-AgNP Pickering emulsions and SiO2NP-AgNP Pickering emulsions that have been stored for 1 month as the catalyst. Inset compares the overall conversion of 4-nitrophenol using fresh and stored SiO2NP-AgNP emulsions. The standard deviations in both charts were calculated from N = 3 independent samples.
