Colloidal cubes for the enhanced degradation of organic dyes

Abstract

The shape of cubic silica colloids is exploited to form close-packed structures, whereas the hollow core of the cubes may host functional substances. A proof-of-principle of this approach is presented for iron oxide particles (hematite, a-Fe 2 O 3 ) confined inside silica cubes that display the ability to accelerate the degradation of the organic dyes methylene blue and rhodamine B in the presence of hydrogen peroxide (modified Fenton reaction). The silica coating does not impede the reaction, since degradation rates similar to those of bare hematite particles are observed. Moreover, the cubic colloids are still functional when densely packed onto a substrate. The degradation reaction is greatly enhanced by illumination with visible or UV light: the degradation time reduces by two orders of magnitude. Although the silica coating is damaged during the degradation reaction, the stability of the coating is improved by heat treatment of the cubes and by illumination.

Shape-shifting colloids via stimulated dewetting

“…A third and most intriguing dewetting mechanism is offered by a modified photo-Fenton reaction 21 , which takes advantage of the photocatalytic properties of the colloidal substrate to degrade the silane hydrophobe layer. While this mechanism only works with photo-active substrates, we found it particularly interesting as the particles can remain in their native aqueous medium at a neutral pH and be dewetted by simply exposing them to light.…”

Porous TiO2with large surface area is an efficient catalyst carrier for the recovery of wastewater containing an ultrahigh concentration of dye

“…The Fe 2 O 3 @DTT also showed a stronger ability to purify the wastewater in contrast with other reported Fenton catalysts (Table 4, ref. [38][39][40][41][42][43][44][45][46][47][48][49]. This encouraging result can be explained by the high dispersion of iron oxide.…”

Quasi-2d fluids of dipolar superballs in an external field

“…A more extended study of colloidal cubes was performed by Castillo et al 24 Their study included hematite cubes and cubes stabilized by a protecting polymer later. Subsequently, Castillo et al 25 demonstrated that silica cubes containing hematite could enhance the degradation of organic dyes. A review on the self-assembly of colloids possessing novel shapes has been written by Sacanna et al 26 Moreover, experimentally Wetterskog et al 21 found the appearance of porous bundles of cubes under a weak external field and more compact ones under a stronger external field.…”