One-Step-Process Composite Colloidal Monolayers and Further Processing Aiming at Porous Membranes

Abstract

Composite materials consisting of a monolayer of polystyrene spheres (diameters of 430 and 520 nm) and porous silica, filling in the interstices, have been fabricated and characterized. The proposed growth method introduces some novelties as far as the fabrication of this kind of monolayers is concerned, as it probes the compatibility of coassembly (in which a silica precursor, tetraethyl orthosilicate (TEOS), is added to the base colloid) with confined growth in a wedge-shaped cell, while profiting from the advantages of both techniques. Using this method, it is possible to fabricate the composite monolayer in a single growth step. A systematic study of the influence of TEOS concentration in the initial colloid was performed in order to improve the quality of the two-dimensional crystals produced. Thus, it was demonstrated that the two methods are compatible. Furthermore, the composites were then subjected to thermal treatment so that the polymer is removed to reveal the inverse structure. After the calcination the membranes still present very good quality and so the proposed approach is effective for the fabrication of porous membranes. A comparison of reflectance spectra, between composite monolayers fabricated using this method and composites achieved by infiltrating polystyrene bare opals with silica chemical vapor deposition, is also established. The procedure presented is expected to establish the route for an easier and quicker fabrication of inverse monolayers of high refractive index materials with applications in light control.

Effect of some industrial dyes on the self-assembly of polymeric opals based on core-shell nanoparticles

“…With acidic-functionalised core-shell particles, the acidic chains can both catalyze the sol gel reaction and bridge between the particles and the inorganic matrix further stabilizing the 3D system. It has been reported that the presence of TEOS during casting results in less cracking between ordered domains for rigid spheres [16,11].…”

“…Solvent properties, especially volatility, have been shown to affect the degree of self ordering of rigid Nps, i.e. alcoholic solvents increase the quality of crystals in some cases [16]; drying speed (i.e. the drying temperature) of the film was also found to influence the quality of the opal, especially when water is used as casting medium.…”

“…Co-deposition of TEOS with charged spheres has been shown to yield a better and faster film formation than a deposition/infiltration process using vertical deposition [16,20] with less cracking and wider crystalline areas.…”

Shape-memory effect for self-healing and biodegradable photonic systems

“…26 The spheres used were made of polystyrene and purchased from Thermo Scientific (polydispersity around 3%). A particle diameter of 870 nm was tested for fabricating the crystals which, in turn, were verified suitable for templating shape-memory structures.…”

Crosslinking of floating colloidal monolayers

“…Crystalline, colloidal monolayers have been shown to be highly useful for nanolithography [1–4], structural color painting [5], or as templates for fabrication of porous materials [6–8]. Common assembly methods to prepare these structures include drop casting, spin coating [9–11], evaporation [11] on solid substrates, or self-assembly at air/liquid interfaces with subsequent transfer [1, 12–19].…”