Seeded Mineralization Leads to Hierarchical CaCO₃ Thin Coatings on Fibers for Oil/Water Separation Applications

Abstract

Like their biogenic counterparts, synthetic minerals with hierarchical architectures should exhibit multiple structural functions, which nicely bridge the boundaries between engineering and functional materials. Nevertheless, design of bioinspired mineralization approaches to thin coatings with distinct micro/nanotextures remains challenging in the realm of materials chemistry. Herein, a general morphosynthetic method based on seeded mineralization was extended to achieve prismatic-type thin CaCO coatings on fibrous substrates for oil/water separation applications. Distinct micro/nanotextures of the overlayers could be obtained in mineralization processes in the presence of different soluble (bio)macromolecules. These hierarchical thin coatings therefore exhibit multiple structural functions including underwater superoleophobicity, ultralow adhesion force of oil in water, and comparable stiffness/strength to the prismatic-type biominerals found in mollusk shells. Moreover, this controllable approach could proceed on fibrous substrates to obtain robust thin coatings, so that a modified nylon mesh could be employed for oil/water separation driven by gravity. Our bioinspired approach based on seeded mineralization opens the door for the deposition of hierarchical mineralized thin coatings exhibiting multiple structural functions on planar and fibrous substrates. This bottom-up strategy could be readily extended for the syntheses of advanced thin coatings with a broad spectrum of engineering and functional constituents.

Seeded Mineralization in Silk Fibroin Hydrogel Matrices Leads to Continuous Rhombohedral CaCO3 Films

“…The granular nature of the nanodomains was next confirmed by AFM imaging (Figure 1e). The rough topography of the seed layers deposited on SF matrices is in contrast with the flat counterparts disclosed on PVA [31] and chitosan [32], respectively. We assume that the appearance of raspberry-shaped nanodomains is Calcium cations and other reacting agents are required to transport through the SF hydrogels for mineralization.…”

“…The protocol of the deposition of rhombohedral CaCO 3 films contains multiple steps (Scheme 1). First, continuous seed layers comprising granular CaCO 3 -PAA constituents were deposited on insoluble SF matrices, according to our previous work [32]. Afterwards, a thin layer of SF solution of different solid contents was coated on the seed layer for gelation, following a standard procedure reported by Falini et al [28].…”

“…The mineralization was performed by the slow diffusion of CO 2 (based on the slow decomposition of (NH 4 ) 2 CO 3 into a volume of 4 mL 50 mM CaCl 2 in the presence of 0.01 g L −1 PAA as the additive in a closed desiccator for about 36 h [32]. SF thin films after the ethanol treatment were positioned at the bottom of the reacting mother liquor for mineralization of the seed layer.…”

“…Moreover, it is worth noting that seeded growth is accompanied by competition between adjacent growing structural units, leading to crystalline films with a structural gradient and orientational preference [30]. For instance, seeded mineralization opens the door for obtaining prismatic-type CaCO 3 films with a vertical orientational preference [31][32][33]. Owing to the high packing density and uniform alignment of prisms, these films can exhibit comparable mechanical performance to their biogenic counterparts [31].…”

Calcium Carbonate Mineralization in a Surface-Tension-Confined Droplets Array

“…Calcium carbonate (CaCO 3 ) is one of the most abundant biominerals in nature [4][5][6][7]. The preparation of highly regulated CaCO 3 with fine structures under ambient conditions has attracted much attention [8][9][10]. Biomineralized calcium carbonate products have good biocompatibility and can be used not only as structural support for organisms [2] but also as biosensors [11], controlled released drug carriers [12,13], and so on.…”