Silica Nanoparticles and Surface Silanization for the Fabrication of Water-Repellent Cotton Fibers

Abstract

Water-repellent and anticorrosive superhydrophobic cotton fabrics were produced via an eco-friendly water-based coating with core–shell fluorescent silica nanoparticles (SiPs) and subsequent immersion in a mixture of two fluorine-free organosilanes (3-(aminopropyl)­trimethoxysilane and trimethoxy­(octadecyl)­silane). Transmission electron microscopy confirmed the spherical and core–shell structure of SiPs, and Fourier-transform infrared spectroscopy characterized their chemical composition. Scanning electron microscopy with energy-dispersive X-ray spectroscopy confirmed the high coating coverage even after realistic laundering cycles. In confocal laser scanning microscopy, the fluorescent core–shell SiPs were used as probes to characterize the coating coverage on the surface of the cotton fibers. The high fluorescent signal provided by the fluorescent core–shell SiP cores enabled their visualization over large surface areas of the modified cotton fibers, before and after several washing cycles. The hydrophobic property of the cotton fiber treatments was evaluated considering the type of particle coating (monolayer or hierarchization), covalent bond with silanes, and a final curing process. Monolayer coating with fluorescent core–shell SiPs and further silanization yielded cotton fibers with high hydrophobicity and excellent durability (tested up to 10 washing processes), maintaining water contact angle (WCA) values above 150°, repellency grade 3, and lower water uptake (165%) compared to pristine (600%) or silanized cotton fibers (340%). Principal component analysis showed that the silanization process increased the SiP-coated cotton fiber resistance to laundering sustaining nonwetting properties up to 10 washing cycles, which was not observed for SiP-coated fibers subjected to no silanization process. Additionally, the silanized and noncured SiP-coated fibers were tested against solvents and corrosive aqueous media, for which high resistance to toluene, chloroform, and strong acid was observed, with the maintenance of static and dynamic WCAs. Thus, this systematic study allowed us to verify the main factors associated with superior hydrophobicity and durability and achieve an optimized and less toxic approach that combines the deposition of fluorescent core–shell SiPs and binary silanization.

Silica Nanoparticles Modified with Fluorescent Dyes as Probes for in Situ Characterization of Natural Rubber Coatings

“…According to ASTM E2865-12, the surface charges of SiP1, SiP2, and ASiP2 presented fairly good stability, while ASiP1 had moderate stability. The synthesis conditions used to produce fluorescent SiPs established by van Blaaderen et al , has been refined by our group in the past few years. , The experimental procedure used in this paper consisted of two steps. First, the fluorescent dye molecule (FITC) is chemically bound to a silane coupling agent (APTMS) containing a secondary amine group (−NH 2 ).…”

“…The SiPs used in this work can be tuned to render NR-based coatings with antimicrobial and osteogenic properties, acting as a robust and multifunctional platform for several biomedical applications. , Moreover, since there is a demand for polymeric materials with optical properties, the homogeneity achieved in the paper for the dispersion of the fluorescent SiPs in the NR coating is of high relevance. We show that by tuning the particle surface charge it is possible to generate transparent and thin fluorescent NR coatings.…”

“…Therefore, the imaging approach enabled us to investigate the stability of NR-based coatings to advance their structural and morphological characterization for technological applications that require resistance/stability under fluid flow. Furthermore, the core of these fluorescent SiPs used in this work can be modified to produce NR-based coatings with antimicrobial and osteogenic properties acting as a versatile platform for biomedical applications. , …”

“…Furthermore, the core of these fluorescent SiPs used in this work can be modified to produce NR-based coatings with antimicrobial and osteogenic properties acting as a versatile platform for biomedical applications. 30,31 ■ EXPERIMENTAL SECTION Materials. Tetraethyl orthosilicate (TEOS, 98%), (3-aminopropyl) trimethoxysilane (APTMS, 97%), and fluorescein isothiocyanate (FITC, 97.5%) were acquired from Sigma-Aldrich (St. Louis, MO, USA).…”

“…The monodisperse fluorescent SiPs were prepared using a modified Stober method. 30 We established the synthesis conditions based on van Blaaderen's works, 33,34 in which are synthesized FITC-labeled SiPs from the system, ammonia, ethanol, TEOS, APTMS, and FITC. We produced two types of SiPs with average diameters of approximately 150 (SiP1) and 700 (SiP2) nm.…”