Triethoxyoctylsilane (TEOS) is an alkoxide organosilane with four ethyl ester sidechains. It is used as a self-assembled monolayer and provides a hydrophobic coating with low surface energy. The water contact angle is in the range of 150-170°.

Green fabrication of highly flame-retardant

Due to their flexibility, renewability, and ease of processing, cellulose-based textiles are extensively utilized in daily life for diverse applications, including clothing, industrial textiles, household textiles, and medical textiles. In this study, we present a simple, cost-effective, and green approach for the in situ synthesis of a MOF, designated as NH2-MIL-53(Al), on carboxymethylated HF through a layer-by-layer synthesis technology. On one hand, NH2-MIL-53(Al) is a straightforward synthetic material with excellent stability, capable of increasing the surface roughness of the fabric and imparting UV resistance. On the other hand, triethoxyoctylsilane was employed as a completely transparent coating for the low surface energy modification of fabric composites to achieve surface protection. The water stability of MOFs is crucial for their practical applications. The SM(Al)HF-9 is fabricated by post-coating technology using triethoxyoctylsilane(TEOS) with low surface energy. Following the Triethoxyoctylsilane coating the M(Al)HF-9, the WCA of the SM(Al)HF-9 increased to 156°, meeting the criteria for superhydrophobicity. SM(Al)HF-9 exhibits excellent superhydrophobicity, which is achieved by combining the micron-sized rough structure formed by NH2-MIL-53(Al) on the fiber surface with the low-surface energy coating of Triethoxyoctylsilane.[1]

The NH2-MIL-53(Al)/Triethoxyoctylsilane-coated superhydrophobic hemp fabric (SM(Al)HF-9) maintains cleanliness over prolonged duration due to the incorporation of self-cleaning functionalities. The SM(Al)HF-9 also demonstrates excellent antifouling characteristics. Upon deposition of water on the SM(Al)HF-9 surface, the spherical water droplets can effortlessly roll off. Several liquids easily penetrated the NH2-MIL-53(Al)/Triethoxyoctylsilane-coated hemp fabrics resulting in HF and M(Al)HF-9 being contaminated by the liquids, whereas the SM(Al)HF-9 surface liquid remained in the form of droplets, manifesting its outstanding anti-stain ability. The combination of NH2-MIL-53(Al) and Triethoxyoctylsilane on the HF surface imparts remarkable coating stability, flame retardancy, anti-UV, self-cleaning, and oil–water separation capabilities. Triethoxyoctylsilane   is utilized as a hydrophobic agent, and MOF is synthesized in the aqueous phase as both UV absorber and flame retardant are employed to modify HF. In this work, we have developed a straightforward, eco-friendly, and versatile method for the efficient preparation of multifunctional fabrics through in situ synthesis of NH2-MIL-53(Al) on HF surface, followed by hydrophobic treatment with TEOS. The synergistic interaction between NH2-MIL-53(Al) and Triethoxyoctylsilane was crucial and indispensable for achieving a superhydrophobic coating with flame-retardant and anti-UV properties.

Kinetic studies of attachment and re-orientation of octyltriethoxysilane

Silanization is becoming one of the most widely used functionalization techniques for modifying silica surfaces with free chemical groups via self-assembled monolayers (SAMs). Due to disparity among different researchers about the time constant in SAM formation kinetics, we studied SAM formation of triethoxyoctylsilane (TEOS) on a silica substrate to determine time constant for molecular attachment and re-orientation. TEOS is less reported octylsilane for preparing hydrophobic surface in spite of providing good hydrophobicity. It has 8 carbon chain attached to the head group that provides hydrophobicity to the surface. Previously, we have reported effect of Triethoxyoctylsilane on surface chemistry for modulating protein adsorption and insulin aggregation.[2]

In this work, we have studied the kinetics of Triethoxyoctylsilane SAM formation on a silica substrate by FTIR, contact angle and AFM. To our best knowledge, kinetics of octylsilane SAM formation on a silica substrate has been reported for the first time by this piece of work. Kinetics of formation of Triethoxyoctylsilane SAM at silica/glass substrates had been studied. Characterization was carried out using FTIR spectroscopy, contact angle and AFM. FTIR data studied in the absorbance range of 2850–3000 cm? 1showed increase in peak height and area which is correlated with increase in the attached molecules with respect to time. Small islands of uniform size of ~ 20 nm were formed which eventually in-fill indicating smooth layer formation. It was supported by the fact that the Ra value initially increased until maximum and then decreased indicating smooth monolayer formation.

Coated and uncoated ZnO nanoparticles in soil

Nanotechnology has developed an increasing number of nano-based products that are currently applied in textiles, electronics, pharmaceuticals and cosmetics. This has raised scientific and public concerns about the potential impact of nanomaterials on the environment. Zinc oxide nanoparticles (ZnO-NP) are among the most commonly used nanoparticles having different uses such as environmental remediation and sunscreen application. To assess the effect of long-term dissolution on bioavailability and toxicity, triethoxyoctylsilane coated and uncoated zinc oxide nanoparticles (ZnO-NP), non-nano ZnO and ZnCl2 were equilibrated in natural soil for up to twelve months. The mass fraction (w/w) of the coated ZnO-NP was 96–99% zinc oxide and 1–4% TEOS (coating). Triethoxyoctylsilane (CAS 2943-75-1, colourless liquid) was purchased from Sigma–Aldrich Chemie BV (≥97.5%). To investigate the toxicity of the coating, five concentrations of TEOS were tested in a 28-day toxicity test with F. candida. For this purpose, 20 g dry soil was spiked with triethoxyoctylsilane dissolved in acetone. After evaporation of the acetone, 180 g dry soil was added and soils were mixed with a spoon to reach nominal concentrations (75–1200 mg/kg).[3]

The coating triethoxyoctylsilane, which represents approx. 3% of the ZnO-NP, may have contributed to the overall toxicity. When applying a mixture toxicity approach, taking into account that on a mass basis the coating represented 3.85% of the Zn mass, it may be assumed that the EC50 for coated ZnO-NP of 873 mg Zn/kg dry soil corresponds with a triethoxyoctylsilane concentration of 33.6 mg/kg dry soil. This means that the toxic strength of the mixture equals 0.5 TU, so the coated ZnO-NP are much more toxic than expected from the EC50 values of uncoated ZnO-NP and triethoxyoctylsilane. The decrease of toxicity of the coated ZnO-NP at the end of the 12-month equilibration period may be explained from the loss of the coating.

References

[1]Chang, Jiang et al. “Green fabrication of highly flame-retardant, anti-ultraviolet radiation and superhydrophobiccellulose-based fabric by constructing dualtielement-containing NH2-MIL-53(Al)@Triethoxyoctylsilane nano coatings.” International journal of biological macromolecules vol. 310,Pt 4 (2025): 143560. doi:10.1016/j.ijbiomac.2025.143560

[2]Hasan, Abshar, and Lalit M Pandey. “Kinetic studies of attachment and re-orientation of octyltriethoxysilane for formation of self-assembled monolayer on a silica substrate.” Materials science & engineering. C, Materials for biological applications vol. 68 (2016): 423-429. doi:10.1016/j.msec.2016.06.003

[3]Waalewijn-Kool, Pauline L et al. “Sorption, dissolution and pH determine the long-term equilibration and toxicity of coated and uncoated ZnO nanoparticles in soil.” Environmental pollution (Barking, Essex : 1987) vol. 178 (2013): 59-64. doi:10.1016/j.envpol.2013.03.003