Fluoro Silanes Research Articles

Surface modification of polypropylene hollow fiber membranes using fluorosilane for CO2 absorption in a gas-liquid membrane contactor

Conventional methods for improving the hydrophobicity of polypropylene (PP) membranes to prevent wetting phenomena require complex pretreatment procedures in order to activate the surface for enabling the reaction with fluorosilane (FS)-based materials. This study successfully prepared PP membrane contactors with enhanced hydrophobicity through a simple single-step dip-coating method using perfluoroether-grafted silanes for CO2 capture. The FS coating layer on the PP membrane surface was confirmed through ATR-FTIR spectroscopy, XPS, FE-SEM, and EDS. Furthermore, the evaluation of the CO2 absorption performance and long-term stability of the FS-coated PP membrane according to the variation of the gas flow rate (50, 100, 200, 400, and 800 mL/min) confirmed the superior chemical stability and durability of our membranes to those of previously reported hydrophobic membranes. The as-prepared FS-coated PP membrane expands the application scope of gas-liquid membrane contactors for CO2 capture from the flue gas of coal-fired power plants.

A colorfast and durable superamphiphobic coating based on organic-titanium fluoride nanoparticles and crystal violet lactone

Colors on the impact or thermal papers fade easily due to the unstable and hydrophilic chromophoric group of pigment molecules. It seriously affects the readability and preservation value of the document. Superamphiphobic coating is an effective alternative solution, depending on the high resistance to water and oil. Herein, we fabricated a stable blue-purple superamphiphobic coating based on crystal violet lactone (CVL), fluoro silane (FAS) modified TiOx (TiOx@FAS), which efficiently avoided color fading of the printed papers. The shielding effect of the fluorocarbon chain and the vertical network aggregation effect protect TiOx@FAS/CVL coating from disadvantageous attacks. Both superamphiphobicity and colorfastness of coating could be maintained under attacks of different solvent gases and UV light. The coating kept purple-blue and superamphiphobic as original over 180 days, showing promising potential in practical applications.

Contamination and carryover free handling of complex fluids using lubricant-infused pipette tips

Cross-contamination of biological samples during handling and preparation, is a major issue in laboratory setups, leading to false-positives or false-negatives. Sample carryover residue in pipette tips contributes greatly to this issue. Most pipette tips on the market are manufactured with hydrophobic polymers that are able to repel high surface tension liquids, yet they lack in performance when low surface tension liquids and viscous fluids are involved. Moreover, hydrophobicity of pipette tips can result in hydrophobic adsorption of biomolecules, causing inaccuracies and loss in precision during pipetting. Here we propose the use of lubricant-infused surface (LIS) technology to achieve omniphobic properties in pipette tips. Using a versatile and simple design, the inner lumen of commercially available pipette tips was coated with a fluorosilane (FS) layer using chemical vapor deposition (CVD). The presence of FS groups on the tips is confirmed by x-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) tests. After lubrication of the tips through a fluorinated lubricant, the omniphobicity and repellent behaviour of the tips drastically enhanced which are revealed via static and hysteresis contact angle measurements. The repellency of the lubricant-infused pipette tips against physical adsorption is investigated through pipetting a food coloring dye as well as human blood samples and are compared to the untreated tips. The results show significantly less amount carryover residue when the lubricant-infused tips are utilized compared to commercially available ones. We also demonstrate the lubricant-infused tips reduce bacteria contamination of the inner lumen by 3 to 6-log (over 99%, depending on the tip size) after pipetting up and down the bacteria solution.

Liquid-like surface modification for effective anti-scaling membrane distillation with uncompromised flux

Membrane scaling is a critical challenge for membrane distillation (MD), especially when treating hypersaline brines. In this study, an anti-scaling membrane was developed with a liquid-like surface coating. This fabrication approach combined electrospun polyvinylidene fluoride (PVDF) membrane with surface fluorination without the addition of nanoparticles. Two fluoro silanes with the same alkyl-chain length but different hydrolysis reaction sites were investigated as the fluorination agents. Membrane characterizations indicated that surface modification with the single hydrolysis site fluoro silane (17-FAS-S) did not change the membrane morphology or structure. On the other hand, surface modification with the triple hydrolysis site fluoro silane (17-FAS-T) generated nanoparticles on the membrane surface, resulting in increased roughness. While both the 17-FAS-S and 17-FAS-T modified membranes exhibited excellent scaling resistance in the MD scaling tests, the 17-FAS-S membrane provided a much higher vapor flux than the 17-FAS-T one. Finally, the mechanism of scaling resistance and vapor permeability provided by the liquid-like modification was discussed.

Hydrophobic/Oleophilic Structures Based on MacroPorous Silicon: Effect of Topography and Fluoroalkyl Silane Functionalization on Wettability.

The effect of the morphology and chemical composition of a surface on the wettability of porous silicon structures is analyzed in the present work. Hydrophobic and superhydrophobic macroporous substrates are attractive for different potential applications. Herein, different hydrophobic macroporous silicon structures were fabricated by the chemical etching of p-type silicon wafers in a solution based on hydrofluoric acid and coated with a fluoro silane self-assembled monolayer. The surface morphology of the final substrate was characterized using a scanning electron microscope. The wettability was assessed from contact angle measurements using water and organic solvents that present low surface energy. The experimental data were compared with the classical wetting states theoretical models described in the literature. Perfluoro-silane functionalized macroporous silicon surfaces presented systematically higher contact angles than untreated silicon substrates. The influence of porosity on the surface wettability of macoporous silicon structures has been established. These results suggest that the combination of etching conditions with a surface chemistry modification could lead to hydrophobic/oleophilic or superhydrophobic/oleophobic structures.

Development of Superhydrophobic Polyester (Polyethylene terephthalate) Fabric for Multiple Applications

This study intended to develop a healthy and environmentally friendly super-hydrophobic PET polyester textile fabric using a specific Fluoro Silane finish (SHF). A novel SHF was prepared and applied on a polyester fabric using a pad-dry-cure method. The finished fabric was evaluated for the degree of hydrophobicity, durability and stain repellence. The finished fabric exhibited static water contact angle greater than 170o and received 90 AATCC (4 ISO) rating that is recognized as super-hydrophobicity and this property was maintained even after a 50,000-cycle abrasion test. FTIR analysis identified the characteristic peaks related to Si-O-Si and C-F asymmetric stretching bands of the finish on the fabric indicating a robust attachment on the fabric. Finished fabric did not show any change in appearance or tactile characteristics of the fabric.

Development of super-hydrophobic and stain repellent fabric finish

This study intended to develop a health and environmental friendly super-hydrophobic textile fabric using a specific Fluoro Silane (Fs) finish. A novel Fs finish was prepared and applied on an acrylic fabric using a pad-dry-cure method. The finished fabric was evaluated for the degree of hydrophobicity, durability and stain repellency. The finished fabric exhibited static water contact angle greater than 170° and received 90 AATCC (4 ISO) rating that is recognized as super-hydrophobicity and this property was maintained even after a 50,000 cycle abrasion test. FTIR analysis identified the characteristic peaks related Si-O-Si and C-F asymmetric stretching bands of the finish on the fabric indicating a robust attachment of the finish on the fabric. Finish fabric did not show any change in appearance or tactile characteristics of the fabric.

Facile fabrication of superhydrophobic hybrid nanotip and nanopore arrays as surface-enhanced Raman spectroscopy substrates

We demonstrate the fabrication of superhydrophobic hybrid nanotip and nanopore arrays (NTNPAs) that can act as sensitive surface-enhanced Raman spectroscopy (SERS) substrates. The large-area substrates were fabricated by following a facile, low-cost process consisting of the one-step voltage-variation anodization of Al foil, followed by Ag nanoparticle deposition and fluorosilane (FS) modification. Uniformly distributed, large-area (5 × 5 cm2) NTNPAs can be obtained rapidly by anodizing Al foil for 1560 s followed by Ag deposition for 400 s, which showed good SERS reproducibility as using1 μM Rhodamine 6G (R6G) as analyte. SERS performances of superhydrophobic NTNPAs with different FS modification and Ag nanoparticle deposition orders were also studied. The nanosamples with FS modification followed by Ag nanoparticle deposition (FS-Ag) showed better SERS sensitivity than the nanosamples with Ag nanoparticle deposition followed by FS modification (Ag-FS). The detection limit of a directly dried R6G droplet can reach 10−8 M on the FS-Ag nanosamples. The results can help create practical high sensitive SERS substrates, which can be used in developing advanced bio- and chemical sensors.

Microscale adhesion patterns for the precise localization of amoeba

In order to get a better understanding of amoeba-substrate interactions in the processes of cellular adhesion and directional movement, we engineered glass surfaces with defined local adhesion characteristics at a micrometric scale. Amoeba ( Dictyostelium dicoideum) are capable to adhere to various surfaces independently on the presence of extracellular matrix proteins. This paper describes the strategy used to create selective adhesion patterns using an appropriate surface chemistry and shows the first results of locally confined amoeba adhesion. The approach is based on the natural ability of Dictyostelium to adhere to various types of surfaces (hydrophilic and hydrophobic) and on its inability to spread on inert surfaces, such as the block copolymer of polyethylene glycol and polypropylene oxide, named Pluronic. We screened diverse alkylsilanes, such as methoxy, chloro and fluoro silanes for their capacity to anchor Pluronic F127 efficiently on a glass surface. Our results demonstrate that hexylmethyldichlorosilane (HMDCS) was the most appropriate silane for the deposition of Pluronic F127. A complex dependence between the physico-chemistry of the silanes and the polyethylene glycol block copolymer attachment was observed. Using this method, we succeed in scaling down the micro-fabrication of Pluronic-based adhesion patterns to the amoeba cell size (10 μm). This original Pluronic patterning method should prove useful as a tool for controlling cell adhesion and directional movement in amoeba.

Nanoparticles by chemical synthesis, processing to materials and innovative applications

AbstractNanoparticles have been fabricated by using chemical synthesis routes under specific conditions. During a precipitation process from liquid phases, surface controlling agents (SCAs) have been added during or shortly after the formation of precipitates. These interfere with the nucleating and growing particle to avoid agglomeration and to control size. Nanoparticles from many systems have been fabricated. If the SCAs are bifunctional, the surfaces chemistry could be tailored and the zeta potential of these particles was tailored also. SiO2 particles have been used for gene targeting using this approach. In other investigations, FeO x nanoparticles have been surface modified by amino groupings together with a sonochemical route to obtain very stable coatings. These particles have been used for in vitro tumor cell penetration and hyperthermal treatment. Boehmite nanoparticles were used to serve as condensation catalysts to prepare very hard transparent coatings for polycarbonate and an overcoat with polymerizable nanoparticles was used to produce anti‐reflective and ultrahard coatings. In systems with incorporated fluoro silanes, leading to low surface free energy coatings, nanoparticles were used to tailor the fluorine depth profile in self‐aligning transparent easy‐to‐clean coatings by influencing the critical micelle concentration. The examples show the usefulness of the chemical nanoparticle approach for nanocomposite fabrication and the high potential of these materials for medical and industrial application. Copyright © 2001 John Wiley & Sons, Ltd.

Effect of heat treatment and additives on the photochromic and mechanical properties of sol-gel derived photochromic coatings containing spirooxazine

The experimental results on the photochromic and mechanical properties of coatings containing 1,3-dihydro-1,3,3-trimethylspiro[2H-indole-2,3′-(3H)-naphth(2,1-b)(1,4) oxazine] (SO) derived from 3-glycidyloxypropyltrimethoxysilane (GPTMS), bisphenol A (BPA) and 1-methylimidazole (MI) by sol-gel processing are presented. It is shown that heat treatment temperature is a conflicting factor to the photochromic intensity (Δ A0), photostability and abrasion resistance of the photochromic coatings. With increasing densification temperature the matrix rigidity increases leading to a decrease of Δ A0 and at the same time an enhancement of both abrasion resistance and photostability, the optimum heat treatment temperature is 110°C under our experimental conditions. By the use of certain additives, e.g., fluorosilanes (FAS), not only Δ A0 but also the photostability and the abrasion resistance of the photochromic coatings have been further improved.

Molecular Interfacial Slip between Solid and Liquid in Polymer Suspensions of Hard Spheres

The viscoelastic properties of dispersions of uniform glass spheres (diameter 10 μm) in poly(dimethylsiloxane) (PDMS) were studied to evaluate the possibility of hydrodynamic slip at boundaries between the spheres and the PDMS matrix. The particle-matrix interfacial interactions are controlled by introducing a fluoro silane coating to the glass beads that reduces the surface energy of bare glass from over 200 mJ/m 2 to a level of ca. 20 mJ/m 2 . It is shown that the filler (i.e., glass beads) contribution to the overall suspension viscosity decreases significantly when the surface energy of treated beads approaches that of the PDMS matrix. From the point of view of stress transfer and rheology, we report the first set of rheological data supporting the concept of ideal slip. Our results also provide evidence for stress-induced interfacial slip. At high stress the difference in viscosity between a suspension of nontreated glass spheres and that of silane-treated spheres is larger than it is at low stress. Currently we do not know whether the stress-induced slip is due to debonding of interfacial chains off the glass beads or disentanglement of these chains with the matrix chains or a combination of both