Silane Molecules Research Articles

Temperature-responsive resistance sensitivity controlled by L-ascorbic acid and silane co-functionalization in flame-retardant GO network for efficient fire early-warning response

Frequent fire disasters have not only caused massive casualties, irreparable property and priceless artefacts loss, but also create severe environmental damage. Therefore, it is imperative, but also challenging, to obtain excellent fire resistance and efficient early-warning alarm response in precombustion of combustible materials. In this work, a green flame-retardant graphene oxide (GO) based paper/coating is designed and constructed via using a facile 3-methacryloxypropyltrimethoxysilane and L-ascorbic acid (LAA) co-functionalization strategy. The optimized co-modified GO network shows good structure stability and improves the flame retardancy of combustible materials. Further, such GO network can provide an ultrafast flame detection signal of only ~1 s and ideal fire early warning responses (e.g. a low responsive temperature of ~120 °C and an extremely rapid responsive time of ~7 s at 300 °C) in precombustion which are among the best performances of the state-of-the-art fire alarm sensors. Moreover, the transformation of silane molecules into a compact protective layer on sheets and the resistance transition of insulating GO network into conductive reduced GO path promoted by LAA molecules are clarified. This work provides a novel strategy and paradigm to achieving excellent flame resistance and ideal fire early warning response of GO network for fire safety and prevention applications.

Mid-infrared spectra of silane dispersed in solid neon.

We report mid-infrared spectra of silane dispersed in solid neon at relative concentrations 1:1000 and 1:5000, recorded with spectral resolution 0.15cm-1. Apart from major lines associated with internal vibrational motions of 28SiH4, 29SiH4 and 30SiH4 in fundamental modes ν3 and ν4, several weak accompanying lines in each region become discernible at the resolution of our experimental measurements, and are tentatively associated with librational motions of silane molecules in the solid neon lattice. The wavenumbers associated with a few overtone and combination modes are also presented.

An easy and innovative one-step in situ synthesis strategy of silica nanoparticles decorated by graphene oxide particles through covalent linkages

This research work presents the development of an easy synthesis method for functionalized and covered graphene oxide (GO) nanosheets with silica nanoparticles through one-step in situ sol-gel approach by using two different silane molecules: a tetraethylorthosilane (TEOS) grafted with N (β-aminoethyl)-γ-aminopropyltrimethoxysilane (Z6020) and a TEOS with γ-aminopropyltriethoxy-silane (A1100). Both synthetized GO/SiO2-Z6020 and GO/SiO2-A1100 nanoparticles were characterized and compared in terms of exfoliation level, GO chemical partial reduction and self-condensation efficiency of silica nanoparticles over carbon planes. This way, microstructural and morphological analysis were performed using UV-visible, Fourier Transform InfraRed and Raman spectroscopies, Wide Angle x-rays Scattering, scanning electron microscopy, confocal optical microscopy and thermogravimetric analysis. Laser granulometry and zeta potential measurements on colloidal solutions in water allowed the determination of the particles size distribution and dispersion quality of these nanohybrid materials.

Fluorescent nanoparticles light up rocks’ pores

A team of researchers has developed a simple, robust method for imaging the pores in rocks using magnetic, fluorescent nanoparticles (ACS Earth Space Chem. 2019, DOI: 10.1021/acsearthspacechem.9b00071). Measuring the porosity of rocks is important in petroleum engineering and for understanding geological carbon dioxide sequestration, groundwater flow, and the use of rocks as building materials. Na Li of the Chengdu University of Technology and colleagues used silane molecules to covalently attach a dye, rhodamine B, to silica-coated Fe3O4 magnetic nanoparticles. The team then used a strong magnetic field to pull the nanoparticles through rock samples about 30 µm thick. The samples showed stronger fluorescence than others that were loaded with nanoparticles that were physically coated with dye, without the silane linker. To measure the sizes of the pores and pore junctions, the team made nanoparticles ranging from 65 to 120 nm in size, each of which had different peak fluorescence wavelengths,

Surface Modification of Jute Fabric by Treating with Silane Coupling Agent for Reducing Its Moisture Regain Characteristics

ABSTRACT In the present study, the effect of silane treatment method on reducing the moisture regain of the jute fabric was investigated. Triethoxyvinylsilane, a widely used hydrophobic silane is used as the silane coupling agent. The treated fabrics were characterized by Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy/Electron dispersive spectroscopy (SEM/EDS) and for contact angle, moisture regain etc. It was observed that the moisture regain of the jute fabric reduced significantly by this treatment. The contact angle measurement showed that after silane treatment, the surface of the jute fabric became exclusively hydrophobic in nature with a contact angle of 111°. FTIR analysis of the treated fabric showed the presence of Si-O-C linkage on the surface which confirms that the hydroxyl groups of the jute fabric react with the silanol molecules forming Si-O-C linkages. The grafting of silane molecules onto the surface of jute fabric was further confirmed by the presence of silicone atoms detected by electron dispersive spectroscopy. It is expected that the findings of the work will open up new horizons for utilization of jute fabric in the area of healthcare, oil absorbent mat, composites and geo-textiles.

Enhanced mechanical property and flame resistance of graphene oxide nanocomposite paper modified with functionalized silica nanoparticles

Graphene oxide (GO) paper with outstanding integrated multiple functionalities (good mechanical performance, thermal stability and flame resistance, etc.) is strongly needed for numerous potential applications in cutting-edge fields. In this work, we report a facile and green process to fabricate GO-based nanocomposite papers via introducing functionalized silica (f-SiO2) nanoparticles. The results reveal that addition of f-SiO2 produces simultaneous improvements in mechanical strength, stiffness and flame resistance for GO paper. With incorporation of 10 wt% f-SiO2, the tensile strength, elastic modulus and toughness of the GO/f-SiO2 nanocomposite papers can be increased by about 51%, 317%, and 69%, respectively. Various characterizations disclose that hydrogen bonds and covalent interactions between GO sheets and f-SiO2 mainly contribute to the effective load transfer and energy dissipation between them, and thus leading to the improvements of mechanical properties. Based on the structural observation and analysis, the improved flame resistance of the GO/f-SiO2 papers should be attributed to the formation of rGO/SiO2 protective char, which are derived from the decomposition and redeposition of the grafted silane molecules and inorganic SiO2 and thermal reduction of GO into rGO. Our results suggest that the mechanical and thermal properties of GO papers can be tuned by introducing inorganic/organic f-SiO2, providing a new route for the rational designing and development of mechanically flexible and flame-retardant GO-based nanocomposite paper materials.

Electron impact elastic scattering from methane and silane molecules

Analytical expressions for the static potentials of the electron scattering from methane (CH4) and silane (SiH4) molecules have been obtained using Gaussian wave functions. Subsequently, we have studied the elastic scattering of electrons from these molecules utilizing their static potentials along with exchange and polarization potentials as well as a purely imaginary absorption potential to represent scattering into inelastic channels. The multi-centre target molecules are represented as STO-6G Gaussian wave functions. We have calculated the differential, integrated and momentum transfer cross sections in a wide range of incident electron energies from 10 to 500 eV. Comparisons of our results for CH4 and SiH4 with the available measurements and theoretical results are presented.

One-Step Synthesis of Epoxy Group-Terminated Organosilica Nanodots: A Versatile Nanoplatform for Imaging and Eliminating Multidrug-Resistant Bacteria and Their Biofilms.

Multidrug-resistant bacteria (MRB) and their biofilms, both of which develop high levels of drug tolerance, cause severe threats to global health. This study demonstrates that biocompatible fluorescent silicon-containing nanodots can be a multifunctional platform for simultaneously imaging and eliminating MRB and their biofilms. Ultrasmall epoxy group (oxirane)-functionalized organosilica nanodots (OSiNDs) with a high photoluminescence quantum yield of ≈31% are synthesized via a simple one-step hydrothermal treatment of an epoxy group-containing silane molecule, 3-glycidoxypropyltrimethoxysilane, and an organic dye, rose bengal. The resultant OSiNDs can be employed as a universal imaging reagent for visualizing various bacteria/biofilms, including MRB and their biofilms. Moreover, the epoxy group-terminated OSiNDs can be conjugated with amine-containing reagents only via the simple stirring of the mixtures at an elevated temperature (e.g., 60 °C) for several hours (e.g., 3 h) without the addition of activating reagents. The amine-containing antibiotic vancomycin (Van) can thus be easily conjugated with the OSiNDs, and the obtained OSiNDs-Van can successfully inhibit the growth of MRB and even eliminate their biofilms. Collectively, the present work may give new impetus to the development of novel antibacterial and anti-biofilm agents for overcoming the drug resistance of bacteria.

Silver Nanowire-Templated Molecular Nanopatterning and Nanoparticle Assembly for Surface-Enhanced Raman Scattering.

Developing simple and cost-efficient methods for fabricating molecular patterns is of great importance in the field of nanoscience and nanotechnology. Here, a simple and convenient method was developed for fabricating nanopatterns composed of positively charged silane molecules by using silver nanowires as templates. The as-obtained silane pattern copies the shape of the silver nanowires and is only 0.7 nm thick, which can later be used for templated assembly of small molecules and nanoparticles of opposite charges. As a proof of concept, the resultant assembly could be further used for surface-enhanced Raman scattering.

Enhanced thermal conductivity of flexible cotton fabrics coated with reactive MWCNT nanofluid for potential application in thermal conductivity coatings and fire warning

It is a challenge to fabricate a flexible and smart cotton fabric sensor with improved thermal conductivity while retaining electrical insulation. Herein, reactive multiwall carbon nanotube (MWCNT) nanofluid exhibiting soft glassy rheological behavior was successfully synthesized through simultaneous surface modification by (3-aminopropyl) triethoxysilane and dimethyloctadecyl[3-(trimethoxysilyl)propyl] ammonium chloride followed by ion-exchange reaction with nonylphenol polyoxyethylene ether sodium sulfate. Then, MWCNT nanofluid was used to coat MWCNT nanofluid/cotton fabrics by simple spraying. It was found that the addition of MWCNT nanofluid improved the thermal conductivity while preserving electrical insulation of the cotton fabric. The maximum thermal conductivity of MWCNT nanofluid/cotton fabric is 2.42 times that of cotton fabric. It was also observed that surface grafted non-conductive silane molecules and organic ion salt of MWCNT hinder the MWCNT inter-contacting with each other to form a conductive network for retaining electrical insulation. In addition, during the combustion process of cotton fabric, surface grafted organic molecules of MWCNT nanofluid began to decompose and thus promote the formation of the MWCNT conductive network, indicated by the presence of electric current. This could be valuable as a low-voltage DC power source for potential applications in fire alarm sensors.

Features of the Initial Stage of the Heteroepitaxy of Silicon Layers on Germanium When Grown from Silicon Hydrides

Data on the dependence of the growth rate of Si layers deposited onto Ge(111) by the hydride method on their thickness at the initial heteroepitaxy stage are reported. The effect of a Ge substrate within ten grown silicon single layers on the Si-film growth rate is demonstrated. Based on the data obtained, the kinetic coefficients responsible for the rate of the main physicochemical processes related to the interaction of hydride molecular beams with the growth surface are calculated. An analysis of the capture probability and rates of pyrolysis of the adsorbed Si(Ge) hydride molecules on the pure Ge(Si) surfaces reveals the dependence of their behavior on the growing-layer thickness. Comparison of the results obtained during Si-layer growth on Ge shows that the pure germanium surface has higher adsorption and catalytic abilities with respect to silane molecules than the pure Si surface. The unstrained pure Si surface has higher adsorption and catalytic characteristics with respect to Ge-hydride molecules.

Surface Functionalization toward Biosensing via Free-Standing Si-OH Bonds on Nonoxidized Silicon Surfaces.

Usually hydroxyl groups present on top of oxidized silicon served as binding centers for a silanization reaction toward surface functionalization. In this study, we developed a novel surface functionalization strategy where hydroxyl functionalization on nonoxidized silicon surfaces are obtained. These surfaces were stable for several weeks even in ambient air at room temperature. This high stability indicates a strong spatial isolation of the hydroxyl groups because they keenly tend to undergo a condensation reaction, forming silicon oxide. To prove the applicability of the obtained hydroxylated silicon surface, we further modified the hydroxyl groups with a commonly used silane molecule, (3-aminopropyl)triethoxysilane (APTES). The functional amino groups of the APTES layer bonded to the surface were subsequently altered by N-maleoyl-β-alanin to generate a surface highly specific for the immobilization of thiol-containing biomolecules (like thiolated single-stranded DNA or cysteine-tagged proteins). All modification steps have been investigated by IR spectroscopic ellipsometry measurements.

Effect of Silanization on the Magnetic and Microwave Absorption Properties of SrFe12O19 Nanostructure Particles

Strontium ferrite nanostructure particles (SrFe12O19), which have a ferrimagnetic nature, were synthesized by a co-precipitation process of chloride salts using a sodium hydroxide solution. The resulting precursors were heat-treated in a furnace at 1100°C for 4 h. After cooling in the furnace, the nanostructure particles were silanized using 3-methacryloxypropyltrimethoxy silane molecules. After applying the silane pretreatment to the surface of the nanoparticles, we studied the effects of the most influential silanizing parameters, including the silane concentration and hydrolyzing time, on the magnetic and microwave absorption properties of the samples. The hysteresis loops showed an optimum saturation magnetization of 0.065T for 1 h hydrolyzing time at 1.25 wt.% silane concentration; however, no change was detected in the coercivity by varying the two factors. The powders with optimum magnetic properties were used to manufacture the samples in order to study the microwave absorption properties. Employing silanized nanostructures resulted in a significant increase in the reflection loss (at the resonance frequency) from − 16 dB up to − 72 dB.

A comparative investigation of aminosilane/ethylene diamine–functionalized graphene epoxy nanocomposites with commercial and chemically reduced graphene: static and dynamic mechanical properties

Incorporation of nanosized fillers into polymers has created new composites by expanding the functions and applications while retaining the excellent engineering and processing flexibility inherent to polymers. Compared with traditional nanofillers, more recently, graphene has been increasingly preferred as a candidate for strengthening and/or functionalizing polymer nanocomposites. The easy synthetic methods, low cost, and non-toxicity of graphene make this material attractive for many technological applications. Herein, we discuss the synthesis of different types of graphene from graphite via graphene oxide reduction. Commercial graphene (CG) as well as the synthesized chemically reduced graphene (CRG) and chemically reduced silane-modified graphene (SMG) were characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and ultraviolet visible (UV-vis) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) studies. The results confirmed that the silane molecules were attached on the surface of graphene sheets. Simultaneously, most of residual oxygen-containing functional groups of GO were reduced and the sp2-hybridized structure of graphene was restored. The utilization of these graphene-based materials in the fabrication of epoxy nanocomposites with enhanced properties has been explored and compared with those of neat epoxy and CG/epoxy nanocomposites. Inclusion of 0.25 phr CRG and SMG in an epoxy resin showed 28% and 32% increases in tensile strength, and the corresponding fracture toughness displayed 67.6% and 66.3% increase respectively. The improved mechanical properties of SMG/epoxy nanocomposites might be due to the uniform dispersion of functionalized graphene and strong interfacial bonding between modified graphene and epoxy resin.

Silane grafted graphene oxide papers for improved flame resistance and fast fire alarm response

Flame-retardant silane-grafted-graphene oxide (silane-GO) papers are fabricated via a green and versatile silane-assisted assembling strategy, and their use as early fire alarm sensors are investigated. Different silane molecules with alkoxy groups can react with GO in aqueous solution via hydrolysis and condensation reactions and thus assemble into the aligned silane-GO papers. The silane-GO papers exhibit good mechanical flexibility, strong acidic/alkaline tolerance, excellent flame resistance and improved thermal stability at low silane content in comparison with pure GO paper. Structure observation and analysis disclose that a compact nano-silica protective layer transformed from the grafted silane molecules during combustion is formed to inhibit the thermal degradation of GO sheet effectively. Furthermore, the insulating silane-GO paper can be thermally reduced into the conductive reduced GO network after encountering high-temperature or flame situation, thus providing ideal early fire alarm response, i.e. rapid flame detecting response time of ∼1.6 s and fire early warning response of ∼5 s when attach on the heat resistor. These results suggest that the silane-GO papers are promising for development of advanced materials as smart sensors in early fire alarm applications.

Preparation and corrosion resistance of chromium-free Zn-Al coatings with two different silane coupling agents

In this paper, the chromium-free Zn-Al coatings prepared with different mixing ratios of 3-glycidoxypropyltrimethoxy (GPTMS) and methyltrimethoxysilane (MTMS) were presented. The morphology, composition and formation mechanism of the coatings were observed and studied by using scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR) and thermal analysis. Polarization tests and immersion tests were used to study the corrosion resistance of the coatings. The results showed that the coatings had similar morphology to Dacromet coatings. The silane molecules were hydrolyzed and condensed to form three-dimensional cross-linking networks. The coatings with GPTMS had nobler corrosion potential and lower corrosion current density. The immersion time of the coating in the 5 wt% NaCl solution could reach 58 days when the mixing ratio of GPTMS/MTMS was equal to 1.

In search for a hydride‐carbene bond

AbstractBy presenting a large group of dimers featuring hydride‐carbene bond between silane and various carbenes, we show that electrophilic properties of singlet carbenes can manifest also to a hydridic, ie, negatively charged, hydrogen atom of a hydride. This type of interaction is traced by the corresponding bond path in 18 cases. However, taking into account the fact that in the case of large interatomic distances, the electrostatic potential maps are better indicators of dominant intermolecular interactions, it is shown that the amount of dimers with the hydride‐carbene bond is even larger, as indicated by both the proximity and correct orientation of the π‐hole on the carbene carbon atom and the negative surface of the hydridic hydrogen of the silane molecule. The hydride‐carbene bond is weak, especially when compared with the hydride‐triel bond also involving the silane. In contrast to the latter, the intermolecular charge transfer is negligible. Moreover, the local electrostatic interaction involving the carbene carbon's π‐hole is not necessarily predominant in stabilization of all the carbene⋯silane complexes.

Silanization of superficially porous silica particles with p-aminophenyltrimethoxysilane

The surface functionalization of silica particles for chromatographic applications is typically achieved by means of silanization reactions. A silane molecule (e.g., chlorosilanes or alkoxysilanes) with a functional group of interest is attached to the silica surface through a siloxane bond. Even though the surface modification via silanization is widely used, how the reaction parameters affect the degree of surface coverage is rarely discussed, particularly when using the less reactive alkoxysilanes reagents. We studied reaction conditions to graft p-aminophenyltrimethoxysilane (p-APTMS) on superficially porous particles. Theoretical calculations predicted that 3 grafts of p-APTMS per nm2 (~5 μmol/m2) can be accommodated on the silica surface. This value is not achieved unless the reaction conditions are optimized. To maximize the surface coverage of the aminophenyl layer at the silica surface, we investigated the influence of temperature, reaction time, and addition of water to the silanization reaction on the surface coverage. After optimization, it was found that using elevated temperatures (130 °C), adding 3.3 equivalents of water per p-APTMS molecule, and reacting for 24 h in decane as the solvent provided a surface coverage as high as 4.5 μmol/m2 (2.7 grafts/nm2), approaching the limit suggested via theoretical density functional theory calculations.

Hydrophobicity of Polyacrylate Emulsion Film Enhanced by Introduction of Nano-SiO₂ and Fluorine.

This study proposes to utilize modified Nano-SiO2/fluorinated polyacrylate emulsion that was synthesized with a semi-continuous starved seed emulsion polymerization to improve the hydrophobicity, thermal stability, and UV-Vis absorption of polyacrylate emulsion film. To verify the proposed method, a series inspection had been conducted to investigate the features of the emulsion film. The morphological analysis indicated that Nano-SiO2 was surrounded by a silane molecule after modification, which can efficiently prevent silica nanoparticles from aggregating. Fourier transform infrared spectra confirmed that modified SiO2 and dodecafluoroheptyl methacrylate (DFMA) were successfully introduced to the copolymer latex. The particle size of latex increased with the introduction of modified Nano-SiO2 and DFMA. UV-Vis absorption spectra revealed that modified silicon nanoparticles can improve the ultraviolet shielding effect obviously. X-ray photoelectron spectroscopy illustrated that the film–air interface was richer in fluorine than film section and the glass side. The contact angle of modified Nano-SiO2/fluorinated polyacrylate emulsion containing 3 wt % DFMA was 112°, slightly lower than double that of polyacrylate emulsion, indicating composite emulsion films possess better hydrophobicity. These results suggest that introducing modified Nano-SiO2 and fluorine into polyacrylate emulsion can significantly enhance the thermal stability of emulsion films.

Adsorption behaviors of deposition-targeted metallic ions onto thiol-containing silane modified liquid crystal polymer surfaces

Here we demonstrate the adsorption behaviors of typical deposition-targeted metallic (Ag, Cu or Ni) ions on thiol-end surfaces during electroless deposition using for fabricating flexible electronics. Specific thiol-containing silane molecules were assembled onto the corona activated liquid crystal polymer surfaces and then metallic ions were adsorbed onto the modified surfaces. By using X-ray photoelectron spectroscopy, scanning electron microscope and atomic force microscope, the assembly processes, inter-reaction mechanism of these ions with thiol-end groups, and adsorption behaviors have been investigated in details. Thickness of the molecule layer was estimated as some nanometers. Besides, zeta-potential and wettability were used to characterize the surfaces and verify the adsorption behaviors. Overall, this work provides a helpful contribution for understanding circuits' deposition processes and fabricating flexible patterns for electronic devices.