Organosilane Groups Research Articles

Green solvothermal synthesis and characterisation of surface organosilylated hierarchical nanozeolite ZSM-5

Micellization of the exterior layer of zeolite precursor seeds with surface passivating organosilane groups is an effective technique to reduce aggregation of growing of crystallites. Simultaneously, this technique produces hierarchically porous material with additional mesopores, to minimise typical diffusional limitations encountered with conventional microporous zeolites. The average particle size and the pore architecture of the zeolite can be altered by changing the synthesis environment of the surface passivation process. In this study, low hazard organic solvents with different hydrophobicities (log P) have been used as an effective matrix for the surface organosilanization and crystallization processes of zeolitic species. A clear interaction of organosilane moieties on the exterior region of hierarchical nanozeolite ZSM-5 clusters is evidenced by solid-state nuclear magnetic resonance (NMR) analysis. In addition, hydrolysis of the organosilane molecules has been followed by mass spectroscopy analysis on the synthesis gel solution, leading to a mechanism proposed for the surface silanization processes of the zeolite nanoparticles using the soft-template surface passivating technique.

Halloysite nanotubes functionalized with epoxy and thiol organosilane groups to improve fracture toughness in nanocomposites

The surface functionalization of nanofillers imbibed within the matrix provides great interfacial adhesion with the epoxy resin and as such, in this study, the pure and functionalized halloysite nanotubes (HNTs) were used as fillers to improve the fracture toughness of an SC-15 epoxy resin. The HNTs were grafted with an organosilane group having terminal epoxy and thiol functional groups as two different crosslinkers and were thoroughly characterized with infrared spectroscopy (IR), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), powder X-ray diffraction (PXRD), and thermogravimetric analysis (TGA). The nanocomposites resulting from these fillers were used in compact tension (CT) testing with varying weight % from 0 to 2%, which were then fabricated and tested as per ASTM D5045 standard to evaluate the fracture toughness. The critical stress intensity factor (KIC) and the critical strain energy release rate (GIC) were measured, and a correlation was established between the test results and the mode of fractured surface images obtained by the SEM. Experimental results showed that the synergistic effect was observed with the addition of HNTs nanofillers into the SC-15 epoxy. The highest improved KIC and GIC were achieved using 2% HNT-thiol, followed by 2% pure HNT, and 1% HNT-epoxy nanofillers, respectively. SEM observation further confirmed that the presence of pure and functionalized HNT in the SC-15 epoxy matrix changed the toughness mechanics from smooth and low pseudo-ductile to several energy absorption mechanisms such as fibrils, river liner, crack bridging, crazing, microvoids, and hackles.

Green synthesis of sulfonated organosilane functionalized multiwalled carbon nanotubes and its catalytic activity for one-pot conversion of high free fatty acid seed oil to biodiesel

An environmentally friendly surface modification method was applied to synthesize solid acid catalyst suitable for biodiesel production. The catalyst was prepared from multiwalled carbon nanotube (MWCNT) and 3-mercaptopropyltrimethoxysilane (3-MPTMS) oxidized in hydrogen peroxide under supercritical carbon dioxide (scCO2). The carbon dioxide under supercritical condition with ethanol as cosolvent allows swift transportation and promotes uniform distribution of organosilane groups on randomly entangled and layered orientation of MWCNT. The catalyst was characterized by using Field emission scanning electron microscopy–energy dispersive x-ray (FESEM-EDX), Thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, X-ray powder diffraction (XRD), Brunauer–Emmett-Teller (BET) analysis and Time-of-Flight secondary ion mass spectrometry (TOF-SIMS). The catalytic activity of the catalyst was tested using a high free fatty acid (FFA)-containing Hibiscus cannabinus (kenaf) oil, and the fatty acid methyl esters (FAME) products from simultaneous esterification and transesterification reactions were quantified. To compare with scCO2 method, an acid catalyst was also prepared using liquid chemical deposition that resulted in only 45.11% biodiesel conversion. On the other hand, the optimum conversion of 93.10% was obtained using a scCO2 synthesized catalyst at the following transesterification conditions: temperature = 63 °C, methanol:oil ratio = 14:1, 10 wt % catalyst and time = 240 min.

Fabrication of superhydrophobic surface with desirable anti-icing performance based on micro/nano-structures and organosilane groups

A superhydrophobic surface was successfully obtained via the combination of specific micro/nano-structures and chemical modification. Herein, microstructures were developed by the poly (styrene-acrylonitrile) (SAN) copolymers through non-solvent induced phase separation method, while the hexamethyldisilazane-modified silica (SiO2) nanoparticles aggregate to form nanostructures. Consequently, the surface was covered with many more micro/nano-structures and organic groups, successfully leading to a superhydrophobic surface. The micro/nano-structures were mainly studied by scanning electron microscopy (SEM), whereas the surface chemistry was investigated by X-ray photoelectron spectroscopy (XPS). XPS analysis revealed that SiO2 nanoparticles tend to enrich on the surface with increasing SiO2 content, yet results showed that the surface wettability reached a saturated state with 5 wt% SiO2 content. With the addition of 5 wt% SiO2, the water contact angle of the relevant surface was 159°, performing superhydrophobicity. Simultaneously, the superhydrophobic surface performed desirable anti-icing property, where the water droplet kept unfrozen on the as-prepared surface for over 97 min at the temperature of −10 °C and humidity of 40%. In general, this study proposed a facile way to prepare superhydrophobic surface with desirable anti-icing property which might have potential applications against ice accumulation.

Facile Fabrication of Organic‐Inorganic Hybrid Material Based on Well‐Dispersed AuNPs on Organo‐Functionalised Zn‐Al‐Layered Double Hydroxides for Hydroamination of 1‐Hexene

AbstractA pioneering technique has been developed to design an organic‐inorganic hybrid material where small sized gold nano particles (2‐5 nm AuNPs) are uniformly dispersed on organo functionalized Zn−Al layered double hydroxide (LDH). Primarily a novel clay based hybrid material can be synthesized by grafting of organo silane groups (i. e. amino propyl triethoxy silane (APTS) and (3‐Mercaptopropyl) trimethoxy silane (MPTS)) onto the LDH layer. This hybrid material can control the crystal growth of AuNPs to generate a very small particle size and lock the position of consecutive AuNPs which prevent agglomeration. A regular characterisation was performed by various techniques. The TEM image revealed the formation of well dispersed AuNPs (having average particle sizes is 2–5 nm) on functionalised LDH. Diffuse reflectance spectra confirmed that the nucleation of AuNPs forms without any aggregation. Successful grafting of APTS and MPTS onto the LDH layers is confirmed from FTIR and NMR spectroscopy. The heterogeneous catalyst proves an excellent catalytic activity towards hydroamination reaction of 1‐hexene (addition of amine to inactivated alkenes). Interestingly AuNPs on organo functionalised LDH showed better catalytic activity and stability as compared to that of parent ZnAl‐LDH. Superior catalytic activity was generally endorsed to the small particle size of gold which is due to the synergistic effect between AuNPs with amine or thiol pendant of organic moiety APTS or MPTS respectively. The heterogeneous catalysts, i. e. AuNPs on thiol functionalized LDH, show 92% product yield and AuNPs on amine functionalized afford 95% product yield towards hydroamination reaction without the requisite of any acid promoters. The hybrid material can be recovered and reused, which is a green and economical process for commercial application.

CO2 conversion to propylene carbonate catalyzed by ionic liquid containing organosilane groups supported on titanate nanotubes/nanowires

The direct conversion of CO2 into propylene carbonate was investigated using pristine sodium titanate nanotubes (TNT) and nanowires (TNW) on which the ionic liquid (IL) 1-methyl-3-(3-trimethoxysilylpropyl)imidazolium chloride was supported, resulting in IL-TNTs and IL-TNWs, respectively. Anchorage of the IL through its organosilane groups (around 28wt%) on the surface of TNT and TNW was confirmed by FTIR, DRX, EDS and TGA analyses. All the nanostructured materials showed good catalytic activity after CO2 cycloaddition to propylene oxide. IL-TNTs and IL-TNWs exhibited high catalytic performance (TOF=46 and 49h−1, respectively) and 100% selectivity in propylene carbonate (propylene/catalyst molar ratio=580, cat/cocat molar ratio=2.4, 4.0MPa of CO2, 383.15K, 6h).

Estimation of the surface interaction mechanism of ZnO nanoparticles modified with organosilane groups by Raman Spectroscopy

Abstract We investigated the surface modification of zinc oxide nanoparticles (ZnO-NPs) with 3-aminopropyltriethoxysilane (APTES). The ZnO-NPs were synthesized by the physical method of continuous arc discharge in controlled atmosphere (DARC-AC). The surface modification was performed using a chemical method with constant stirring and reflux for 24 h at room temperature. This surface functionalization of the ZnO nanoparticles (funct-ZnO-NPs) was experimentally confirmed by infrared spectroscopy (FT-IR), Raman spectroscopy, TGA, UV–Visible and XRD, while its morphological characterization was performed by HRTEM. Using Raman spectroscopy, it was possible to study the functionalization process after the change, as well as the appearance of new bands of the molecular vibrations produced by the chemical interaction of the surface of the nanoparticles with the silane coupling agent. Comparing the Raman spectra of the ZnO-NPs, APTES and funct-ZnO-NPs, it was observed that the area between 2700 and 3200 cm −1 related to the vibrations of the CH 2 and CH 3 bonds of the APTES molecule. The funct-ZnO-NPs showed a decrease in the peak intensity, which indicates a deactivation of the degrees of freedom of the APTES at the time of the surface functionalization with the ZnO-NPs, suggesting a redistribution of the APTES CH 2 groups, as they interact with the surface of the ZnO-NPs. The APTES molecule is anchored to the surface of the ZnO-NPs via one or two Si-O-Zn bonds and not by three, as is commonly reported. The above finding is attributable to steric impediment of the side groups of the APTES and the strain of the Si-O-Zn bonds that hinders the trivalent interaction with the surface of the nanostructured ZnO. Similarly, the results obtained by Raman were verified and complemented by means of FT-IR due to the presence of bands at specific wavelengths.

Separation of (+)-catechin and quercetin on mesoporous MCM-41 composites: Dynamics of the sorption of flavonoids

An analysis of conditions for chromatographic separation of quercetin and (+)-catechin based on experimental data and using the equations of an asymptotic model of sorption dynamics for substances characterized by convex isotherms of sorption is presented. The effects of the equilibrium (distribution coefficient) and kinetic (diffusion coefficient) factors on the dynamics of the sorption of flavonoids by ordered mesoporous material of the MCM-41 type and its composites with grafted organosilane groups is considered. The effects of kinetic and equilibrium parameters on the broadening of adsorption fronts is demonstrated with allowance for the inner and outer diffusion limitations of the sorption process.

Surface decoration of carbon nanosheets with amino-functionalized organosilica nanoparticles

Carbonaceous nanosheets decorated with amino-functionalized organosilica nanoparticles have been synthesized by a direct pyrolysis of betaine at 400°C in air, followed by a simple surface treatment with ([3-(2-aminoethylamino) propyl]trimethoxysilane under reflux conditions. Both pristine and organosilica modified carbon nanosheets (OMCNs), were characterized by Fourier-transform infrared (FTIR), Raman, and electron paramagnetic resonance (EPR) spectroscopies, transmission electron microscopy and thermal analysis methods. The experimental data reveal a dramatic increase in the number of radical centers on the surface of the developed OMCN hybrid. The organosilica nanoparticles, ranging in size between 3 and 15nm, are spherical and homogenously anchored on the surface of carbon nanosheets. The formation of COSi bridges between carbon sheets and the organosilica nanoparticles has been supported by FTIR and EPR. These nanoparticles are bound to the nanosheet surface together with individual functional organosilane groups at a spacing of about 4Å distance. The final hybrid is the complex nanosystem composed of 2D carbon nanosheets, spherical organosilica nanoparticles and immobilized amino organosilane molecules.

Controlled Direct Synthesis of C-Mono- and C-Disubstituted Derivatives of [3,3′-Co(1,2-C2B9H11)2]− with Organosilane Groups: Theoretical Calculations Compared with Experimental Results

Mono- and dilithium salts of [3,3'-Co(1,2-C(2)B(9)H(11))(2)](-), (1(-)), react with different chlorosilanes (Me(2)SiHCl, Me(2)SiCl(2), Me(3)SiCl and MeSiHCl(2)) with an accurate control of the temperature to give a set of novel C(c)-mono- (C(c) = C(cluster)) and C(c)-disubstituted cobaltabis(dicarbollide) derivatives with silyl functions: [1-SiMe(2)H-3,3'-Co(1,2-C(2)B(9)H(10))(1',2'-C(2)B(9)H(11))](-) (3(-)); [1,1'-mu-SiMe(2)-3,3'-Co(1,2-C(2)B(9)H(10))(2)](-) (4(-)); [1,1'-mu-SiMeH-3,3'-Co(1,2-C(2)B(9)H(10))(2)](-) (5(-)); [1-SiMe(3)-3,3'-Co(1,2-C(2)B(9)H(10))(1',2'-C(2)B(9)H(11))](-) (6(-)) and [1,1'-(SiMe(3))(2)-3,3'-Co(1,2-C(2)B(9)H(10))(2)](-) (7(-)). In a similar way, the [8,8'-mu-(1'',2''-C(6)H(4))-1,1'-mu-SiMe(2)-3,3'-Co(1,2-C(2)B(9)H(9))(2)](-) (8(-)); [8,8'-mu-(1'',2''-C(6)H(4))-1,1'-mu-SiMeH-3,3'-Co(1,2-C(2)B(9)H(9))(2)](-) (9(-)) and [8,8'-mu-(1'',2''-C(6)H(4))-1-SiMe(3)-3,3'-Co(1,2-C(2)B(9)H(9))(1',2'-C(2)B(9)H(10))](-) (10(-)) ions have been prepared from [8,8'-mu-(1'',2''-C(6)H(4))-3,3'-Co(1,2-C(2)B(9)H(10))(2)](-) (2(-)). Thus, depending on the chlorosilane, the temperature and the stoichiometry of nBuLi used, it has been possible to control the number of substituents on the C(c) atoms and the nature of the attached silyl function. All compounds were characterised by NMR and UV/Vis spectroscopy and MALDI-TOF mass spectrometry; [NMe(4)]-3, [NMe(4)]-4 and [NMe(4)]-7 were successfully isolated in crystalline forms suitable for X-ray diffraction analyses. The 4(-) and 8(-) ions, which contain one bridging -mu-SiMe(2) group between each of the dicarbollide clusters, were unexpectedly obtained from the reaction of the monolithium salts of 1(-) and 2(-), respectively, with Me(2)SiHCl at -78 degrees C in 1,2-dimethoxyethane. This suggests that an intramolecular reaction has taken place, in which the acidic C(c)-H proton reacts with the hydridic Si-H, with subsequent loss of H(2). Some aspects of this reaction have been studied by using DFT calculations and have been compared with experimental results. In addition, DFT theoretical studies at the B3 LYP/6-311G(d,p) level of theory were applied to optimise the geometries of ions 1(-)-10(-) and calculate their relative energies. Results indicate that the racemic mixtures, rac form, are more stable than the meso isomers. A good concordance between theoretical studies and experimental results has been achieved.

Oxidative Coupling Polymerization of Diethynylsilane Derivatives and 1,2-Diethynyl-1,1,2,2-tetramethyldisilane

We have carried out the Glaser oxidative coupling polymerizations of diethynyldiphenylsilane, diethynylmethylphenylsilane, diethynylmethyloctylsilane, and l,2-diethynyl-l,l,2,2-tetramethyldisilane to afford polycarbosilanes containing diethynyl and organosilane groups in the main chain, such as poly(diethynyldiphenylsilane), poly(diethynylmethylphenylsilane), poly(diethynylmethyloctylsilane), and poly(1,2-diethynyl-1,1,2,2-tetramethyldisilane), respectively. These obtained materials are almost insoluble in common organic solvents such as CHCl 3 and THF probably due to the presence of a rigid rod diacetylene group along the polymer main chain. Therefore, the polymers were characterized using several spectroscopic methods in solid state. FTIR spectra of all the polymeric materials show that the characteristic C≡C stretching frequencies appear at 2147-2154 cm -1 , in particular. The polymers in the solid state exhibit that the strong maximum excitation peaks appear at 260-283 nm and the strong maximum fluorescence emission bands at 367-412 nm, especially. Tnermogravimetric analysis of the materials shows that about 55-68% of the initial polymer weights remain at 400 °C in nitrogen.

Some features associated with organosilane groups grafted by the sol–gel process onto synthetic talc-like phyllosilicate

Two new lamellar inorganic–organic magnesium silicates have been successfully synthesized by using sol–gel based processes under mild temperature conditions. The talc-organosilicates derived using two silylating agents as the silicon source, (i) 3-chloropropyltrimethoxysilane, and (ii) from the attachment of 5-amino-1,3,4-thiadiazole-2-thiol molecule to this precursor agent, yielded PhMg-Cl and PhMg-Tz phyllosilicates. These organoclays were characterized through elemental analyses, infrared spectroscopy, X-ray diffractometry, surface area, thermogravimetry, and carbon and silicon solid state nuclear magnetic resonance spectroscopy. The results confirmed the presence of organic moieties covalently bonded to the inorganic silicon sheet network of the 2:1 class of phyllosilicates, with a density of organic molecules of 6.6 ± 0.1 and 2.7 ± 0.2 mmol g −1 anchored on the inorganic layer and with interlayer distances of 1158 and 1628 pm, respectively. The nuclear magnetic resonances results in the solid state are in agreement with the sequence of carbons distributed in the pendant chains of the original silylating agents and the silicon bonded to oxygen atoms or carbon atoms of the inorganic sheets, as expected for the organically functionalized phyllosilicates. The enhanced potential of the new compound PhMg-Tz as a multi property material was explored in adsorbing cations from aqueous solution. The basic sulfur and nitrogen centers attached to the pendant chains inside the lamellar cavity can coordinate mercury, by presenting an isotherm saturated at 0.19 mmol g −1 of this heavy metal. The functionality of this organoclay-like material expresses its potential for heavy cation removal from an ecosystem.

Improved thermal resistance of spherical BaMgAl 10O 17:Eu blue phosphor prepared by spray pyrolysis

The thermal degradation characteristics of BaMgAl 10O 17:Eu (BAM) blue phosphor with spherical shape were investigated. In this work, we developed a strategy that is very simple, but very effective to minimize the thermal degradation of BAM blue phosphor. In order to improve the thermal degradation properties of BAM particles prepared by spray pyrolysis, the as-prepared particles were treated by a two-step post thermal treatment. That is, the particles were treated under a vacuum atmosphere at 400 °C and successively in situ reduced at 1400 °C. It was found that the two-step treatment effectively reduces the color shift of the BAM particles, which is known as a big problem generally observed in the fabrication processes of plasma display panels (PDPs). According to FT-IR analysis, the vacuum treatment produced a stable hydrophobic surface which was maintained even after the baking process. For further improving the photoluminescence intensity under VUV irradiation, in this work, the surface of BAM particles treated by the above two-step treatment was modified with alkyl and organosilane groups. As a result, the photoluminescence intensity was enhanced. Therefore, it was concluded that removing the water (OH groups) existing on the surface or in the matrix as well as making a hydrophobic surface are promised to minimize the thermal degradation of BAM particles.

Structural Solution of Mesocaged Material AMS-8

A novel mesoporous material prepared using the recently reported co-assembly of anionic surfactants with organosilane groups has been studied in depth using high-resolution transmission electron microscopy (HRTEM) and electron crystallography. A three-dimensional (3D) structural solution of AMS-8 was obtained by Fourier analysis of HRTEM images, revealing a complex cubic mesocaged solid (space group Fd3̄m) composed of bimodal cages 3D-connected by cage windows. HRTEM images also indicate the presence of structural defects associated with the cubic close packing of spheres, while analysis by nitrogen adsorption−desorption isotherms reveals that accessibility to smaller cages may be restricted in this material. The opened and closed models of this structure derived from a combination of electron crystallography and nitrogen adsorption data are discussed with respect to the arrangement of cages and cage connectivities. Considerations of the nature of the micellar system playing part in this novel templating mechanism are discussed.