Silane Si Research Articles

Photocatalytic mediated marine biofouling inhibition using nano CuO: TiO2-carbon dot embedded on organo silane surface modified polyethylene aquaculture cage nets

Biofouling in aquaculture cages is a potential problem and its management become major concern to the planners and farmers. The study aimed to modify the surface of polyethylene aquaculture cage nets using organo silane and to evaluate the effectiveness of a nano CuO:TiO2-carbon dot biocide treatment in inhibiting marine biofouling through photocatalytic action. Polyethylene aquaculture cage net surface modified using organo silane and the surface embedded with biocide of nano CuO:TiO2 and carbon dot (CD) derived from fish eye. The biocide-treated surface was characterized using UV–Visible and Fourier Transform Infrared spectrometry. The organo silane interacts with polyethylene via hydrogen bonding, CuO:TiO2 interacts with the silane's Si, and the carbon dots' conjugated CC bonds interact with the transition metal and silane through van der Waals electrostatic forces and hydrogen bonding. Varied concentrations of CuO:TiO2 and CD was coated sequentially over silane surface modified polyethylene, exposed in the marine environment to evaluate biofouling inhibition efficiency and found 0.05% each of CuO:TiO2 and CD was optimum. The CuO:TiO2–CD coated polyethylene cage net tested for its biofouling inhibition for 8 months in marine environment and exhibited excellent biofouling inhibition. The inhibition of biofouling was attributed to the enhanced photocatalytic action, resulting from increased electron-hole recombination, thus generating ROS, O2٠, and OH٠ radicals. This led to the highest electronic activity around the cage net and also the formation of an acidic environment deterred microorganisms. The study highlighted the use of organo silane for surface modification of polyalkenes to load the biocide and also CuO:TiO2–CD is a potential biocide for biofouling inhibition in aquaculture cages.

Tuning the Lewis Acidity of Neutral Silanes Using Perfluorinated Aryl‐ and Alkoxy Substituents

AbstractThe emerging field of Lewis acidic silanes demonstrates the versability of molecular silicon compounds for catalytic applications. Nevertheless, when compared to the multifunctional boron Lewis acid B(C6F5)3, silicon derivatives still lack in terms of reactivity. In this regard, we demonstrate the installation of perfluorotolyl groups (TolF) on neutral silicon atoms to obtain the respective tetra‐ and trisubstituted silanes Si(TolF)4 and HSi(TolF)3. These compounds were fully characterized including SC‐XRD analysis but unexpectedly showed no significant Lewis acidity. By using strongly electron‐withdrawing perfluorocresolato groups (OTolF) the tetrasubstituted silane Si(OTolF)4 was obtained, bearing an 8 % increased Δδ(31P) shift when applying the Gutmann‐Beckett method, compared to literature‐known Si(OPhF)4. Ultimately the heteroleptic Si(PhF)2pinF was successfully synthesized and fully characterized including SC‐XRD analysis, introducing a highly Lewis acidic silicon atom holding two silicon‐carbon bonds.

Ring-Opening Polymerization of Lactones Catalyzed by Silicon-Based Lewis Acid

Many catalysts containing various elements at their active sites have been reported for the ring-opening polymerization (ROP) of cyclic esters. However, to our knowledge, silicon-based catalysts for ROP have never been reported. Here we report the ROP of cyclic esters and cyclic carbonates catalyzed by the derivatives of bis(perchlorocatecholato)silane (Si(catCl)2), which is a neutral silicon-based Lewis acid recently reported by Greb et al. The catalyst systems show high activity for the ROP of seven- and six-membered ring monomers such as ε-caprolactone, δ-valerolactone, and trimethylene carbonate to produce the polymers with molecular weights up to 32 kg/mol. The matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and nuclear magnetic resonance analysis of the obtained polymers indicates the predominant formation of cyclic polymers.

Modification of PET Ion-Track Membranes by Silica Nanoparticles for Direct Contact Membrane Distillation of Salt Solutions.

The paper describes desalination by membrane distillation (MD) using ion-track membranes. Poly(ethylene terephthalate) (PET) ion-track membranes were hydrophobized by the immobilization of hydrophobic vinyl-silica nanoparticles (Si NPs). Si NPs were synthesized by the sol-gel method, and the addition of the surfactant led to the formation of NPs with average size of 40 nm. The thermal initiator fixed to the surface of membranes allowed attachment of triethoxyvinyl silane Si NPs at the membrane surface. To further increase hydrophobicity, ethoxy groups were fluorinated. The morphology and chemical structure of prepared membranes were characterized by SEM, FTIR, XPS spectroscopy, and a gas permeability test. Hydrophobic properties were evaluated by contact angle (CA) and liquid entry pressure (LEP) measurements. Membranes with CA 125–143° were tested in direct contact membrane distillation (DCMD) of 30 g/L saline solution. Membranes showed water fluxes from 2.2 to 15.4 kg/(m2·h) with salt rejection values of 93–99%.

A Green Approach to Modify Surface Properties of Polyurethane Foam for Enhanced Oil Absorption.

The non-selective property of conventional polyurethane (PU) foam tends to lower its oil absorption efficiency. To address this issue, we modified the surface properties of PU foam using a rapid solvent-free surface functionalization approach based on the chemical vapor deposition (CVD) method to establish an extremely thin yet uniform coating layer to improve foam performance. The PU foam was respectively functionalized using different monomers, i.e., perfluorodecyl acrylate (PFDA), 2,2,3,4,4,4-hexafluorobutyl acrylate (HFBA), and hexamethyldisiloxane (HMDSO), and the effect of deposition times (1, 5 and 10 min) on the properties of foam was investigated. The results showed that all the modified foams demonstrated a much higher water contact angle (i.e., greater hydrophobicity) and greater absorption capacities compared to the control PU foam. This is due to the presence of specific functional groups, e.g., fluorine (F) and silane (Si) in the modified PU foams. Of all, the PU/PHFBAi foam exhibited the highest absorption capacities, recording 66.68, 58.15, 53.70, and 58.38 g/g for chloroform, acetone, cyclohexane, and edible oil, respectively. These values were 39.19–119.31% higher than that of control foam. The promising performance of the PU/PHFBAi foam is due to the improved surface hydrophobicity attributed to the original perfluoroalkyl moieties of the HFBA monomer. The PU/PHFBAi foam also demonstrated a much more stable absorption performance compared to the control foam when both samples were reused for up to 10 cycles. This clearly indicates the positive impact of the proposed functionalization method in improving PU properties for oil absorption processes.

Bond Strength of Composite Resin Restoration Repair: Influence of Silane and Adhesive Systems

The aim of this study is to evaluate the effect of silane (Si) application and different adhesive systems on the bond strength of composite resin repair. One hundred composite truncated cone-shaped specimens were prepared and submitted to 5,000 thermal cycles to simulate existing restorations. Their top surfaces were airborne particle abraded with aluminum oxide, etched with phosphoric acid, and divided into two groups (n = 50) with or without Si application. Each group was divided into five subgroups (n = 10) according to the adhesive system applied: Solobond Plus Primer and Adhesive (SPA)-two-bottle, Solobond Plus adhesive (SA), Admira Bond (A)-one bottle, Futurabond DC (FDC)-self-etch, and Futurabond M (FM)-self-etch. New composite resin was applied over the bonded area. A control group was prepared to evaluate the cohesive strength of the composite resin. Specimens were submitted to tensile stress. Data were analyzed with two-way analysis of variance (ANOVA), and the Tukey and Dunnett tests. Si application reduced the bond strength of all adhesives (p = 0.001). Groups SA and SPA showed higher bond strengths in relation to other groups (p = 0.01). Groups FDC + Si, FM, FM + Si, and A + Si showed smaller mean bond strength values than that of the control group (p < 0.05). Previous Si application reduced bond strength values. The two-bottle adhesive showed better results than one-bottle or self-etching systems for composite resin repairs. The kind of adhesive system applied for composite resin repairs has a great influence on bond strength values. The use of Si in this situation is not recommended.

Porphyrin Dye/TiO2 imbedded PET to improve visible-light photocatalytic activity and organosilicon attachment to enrich hydrophobicity to attain an efficient self-cleaning material

A visible-light sensitized, superhydrophobic, self-cleaning Polyethylene terephthalate (PET) fabric exhibiting photocatalytic dye degrading properties has been prepared by depositing anatase TiO2, porphyrin (TPPS, CuTPPS), and trimethoxy(octadecyl)silane (Si) onto the PET samples. The modified PET fabric showed superhydrophobicity, exhibiting a water contact angle (WCA) of 147°, and the ability to photodegrade rhodamine dye (RB), and the dye degradation ability of the modified fabric under visible light was monitored at different time intervals by UV–Vis spectroscopy. The degradation efficiency was found to be in the order PET/TiO2/TPPS > PET/TiO2/TPPS/Si > PET/TiO2/CuTPPS > PET/TiO2/CuTPPS/Si > PET/TiO2 > PET. The photodegradation ability and superhydrophobicity of the modified PET samples in relation to coffee and ketchup stains were examined qualitatively. Due to its superhydrophobicity, water soluble impurities/coffee drops roll off the surface of the modified PET fabrics, resulting in stain-free fabric. The fabrics were characterized by UV–Vis, FESEM, XRD and XPS. The structures of the synthesized porphyrin and TiO2 were confirmed by 1H NMR spectroscopy and XRD analysis, respectively.

Selective Cell Isolation by Transferrin Functionalized Silane–Carbon Soot Mediated Superhydrophobic Micropatterns

AbstractSurfaces that facilitate selective cell adhesion using specific targeting moieties have great implications in diagnostics, tissue engineering, and high throughput screenings. However, designing robust and spatially confined micropatterns for selective cell isolation on portable platform is highly challenging. Here, wettable, silane (Si) micropatterns holding covalently attached transferrin (Tf) for targeting Tf overexpressing cancer cells are reported. These micropatterns are separated by carbon soot based superhydrophobic regions that turn these targeting sites into surface tension confined “microwells.” These microwells facilitate capture of human colorectal carcinoma cells (HCT 116) and human cervical adenocarcinoma cells (HeLa) by confining their attachment to wettable region, thereby making isolation and spotting of the targeted cells more efficient. In addition, owing to its transparent trait, the Tf conjugated wettability based patterned chip offer real time optical monitoring of cell adhesion, cell growth, and cell behavior. The specific cell isolation using such surface has applications in devising cancer recurrence monitoring tests.

Insight into catalytic reduction of CO2 to methane with silanes using Brookhart's cationic Ir(iii) pincer complex.

Using density functional theory computations, we investigated in detail the underlying reaction mechanism and crucial intermediates present during the reduction of carbon dioxide to methane with silanes, catalyzed by the cationic Ir-pincer complex ((POCOP)Ir(H)(acetone)+, POCOP = 2,6-bis(dibutylphosphinito)phenyl). Our study postulates a plausible catalytic cycle, which involves four stages, by sequentially transferring silane hydrogen to the CO2 molecule to give silylformate, bis(silyl)acetal, methoxysilane and the final product, methane. The first stage of reducing carbon dioxide to silylformate is the rate-determining step in the overall conversion, which occurs via the direct dissociation of the silane Si–H bond to the C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> O bond of a weakly coordinated Ir–CO2 moiety, with a free energy barrier of 29.5 kcal mol−1. The ionic SN2 outer-sphere pathway in which the CO2 molecule nucleophilically attacks at the η1-silane iridium complex to cleave the η1-Si–H bond, followed by the hydride transferring from iridium dihydride [(POCOP)IrH2] to the cation [OC–OSiMe3]+, is a slightly less favorable pathway, with a free energy barrier of 33.0 kcal mol−1 in solvent. The subsequent three reducing steps follow similar pathways: the ionic SN2 outer-sphere process with silylformate, bis(silyl)acetal and methoxysilane substrates nucleophilically attacking the η1-silane iridium complex to give the ion pairs [(POCOP)IrH2] [HC(OSiMe3)2]+, [(POCOP)IrH2] [CH2(OSiMe3)2(SiMe3)]+, and [(POCOP)IrH2] [CH3O(SiMe3)2]+, respectively, followed by the hydride transfer process. The rate-limiting steps of the three reducing stages are calculated to possess free energy barriers of 12.2, 16.4 and 22.9 kcal mol−1, respectively. Furthermore, our study indicates that the natural iridium dihydride [(POCOP)IrH2] generated along the ionic SN2 outer-sphere pathway could greatly facilitate the silylation of CO2, with a potential energy barrier calculated at a low value of 16.7 kcal mol−1.

SHEAR BOND STRENGTH OF UNIVERSAL-ADHESIVE TO DIFFERENT FIXED PROSTHODONTIC MATERIALS

Objectives: To evaluate the shear bond strength (SBS) of Universal adhesive (Single Bond Universal SBU), that contain silane and MDP adhesive molecules, to different fixed prosthodontic materials (High-Leucite ceramics, Zirconia ceramics and base metal alloys).Methods: Twenty high-leucite based ceramics IPS Empress (Ivoclar) and twenty Ni-cr alloys Remanium-CSe(Dentaurum) specimens were constructed in discs of 5mm diameter and 3mm thickness. Twenty Zirconia based ceramics INcoris-TZI (Sirona) specimens were prepared of 19X15X3mm blocks. All specimens were embedded into acrylic resin blocks of 2x2X2cm. Composite discs 3mm in diameter Z-350(3M ESPE) were prepared and bonded to each material, divided into 2 groups according to the bonding procedures (N=10). High-Leucite ceramics etched with 5%HF acid then for Group1 composite discs were bonded with Single Bond2 SB2 and RelyX ultimate resin-cement RXU, after Silane Si application (Si+SB2+RXU), for Group 2 composite discs were bonded with Single Bond Universal adhesive and RelyX Ultimate without separate Silane application (SBU+RXU). Metal and zirconia specimens were air abraded 50µm AL2O3 then for Group 1; composite discs were bonded with Panavia cement only (Pa). For Group 2, composite discs were bonded with Single Bond Universal and RelyX Ultimate (SBU+RXU). All the specimens were thermo-cycled in water baths 5-55°C for 5000 cycles. The SBS was tested in a universal testing machine (Tira) using a chisel-edge blade. The results were statistically analyzed using Mann-Whitney test.Results: bThe mean (SBS±SD) in MPa were: In high leucite ceramics (23.1±2.5), (23.6± 1.9) for (Si+SB2+RUX) and (SBU+RUX) respectively. In Zirconia ceramics: (7.96± 3.1) and (16.8± 5.4) for (Pa) and (SBU+RXU) respectively. In Base metal alloys: (14.8±5.4) and (20.9±2.7) for (Pa) and (SBU+ RXU) respectively. Statistical analysis using Mann-Whitney test showed no significant difference for the high leucite and base metal groups (P>0.05) while there was significant difference for the zirconia groups (P<0.05). Conclusion: The Universal-adhesive SBU produced bond strength to high leucite-ceramics comparable to that of resin cement with separate Silane application. It produced higher bond strength to zirconia ceramics and base metal alloys in comparison to Panavia adhesive-resin cement.

Transition-Metal-Free Cleavage of CO.

Tertiary silane 1H, 2‐[(diphenylsilyl)methyl]‐6‐methylpyridine, reacts with tris(pentafluorophenyl)borane (BCF) to form the intramolecular pyridine‐stabilized silylium 1+‐HBCF. The corresponding 2‐[(diphenylsilyl)methyl]pyridine, lacking the methyl‐group on the pyridine ring, forms classic N(py)→B adduct 2H‐BCF featuring an intact silane Si−H fragment. Complex 1+‐HBCF promotes cleavage of the C≡O triple bond in carbon monoxide with double C−Csp2 bond formation, leading to complex 3 featuring a B‐(diarylmethyl)‐B‐aryl‐boryloxysilane fragment. Reaction with pinacol generates bis(pentafluorophenyl)methane 4 as isolable product, proving the transition‐metal‐free deoxygenation of carbon monoxide by this main‐group system. Experimental data and DFT calculations support the existence of an equilibrium between the silylium–hydroborate ion pair and the silane–borane mixture that is responsible for the observed reactivity.

Tetraphosphines with tetra(biphenyl)silane and -stannane cores as rigid scaffold linkers for immobilized catalysts

The silane Si(p-C6H4-p-C6H4Br)4 and the stannane Sn(p-C6H4-p-C6H4Br)4 have been synthesized and characterized. For the silane a single crystal X-ray structure has been obtained. Tetralithiation of the silane with nBuLi and quenching with the corresponding chlorophosphines gave the tetraphosphines Si(p-C6H4-p-C6H4PR2)4 with (R = Ph, Cy, iPr, tBu). Tetralithiation of Sn(p-C6H4-p-C6H4Br)4 led to cleavage of the Sn-C bonds. Therefore, Sn(p-C6H4-p-C6H4PPh2)4 was synthesized by Br/Li exchange of p-Br-C6H4-p-C6H4PPh2 with nBuLi and reaction with SnCl4. The silanes have been immobilized on silica by generating three phosphonium groups per molecule that were bound to the surface via strong electrostatic interactions. The remaining phosphine group was subsequently coordinated to Wilkinson's catalyst via ligand exchange. All solids have been characterized by quantitative 31P solid-state NMR spectroscopy. The catalysts, immobilized via the tetraphosphine linker scaffolds with biphenyl spacers, showed high activities and selectivities with respect to the hydrogenation of 1-dodecene. They have been recycled 9 times in a batchwise manner. All immobilized catalysts eventually formed rhodium nanoparticles that retained their catalytic activity even after being exposed to air.

Microtensile Bond Strength of Composite Cement to Novel CAD/CAM Materials as a Function of Surface Treatment and Aging.

To evaluate the effect of different surface treatments on the bond strength to a composite and a polymer-infiltrated ceramic CAD/CAM block after six-month artificial aging. Two types of CAD/CAM blocks (Cerasmart, GC; Enamic, Vita Zahnfabrik) were cut in slabs of 4-mm thickness, divided into six groups, and subjected to the following surface treatments: group 1: no treatment; group 2: sandblasting (SB); group 3: SB + silane (Si); group 4: SB + Si + flowable composite (see below); group 5: 5% hydrofluoric acid etching (HF) + Si; and group 6: 37% phosphoric acid etching (H3PO4) + Si. Sections of the same group were luted together (n=3: 3 sandwich specimens/group) using a dual-cure self-adhesive cement for all groups, except for the sections of group 4 that were luted using a light-curing flowable composite. After three weeks of storage in 0.5% chloramine at 37°C, the sandwich specimens were sectioned in rectangular microspecimens and trimmed at the interface to a dumbbell shape (1.1-mm diameter). One half of the specimens was subjected to a microtensile bond strength (μTBS) test, and the other half was tested after six months of water storage (aging). Data were statistically analyzed with a linear mixed-effects model for the factors surface treatment, material type, and aging, together with their first-degree interactions (α=0.05). The lowest bond strengths were obtained in the absence of any surface treatment (group 1), while the highest μTBSs were obtained when the surface was roughened by either SB or HF, this in combination with chemical adhesion through Si. Loss in bond strength was observed after six-month aging when either surface roughening or silanization, or both, were omitted. Both the composite and polymer-infiltrated ceramic CAD/CAM blocks appeared equally bonding-receptive regardless of the surface treatment used. Creating a microretentive surface by either SB or HF, followed by chemical adhesion using Si, is mandatory to maintain the bond strength after six months.

Air stable colloidal copper nanoparticles: Synthesis, characterization and their surface-enhanced Raman scattering properties

Air stable colloidal copper nanoparticles are synthesized by a simple chemical reduction method using octadecylsilane as a reducing agent and octadecylamine as a stabilizing agent in toluene without any inert gas. The formation of nanosized copper was confirmed by its characteristic surface plasmon absorption peaks in UV–visible spectra. The transmission electron microscopic (TEM) images show that the resulting copper nanoparticles are distributed uniformly with a narrow size distribution. The X-ray diffraction (XRD) demonstrated that the obtained copper nanoparticles are single crystalline nanoparticles. Fourier transform infra-red (FT-IR) spectroscopic data suggested that the silane Si–H is responsible for the reduction of copper ions. And also the resulting colloidal copper nanoparticles exhibit large surface-enhanced Raman scattering (SERS) signals.

Lewis Acidity of Bis(perfluorocatecholato)silane: Aldehyde Hydrosilylation Catalyzed by a Neutral Silicon Compound.

Bis(perfluorocatecholato)silane Si(cat(F))2 was prepared, and stoichiometric binding to Lewis bases was demonstrated with fluoride, triethylphosphine oxide, and N,N'-diisopropylbenzamide. The potent Lewis acidity of Si(cat(F))2 was suggested from catalytic hydrosilylation and silylcyanation reactions with aldehydes. Mechanistic studies of hydrosilylation using an optically active silane substrate, R-(+)-methyl-(1-naphthyl)phenylsilane, proceeded with predominant stereochemical retention at silicon, consistent with a carbonyl activation pathway. The enantiospecificity was dependent on solvent and salt effects, with increasing solvent polarity or addition of NBu4BAr(F)4 leading to a diminished enantiomeric ratio. The medium effects are consistent with an ionic mechanism, wherein hydride transfer occurs prior to silicon-oxygen bond formation.

The Effects of Coupling Agents on the Mechanical and Thermal Properties of Eucalyptus Flour/HDPE Composite

The aim of this research was to study the effects of the coupling agents, FusabondTM E-528 (polyethylene-grafted maleic anhydride; PE-g-MA, MA) and Amino Silane (Si), on the thermal properties, and mechanical properties of Eucalyptus flour-HDPE composite. Variation of the Eucalyptus flour contents in the HDPE resulted in properties of the composite. With increasing in the contents of Eucalyptus flour in polymer matrix, the mechanical properties of the HDPE composite decreased in EU-MA series samples while they were gradually decreased in EU-Si series samples. SEM micrographs showed the fracture surface of the HDPE/Eucalyptus composite at different ratios of Eucalyptus flour. SEM micrograpgh exhibited the dispersion of EU flour in polymer matrix. The samples of both coupling agents showed an increase in interfacial adhesion, observed for the considerable decreased of gaps between the matrix and the dispersed phase. However, the EU-MA sample appeared to be more uniformly than the EU-Si sample.

Recyclable Functionalization of Silica with Alcohols via Dehydrogenative Addition on Hydrogen Silsesquioxane

Synthesis of class II hybrid silica materials requires the formation of covalent linkage between organic moieties and inorganic frameworks. The requirement that organosilylating agents be present to provide the organic part limits the synthesis of functional inorganic oxides, however, due to the water sensitivity and challenges concerning purification of the silylating agents. Synthesis of hybrid materials with stable molecules such as simple alcohols, rather than with these difficult silylating agents, may therefore provide a path to unprecedented functionality. Herein, we report the novel functionalization of silica with organic alcohols for the first time. Instead of using hydrolyzable organosilylating agents, we used stable organic alcohols with a Zn(II) catalyst to modify the surface of a recently discovered highly reactive macro-mesoporous hydrogen silsesquioxane (HSQ, HSiO1.5) monolith, which was then treated with water with the catalyst to form surface-functionalized silica. These materials were comprehensively characterized with FT-IR, Raman, solid-state NMR, fluorescence spectroscopy, thermal analysis, elemental analysis, scanning electron microscopy, and nitrogen adsorption-desorption measurements. The results obtained from these measurements reveal facile immobilization of organic moieties by dehydrogenative addition onto surface silane (Si-H) at room temperature with high loading and good tolerance of functional groups. The organic moieties can also be retrieved from the monoliths for recycling and reuse, which enables cost-effective and ecological use of the introduced catalytic/reactive surface functionality. Preservation of the reactivity of as-immobilized organic alcohols has been confirmed, moreover, by successfully performing copper-catalyzed azide-alkyne cycloaddition (CuAAC) "click" reactions on the immobilized silica surfaces.

Sisal fiber (SF) reinforced recycled polypropylene (RPP) composites

The article focuses on the effect of fiber surface treatment on the properties and performance of sisal fiber (SF) reinforced recycled polypropylene (RPP) composites. Sisal fiber was functionalized using different surface modification methods using silane (Si), glycidyl methacrylate (GMA) and o-hydroxybenzene diazonium chloride (OBDC) in order to improve the compatibility with matrix polymer. The experimental results revealed an improvement in the tensile strength to the tune of 11 %, 20 % and 31.36 % and impact strength to 78.72 %, 77 % and 81 % for silane, GMA and OBDC treated SF reinforced RPP composites, respectively as compared to RPP. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and heat deflection temperature (HDT) studies revealed enhanced thermal stability of RPP after SF reinforcement. The flammability behavior of surface modified SF/RPP composites were also investigated using horizontal burning method. Improved surface interaction between fiber and polymer matrix was confirmed from scanning electron micrographs (SEM).

Optical and structural proprieties of nc-Si:H prepared by argon diluted silane PECVD

Using argon as a diluent of Silane, hydrogenated amorphous and nanorocrystalline silicon films Si:H were prepared by radio-frequency (13.56MHz) plasma enhanced chemical vapor deposition (rf-PECVD). The deposition rate and crystallinity varying with the deposition pressure and rf power, were systematically studied. Structural analysis (Raman scattering spectroscopy and X-ray diffraction), combined with optical measurements spectroscopy were used to characterize the films. The argon dilution of silane for all samples studied was 95% by volume, and the substrate temperature was 200°C. The deposition pressure was varied from 400mTorr to 1400mTorr and varying rf power from 50 to 250W. The structural evolution studies, shows that beyond 200W of rf power, an amorphous-nanocrystalline transition was observed, with an increase in crystalline fraction by increasing rf power and working pressure. The films were grown at high deposition rates. The deposition rates of the films near the amorphous-nanocrystalline phase transition region were found in the range 6–10Å/s. A correlation between structural and optical properties has been found and discussed.

Permeation of Solvents Through Disk Type Rice Husk Silica Membrane Modified with Alkyl Silylation Reagents

Rice husk silica (RHS) which was obtained with thermal treatment of rice husk has the size of approximately 10 micrometer with 4-5 nm pore. RHS can be mold to a disk type membrane. The membrane may have submicron pore originated from the space among the particles, and the nano pores of the rice husk silica (RHS pore). Even it is difficult to adjust the size of the pores, we can suggest that the membrane shows different permeability for the organic/inorganic solvents if the affinity between the surface of the pores and the permeating molecule is changed. In this study, we investigated the permeation of the typical solvents such as water, ethanol and toluene to the RHS membranes sintered at 1100 degrees C, 1150 degrees C and 1200 degrees C and modified with triethoxymethyl silane (CH3)Si(C2H5O)3, diethoxydiemethyl silane (CH3)2Si(C2H5O)2 and ethoxytriemethyl silane (CH3)3Si (C2H5O). The result showed that permeability of original membranes for water (e.g., 1100 degrees C, 2.87 x 10(-3) mol/m2 s Pa) was larger than ethanol (1100 degrees C, 5.51 x 10(-4) mol/m2 s Pa) and toluene (1100 degrees C, 3.09 x 10(-4) mol/m2 s Pa) at the sintering temperatures. For the silane modified membranes, the permeability for water decreased drastically while those for ethanol and toluene increased.