Silicon
Monolithic inorganic-organic hybrid materials have been synthesized via sol-gel processing of an ethylene glycol-modified ethane-bridged silane precursor in aqueous solution of the non-ionic block copolymer Pluronic™ P123. The influence of different sol compositions on the final gel structure was investigated in detail. The resulting materials consist of macroporous networks comprising periodically...
In an initial report we demonstrated that some serine proteases were suitable candidates for the hydrolysis and condensation of tetraethoxysilane and phenyltrimethoxysilane under solvent-free conditions. Using trypsin as a model enzyme, we have demonstrated the generality of this method by expanding the number of available silicon-based substrates that can be processed by the enzyme, as well as including...
Pepsin [EC, 3.4.23.1] from Porcine stomach mucosa was immobilized in silicone elastomers utilizing condensation-cure room temperature vulcanization (RTV) of silanol-terminated poly(dimethylsiloxane) (PDMS). Two network precursor chain molar masses were used in this investigation: in pepsin–silicone (A), M n ∼26,000 g mol−1 and in pepsin–silicone (B) M n ∼750 g mol−1. Tetraethyl orthosilicate (TEOS)...
Silica-bound aldehyde functional silane was used as a versatile bridge to attach porphyrin to the surface of silica and as a surface-bound free radical initiator to yield PMMA brushes. The aldehyde functionality is obtained by a simple ozonolysis of the surface-bound allylsilane, whereby the double bonds are oxidized in high yield to the desired aldehyde. Mono-amino porphyrin was attached to the silica...
The tetrakis(arylethynyl)silanes 1–4 of which 2–4 are new compounds have been synthesized and determined by single crystal structure analysis to show their tetrahedral molecular geometries reflected in slightly disturbed S4 symmetry in the crystal lattices. The lattice structures are mainly determined by close packing effects while the interactions of π-stacking type or C–H···π contacts are rather...
The fluorene diol (I) has been chemically incorporated into a sol-gel formulation that was coated to produce a thin overcoat on an organic photoreceptor and cured into a silsesquioxane matrix that efficiently transports holes. The residual potential of the photoreceptor decreased as the amount of hole transport material (I) incorporated into the silsesquioxane matrix was increased. The charge transport...
Multiwalled carbon nanotubes (MWCNTs) have been coated with silicon carbide (SiC) using polycarbosilane as precursor in order to improve their thermo oxidative stability. The polycarbosilane coated MWCNTs were heated to ~1300°C under an inert atmosphere to generate the SiC coating. X-ray diffraction, energy dispersive X-ray analysis and scanning electron microscopy have confirmed the formation of...
We report an elegant and simple method to fabricate silica films with controlled thickness and roughness using protein coated solid surfaces as substrates. Bovine serum albumin (BSA) and lysozyme having different inherent charges have been used as model proteins (templates) to fabricate silica films. The formation of silica films was achieved by immobilization of BSA and lysozyme on amine (poly(allylamine)...
Silica and carbon are naturally occurring in rice husks (RH) and these were used for the production of ceramic materials made of Si, C, N and O as the main constituents. The various “silicon-based” ceramics were produced from the thermal decomposition of rice husks and posterior heat treatment at temperatures varying from 1200–1450 °C under a pure nitrogen atmosphere. FeSO4 in various concentrations...
Silicon isotope geochemistry is a relatively new branch of environmental change research. Here we review the recent developments in the preparation of materials, analytical methods and applications of stable silicon isotope geochemistry in the most common types of biogenic silica currently being analysed. These materials are: diatom, radiolarian and siliceous sponges in lake and ocean sediments and...
A novel redox initiator system for carrying out the cationic polymerization of epoxide, oxetane and vinyl ether monomers has been developed. The redox couple is based on a triarylsulfonium salt as the oxidant with an organosilane as the reducing agent. The reaction between these two agents is markedly catalyzed by platinum and palladium complexes. Cationic polymerizations using this redox initiator...
The effect of turbulence on several freshwater diatom taxa was investigated and our findings are described herein. We have compared diatom morphology in shallow natural systems that experience turbulence due to wind and in river/waterfall systems where turbulence is due to high flow rates. We have also introduced turbulence into diatom laboratory cultures by mechanical shaking and by forcing air into...
This paper focuses on the improvement of hydrophicility and water content of poly(dimethylsiloxane) (PDMS) by bonding a hydrophilic macromer, hydroxyl-terminated linear poly(ethylene glycol) (PEG), into a highly hydrophobic macromer, hydroxyl-terminated linear PDMS to prepare amphiphilic conetworks (APCNs) with the crosslinkers, tetraethoxysilane (TEOS) and bis[(3-methyldimethoxysilyl)propyl]-polypropylene...
This paper focuses on some issues regarding rubber nanocomposites especially silicone rubbers. An outstanding affinity of carbon nanotubes towards poly(dimethylsiloxane) (PDMS) has been observed. The reinforcing effect of carbon nanotubes is much more important than that imparted by in situ generated silica particles that are well known to lead to significant improvement in the mechanical properties...
Immobilized lipase B from Candida antarctica was used to synthesize copolymers of poly(ε-caprolactone) (PCL) with α,ω-(dihydroxy alkyl) terminated poly(dimethylsiloxane) (PDMS). The reactions were carried out in toluene with a 1:2 w/v ratio of the monomers to solvent at 70 ºC. The PCL−PDMS−PCL triblock copolymer composition was varied by changing the feed ratio of the reactants [CL]/[PDMS] (80:20;...
Montmorillonite modified with distearyldimethyl ammonium chloride (C18-QAC) (Nanofil-15) (NF15) was incorporated into polydimethylsiloxane-urea (silicone-urea, PSU) copolymers. PSU was obtained by the reaction of equimolar amounts of aminopropyl terminated polydimethylsiloxane (PDMS) oligomer (<Mn> = 3,200 g/mol) and bis(4-isocyanatohexyl)methane (HMDI). A series of PSU/NF15 nanocomposites were...