Ammonia Catalyzed Hydrolysis-Condensation Kinetics of Tetraethoxysilane/Dimethyldiethoxysilane Mixtures Studied by 29 Si NMR and SAXS

Enhancing Slurry Stability and Surface Flatness of Silicon Wafers through Organic Amine-Catalyzed Synthesis Silica Sol

The stability of slurries used for chemical mechanical polishing (CMP) is a crucial concern in industrial chip production, influencing both the quality and cost-effectiveness of polishing fluids. In silicon wafer polishing, the conventional use of commercial neutral silica sol combined with organic bases often leads to slurry instability. To address this issue, this study proposes organic amines-specifically ethanolamine (MEA), ethylenediamine (EDA), and tetramethylammonium hydroxide (TMAOH)-as catalysts for synthesizing alkaline silica sol tailored for silicon wafer polishing fluids. Sol-gel experiments and zeta potential measurements demonstrate the efficacy of this approach in enhancing the stability of silica sol. The quantitative analysis of surface hydroxyl groups reveals a direct correlation between enhanced stability and increased hydroxyl content. The application of the alkaline silica sol in silicon wafer polishing fluids improves polishing rates and enhances surface flatness according to atomic force microscopy (AFM). In addition, electrochemical experiments validate the capability of this polishing solution to mitigate corrosion on silicon wafer surfaces. These findings hold significant implications for the advancement of chemical mechanical polishing techniques in the field of integrated circuit fabrication.

Synthesis of dendritic mesoporous organosilica nanoparticles under a mild acidic condition with homogeneous wall structure and near-neutral surface

Dendritic mesoporous organosilica nanoparticles were synthesized under a mild acidic condition (pH 6.2), featuring a molecularly homogeneous wall structure and an unusual near-neutral charged surface, consequently enabling reduced protein fouling property.

Fast nucleation for silica nanoparticle synthesis using a sol-gel method

We have developed a method that for the first time allowed us to synthesize silica particles in 20 minutes using a sol-gel preparation. Therefore, it is critically important to understand the synthesis mechanism and kinetic behavior in order to achieve a higher degree of fine tuning ability during the synthesis. In this study, we have employed our ability to modulate the physical nature of the reaction medium from sol-gel to emulsion, which has allowed us to halt the reaction at a particular time; this has allowed us to precisely understand the mechanism and chemistry of the silica polymerization. The synthesis medium is kept quite simple with tetraethyl orthosilicate (TEOS) as a precursor in an equi-volumetric ethanol-water system and with sodium hydroxide as a catalyst. Synthesis is performed under ambient conditions at 20 °C for 20 minutes followed by phasing out of any unreacted TEOS and polysilicic acid chains via their emulsification with supersaturated water. We have also demonstrated that the developed particles with various sizes can be used as seeds for further particle growth and other applications. Luminol, a chemiluminescent molecule, has been entrapped successfully between the layers of silica and was demonstrated for the chemiluminescence of these particles.

One-pot synthesis of antibacterial monomers with dual biocidal modes

OBJECTIVES

The present study reported a method for preparing a blend of antibacterial quaternary ammonium silanes and quaternary ammonium methacryloxy silane (QAMS) based on the sol-gel reaction between dimethyldiethoxy silane and two trialkoxysilanes, one with an antibacterial quaternary ammonium functionality and the other with a methacryloxy functionality.

METHODS

Reaction products of the sol-gel reaction were characterised by direct infusion mass spectrometry, FTIR and proton, carbon and silicon NMR. This blend of monomers was incorporated into an experimental universal adhesive for evaluation of antimicrobial activity against Streptococcus mutans biofilms, microtensile bond strength and cytotoxicty. Retention of quaternary ammonium species on polymerised adhesive, leaching of these species from the adhesive and the ability of resin-dentine interfaces to inhibit S. mutans biofilms were evaluated over a 3-month water-ageing period.

RESULTS

The antibacterial adhesive version killed bacteria in S. mutans biofilms not only through the release of non-copolymerisable quaternary ammonium silane species (release-killing), but also via immobilised quaternary ammonium methacryloxy silane that are copolymerised with adhesive resin comonomers (contact-killing). Contact-killing was retained after water-ageing. The QAMS-containing universal adhesive has similar tensile bond strength as the control and two commercially available universal adhesives, when it was used for bonding to dentine in the etch-and-rinse mode and self-etching mode. Incorporation of the antimicrobial quaternary ammonium species blend did not adversely affect the cytotoxicity of the universal adhesive formulation.

CONCLUSIONS

Instead of using quaternary ammonium dimethacrylates and nanosilver, an alternative bimodal antimicrobial strategy for formulating antimicrobial universal dentine adhesives is achieved using the one-pot sol-gel synthesis scheme.

CLINICAL SIGNIFICANCE

The QAMS containing universal dentine adhesives with dual antimicrobial activity is a promising material aimed at preventing second caries and prolonging the longevity of resin composite restorations.