Surface modification of silica nanoparticles to reduce aggregation and nonspecific binding.

In this article, a systematic study of the design and development of surface-modification schemes for silica nanoparticles is presented. The nanoparticle surface design involves an optimum balance of the use of inert and active surface functional groups to achieve minimal nanoparticle aggregation and reduce nanoparticle nonspecific binding. Silica nanoparticles were prepared in a water-in-oil microemulsion and subsequently surface modified via cohydrolysis with tetraethyl orthosilicate (TEOS) and various organosilane reagents.

A rapid bioassay for single bacterial cell quantitation using bioconjugated nanoparticles.

The rapid and sensitive determination of pathogenic bacteria is extremely important in biotechnology, medical diagnosis, and the current fight against bioterrorism. Current methods either lack ultrasensitivity or take a long time for analysis. Here, we report a bioconjugated nanoparticle-based bioassay for in situ pathogen quantification down to single bacterium within 20 min.

Optimization of dye-doped silica nanoparticles prepared using a reverse microemulsion method.

Fluorescent labeling based on silica nanoparticles facilitates unique applications in bioanalysis and bioseparation. Dye-doped silica nanoparticles have significant advantages over single-dye labeling in signal amplification, photostability and surface modification for various biological applications. We have studied the formation of tris(2,2'-bipyridyl)dichlororuthenium(II) (Ru(bpy)) dye-doped silica nanoparticles by ammonia-catalyzed hydrolysis of tetraethyl orthosilicate (TEOS) in water-in-oil microemulsion.

Bionanotechnology based on silica nanoparticles.

We have developed uniform core/shell nanoparticles, consisting of a silica layer coating and pigments or magnetite core, using a water-in-oil microemulsion method. The nanoparticles are highly luminescent and photostable with the size ranging from 5 nm to 400 nm. Bioconjugation of these silica nanoparticles adds unique biofunctions with various molecules such as enzymes, antibodies, and DNA molecules.

Effect of counterions on surface and foaming properties of dodecyl sulfate.

The influence of counterions of surfactant on interfacial properties is studied by measuring foamability, foam stability, equilibrium and dynamic surface tension, and surface viscosity. The surfactant chosen is anionic dodecyl sulfate with various counterions, Li(+), Na(+), Cs(+), and Mg(++). Surface tension measurements show a decrease in the following order: LiDS > NaDS > CsDS > Mg(DS)(2).

Kinetics of the Formation of Nano-Sized Platinum Particles in Water-in-Oil Microemulsions.

The effect of surfactant type and temperature on the kinetics of the formation of platinum nanoparticles in water-in-oil microemulsions by chemical reduction of PtCl(6)(2-) were examined with time-resolved UV-vis absorption spectroscopy. The surfactants used were poly(ethylene glycol)monododecyl ethers (C(12)E(4), C(12)E(5), C(12)E(6)), sodium bis(2-ethylhexyl)sulphosuccinate (AOT), and mixtures of the alcohol ethoxylates and AOT. The oil domain was n-heptane.