Interfacial properties of cetyltrimethylammonium-coated SiO2 nanoparticles in aqueous media as studied by using different indicator dyes

Silica nanoparticles with a substrate switchable luminescence

“…DLS measurements performed for the aqueous dispersions of nanoparticles reveal the high monodispersity (polydispersity index is within 0.1-0.3) with the particle size being 223±4 nm for Tb(III)-TCAS doped and 262±4 nm for Yb(III)-TCAS doped silica nanoparticles, which stays unchanged within the concentration range from 0.0175 to 0.67 g L -1 (table 1). The gap between the sizes determined from the TEM (40±5 nm and 32±5 nm) and DLS data is rather high and can not be explained by the thickness of the hydration shell [7,12]. Thus Ln(III)-TCAS doped nanoparticles are somewhat aggregated in aqueous dispersions.…”

“…The decoration of the silica surface through the non-covalent interactions represents more convenient alternative to covalent anchoring due to the lack of multistep purification procedures [6]. For example the decoration of silica nanoparticles by adsorption of cationic surfactants enables to get non-aggregated positively charged silica nanoparticles [7] for a development of nanoparticles, exhibiting sensing function to anions. Anions play an important role in living organisms and even phospholipids membranes of cells are negatively charged.…”

“…The decoration of silica nanoparticles with various surfactants is well developed way to modify the aggregation stability and binding ability of nanoparticles [6,7,15]. The adsorption of surfactants at a silica/water interface is contributed by van der Waals, electrostatic interactions and multiple hydrogen bonding [16].…”

“…Taking into account that in neutral media silica surface is negatively charged due to the dissociation of Si-OH groups (pK a =8.4) [17], cationic surfactants are most convenient for adsorption at a silica/water interface. The aggregation of cationic surfactants at the silica nanoparticles is exemplified in literature in most details by cetyltrimethylammonium bromide (CTAB) [7,15], which is monocationic surfactant. Amphiphilic cations cethyltrimethylammonium (CTA + ) form doubly charged bilayer at the silica/water interface, resulting in the recharging of the silica surface from minus to plus [7,18].…”

Polymeric nanoparticles for optical sensing

“…This is due to the aggregation process triggered by water (a poor solvent for TPE) and heat ). The emission intensity of the former changes in response to pH due to its transition between monoand di-anionic states (Bryleva et al, 2007), the latter was employed to develop fluorescent polymeric micelles for the detection of peroxynitrite. In the presence of ONOO -, BzSe-Cy undergoes oxidation, with a consequent decrease in fluorescence emission, allowing intracellular imaging of ONOO -in living cells (Tian et al, 2011).…”