Charge Induced Chi(3) Susceptibility in Interfacial Nonlinear Optical Spectroscopy Beyond the Bulk Aqueous Contributions: The Case for Silica/Water Interface

The electric field induced (EFI) bulk Chi(3) contribution to the second harmonic generation (SHG) signal from charged interfaces was discovered and applied to study the interfacial chemistry of various charged interfaces three decades ago. For both the buried fused silica/water interface and the exposed charged monolayer covered air/water interface, such bulk Chi(3) contribution was all attributed to the Chi(3) term of the polarized water molecules near the charged interfaces. The puzzling experimental observation of the more than one-order of magnitude difference of the EFISHG intensity between the fully charged silica/water interface and the charged molecular covered air/water interface was generally overlooked in the EFISHG literature. Nevertheless, this significant signal difference suggests additional source for the Chi(3) contribution at the fully charged silica/water interface other than the polarized water molecules as in the case of charged monolayer covered air/water interface. In this report, we re-examine the treatment of the Chi(3) mechanism at the charged silica/water interface by including the contributions from the bulk silica using proper boundary condition and image charge distributions for the change screening effects inside bulk silica phase. We show that the Chi(3) contribution from the bulk silica is in similar form as that of the aqueous bulk phase, and it is with more than one-order of magnitude and with opposite sign. The treatment reported here can be extended to other charged interfaces.

One pot rapid synthesis of ultra high strength hydrophobic bulk silica aerogels

One-step rapid synthesis of ultra-high strength hydrophobic bulk silica aerogels through neck-strengthening effect induced by high polycondensation reaction.

Nanosized Particles of Silica and Its Derivatives for Applications in Various Branches of Food and Nutrition Sectors

Nanosized particles of silica and its derivatives have been identified as versatile for a broad range of science, technology, and engineering applications. In this paper, an effort has been made to provide a short review from the available literature information on their applications in various branches of food and nutrition sectors. The information provided in this paper describes various parameters affecting their performances and efficiencies. The properties and applications of nanosilica and its derivatives have been compared with microsilica and bulk-silica for their performances. The use of nanosized particles of silica and its derivatives provides a number of advantages. Their efficiencies and performances are significantly higher than those of the traditional ones.