PySHS: Python Open Source Software for Second Harmonic Scattering

Hydrophobic dye solubilization via hybrid imogolite nanotubes probed using second harmonic scattering

This article explores the organization and interactions of Disperse Orange 3 (DO3) hydrophobic dye molecules within hybrid organic-inorganic imogolite nanotubes. In pure water, the DO3 dye molecules self assemble into large insoluble 2D nanosheets whose structure is also explored by molecular dynamics simulations. The dye molecules are however efficiently solubilized in the presence of hybrid imogolite nanotubes. The filling of the internal hydrophobic cavity of the nanotubes is quantified. The organization of the molecules inside the nanotube is probed using the polarization resolved second harmonic scattering (SHS) technique coupled with simulation. At the highest loading, the dyes fill the nanotube with their principal axis parallel to the nanotube walls showing a strong SHS signal due to this encapsulation.

Monitoring membranes: The exploration of biological bilayers with second harmonic generation

Nature's seemingly controlled chaos in heterogeneous two-dimensional cell membranes stands in stark contrast to the precise, often homogeneous, environment in an experimentalist's flask or carefully designed material system. Yet cell membranes can play a direct role, or serve as inspiration, in all fields of biology, chemistry, physics, and engineering. Our understanding of these ubiquitous structures continues to evolve despite over a century of study largely driven by the application of new technologies. Here, we review the insight afforded by second harmonic generation (SHG), a nonlinear optical technique. From potential measurements to adsorption and diffusion on both model and living systems, SHG complements existing techniques while presenting a large exploratory space for new discoveries.

Water Organization around Inorganic Nanotubes in Suspension Probed by Polarization-Resolved Second Harmonic Scattering

Imogolite nanotube (INT) is a fascinating one-dimensional (1D) material that can be synthesized in the liquid phase. Its behavior in solution is crucial for many applications and depends on the organization of water at the liquid-wall interface. We study here this water organization by using the nonlinear optical technique of polarization-resolved second harmonic scattering (SHS). A microscopic model is proposed to interpret the origin of the coherent SHS signal recovered in this 1D colloidal system. This work demonstrates that the SHS technique is able to probe the shell of water molecules oriented around the nanotubes. Water organization results from the electric field induced by the nanotube walls, and it is strongly dependent on the ionic strength of the suspension.

Driving Forces of Cationic Dye Adsorption, Confinement, and Long-Range Correlation in Zeolitic Materials

Zeolitic materials are commonly used to capture emergent contaminants in water or complex aqueous effluents. The efficiency of this adsorption depends strongly on the guest-host interactions and on the surrounding environment with possible coadsorption of the solvent. Only a few experimental techniques are available to probe in situ the sequestration processes at the solid/liquid interface. We propose in the present work to combine the second harmonic scattering technique with isothermal titration calorimetry in order to investigate the adsorption and the confinement of a hemicyanine dye adsorbed inside faujasite materials. The methodology described here permits the quantification of the correlations between the confined dyes in the material and thus gives local information about the organization at the nanometer scale. Various impacts, such as the effect of the solvent type and the silicon to aluminum ratio of the zeolitic adsorbent, are quantitatively estimated and discussed. This work highlights that the most correlated system matches the higher adsorption capacity associated with the lower entropic contribution.