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

Abstract

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.

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

“…Recently, a new type of optical measurement has shown promising results to probe supramolecular organization [12][13][14] and self-assembly process at the molecular level. 15,16 This technique is based on the nonlinear optical process of second harmonic scattering (SHS), a nonlinear optical phenomenon involving the conversion of two photons at the fundamental frequency o into one photon at the harmonic frequency 2o.…”

Liquid Water: When Hyperpolarizability Fluctuations Boost and Reshape the Second Harmonic Scattering Intensities

“…Among other experimental techniques, such as nuclear magnetic resonance, IR-spectroscopies, and X-ray or neutron scattering, second harmonic scattering (SHS) is a method of choice to investigate the molecular structure of liquids. The contribution of orientational correlations in SHS intensities has been known for decades − and has recently found renewed interest in probing the molecular structure of various liquids such as organic solvents, ionic liquids, surfactant solutions, , and salted or pure water. ,− In particular, for water, the impact of orientational correlations on the second harmonic intensity has been investigated, underlining the importance of both short- and long-range structuration, − or density heterogeneities appearing transiently in liquid water. , The effects induced by interfaces or nano-objects have also been explored. − However, a quantitative interpretation of all contributions is still missing. The frameworks developed to investigate orientational correlations from SHS data ,, are often based on the assumption that all the molecules of the system have the same second harmonic response, i.e., the same first hyperpolarizability tensor β.…”

Liquid Water : When Hyperpolarizability Fluctuations Boost and Reshape the Second Harmonic Scattering Intensities

“…[18][19][20][21][22][23] The effects induced by interfaces or nano-objects have also been explored. [24][25][26][27] However, a quantitative interpretation of all contributions is still missing.…”