Vibrational Sum Frequency Generation Spectroscopy of Surface Hydroxyls on Nickel Phyllosilicate Nanoscrolls

Phyllosilicate days are layered structures with diverse nanoscale morphology depending on the composition. Size mismatch between the sheets can cause them to form nanoscrolls, a spiral structure with different inner and outer surface charges. The hydroxyls on the exposed surface of the nanoscrolls determine the adsorption properties and hydrophilicity of the surface. Vibrational sum frequency generation (VSFG) spectroscopy was applied to study the surface hydroxyls of nickel phyllosilicate (Ni3Si2O5(OH)(4)), revealing three distinct in-phase OH-stretch modes: 3642, 3645, and 3653 cm(-1). The relative signs of the peaks allow their assignment as outward and inward pointing hydroxyls on the opposite sides of the scrolled sheet, consistent with the crystal structure. Orientational analysis of polarization-selected VSFG spectra is consistent with a broad (140-164 degrees) step-function distribution of the OH-stretch tilt angles, which we attribute to the uncompensated portion of the scroll rolled more than a whole number of full turns.

Automated summary

This study utilized VSFG spectroscopy to investigate the surface hydroxyls of nickel phyllosilicate (Ni3Si2O5(OH)(4)), identifying three distinct in-phase OH-stretch modes. The analysis revealed that the hydroxyls are distributed on the opposite sides of the scrolled sheet and exhibit a broad distribution of tilt angles.