Abstract
Nanoporous layers are widely spread in nature and among artificial devices. However, complex characterization of extensively nanoporous thin films showing porosity-dependent softening lacks consistency and reliability when using different analytical techniques. We introduce herein, a facile and precise method of such complex characterization by multi-harmonic QCM-D (Quartz Crystal Microbalance with Dissipation Monitoring) measurements performed both in the air and liquids (Au-Zn alloy was used as a typical example). The porosity values determined by QCM-D in air and different liquids are entirely consistent with that obtained from parallel RBS (Rutherford Backscattering Spectroscopy) and GISAXS (Grazing-Incidence Small-Angle Scattering) characterizations. This ensures precise quantification of the nanolayer porosity simultaneously with tracking their viscoelastic properties in liquids, significantly increasing sensitivity of the viscoelastic detection (viscoelastic contrast principle). Our approach is in high demand for quantifying potential-induced changes in nanoporous layers of complex architectures fabricated for various electrocatalytic energy storage and analytical devices.
Highlights
Nanoporous layers are widely spread in nature and among artificial devices
Since the QCM measurements were performed in air, it is not clear whether the highly porous Au host keeps the same porosity and rigidity when immersed from air into liquids since this check would imply the use of QCM-D (QCM with dissipation monitoring) on multiple harmonics instead of conventional QCM
The attempt of a simultaneous determination of porosity and viscoelasticity changes caused by adsorption of TiO2 nanoparticles onto extensively rough Si host from the related QCM-D measurements in liquid[18] has completely failed for the following two reasons: (i) The combination of viscoelastic and hydrodynamic modeling is valid only for slight roughness of the host matrix rather than for host matrices with strong roughness[19]: the host considered in this paper possesses strong roughness; (ii) The authors report that the fitted values of permeability lengths are significantly larger than that of the porous layer thickness itself
Summary
Nanoporous layers are widely spread in nature and among artificial devices. complex characterization of extensively nanoporous thin films showing porosity-dependent softening lacks consistency and reliability when using different analytical techniques. The attempt of a simultaneous determination of porosity and viscoelasticity changes caused by adsorption of TiO2 nanoparticles onto extensively rough Si host from the related QCM-D measurements in liquid[18] has completely failed for the following two reasons: (i) The combination of viscoelastic and hydrodynamic modeling is valid only for slight (shallow) roughness of the host matrix rather than for host matrices with strong roughness[19]: the host considered in this paper possesses strong roughness; (ii) The authors report that the fitted values of permeability lengths are significantly larger than that of the porous layer thickness itself. The above discussed previous studies provide excellent driving force for the studies described in this paper
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