Quantification of porosity in extensively nanoporous thin films in contact with gases and liquids

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.

Electrodeposition of Nanoporous Gold Thin Films

“…The physical and morphological properties of nanoporous thin films are strongly linked with material's porosity (defined as the ratio of void volume to the total volume of the film). Hence, many efforts have been devoted to developing a reliable self-consistent quantitative characterization of their porosity [78]. The physical characteristics of thin films have been characterized by a combination of X-ray photoelectron spectroscopy (XPS), grazing-incidence small-angle X-ray scattering (GISAXS) along with adsorption isotherm surface area measurements.…”

Mechanical Properties of Nanoporous Metallic Ultrathin Films: A Paradigmatic Case

“…In particular, the nanoporous gold was characterized by an irregular ligament geometry, presenting a local defect structure, which is believed to explain the trend of the increasing strength of the material for ligament sizes down to 10 nm. In the hypothesis that nanoporous Au behaves as an open-cell foam, the conventional macroscopic scaling law for macroporous cellular materials [96] takes the form of E*/E = C E (ρ*/ρ s ) 2 , where E* and ρ* are the overall effective nanoporous system's elastic modulus and density, and E and ρ s are the elastic modulus and density of the bulk solid. The adimensional prefactor C E is a function of the system geometry.…”

“…Typical porous films are formed by a metallic network containing pores, with sizes ranging from a few nanometers to more than one micron, depending on the synthesis technique [1], and with a thickness of more than 100 nm. The nanostructured nature of these systems provides a unique combination of physical properties-in particular, low density, high specific surface area [2], non-ohmic electric transport [3,4], and high specific strength [5]-while retaining some characteristics of bulk metals [1,6]. This results in a wide range of potential applications where such materials may be employed, e.g., bendable electronics [7,8], surface-enhanced Raman scattering [9][10][11], catalysis [12,13] and sensing [13,14], optical metamaterials [6], and microbicidal coatings [15][16][17].…”

Determination of Nano-sized Adsorbate Mass in Solution using Mechanical Resonators: Elimination of the so far Inseparable Liquid Contribution

“…8 Still, the rich information contained in combined ∆f n and ∆D n measurements, especially when combined with theoretical models representing the response for viscoelastic films, 9,10 has turned out very valuable in multiple research areas, including hydration analysis of organic polymers 11,12 , proteins 13 and biological membranes 13,14 . The method is also widely applied to investigate material porosity 15,16 , growth of mesoporous material 17 , characterization of biomimetic membranes 18,19 , development of bioanalytical sensors [20][21][22][23] , as well as in studies of biomolecular interactions 24,25 , including interrogations of their structural 26 and orientational 27 changes.…”

“…Yet, the inseparable nature of the adsorbate and liquid contributions to the measured response puts significant limitation on quantitative interpretation of adsorption measurements in liquid environment. In particular, this shortcoming makes mass determination using mechanical resonators non-conclusive, unless complementary methods, such as surface plasmon resonance (SPR), ellipsometry and/or atomic force microscopy (AFM) are employed in parallel 16,[28][29][30] .…”