Surface roughness analysis of hydrophilic SiO2/TiO2/glass nano bilayers by the level crossing approach

Abstract

The effect of etching time on the statistical properties of the hydrophilic surface of SiO2/TiO 2 /Glass nano bi-layer has been studied using Atomic Force Microscopy (AFM) and stochastic approach based on the level crossing analysis. We have created a rough surface of the hydrophilic SiO 2 /TiO 2 nano bi-layer system by using 26% Potassium Hydroxide (KOH) solution.Measuring the average apparent contact angle assessed the degree of hydrophilicity and the optimum condition was determined at 10 min etching time. Level crossing analysis based on AF images provided deeper insight into the microscopic details of the surface topography. For different etching time, it has been shown that the average frequency of visiting a height with positive slope behaves Gaussian for heights near the mean value and obeys power law for the heights far away from the mean value. Finally, by applying the generalized total number of crossings with positive slope, it was found that the both high heights and deep valleys of the surface are extremely effective in hydrophilic degree of the SiO 2 /TiO 2 /Glass nano bi-layer investigated system.

Heterostructured TiO2/SiO2/γ-Fe2O3/rGO Coating with Highly Efficient Visible-Light-Induced Self-Cleaning Properties for Metallic Artifacts

“…The AFM results imply that the average roughness ( R a ) of the films coated with TiO 2 , TiO 2 @Si, TiO 2 @Si:Fe, and TiO 2 @Si:Fe:rGO are 40, 47, 69, and 200 nm, respectively. As can be seen, R a has a slight increase with the addition of SiO 2 and γ-Fe 2 O 3 and a sharp increase with the addition of rGO. , This result could be correlated to sloppy stacking of rGO sheets, which results in larger channels around the rGO stacks, compatible with the variation in surface roughness . In other words, the rGO assembled layers in TiO 2 @Si:Fe:rGO coating probably are in random order and, therefore, are very rough on the surface …”

Development, Processing and Applications of a UV-Curable Polymer with Surface Active Thiol Groups

“…The O2 plasma changes more drastically the contact angle, and leads to a more durable change, since it also introduces a nanoscopic surface roughness. And, in hydrophilic surfaces, higher roughness leads to lower WCA [27,28]. Since the O2 plasma etches the polymer (in our case, <5 nm/min), it should be used with precaution, especially when dealing with features with small dimensions, or when the roughness of the surface is a critical parameter.…”

“…The O 2 plasma changes more drastically the contact angle, and leads to a more durable change, since it also introduces a nanoscopic surface roughness. And, in hydrophilic surfaces, higher roughness leads to lower WCA [ 27 , 28 ].…”

On the Role of γ-Fe2O3 Nanoparticles and Reduced Graphene Oxide Nanosheets in Enhancing Self-Cleaning Properties of Composite TiO2 for Cultural Heritage Protection

“…Adding 0.02 g rGO causes a sharp increase in roughness due to the sloppy stacking of rGO sheets, which creates some large channels around the rGO stacks, while a lower amount of rGO does not have significant impact. The presence of stacks may be correlated to the fact that rGO sheets assemble in random order, inconsistent with the change in surface roughness [51][52][53][54]. However, overloading rGO in the TSF 32 G 3 coated film resulted in a decrease in roughness probably due to channels covering around the rGO stacks (Figure 8).…”