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Special Issue "Self-Cleaning Surfaces"

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Thin Films".

Deadline for manuscript submissions: closed (8 April 2019).

Special Issue Editors

Guest Editor
Prof. Dr. Urška Lavrenčič Štangar

University of Ljubljana, Faculty of Chemistry and Chemical Technology, Department of Chemistry and Biochemistry, Večna pot 113, 1000 Ljubljana, Slovenia
University of Nova Gorica, Laboratory for Environmental and Life Sciences, Vipavska 13, 5000 Nova Gorica, Slovenia
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Interests: soft chemical routes; sol-gel chemistry; thin films; metal oxides; photocatalysis
Guest Editor
Dr. Andrijana Sever Škapin

Slovenian National Building and Civil Engineering institute, Dimičeva 12, 1000 Ljubljana, Slovenia
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Interests: building materials, nanomaterials, consolidation, photocatalysis, cultural heritage, durability, indoor air quality, microstructure

Special Issue Information

Dear Colleagues,

Although self-cleaning technology is already used in a variety of products today (glass and ceramic tiles, anti-fogging mirrors, pollutant-abating paints, mortars, asphalts and concrete), there is still a need for improved performance characteristics of coatings, their durability, cost efficiency and relevant testing methods. This is a driving force in the development of new materials, for finding innovative synthesis and technological solutions, as well as understanding the functional-to-properties relationships, which all may reflect in your scientific contributions to this Special Issue. Regarding photoactive coatings, the development of visible-light-active surfaces is crucial for indoor applications, while for outdoor applications an increase of the efficiency of active materials under solar light and prolongation of their durability are still the hot topics in present research. The self-cleaning function is mainly based on either superhydrophobic or photocatalytic-superhydrophilic surfaces, however, other proposals and related studies are also welcome. The forthcoming Special Issue of Materials aims to follow the previous one entitled “Self-Cleaning and Antimicrobial Surfaces” in 2016 (edited by F. D. Magalhães) with new advances in this attractive field of research. It is our pleasure to invite you to contribute your research article, communication or review for this Special Issue.

Prof. Dr. Urška Lavrenčič Štangar
Dr. Andrijana Sever Škapin
Guest Editors

Manuscript Submission Information

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Keywords

  • self-cleaning
  • anti-fogging
  • thin films
  • superhydrophobic
  • superhydrophilic
  • photocatalytic

Published Papers (17 papers)

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Research

Open AccessArticle
Field Test of Self-Cleaning Zr-Modified-TiO2-SiO2 Films on Glass with a Demonstration of Their Anti-Fogging Effect
Materials 2019, 12(13), 2196; https://doi.org/10.3390/ma12132196
Received: 9 June 2019 / Revised: 4 July 2019 / Accepted: 5 July 2019 / Published: 8 July 2019
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Abstract
The number of commercial products claiming self-cleaning properties is rising and testing of long-term activity and durability of such coatings needs to be addressed more. The time-dependent changes of different characteristics like haze, transparency, and color are essential for transparent glazing materials. Herein, [...] Read more.
The number of commercial products claiming self-cleaning properties is rising and testing of long-term activity and durability of such coatings needs to be addressed more. The time-dependent changes of different characteristics like haze, transparency, and color are essential for transparent glazing materials. Herein, we aimed to examine whether the laboratory results obtained on the Zr-modified-titania-silica (TiZr) self-cleaning materials would translate to larger-scale outdoor-exposed testing. TiZr thin films were deposited via spraying onto float glass window surfaces and exposed into three different environments for 20 months. For comparison, a commercially available active SGG BIOCLEANTM glass and standard float glass were simultaneously exposed in the same conditions. It was shown that the self-cleaning property of either a commercial product or TiZr-coated float glass was not considerably effective in real field test conditions, although the previous laboratory tests showed pronounced photocatalytic activity of TiZr thin films. The inclination angle; however, was shown to have a considerable effect on the self-cleaning ability of samples, as did the rain patterns during the testing period. On the other hand, the anti-fogging effect of our TiZr material was very well expressed in controlled laboratory conditions (measuring droplet formation time) as well as in the real outdoor environment. Full article
(This article belongs to the Special Issue Self-Cleaning Surfaces)
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Open AccessArticle
Characterization of Photoactive Fe-TiO2 Lime Coatings for Building Protection: The Role of Iron Content
Materials 2019, 12(11), 1847; https://doi.org/10.3390/ma12111847
Received: 2 May 2019 / Revised: 30 May 2019 / Accepted: 4 June 2019 / Published: 6 June 2019
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Abstract
Iron-doped TiO2 nanoparticles, ranging in Fe concentrations from 0.05 up to 1.00% w/w, were synthesized through a simple sol-gel method. Fourier-transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), Ultraviolet-Visible (UV-Vis) spectroscopy, nitrogen adsorption−desorption isotherms, X-ray photoelectron spectroscopy (XPS), and X-ray absorption near-edge [...] Read more.
Iron-doped TiO2 nanoparticles, ranging in Fe concentrations from 0.05 up to 1.00% w/w, were synthesized through a simple sol-gel method. Fourier-transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), Ultraviolet-Visible (UV-Vis) spectroscopy, nitrogen adsorption−desorption isotherms, X-ray photoelectron spectroscopy (XPS), and X-ray absorption near-edge structure spectroscopy (XANES) were used to characterize the synthesized nanoparticles. The characterization of the Fe-doped TiO2 nanoparticles revealed the predominant presence of anatase crystalline form, as well as the incorporation of the Fe3+ ions into the crystal lattice of TiO2. The photocatalytic assessment of the Fe-doped TiO2 nanoparticles indicated that the low iron doping titania (0.05 and 0.10% w/w) have a positive effect on the photocatalytic degradation of Methyl Orange under visible radiation. Moreover, FTIR monitoring of calcium hydroxide pastes enriched with low Fe-doped TiO2 revealed enhancement of carbonation at both early and later stages. Improved photocatalytic performance and increased lime carbonation, observed in lime coatings with low Fe-doped TiO2 admixtures, established them as invaluable contributors to the protection of the built environment. Full article
(This article belongs to the Special Issue Self-Cleaning Surfaces)
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Open AccessArticle
Amphiphobic Nanostructured Coatings for Industrial Applications
Materials 2019, 12(5), 787; https://doi.org/10.3390/ma12050787
Received: 25 January 2019 / Revised: 27 February 2019 / Accepted: 5 March 2019 / Published: 7 March 2019
Cited by 1 | PDF Full-text (10754 KB) | HTML Full-text | XML Full-text
Abstract
The search for surfaces with non-wetting behavior towards water and low-surface tension liquids affects a wide range of industries. Surface wetting is regulated by morphological and chemical features interacting with liquid phases under different ambient conditions. Most of the approaches to the fabrication [...] Read more.
The search for surfaces with non-wetting behavior towards water and low-surface tension liquids affects a wide range of industries. Surface wetting is regulated by morphological and chemical features interacting with liquid phases under different ambient conditions. Most of the approaches to the fabrication of liquid-repellent surfaces are inspired by living organisms and require the fabrication of hierarchically organized structures, coupled with low surface energy chemical composition. This paper deals with the design of amphiphobic metals (AM) and alloys by deposition of nano-oxides suspensions in alcoholic or aqueous media, coupled with perfluorinated compounds and optional infused lubricant liquids resulting in, respectively, solid–liquid–air and solid–liquid–liquid working interfaces. Nanostructured organic/inorganic hybrid coatings with contact angles against water above 170°, contact angle with n-hexadecane (surface tension γ = 27 mN/m at 20 °C) in the 140–150° range and contact angle hysteresis lower than 5° have been produced. A full characterization of surface chemistry has been undertaken by X-ray photoelectron spectroscopy (XPS) analyses, while field-emission scanning electron microscope (FE-SEM) observations allowed the estimation of coatings thicknesses (300–400 nm) and their morphological features. The durability of fabricated amphiphobic surfaces was also assessed with a wide range of tests that showed their remarkable resistance to chemically aggressive environments, mechanical stresses and ultraviolet (UV) radiation. Moreover, this work analyzes the behavior of amphiphobic surfaces in terms of anti-soiling, snow-repellent and friction-reduction properties—all originated from their non-wetting behavior. The achieved results make AM materials viable solutions to be applied in different sectors answering several and pressing technical needs. Full article
(This article belongs to the Special Issue Self-Cleaning Surfaces)
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Open AccessFeature PaperArticle
Hydrothermal Synthesis of Rare-Earth Modified Titania: Influence on Phase Composition, Optical Properties, and Photocatalytic Activity
Materials 2019, 12(5), 713; https://doi.org/10.3390/ma12050713
Received: 31 January 2019 / Revised: 18 February 2019 / Accepted: 23 February 2019 / Published: 28 February 2019
Cited by 3 | PDF Full-text (2352 KB) | HTML Full-text | XML Full-text
Abstract
In order to expand the use of titania indoor as well as to increase its overall performance, narrowing the band gap is one of the possibilities to achieve this. Modifying with rare earths (REs) has been relatively unexplored, especially the modification of rutile [...] Read more.
In order to expand the use of titania indoor as well as to increase its overall performance, narrowing the band gap is one of the possibilities to achieve this. Modifying with rare earths (REs) has been relatively unexplored, especially the modification of rutile with rare earth cations. The aim of this study was to find the influence of the modification of TiO2 with rare earths on its structural, optical, morphological, and photocatalytic properties. Titania was synthesized using TiOSO4 as the source of titanium via hydrothermal synthesis procedure at low temperature (200 °C) and modified with selected rare earth elements, namely, Ce, La, and Gd. Structural properties of samples were determined by X-ray powder diffraction (XRD), and the phase ratio was calculated using the Rietveld method. Optical properties were analyzed by ultraviolet and visible light (UV-Vis) spectroscopy. Field emission scanning electron microscope (FE-SEM) was used to determine the morphological properties of samples and to estimate the size of primary crystals. X-ray photoelectron spectroscopy (XPS) was used to determine the chemical bonding properties of samples. Photocatalytic activity of the prepared photocatalysts as well as the titania available on the market (P25) was measured in three different setups, assessing volatile organic compound (VOC) degradation, NOx abatement, and water purification. It was found out that modification with rare earth elements slows down the transformation of anatase and brookite to rutile. Whereas the unmodified sample was composed of only rutile, La- and Gd-modified samples contained anatase and rutile, and Ce-modified samples consisted of anatase, brookite, and rutile. Modification with rare earth metals has turned out to be detrimental to photocatalytic activity. In all cases, pure TiO2 outperformed the modified samples. Cerium-modified TiO2 was the least active sample, despite having a light absorption tail up to 585 nm wavelength. La- and Gd-modified samples did not show a significant shift in light absorption when compared to the pure TiO2 sample. The reason for the lower activity of modified samples was attributed to a greater Ti3+/Ti4+ ratio and a large amount of hydroxyl oxygen found in pure TiO2. All the modified samples had a smaller Ti3+/Ti4+ ratio and less hydroxyl oxygen. Full article
(This article belongs to the Special Issue Self-Cleaning Surfaces)
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Open AccessFeature PaperArticle
Use of Steel Industry Wastes for the Preparation of Self-Cleaning Mortars
Materials 2019, 12(4), 621; https://doi.org/10.3390/ma12040621
Received: 3 January 2019 / Revised: 12 February 2019 / Accepted: 15 February 2019 / Published: 19 February 2019
Cited by 2 | PDF Full-text (2427 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
An important problem, which must be solved, is the accumulation of industrial waste in landfills. Science has an obligation to transform this waste into new products and, if possible, with high added value. In this sense, we propose the valorization of the waste [...] Read more.
An important problem, which must be solved, is the accumulation of industrial waste in landfills. Science has an obligation to transform this waste into new products and, if possible, with high added value. In this sense, we propose the valorization of the waste which is generated in the steel lamination process (HSL) through its conversion into a new material with photocatalytic activity which is suitable for use as an additive to obtain a self-cleaning construction material. The valorization of steel husk lamination waste is achieved through a grinding process, which allows the sample to be homogenized, in size, without altering its phase composition, and a thermal treatment that turns it into iron oxide, which acts as a photocatalyst. These residues, before and after treatment, were characterized by different techniques such as PXRD (Powder X-Ray Diffraction), TGA (Thermogravimetric Analysis), SBET (Specific surface area, Brunauer-Emmett-Teller), SEM (Scanning Electron Microscopy) and Diffuse reflectance (DR). MB and RhB tests show that this material is capable of self-cleaning, both of the material itself and when it is incorporated into a construction material (mortar). In addition, the NOx gas elimination test shows that it is also capable of acting on greenhouse gases such as NOx. Full article
(This article belongs to the Special Issue Self-Cleaning Surfaces)
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Open AccessArticle
Efficiency of Novel Photocatalytic Coating and Consolidants for Protection of Valuable Mineral Substrates
Materials 2019, 12(3), 521; https://doi.org/10.3390/ma12030521
Received: 5 December 2018 / Revised: 14 January 2019 / Accepted: 29 January 2019 / Published: 9 February 2019
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Abstract
In the process of protection and consolidation of valuable materials, the efficiency is the crucial property that needs to be considered. TiO2/ZnAl layered double hydroxide (LDH) coating and silicate- and carbonate-based consolidants were synthesized and proposed to be used for protection [...] Read more.
In the process of protection and consolidation of valuable materials, the efficiency is the crucial property that needs to be considered. TiO2/ZnAl layered double hydroxide (LDH) coating and silicate- and carbonate-based consolidants were synthesized and proposed to be used for protection and consolidation of four porous mineral substrates: brick, stone, render and mortar. The photocatalytic efficiency of TiO2/ZnAl LDH coating, as well as consolidation efficiency of two consolidants, both applied on model substrates, were studied. The photocatalytic coating showed significant activity and performed well after the durability tests involving rinsing and freezing/thawing procedures. After treatment with both consolidants, a serious enhancement of consolidation of the used substrates was found. On the other hand, the application of TiO2/ZnAl LDH, as well as consolidants, caused negligible changes in the water vapour permeability values and in appearance of the porous mineral substrates, indicating a high level of compatibility. Full article
(This article belongs to the Special Issue Self-Cleaning Surfaces)
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Open AccessArticle
Quantification of the Photocatalytic Self-Cleaning Ability of Non-Transparent Materials
Materials 2019, 12(3), 508; https://doi.org/10.3390/ma12030508
Received: 20 December 2018 / Revised: 25 January 2019 / Accepted: 2 February 2019 / Published: 8 February 2019
Cited by 3 | PDF Full-text (1730 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The photo-induced reactivity of compounds at the surface of photocatalytic materials is used to maintain the cleanliness of the surface of glass, concretes and paints. A standard method to quantify the photocatalytic self-cleaning (SC) properties of non-transparent materials was recently published. It is [...] Read more.
The photo-induced reactivity of compounds at the surface of photocatalytic materials is used to maintain the cleanliness of the surface of glass, concretes and paints. A standard method to quantify the photocatalytic self-cleaning (SC) properties of non-transparent materials was recently published. It is based on the covering of the sample surface with a defined amount of dye and on the evaluation of the reflectance spectra of the coloured surface under irradiation. The calibration of the spectral changes allowed the quantification of the surface residual dye and the evaluation of the self-cleaning kinetics. The method was tested on seven white and coloured photocatalytic materials using methylene blue (MB), rhodamine B (RhB) and metanil yellow (MY). The main by-products of the MB photocatalytic degradation at the solid/solid interface were identified, showing that MB degradation in solution follows a path quite different from that at the solid/solid interface. Also MY showed a different order of photoreactivity. Furthermore, experiments at the solid/solid interface are more trustworthy than tests in solution for evaluating the self-cleaning ability. The differences of the photocatalytic phenomena at the solid/solid interface in comparison with the most studied photoactivated processes at the solid/liquid interface are outlined. Furthermore, photocatalytic materials showed selectivity toward some specific dyes. This encourages the use of more than one dye for the evaluation of the self-cleaning ability of a photocatalytic material. Full article
(This article belongs to the Special Issue Self-Cleaning Surfaces)
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Open AccessArticle
Improved Self-Cleaning Properties of Photocatalytic Gypsum Plaster Enriched with Glass Fiber
Materials 2019, 12(3), 357; https://doi.org/10.3390/ma12030357
Received: 19 December 2018 / Revised: 16 January 2019 / Accepted: 22 January 2019 / Published: 24 January 2019
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Abstract
In the study the self-cleaning properties of photoactive gypsum plasters are presented. The modified gypsum plasters were obtained by addition of 1 and 3 wt.% of nitrogen-modified titanium dioxide (TiO2/N) and 0.1, 0.3, and 0.5 wt.% of glass fiber. The self-cleaning [...] Read more.
In the study the self-cleaning properties of photoactive gypsum plasters are presented. The modified gypsum plasters were obtained by addition of 1 and 3 wt.% of nitrogen-modified titanium dioxide (TiO2/N) and 0.1, 0.3, and 0.5 wt.% of glass fiber. The self-cleaning ability of the obtained materials was tested during two dyes decomposition: Methylene Blue (MB) and Reactive Orange (RO). It was found that presence of glass fiber increased photocatalytic activity of modified gypsum plasters, which may be due to the fact glass fiber may act as ducts for light and transport it to sites screened by TiO2 or glass fiber can retard charge recombination. Moreover, unexpectedly the addition of glass fiber did not increase the mechanical properties of modified gypsum plasters, which may be because gypsum does not strongly adhere to the surface of glass fibers. Full article
(This article belongs to the Special Issue Self-Cleaning Surfaces)
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Open AccessArticle
Electrophoresis Assembly of Novel Superhydrophobic Molybdenum Trioxide (MoO3) Films with Great Stability
Materials 2019, 12(3), 336; https://doi.org/10.3390/ma12030336
Received: 5 December 2018 / Revised: 27 December 2018 / Accepted: 2 January 2019 / Published: 22 January 2019
Cited by 1 | PDF Full-text (5091 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
This work presents a hydrothermal synthesis approach to produce novel schistose molybdenum trioxide (MoO3) powders with wide application, and introduces a facile electrophoresis assembly technique to construct the superhydrophobic MoO3 films (SMFs) with contact angle up to 169 ± 1° [...] Read more.
This work presents a hydrothermal synthesis approach to produce novel schistose molybdenum trioxide (MoO3) powders with wide application, and introduces a facile electrophoresis assembly technique to construct the superhydrophobic MoO3 films (SMFs) with contact angle up to 169 ± 1° at normal pressure and temperature. The microstructures and chemical compositions of product were analyzed by field emission scanning electron microcopy (FESEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD). The wettability and stability studies indicate that the SMFs all show great resistance in various environments with adjusting factors, including droplets with different surface tension, pH, relative humidity, etc., and the stability can be maintained at least for five months. Notably, this paper will provides a valuable reference for designing novel oxide powders and their high-efficient hydrophobic film formation with self-cleaning or water proof properties. Full article
(This article belongs to the Special Issue Self-Cleaning Surfaces)
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Open AccessArticle
Super-Efficient Synthesis of Mesh-like Superhydrophobic Nano-Aluminum/Iron (III) Oxide Energetic Films
Materials 2019, 12(2), 234; https://doi.org/10.3390/ma12020234
Received: 22 November 2018 / Revised: 15 December 2018 / Accepted: 25 December 2018 / Published: 11 January 2019
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Abstract
In this study, a novel superhydrophobic nano-aluminum/iron (III) oxide composite has been prepared by a facile one-step process of electrophoretic deposition, with wide potential applications. The optimal suspension included ethanol, acetyl-acetone, and the additives of fluorotriphenylsilane and perfluorodecyltriethoxysilane. The microstructure, wettability, and exothermic [...] Read more.
In this study, a novel superhydrophobic nano-aluminum/iron (III) oxide composite has been prepared by a facile one-step process of electrophoretic deposition, with wide potential applications. The optimal suspension included ethanol, acetyl-acetone, and the additives of fluorotriphenylsilane and perfluorodecyltriethoxysilane. The microstructure, wettability, and exothermic performance were analyzed by field emission scanning electron microcopy (FESEM), X-ray diffraction (XRD), water contact angle measurements, and the differential scanning calorimetry (DSC) technique. The water contact angle and the heat-release of the target composites could reach to ~170° and 2.67 kJ/g, and could still keep stable, after exposure for six months, showing a great stability. These results provided an exquisite synthesis of ideas, for designing other superhydrophobic energetic materials with self-cleaning properties, for real industrial application. Full article
(This article belongs to the Special Issue Self-Cleaning Surfaces)
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Open AccessFeature PaperArticle
Solid-Gas Phase Photo-Catalytic Behaviour of Rutile and TiOn (1 < n < 2) Sub-Oxide Phases for Self-Cleaning Applications
Materials 2019, 12(1), 170; https://doi.org/10.3390/ma12010170
Received: 18 November 2018 / Revised: 20 December 2018 / Accepted: 29 December 2018 / Published: 7 January 2019
Cited by 1 | PDF Full-text (4985 KB) | HTML Full-text | XML Full-text
Abstract
The solid-gas phase photo-catalytic activities of rutile TiO2 and TiOn (1 < n < 2) sub-oxide phases have been evaluated. Varying concentrations of Ti3+ defects were introduced into the rutile polymorph of titanium dioxide through carbo-thermal reduction at temperatures ranging [...] Read more.
The solid-gas phase photo-catalytic activities of rutile TiO2 and TiOn (1 < n < 2) sub-oxide phases have been evaluated. Varying concentrations of Ti3+ defects were introduced into the rutile polymorph of titanium dioxide through carbo-thermal reduction at temperatures ranging from 350 °C to 1300 °C. The resulting sub-oxides formed were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, impedance spectroscopy and UV-visible diffuse reflectance spectroscopy. The presence of Ti3+ in rutile exposed to high reduction temperatures was confirmed by X-ray diffraction. In addition, a Ti3+-Ti4+ system was demonstrated to enhance the photo-catalytic properties of rutile for the degradation of the air pollutants NO2 and CO2 under UV irradiation of wavelengths (λ) 376–387 nm and 381–392 nm. The optimum reduction temperature for photo-catalytic activity was within the range 350–400 °C and attributed to improved charge-separation. The materials that were subject to carbo-thermal reduction at temperatures of 350 °C and 400 °C exhibited electrical conductivities over one hundred times higher compared to the non-reduced rutile. The results highlight that sub-oxide phases form an important alternative approach to doping with other elements to improve the photo-catalytic performance of TiO2. Such materials are important for applications such as self-cleaning where particles can be incorporated into surface coatings. Full article
(This article belongs to the Special Issue Self-Cleaning Surfaces)
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Open AccessArticle
Hydrophobicity and Photocatalytic Activity of a Wood Surface Coated with a Fe3+-Doped SiO2/TiO2 Film
Materials 2018, 11(12), 2594; https://doi.org/10.3390/ma11122594
Received: 6 December 2018 / Revised: 16 December 2018 / Accepted: 17 December 2018 / Published: 19 December 2018
Cited by 1 | PDF Full-text (4286 KB) | HTML Full-text | XML Full-text
Abstract
A Fe3+-doped SiO2/TiO2 composite film (Fe3+-doped STCF) was prepared on a wood surface via a sol–gel method to improve its photocatalytic activity and hydrophobicity. The structure of the composite film was analyzed by Fourier Transform infrared [...] Read more.
A Fe3+-doped SiO2/TiO2 composite film (Fe3+-doped STCF) was prepared on a wood surface via a sol–gel method to improve its photocatalytic activity and hydrophobicity. The structure of the composite film was analyzed by Fourier Transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity toward degradation of methyl orange and its hydrophobic nature were investigated. The results showed that the composite film was anatase TiO2 crystal form, and the addition of Fe3+ ions and SiO2 enhanced the diffraction peaks for the anatase crystal form. The photocatalytic activity of the wood coated with the composite film was enhanced. The highest degradation percentage was at 1 wt % Fe3+ (40.37%), and the degradation ability of the wood towards methyl orange solution was further improved under acidic conditions. In addition, the composite film was hydrophobic, and the hydrophobic property was enhanced as the immersion time in the sol increased. The wood surface coated with Fe3+-doped STCF exhibited strong hydrophobicity and photocatalytic activity, which could effectively prevent moisture from adhering to the surface and degrade organic pollutants; thus, the modified wood surface had good self-cleaning function. Full article
(This article belongs to the Special Issue Self-Cleaning Surfaces)
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Open AccessArticle
Preparation of Assembled Carbon Soot Films and Hydrophobic Properties
Materials 2018, 11(11), 2318; https://doi.org/10.3390/ma11112318
Received: 9 October 2018 / Revised: 8 November 2018 / Accepted: 12 November 2018 / Published: 19 November 2018
Cited by 1 | PDF Full-text (7023 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this paper, a simple, inexpensive, and rapid method for the fabrication of controlled layer candle soot film has been reported by interface self-assembly and transferred method. The mechanism of candle soot self-assembly is explained and their morphology, elemental composition, optical, and wetting [...] Read more.
In this paper, a simple, inexpensive, and rapid method for the fabrication of controlled layer candle soot film has been reported by interface self-assembly and transferred method. The mechanism of candle soot self-assembly is explained and their morphology, elemental composition, optical, and wetting properties are characterized. The uniformity and thickness of prepared films especially depend on the concentration of candle soot mixed solution (alcohol and deionized water). The results show that the optimal concentration of candle soot solution is approximately ~0.2% wt/mL. In addition, the absorption spectra of the controlled-layer candle soot films are determined by the number of layers and the surface morphology. The hydrophobic properties of candle soot films are closely related to their layer number. When these films reach to the fourth layer, the water contact angle and roll-off angle are measured as 142° ± 2° and 6°, respectively. The controlled assembly CS films have the potential application in photo/electrocatalysis, solar cells, lithium-ion batteries, and water splitting. Full article
(This article belongs to the Special Issue Self-Cleaning Surfaces)
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Open AccessArticle
Preparation and Surface Properties Study of Novel Fluorine-Containing Methacrylate Polymers for Coating
Materials 2018, 11(11), 2258; https://doi.org/10.3390/ma11112258
Received: 30 September 2018 / Revised: 2 November 2018 / Accepted: 7 November 2018 / Published: 13 November 2018
Cited by 1 | PDF Full-text (5768 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A new structural fluorine-containing methacrylate monomer CH2=C(CH3)COOC–(CF3)2CF2CF2CF3 (5) was synthesized derived from perfluoro-2-methyl-2-pentene (D2). A homopolymer of 5 and copolymers of 5 and methacrylate with different [...] Read more.
A new structural fluorine-containing methacrylate monomer CH2=C(CH3)COOC–(CF3)2CF2CF2CF3 (5) was synthesized derived from perfluoro-2-methyl-2-pentene (D2). A homopolymer of 5 and copolymers of 5 and methacrylate with different alkyl chain length (chain length n = 1, 2, 4, 6, 8, 12, 18) were obtained. These new fluorinated acrylate polymers showed excellent water and oil repellency. The contact angle of the films of the homopolymer and part of the copolymers were similar with the corresponding polymers prepared from CH2=CHC(O)OCH(C3F7)(CF(CF3)2), but greater than that of the C6F13(CF3)CHOC(O)CH=CH2 homopolymer. The structure-property relationship research indicated that the copolymers’ hydrophobicity decreased first and then increased with the increase of alkyl chain length. Td of all the polymers were greater than 220 °C and Tg fluctuated within the range of −51~103.8 °C. Contact angle and Tg could be adjusted by controlling the feed ratio of monomer to meet the requirements of technical indicators in the practical applications. The outstanding liquid repellency and thermal stability make monomer 5 a promising alternative to perfluorinated long-chain fluorosurfactants. Full article
(This article belongs to the Special Issue Self-Cleaning Surfaces)
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Open AccessArticle
Transparent Photocatalytic Thin Films on Flexible Polymer Substrates
Materials 2018, 11(10), 1945; https://doi.org/10.3390/ma11101945
Received: 3 August 2018 / Revised: 19 September 2018 / Accepted: 6 October 2018 / Published: 11 October 2018
Cited by 2 | PDF Full-text (4555 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Self-cleaning and/or photocatalytic films on polymer substrates have found numerous applications during the past decades. However, the common demand for high-temperature post synthesis treatment limits the application to temperature resistant substrates only. Herein, we prepared self-cleaning photocatalytic films on four thermosensitive polymeric substrates: [...] Read more.
Self-cleaning and/or photocatalytic films on polymer substrates have found numerous applications during the past decades. However, the common demand for high-temperature post synthesis treatment limits the application to temperature resistant substrates only. Herein, we prepared self-cleaning photocatalytic films on four thermosensitive polymeric substrates: polyvinyl chloride (PVC), polymethyl methacrylate (PMMA), and acryl coated polyester (PES) fabric (D2) with poly(vinylidene fluoride) (PVDF) containing lacquer (D1). TiO2 was prepared via a low-temperature sol-gel process using titanium(IV) isopropoxide and zirconium(IV) butoxide as precursors with various loading levels of Zr; 0, 5, 10, and 20 mol.%, and deposited on the substrates by using a SiO2 binder in form of thin films (ca. 200 nm thick) via dip-coating. The films were characterized by SEM, hardness test, UV-Vis, photothermal beam deflection spectroscopy, and IR spectroscopy, while photocatalytic activity was measured by the fluorescence-based method of the terephthalic acid probe and wetting by contact angle measurements. Films containing 10 mol.% of Zr showed the best compromise regarding photocatalytic activity and mechanical stability while from substrates point of view PVC performed the best, followed by PMMA, D1, and D2. The beneficial role of SiO2 binder was not only guaranteeing excellent mechanical stability, but also to prevent the D1 polymer from deterioration; the latter was found to be labile to long-term solar-light exposure due to degradation of the top PVDF layer. Full article
(This article belongs to the Special Issue Self-Cleaning Surfaces)
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Open AccessArticle
Preparation of Parabolic Superhydrophobic Material for Oil-Water Separation
Materials 2018, 11(10), 1914; https://doi.org/10.3390/ma11101914
Received: 19 August 2018 / Revised: 28 September 2018 / Accepted: 29 September 2018 / Published: 9 October 2018
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Abstract
In order to prepare parabolic superhydrophobic materials, copper meshes were used as the substrate and ultrasonic etching and oxidative corrosion were carried out with FeCl3 solution and H2O2 solution, respectively, and then the surface was modified with stearic acid [...] Read more.
In order to prepare parabolic superhydrophobic materials, copper meshes were used as the substrate and ultrasonic etching and oxidative corrosion were carried out with FeCl3 solution and H2O2 solution, respectively, and then the surface was modified with stearic acid (SA). The topological structure and surface wettability of the prepared mesh were characterized by fluorescence microscope, scanning electron microscopy and contact angle measurement. Finally, the as-prepared copper meshes were applied to oil-water separation. The results showed that the micro-nano-mastoid structure on the surface of the copper mesh was flaky bulges, forming a rough structure similar to a paraboloid. When the oxidative corrosion time of H2O2 was 1 min, it is more beneficial to increase the hydrophobicity of the surface of the copper mesh and increase the contact angle of water droplets on the surface of the membrane. Additionally, based on superhydrophobic materials of the parabolic copper mesh, the static contact angles of the water droplets, engine oil and carbon tetrachloride with the surface were approximately 153.6°, 5° and 0.1°, respectively and the sliding angle of the water droplets with the surface were approximately 4.9°. The parabolic membrane was applied to discuss the separation efficiency of different oils with deionized water and the separation efficiency was obtained as benzene > carbon tetrachloride > oil > machine oil. Therefore, based on the research, the parabolic superhydrophobic material has good efficiency of oil-water separation. Full article
(This article belongs to the Special Issue Self-Cleaning Surfaces)
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Open AccessArticle
Biomimetic Superhydrophobic Hollowed-Out Pyramid Surface Based on Self-Assembly
Materials 2018, 11(5), 813; https://doi.org/10.3390/ma11050813
Received: 31 March 2018 / Revised: 10 May 2018 / Accepted: 14 May 2018 / Published: 16 May 2018
Cited by 2 | PDF Full-text (2575 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we present a periodic hollowed-out pyramid microstructure with excellent superhydrophobicity. In our approach, T-topping pillars and capillary-induced self-assembly methods were combined with the photolithography process to fabricate a hollowed-out pyramid structure. First, a wideband ultraviolet source without a filter was [...] Read more.
In this paper, we present a periodic hollowed-out pyramid microstructure with excellent superhydrophobicity. In our approach, T-topping pillars and capillary-induced self-assembly methods were combined with the photolithography process to fabricate a hollowed-out pyramid structure. First, a wideband ultraviolet source without a filter was used to fabricate the T-topping pillars during the exposure process; then, the evaporation-induced assembly collapsed the pillars and formed the hollowed-out pyramid structure. Scanning electron microscopy images showed the microstructures of the prepared surface. The contact angle of the surface was 154°. The surface showed excellent high temperature and ultraviolet irradiation tolerance, and the contact angle of the surface barely changed when the temperature dropped. This excellent environmental durability of our superhydrophobic surface has potential applications for self-cleaning and friction drag reduction under water. Full article
(This article belongs to the Special Issue Self-Cleaning Surfaces)
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