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Photocalytic Coatings for Air-Purifying, Self-Cleaning and Antimicrobial Properties
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Photocalytic Coatings for Air-Purifying, Self-Cleaning and Antimicrobial Properties

A special issue of Coatings (ISSN 2079-6412).

Deadline for manuscript submissions: closed (31 March 2015) | Viewed by 115000

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editor

Prof. Dr. Anibal C. Maury-Ramirez

E-Mail Website
Guest Editor
CHOC-IZONE Research Group, Engineering Faculty, Universidad El Bosque, Bogota 111711, Colombia
Interests: green walls and roofs; photocatalytic materials; nanomaterials; recycling in concrete
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

With the latest nanotechnology developments, the application of nanoparticle-based coatings, which give novel properties to different materials, has become very attractive to scientists and industries worldwide. For example, photocatalytic coatings may potentially develop air-purifying, self-cleaning, and antimicrobial properties using light irradiation as the only energy source. The application of these novel functionalities on ceramic, polymeric, metal, and composite (e.g., concrete or mortar) substrates has been significantly increasing in recent years. Furthermore, although several standard test methods for evaluating photocatalytic properties have been recently launched, a significant amount of photocatalytic performances have been reported in existing literature using various in-house tests. This makes comparison a complex task. Moreover, the applicability of different coating technologies developed for photocatalytic coatings on different substrates has been inadequately investigated. Thus, by including all types of substrates and coating technologies, this Special Issue aims to provide better comparisons and assessments of the application potentials of different photocatalytic coating technologies on different substrates for developing air-purifying, self-cleaning, and antimicrobial properties.

Dr. Anibal Maury-Ramirez
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Coatings is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • air-purifying
  • self-cleaning
  • easy-to-clean
  • antimicrobial
  • coatings
  • TiO2
  • hydrophilicity
  • air pollution
  • building maintenance
  • photocatalysis

Published Papers (12 papers)

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Research

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2918 KiB  
Article
Photocatalytic Properties of Nb/MCM-41 Molecular Sieves: Effect of the Synthesis Conditions
by Caterine Daza Gomez and J. E. Rodriguez-Paez
Coatings 2015, 5(3), 511-526; https://doi.org/10.3390/coatings5030511 - 20 Aug 2015
Cited by 3 | Viewed by 5508
Abstract
The effect of synthesis conditions and niobium incorporation levels on the photocatalytic properties of Nb/MCM-41 molecular sieves was assessed. Niobium pentoxide supported on MCM-41 mesoporous silica was obtained using two methods: sol-gel and incipient impregnation, in each case also varying the percentage of [...] Read more.
The effect of synthesis conditions and niobium incorporation levels on the photocatalytic properties of Nb/MCM-41 molecular sieves was assessed. Niobium pentoxide supported on MCM-41 mesoporous silica was obtained using two methods: sol-gel and incipient impregnation, in each case also varying the percentage of niobium incorporation. The synthesized Nb-MCM-41 ceramic powders were characterized using the spectroscopic techniques of infrared spectroscopy (IR), Raman spectroscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The photodegradation capacity of the powders was studied using the organic molecule, methylene blue. The effect of both the method of synthesis and the percentage of niobium present in the sample on the photodegradation action of the solids was determined. The mesoporous Nb-MCM-41 that produced the greatest photodegradation response was obtained using the sol-gel method and 20% niobium incorporation. Full article
(This article belongs to the Special Issue Photocalytic Coatings for Air-Purifying, Self-Cleaning and Antimicrobial Properties)
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972 KiB  
Article
Evaluation of Photocatalytic Properties of Portland Cement Blended with Titanium Oxynitride (TiO2−xNy) Nanoparticles
by Juan D. Cohen, G. Sierra-Gallego and Jorge I. Tobón
Coatings 2015, 5(3), 465-476; https://doi.org/10.3390/coatings5030465 - 31 Jul 2015
Cited by 22 | Viewed by 6460
Abstract
Photocatalytic activity of Portland cement pastes blended with nanoparticles of titanium oxynitride (TiO2−xNy) was studied. Samples with different percentages of TiO2−xNy (0.0%, 0.5%, 1%, 3%) and TiO2 (1%, 3%) were evaluated in order [...] Read more.
Photocatalytic activity of Portland cement pastes blended with nanoparticles of titanium oxynitride (TiO2−xNy) was studied. Samples with different percentages of TiO2−xNy (0.0%, 0.5%, 1%, 3%) and TiO2 (1%, 3%) were evaluated in order to study their self-cleaning properties. The presence of nitrogen in the tetragonal structure of TiO2 was evidenced by X-ray diffraction (XRD) as a shift of the peaks in the 2θ axis. The samples were prepared with a water/cement ratio of 0.5 and a concentration of Rhodamine B of 0.5 g/L. After 65 h of curing time, the samples were irradiated with UV lamps to evaluate the reduction of the pigment. The color analysis was carried out using a Spectrometer UV/Vis measuring the coordinates CIE (Commission Internationale de l’Eclairage) L*, a*, b*, and with special attention to the reddish tones (Rhodamine B color) which correspond to a* values greater than zero. Additionally, samples with 0.5%, 1%, 3% of TiO2−xNy and 1%, 3% of TiO2 were evaluated under visible light with the purpose of determining the Rhodamine B abatement to wavelengths greater than 400 nm. The results have shown a similar behavior for both additions under UV light irradiation, with 3% being the addition with the highest photocatalytic efficiency obtained. However, TiO2−xNy showed activity under irradiation with visible light, unlike TiO2, which can only be activated under UV light. Full article
(This article belongs to the Special Issue Photocalytic Coatings for Air-Purifying, Self-Cleaning and Antimicrobial Properties)
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1215 KiB  
Article
Antibiofilm Activity of Epoxy/Ag-TiO2 Polymer Nanocomposite Coatings against Staphylococcus Aureus and Escherichia Coli
by Santhosh S. M. and Kandasamy Natarajan
Coatings 2015, 5(2), 95-114; https://doi.org/10.3390/coatings5020095 - 14 Apr 2015
Cited by 55 | Viewed by 11635
Abstract
Dispersion of functional inorganic nano-fillers like TiO2 within polymer matrix is known to impart excellent photobactericidal activity to the composite. Epoxy resin systems with Ag+ ion doped TiO2 can have combination of excellent biocidal characteristics of silver and the photocatalytic [...] Read more.
Dispersion of functional inorganic nano-fillers like TiO2 within polymer matrix is known to impart excellent photobactericidal activity to the composite. Epoxy resin systems with Ag+ ion doped TiO2 can have combination of excellent biocidal characteristics of silver and the photocatalytic properties of TiO2. The inorganic antimicrobial incorporation into an epoxy polymeric matrix was achieved by sonicating laboratory-made nano-scale anatase TiO2 and Ag-TiO2 into the industrial grade epoxy resin. The resulting epoxy composite had ratios of 0.5–2.0 wt% of nano-filler content. The process of dispersion of Ag-TiO2 in the epoxy resin resulted in concomitant in situ synthesis of silver nanoparticles due to photoreduction of Ag+ ion. The composite materials were characterized by DSC and SEM. The glass transition temperature (Tg) increased with the incorporation of the nanofillers over the neat polymer. The materials synthesized were coated on glass petri dish. Anti-biofilm property of coated material due to combined release of biocide, and photocatalytic activity under static conditions in petri dish was evaluated against Staphylococcus aureus ATCC6538 and Escherichia coli K-12 under UV irradiation using a crystal violet binding assay. Prepared composite showed significant inhibition of biofilm development in both the organisms. Our studies indicate that the effective dispersion and optimal release of biocidal agents was responsible for anti-biofilm activity of the surface. The reported thermoset coating materials can be used as bactericidal surfaces either in industrial or healthcare settings to reduce the microbial loads. Full article
(This article belongs to the Special Issue Photocalytic Coatings for Air-Purifying, Self-Cleaning and Antimicrobial Properties)
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1619 KiB  
Article
The Effect of Tween® Surfactants in Sol-Gel Processing for the Production of TiO2 Thin Films
by Ann-Louise Anderson and Russell Binions
Coatings 2014, 4(4), 796-809; https://doi.org/10.3390/coatings4040796 - 19 Dec 2014
Cited by 15 | Viewed by 8255
Abstract
Titanium dioxide thin films were deposited using a Tween® surfactant modified non-aqueous sol-gel method onto fluorine doped tin oxide glass substrates. The surfactant concentration and type in the sols was varied as well as the number of deposited layers. The as deposited [...] Read more.
Titanium dioxide thin films were deposited using a Tween® surfactant modified non-aqueous sol-gel method onto fluorine doped tin oxide glass substrates. The surfactant concentration and type in the sols was varied as well as the number of deposited layers. The as deposited thin films were annealed at 500 °C for 15 min before characterisation and photocatalytic testing with resazurin intelligent ink. The films were characterised using scanning electron microscopy, atomic force microscopy, X-ray diffraction, Raman spectroscopy and UV-Vis spectroscopy. Photocatalytic activity of the films was evaluated using a resazurin dye-ink test and the hydrophilicity of the films was analysed by water-contact angles measurements. Characterisation and photocatalytic testing has shown that the addition of surfactant in varying types and concentrations had a significant effect on the resulting thin film microstructure, such as changing the average particle size from 130 to 25 nm, and increasing the average root mean square roughness from 11 to 350 nm. Such structural changes have resulted in an enhanced photocatalytic performance for the thin films, with an observed reduction in dye half-life from 16.5 to three minutes. Full article
(This article belongs to the Special Issue Photocalytic Coatings for Air-Purifying, Self-Cleaning and Antimicrobial Properties)
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458 KiB  
Article
Antibacterial Activity of TiO2 Photocatalyst Alone or in Coatings on E. coli: The Influence of Methodological Aspects
by Thomas Verdier, Marie Coutand, Alexandra Bertron and Christine Roques
Coatings 2014, 4(3), 670-686; https://doi.org/10.3390/coatings4030670 - 22 Aug 2014
Cited by 179 | Viewed by 14097
Abstract
In damp environments, indoor building materials are among the main proliferation substrates for microorganisms. Photocatalytic coatings, including nanoparticles of TiO2, could be a way to prevent microbial proliferation or, at least, to significantly reduce the amount of microorganisms that grow on [...] Read more.
In damp environments, indoor building materials are among the main proliferation substrates for microorganisms. Photocatalytic coatings, including nanoparticles of TiO2, could be a way to prevent microbial proliferation or, at least, to significantly reduce the amount of microorganisms that grow on indoor building materials. Previous works involving TiO2 have already shown the inactivation of bacteria by the photocatalysis process. This paper studies the inactivation of Escherichia coli bacteria by photocatalysis involving TiO2 nanoparticles alone or in transparent coatings (varnishes) and investigates different parameters that significantly influence the antibacterial activity. The antibacterial activity of TiO2 was evaluated through two types of experiments under UV irradiation: (I) in slurry with physiological water (stirred suspension); and (II) in a drop deposited on a glass plate. The results confirmed the difference in antibacterial activity between simple drop-deposited inoculum and inoculum spread under a plastic film, which increased the probability of contact between TiO2 and bacteria (forced contact). In addition, the major effect of the nature of the suspension on the photocatalytic disinfection ability was highlighted. Experiments were also carried out at the surface of transparent coatings formulated using nanoparticles of TiO2. The results showed significant antibacterial activities after 2 h and 4 h and suggested that improving the formulation would increase efficiency. Full article
(This article belongs to the Special Issue Photocalytic Coatings for Air-Purifying, Self-Cleaning and Antimicrobial Properties)
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1437 KiB  
Article
Photocatalytic Activity and Stability of Porous Polycrystalline ZnO Thin-Films Grown via a Two-Step Thermal Oxidation Process
by James C. Moore, Robert Louder and Cody V. Thompson
Coatings 2014, 4(3), 651-669; https://doi.org/10.3390/coatings4030651 - 15 Aug 2014
Cited by 33 | Viewed by 6733
Abstract
The photocatalytic activity and stability of thin, polycrystalline ZnO films was studied. The oxidative degradation of organic compounds at the ZnO surface results from the ultraviolet (UV) photo-induced creation of highly oxidizing holes and reducing electrons, which combine with surface water to form [...] Read more.
The photocatalytic activity and stability of thin, polycrystalline ZnO films was studied. The oxidative degradation of organic compounds at the ZnO surface results from the ultraviolet (UV) photo-induced creation of highly oxidizing holes and reducing electrons, which combine with surface water to form hydroxyl radicals and reactive oxygen species. Therefore, the efficiency of the electron-hole pair formation is of critical importance for self-cleaning and antimicrobial applications with these metal-oxide catalyst systems. In this study, ZnO thin films were fabricated on sapphire substrates via direct current sputter deposition of Zn-metal films followed by thermal oxidation at several annealing temperatures (300–1200 °C). Due to the ease with which they can be recovered, stabilized films are preferable to nanoparticles or colloidal suspensions for some applications. Characterization of the resulting ZnO thin films through atomic force microscopy and photoluminescence indicated that decreasing annealing temperature leads to smaller crystal grain size and increased UV excitonic emission. The photocatalytic activities were characterized by UV-visible absorption measurements of Rhodamine B dye concentrations. The films oxidized at lower annealing temperatures exhibited higher photocatalytic activity, which is attributed to the increased optical quality. Photocatalytic activity was also found to depend on film thickness, with lower activity observed for thinner films. Decreasing activity with use was found to be the result of decreasing film thickness due to surface etching. Full article
(This article belongs to the Special Issue Photocalytic Coatings for Air-Purifying, Self-Cleaning and Antimicrobial Properties)
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481 KiB  
Article
Self-Cleaning Photocatalytic Polyurethane Coatings Containing Modified C60 Fullerene Additives
by Jeffrey G. Lundin, Spencer L. Giles, Robert F. Cozzens and James H. Wynne
Coatings 2014, 4(3), 614-629; https://doi.org/10.3390/coatings4030614 - 13 Aug 2014
Cited by 14 | Viewed by 7274
Abstract
Surfaces are often coated with paint for improved aesthetics and protection; however, additional functionalities that impart continuous self-decontaminating and self-cleaning properties would be extremely advantageous. In this report, photochemical additives based on C60 fullerene were incorporated into polyurethane coatings to investigate their [...] Read more.
Surfaces are often coated with paint for improved aesthetics and protection; however, additional functionalities that impart continuous self-decontaminating and self-cleaning properties would be extremely advantageous. In this report, photochemical additives based on C60 fullerene were incorporated into polyurethane coatings to investigate their coating compatibility and ability to impart chemical decontaminating capability to the coating surface. C60 exhibits unique photophysical properties, including the capability to generate singlet oxygen upon exposure to visible light; however, C60 fullerene exhibits poor solubility in solvents commonly employed in coating applications. A modified C60 containing a hydrophilic moiety was synthesized to improve polyurethane compatibility and facilitate segregation to the polymer–air interface. Bulk properties of the polyurethane films were analyzed to investigate additive–coating compatibility. Coatings containing photoactive additives were subjected to self-decontamination challenges against representative chemical contaminants and the effects of additive loading concentration, light exposure, and time on chemical decontamination are reported. Covalent attachment of an ethylene glycol tail to C60 improved its solubility and dispersion in a hydrophobic polyurethane matrix. Decomposition products resulting from oxidation were observed in addition to a direct correlation between additive loading concentration and decomposition of surface-residing contaminants. The degradation pathways deduced from contaminant challenge byproduct analyses are detailed. Full article
(This article belongs to the Special Issue Photocalytic Coatings for Air-Purifying, Self-Cleaning and Antimicrobial Properties)
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792 KiB  
Article
Tuning the Photocatalytic Activity of Anatase TiO2 Thin Films by Modifying the Preferred <001> Grain Orientation with Reactive DC Magnetron Sputtering
by B. Stefanov and L. Österlund
Coatings 2014, 4(3), 587-601; https://doi.org/10.3390/coatings4030587 - 08 Aug 2014
Cited by 23 | Viewed by 9484
Abstract
Anatase TiO2 thin films were deposited by DC reactive magnetron sputtering on glass substrates at 20 mTorr pressure in a flow of an Ar and O2 gas mixture. The O2 partial pressure (PO2) was varied from [...] Read more.
Anatase TiO2 thin films were deposited by DC reactive magnetron sputtering on glass substrates at 20 mTorr pressure in a flow of an Ar and O2 gas mixture. The O2 partial pressure (PO2) was varied from 0.65 mTorr to 1.3 mTorr to obtain two sets of films with different stoichiometry. The structure and morphology of the films were characterized by secondary electron microscopy, atomic force microscopy, and grazing-angle X-ray diffraction complemented by Rietveld refinement. The as-deposited films were amorphous. Post-annealing in air for 1 h at 500 °C resulted in polycrystalline anatase film structures with mean grain size of 24.2 nm (PO2 = 0.65 mTorr) and 22.1 nm (PO2 = 1.3 mTorr), respectively. The films sputtered at higher O2 pressure showed a preferential orientation in the <001> direction, which was associated with particle surfaces exposing highly reactive {001} facets. Films sputtered at lower O2 pressure exhibited no, or very little, preferential grain orientation, and were associated with random distribution of particles exposing mainly the thermodynamically favorable {101} surfaces. Photocatalytic degradation measurements using methylene blue dye showed that <001> oriented films exhibited approximately 30% higher reactivity. The measured intensity dependence of the degradation rate revealed that the UV-independent rate constant was 64% higher for the <001> oriented film compared to randomly oriented films. The reaction order was also found to be higher for <001> films compared to randomly oriented films, suggesting that the <001> oriented film exposes more reactive surface sites. Full article
(This article belongs to the Special Issue Photocalytic Coatings for Air-Purifying, Self-Cleaning and Antimicrobial Properties)
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2773 KiB  
Article
Transparent, Adherent, and Photocatalytic SiO2-TiO2 Coatings on Polycarbonate for Self-Cleaning Applications
by Sanjay S. Latthe, Shanhu Liu, Chiaki Terashima, Kazuya Nakata and Akira Fujishima
Coatings 2014, 4(3), 497-507; https://doi.org/10.3390/coatings4030497 - 29 Jul 2014
Cited by 79 | Viewed by 14010
Abstract
Photocatalytic TiO2 coatings are famously known for their excellent self-cleaning behavior, where very thin water layer formed on the superhydrophilic surface can easily wash-off the dirt particles while flowing. Here we report the preparation of the optically transparent, adherent, highly wettable towards [...] Read more.
Photocatalytic TiO2 coatings are famously known for their excellent self-cleaning behavior, where very thin water layer formed on the superhydrophilic surface can easily wash-off the dirt particles while flowing. Here we report the preparation of the optically transparent, adherent, highly wettable towards water and photocatalytic SiO2-TiO2 coatings on polycarbonate (PC) substrate for self-cleaning applications. The silica barrier layer was applied on UV-treated PC substrate before spin coating the SiO2-TiO2 coatings. The effect of different vol% of SiO2 in TiO2 and its influence on the surface morphology, mechanical stability, wettability, and photocatalytic properties of the coatings were studied in detail. The coatings prepared from 7 vol% of SiO2 in TiO2 showed smooth, crack-free surface morphology and low surface roughness compared to the coatings prepared from the higher vol% of SiO2 in TiO2. The water drops on this coating acquires a contact angle less than 10° after UV irradiation for 30 min. All the coatings prepared from different vol% (7 to 20) of SiO2 in TiO2 showed high transparency in the visible range. Full article
(This article belongs to the Special Issue Photocalytic Coatings for Air-Purifying, Self-Cleaning and Antimicrobial Properties)
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1412 KiB  
Article
Photocatalytic TiO2 and Doped TiO2 Coatings to Improve the Hygiene of Surfaces Used in Food and Beverage Processing—A Study of the Physical and Chemical Resistance of the Coatings
by Parnia Navabpour, Soheyla Ostovarpour, Carin Tattershall, Kevin Cooke, Peter Kelly, Joanna Verran, Kathryn Whitehead, Claire Hill, Mari Raulio and Outi Priha
Coatings 2014, 4(3), 433-449; https://doi.org/10.3390/coatings4030433 - 15 Jul 2014
Cited by 18 | Viewed by 8261
Abstract
TiO2 coatings deposited using reactive magnetron sputtering and spray coating methods, as well as Ag- and Mo-doped TiO2 coatings were investigated as self-cleaning surfaces for beverage processing. The mechanical resistance and retention of the photocatalytic properties of the coatings were investigated [...] Read more.
TiO2 coatings deposited using reactive magnetron sputtering and spray coating methods, as well as Ag- and Mo-doped TiO2 coatings were investigated as self-cleaning surfaces for beverage processing. The mechanical resistance and retention of the photocatalytic properties of the coatings were investigated over a three-month period in three separate breweries. TiO2 coatings deposited using reactive magnetron sputtering showed better mechanical durability than the spray coated surfaces, whilst the spray-deposited coating showed enhanced retention of photocatalytic properties. The presence of Ag and Mo dopants improved the photocatalytic properties of TiO2 as well as the retention of these properties. The spray-coated TiO2 was the only coating which showed light-induced hydrophilicity, which was retained in the coatings surviving the process conditions. Full article
(This article belongs to the Special Issue Photocalytic Coatings for Air-Purifying, Self-Cleaning and Antimicrobial Properties)
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846 KiB  
Article
Tin Oxide-Silver Composite Nanomaterial Coating for UV Protection and Its Bactericidal Effect on Escherichia coli (E. coli)
by Gil Nonato C. Santos, Eduardo B. Tibayan, Gwen B. Castillon, Elmer Estacio, Takashi Furuya, Atsushi Iwamae, Kohji Yamamoto and Masahiko Tani
Coatings 2014, 4(2), 320-328; https://doi.org/10.3390/coatings4020320 - 06 May 2014
Cited by 7 | Viewed by 8305
Abstract
SnO2-Ag composite nanomaterials of mass ratio 1:4, 2:3, 3:2 and 4:1 were fabricated and tested for toxicity to E. coli using the pour-plate technique. The said nanomaterials were mixed with laminating fluid and then coated on glass slides. The intensity [...] Read more.
SnO2-Ag composite nanomaterials of mass ratio 1:4, 2:3, 3:2 and 4:1 were fabricated and tested for toxicity to E. coli using the pour-plate technique. The said nanomaterials were mixed with laminating fluid and then coated on glass slides. The intensity of UVA transmitted through the coated glass slides was measured. Results revealed that the 1:4 ratios of SnO2-Ag composite nanomaterials have the optimum toxicity to E. coli. Furthermore, the glass slides coated with SnO2 nanomaterial showed the lowest intensity of transmitted UVA. Full article
(This article belongs to the Special Issue Photocalytic Coatings for Air-Purifying, Self-Cleaning and Antimicrobial Properties)
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Review

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2308 KiB  
Review
Recent Photocatalytic Applications for Air Purification in Belgium
by Elia Boonen and Anne Beeldens
Coatings 2014, 4(3), 553-573; https://doi.org/10.3390/coatings4030553 - 31 Jul 2014
Cited by 115 | Viewed by 13179
Abstract
Photocatalytic concrete constitutes a promising technique to reduce a number of air contaminants such as NOx and VOC’s, especially at sites with a high level of pollution: highly trafficked canyon streets, road tunnels, the urban environment, etc. Ideally, the photocatalyst, titanium dioxide, [...] Read more.
Photocatalytic concrete constitutes a promising technique to reduce a number of air contaminants such as NOx and VOC’s, especially at sites with a high level of pollution: highly trafficked canyon streets, road tunnels, the urban environment, etc. Ideally, the photocatalyst, titanium dioxide, is introduced in the top layer of the concrete pavement for best results. In addition, the combination of TiO2 with cement-based products offers some synergistic advantages, as the reaction products can be adsorbed at the surface and subsequently be washed away by rain. A first application has been studied by the Belgian Road Research Center (BRRC) on the side roads of a main entrance axis in Antwerp with the installation of 10.000 m² of photocatalytic concrete paving blocks. For now however, the translation of laboratory testing towards results in situ remains critical of demonstrating the effectiveness in large scale applications. Moreover, the durability of the air cleaning characteristic with time remains challenging for application in concrete roads. From this perspective, several new trial applications have been initiated in Belgium in recent years to assess the “real life” behavior, including a field site set up in the Leopold II tunnel of Brussels and the construction of new photocatalytic pavements on industrial zones in the cities of Wijnegem and Lier (province of Antwerp). This paper first gives a short overview of the photocatalytic principle applied in concrete, to continue with some main results of the laboratory research recognizing the important parameters that come into play. In addition, some of the methods and results, obtained for the existing application in Antwerp (2005) and during the implementation of the new realizations in Wijnegem and Lier (2010–2012) and in Brussels (2011–2013), will be presented. Full article
(This article belongs to the Special Issue Photocalytic Coatings for Air-Purifying, Self-Cleaning and Antimicrobial Properties)
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