Design of Novel Photocatalytic Films for the Protection of Architectural Surfaces via the Incorporation of Green Photocatalysts

Abstract

In conservation science the demand of multifunctional green materials displaying water repellency, consolidation, resistance to organic pollutants and pigments is constantly increasing. This research developed a green nanocomposite exhibiting photocatalytic, hydrophobic, consolidation and self-cleaning properties. This was achieved by synthesizing a TiO2 photocatalyst enriched with carbon dots (C-dots) and successfully incorporated into a tetraethoxysilane nanocomposite modified with nano-calcium oxalate and polydimethylsiloxane. The TiO2/C-dots that were prepared with a simple, low temperature, cost-effective and large-scale procedure were assessed via analytical and spectroscopic techniques and were resulted in anatase structure ranging in size from 10 to 40 nm. Photooxidation measurements displayed that TiO2/C-dots nanoparticles could photodegrade completely Methyl Orange (MO) under UV and visible irradiation after 120 min. The photocatalytic performance of the nanocomposite with TiO2/C-dots resulted promising under UV after longer irradiation time. The degradation of MO was faster on bulk xerogels containing the TiO2/C-dots than the corresponding ones with TiO2. The treatment of concrete, limestone and lime mortars with the nanocomposite proved to be compatible with the substrates in terms of aesthetical aspects. This study demonstrates encouraging potential for large-scale production of a multifunctional protective composite that offers hydrophobicity, self-cleaning properties and consolidation to architectural surfaces.

TiO2-Based Mortars for Rendering Building Envelopes: A Review of the Surface Finishing for Sustainability

“…Concerning TiO 2 -based photocatalytic colored mortars, a search on the Scopus database for the query string "mortar AND (titanium AND dioxide OR TiO 2 ) AND photocatal* AND pigment" within the title, abstract and keywords of scientific papers in English retrieved four results [31,33,55,103]. In the Web of Science, the query string returned eight journal articles; four of them were already gathered in Scopus, and the other four were from Dantas et al [52], Guo and Poon [104], Stefanakis et al [105] and Sugrañez et al [106]. To expand the search and check its coverage, an additional round comprising concretes with the query string "concrete AND (titanium AND dioxide OR TiO 2 ) AND photocatal* AND pigment" was carried out, resulting in two papers in English from journals in Scopus (Guo and Poon [104] and Pal et al [107]) and three papers in the Web of Science, two of which were already identified for mortars [105,106].…”

“…In the Web of Science, the query string returned eight journal articles; four of them were already gathered in Scopus, and the other four were from Dantas et al [52], Guo and Poon [104], Stefanakis et al [105] and Sugrañez et al [106]. To expand the search and check its coverage, an additional round comprising concretes with the query string "concrete AND (titanium AND dioxide OR TiO 2 ) AND photocatal* AND pigment" was carried out, resulting in two papers in English from journals in Scopus (Guo and Poon [104] and Pal et al [107]) and three papers in the Web of Science, two of which were already identified for mortars [105,106]. From this search, the study of Bahreini et al [108] was added.…”

“…As presented in Table 3, Fe, Co and Cr are part of the chemical composition of different pigments. Stefanakis et al [105] synthesized TiO 2 photocatalysts enriched with carbon dots (C-dots) to narrow the semiconductor bandgap.…”

Synthesis and Characterization of Transparent Photocatalytic Zto Coatings

“…Photocatalytic decomposition of organic substances occurs on the surface of a photocatalyst [11][12][13][14]. It is known that an increase in the specific surface increases the photocatalytic activity of coatings [15,16].…”

Self-Cleaning Coatings for the Protection of Cementitious Materials: The Effect of Carbon Dot Content on the Enhancement of Catalytic Activity of TiO2

“…Recently, we developed an efficient, simple and low-cost method for the synthesis of pure TiO 2 and TiO 2 /C-dots and studied comparatively into the photodegradation of MO under UV-A and visible light, with promising results [26]. MO was used as a model compound because it is a common, highly toxic dye that exhibits good photostability upon light irradiation under different conditions [27] and resistance to complete biodegradation.…”