Nano-Structured Glassy and Ceramic Surfaces: Development of "Active" Materials for an Innovative Approach to Building Industry

Abstract:

In the last years there was an increasing interest of the scientific and technological community in the field of healthy and ecological buildings. Nanotechnology gives a substantial contribution in the development of new advanced materials, environmentally sustainable and safe for the consumers. Due to their multi-functional behaviour, nano-materials are at the basis of a revolutionary technical improvement in buildings: titania nano-structured films are applied on ceramic and glass surfaces increasing drastically the self-cleaning and anti bacterial activity. Substrates with controlled porosity can be designed to obtain anti-pollution surfaces either for external and internal environments, a photo reactor has been developed in our laboratory: a device to assess the photo degradation kinetic of pollutants (NOx and VOC’s) and help customers in the certification of eco-buildings. Surfaces based on nano-silver have been also developed leading to an anti bacterial effect in absence of light meanwhile anti-scratch and zero porosity substrates can be obtained from nano-zirconia and nano-silica suspensions. CERICOL has developed and scaled-up a “green chemistry” synthesis in water or glycols allowing simple industrial applications on different substrates as tiles, glass, plastic, paint, wood and concrete.

• Periodical: Advances in Science and Technology (Volume 68)
• Pages: 135-144
• DOI: https://doi.org/10.4028/www.scientific.net/AST.68.135
• Online since: October 2010
• Authors: Giovanni Baldi, Andrea Cioni, Valentina Dami, Annalisa Soldi, Arianna Signorini
• Keywords: Antibacterial, De-Pollution Activity, Nano Titania, Nano-Silver, Nanostructure, Photocatalytic Surface, Self-Cleaning

References

[10] [20] [30] [40] [50] [60] [70] [80] [90] 100 depletion NO (%) time (hours) depletion NO fitting # = 6 0. 00 0. 25 0. 50 0. 75 1. 00 1. 25 1. 50 1. 75 2. 00.

[10] [20] [30] [40] [50] [60] [70] [80] [90] 100 depletion NOx (%) time (hours) depletion NOx fitting # = 6 Fig. 6. NO and NOx depletion in titania nano- structured fibrous cement. In fig. 7 concrete (fibrous cement) has been used for evaluating the BTEX (benzene, toluene, etilbenzene and o-xilene) abatement. In this case, sampling period of 5 minutes every 10 minutes for a total of 13 measures were chosen. The reduction of 95% of BTEX occurs after only 1 hour. 0. 0 0. 5 1. 0 1. 5 2. 0 2. 5 3. 0 3. 5.

[10] [20] [30] [40] [50] [60] [70] [80] [90] 100 depletion Benzene (%) time (hours) depletion Benzene fitting # = 13 0. 0 0. 5 1. 0 1. 5 2. 0 2. 5 3. 0 3. 5.

[10] [20] [30] [40] [50] [60] [70] [80] [90] 100 depletion Toluene (%) time (hours) depletion Toluene fitting # = 13 0. 0 0. 5 1. 0 1. 5 2. 0 2. 5 3. 0.

[10] [20] [30] [40] [50] [60] [70] [80] [90] 100 depletion Etil benzene (%) time (hours) depletion Etil benzene fitting# = 13 0. 0 0. 5 1. 0 1. 5 2. 0 2. 5 3. 0.

[10] [20] [30] [40] [50] [60] [70] [80] [90] 100 depletion O-xilene (%) time (hours) depletion O-xilene fitting # = 13 Fig. 7. BTEX abatement depletion in titania nano structured fibrous cement. Microbiological activity on ceramic and glass. Antibacterial test results (fig. 8) show the percentage depletion of bacteria population on treated surfaces. We can notice the effectiveness of titania application both on ceramic tiles and glass, while doped samples with Ag and Au don't lead to the same significant results. Nano-titania expresses a strong photo-catalytic activity under light irradiation and it's necessary only a 15 g/m2 application to show its effectiveness, Ag.

has instead a chemo-toxic behaviour and its antibacterial/bacteriostatic mechanism is strongly dependent on the concentration of Ag.

nano-particles on the surface. As we can see in the graph below, samples coated with metallic silver confirm this relationship between application and antimicrobial effect.

[10] [20] [30] [40] [50] [60] [70] [80] [90] 100 Antimicrobial activity Depletion % 88, 8 67, 9 81, 4 93, 5 54 28 100 PH010108 IG010203.

[40] g/m2 IG010203.

[80] g/m2 IG010203 120 g/m2 PH010108+ IG010304 PH010108+ IN120402 PH010109 Fig. 8. Microbiological test results. First six samples refer to treated ceramic tiles and the last one to a treated glass. Ageing test. The test was performed on nano-structured TiO2 treated tiles. The ageing test was used to evaluate the resistance to cleaning cycles of TiO2 coating on ceramic tiles and the data obtained with the contact angle method are reported in the graph below (fig. 9). wear resistance graph of the titania coating 0, 0 10, 0 20, 0 30, 0 40, 0 50, 0 60, 0 70, 0 80, 0 0 1000 2000 3000 4000 5000 6000 n° cycles contact angle (°) t=0 t=4h UV irr. Fig. 9. Contact angle versus number of cleaning cycles. Empirically we have defined the resistance to abrasion in years (t) as shown in equation 3. 150/nt = (3) Where n is the cycle number and t is the time in years for which a coated tile continues to be photoactive, considering three washes per week with a solution of 20 ml of a common household product in water. The graph shows that the samples is still photo-active after 5400 abrasion cycles that corresponds to 36 years of wear resistant coating. Conclusions Due to their multi functional behaviour nano-materials can give an extraordinary impulse to the development of new materials in building industry. Nano-titania and nano-silver applied on different substrates as glass, paint, tiles, mortars, even textiles, wood and stones can improve the healthiness of domestic and urban environment. We have demonstrated that products based on these nano-structured materials can reduce NOx and VOC's pollution together with a significant abatement of bacteria. The water-based suspensions of nano-silver and nano-titania allow the application on a wide range of different surfaces with common industrial techniques and a remarkable reduction of cost. The compatibility of silver and titania nano-suspensions allows an antibacterial and bacteriostatic action in presence and absence of light. A photo reactor has been developed by CERICOL to study the NOx and VOC's depletion kinetic. In this equipment can be simulated the environmental conditions in terms of irradiance, contaminants, gas flow, pressure and humidity for materials engineered for indoor and outdoor de-pollution. Nano-materials applied on concrete, glass and tiles have shown an evident photo-catalytic activity, reducing over 98% of NOx and 91% of VOC's. For the enhanced photo catalytic and bacteriostatic activity observed, we can say that functional substrates based on TiO2, doped TiO2 and silver nanostructures could have interesting industrial application in building materials for de-pollution of indoor and outdoor environment. Nanotechnology can open a new era in the industrial research and new markets can be achieved with high added-value products, this means new industrial politics, probably less energyconsuming, and improved competences in terms of manpower. References 1. World Health Organization (WHO), Organization Regional Office for Europe, Air Quality Guidelines for Europe, Copenhagen, Denmark, 1987. 2. EEC, 1989a, Sick Building Syndrome - A Practical Guide, European Concerted Action: Indoor Air Quality and its impact on man (COST Project 613), Report n. 4, Commission of the European Communities, Luxembourg. 3. EEC, 1989b, Indoor Pollution by NO2 in European Countries, European Concerted Action: Indoor Air Quality and its impact on man (COST Project 613), Report n. 3, Commission of the European Communities, Luxembourg. 4. Diebold, U., Science Reports 2003, 48, 53-229. 5. Linsebigler, A. L. et al., Chem. Rev. 1995, 95, 753-758 6. PCT/EP03/02281 7. PCT/EP2005/056478 8. Patent pending 9. ISO 27447; 2009(E) Fine ceramics (advanced ceramics, advanced technical ceramics) - Test method for antibacterial activity of semiconducting photocatalytic materials 10. Sun, R., et al., J. Phys. Chem. B 2001, 105, 1984-1990 11. Hoffmann, M.R. et al., Chem. REv. 1995, 95, 69-96 12. Fox, M.A., Dulay, M.T., Chem. Rev. 1993, 93, 351-357 13. Fujishima, A. et al., J. Photochem Photobiol. C.: Photochem. Review 2000, 1, 1-21 14. Diebold, U., Science Reports, 2003, 48, 53-229.