Synthesis and characterization of nanocrystalline TiO2 with application as photoactive coating on stones (original) (raw)
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Nanocrystalline TiO2 coatings by sol–gel: photocatalytic activity on Pietra di Noto biocalcarenite
Journal of Sol-Gel Science and Technology, 2015
Self-cleaning photocatalytic coatings based on TiO 2 nanoparticles obtained by sol-gel techniques at two different pH values (1.3-10.6) have been investigated on carbonatic stone. The selected material is the yellowish lithofacies of Palazzolo Formation calcarenite, commonly named Pietra di Noto, widely used in the Baroque monuments of the Noto Valley (Sicily, Italy). SEM-EDS, XRD and Raman investigations were carried out to characterize the TiO 2 nanoparticles (mainly nanocrystalline anatase) obtained by the acid and basic nanosols and the corresponding coatings on pietra di Noto. To evaluate the effects of the treatments at two different pH values, changes in the stone color appearance, water absorption by capillarity and the behavior for salt crystallization were measured. The photocatalytic activity of the coatings was evaluated under UV irradiation, by monitoring methyl orange and methylene blue dye degradation as a function of time. The results highlight the compatibility of both treatments with respect to the properties of the calcarenite stone, showing no chromatic changes, no alteration of physical properties, an improvement in the resistance to salts crystallization and the good photocatalytic activity on both dyes. The experimental data suggest that the basic coating has to be preferred for carbonatic stones for its harmlessness and better performances in terms of selfcleaning action and protection against water and salts. Graphical Abstract Self-cleaning photocatalytic coatings based on TiO 2 , obtained by sol-gel at two different pH values, are applied on Pietra di Noto carbonatic stone. TiO 2 nanoparticles and coatings are characterized by SEM, XRD and Raman. The photocatalytic activity of the coatings is evaluated under UV irradiation, by monitoring methyl orange and methylene blue dye degradation as a function of time. The basic coating is suitable for carbonatic stones for its harmlessness and better performances in terms of self-cleaning action and protection against water and salts.
Gels
A sol–gel synthesis technique was employed for the preparation of anatase phase {001}-TiO2/Au hybrid nanocomposites (NCs). The scalable, schematic, and cost-efficient method was successfully modified using HF and NH4OH capping agents. The photocatalytic activity of the as-synthesized {001}-TiO2/Au NCs were tested over 2-cycle degradation of methylene blue (MB) dye and pharmaceutical active compounds (PhACs) of ibuprofen and naproxen under direct sunlight illumination at 35 °C and 44,000 lx. Transmission electron microscopy (TEM), high resolution transmission electron microscopy (HR-TEM), fast Fourier transform (FFT), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDS), and ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS) were employed for the characterization of the as-prepared sample. The characterization results from the TEM, XPS, and XRD studies established both the distribution of Au colloids on the surface...
The Open Materials Science Journal, 2010
The use of photocatalytic titania nanoparticles in the development of self-cleaning and depolluting paints and microbiological surfaces is demonstrated. In the former case surface erosion and sensitised photooxidation is shown to be controlled by the use of catalytic grades of anatase nanoparticles. For environmental applications in the development of coatings and cementitious materials for destroying atmospheric pollutants such as nitrogen oxides (NOX) stable substrates are also illustrated with photocatalytic nanoparticles. Here porosity of the coatings through calcium carbonate doping is shown to be crucial in the control of the effective destruction of atmospheric NOX gases. Good environmental stability of the coatings is also crucial for long term durability and this aspect is examined for a variety of material substrates. For the development of microbiological substrates for the destruction of harmful bacteria/fungi effective nanoparticle anatase titania is shown to be important with hydrated high surface area particles giving the greatest activity. Data from commercial pilot studies is used to signify the important practicalities of this type of new technology.
Applied Surface Science, 2013
A self-cleaning photocatalytic coating for limestone materials, based on TiO 2 nanoparticles obtained by the sol-gel process has been studied. TiO 2 sol was applied directly to the surface or after a SiO 2 intermediate layer. The selected test materials are the Modica and the Comiso calcarenites, limestones of Ragusa Formation outcropping in the south eastern Sicily (Italy). SEM-EDS, XRD and Raman investigations were carried out to characterize the TiO 2 nanoparticles and coating. Nanocrystalline anatase and, to a lesser extent, brookite forms are obtained. To evaluate the harmlessness of the treatment, colorimetric tests, water absorption by capillarity and crystallization of salts measurements were performed. Photocatalytic activity of the TiO 2 colloidal suspension and of the coatings (TiO 2 and SiO 2 /TiO 2) was assessed under UV irradiation through methyl orange dye degradation tests. The results show good photodegradation activity and satisfactory compatibility between the sol and the surface of the investigated limestones.
Journal of Photochemistry and Photobiology A: Chemistry, 2004
In this paper, the effects of various inorganic anions (NO 3 − , Cl − , SO 4 2− , HCO 3 − , H 2 PO 4 − ) on the photodegradation of an azo dye, acid orange 7 (AO7) were investigated under UV or visible light irradiation in the presence of TiO 2 particles. The effects of inorganic anions on the photodegradation of AO7 under visible light irradiation were significantly different from UV irradiation pathway. In TiO 2 /UV system, inorganic anions inhibited the photodegradation of the dye by their trapping hydroxyl radicals. In TiO 2 /Vis system, the observed inhibition effects of inorganic anions can be interpreted by competitive adsorption. In addition, the results indicated that the photodegradation of AO7 took place mainly in the bulk solution under UV light irradiation, while under visible light irradiation, the reaction occurred on the catalyst surface.
Journal of Photochemistry and Photobiology A: Chemistry, 2004
In this paper, silica gel supported titanium dioxide particles (TiO 2 /SiO 2 ) prepared by acid-catalyzed sol-gel method was as photocatalyst in the degradation of acid orange 7 (AO7) in water under visible light irradiation. The particles were characterized by X-ray diffraction, BET specific surface area determination, and point of zero charge measurement. The supported catalyst had large surface area, high thermal stability and good sedimentation ability. The photodegradation rate of AO7 under visible light irradiation depended strongly on adsorption capacity of the catalyst, and the photoactivity of the supported catalyst was much higher than that of the pure titanium dioxides. The photodegradation rate of AO7 using 31% TiO 2 /SiO 2 particles was faster than that using P-25 and TiO 2 (Shanghai) as photocatalyst by 2.3 and 12.3 times, respectively. The effect of the calcination temperature and the TiO 2 loading on the photoactivity of TiO 2 /SiO 2 particles was also discussed.
Photocatalytic degradation of Acid Red 88 using Au–TiO2 nanoparticles in aqueous solutions
Water Research, 2008
Acid Red 88 Electron acceptors Photocatalytic degradation a b s t r a c t Metal loaded semiconductors in general possess greater photocatalytic activity than pure semiconductors. Hence, with an attempt to achieve higher photocatalytic activity, Au-TiO 2 photocatalysts were prepared by deposition-precipitation method and used for the photocatalytic degradation of an azo dye (Acid Red 88; AR88). The materials were characterized by different analytical techniques. A possible mechanism for the photocatalytic degradation of AR88 by Au-TiO 2 in the absence and presence of other oxidizing agents (peroxomonosulfate (PMS), peroxodisulfate (PDS) & hydrogen peroxide (H 2 O 2 )) has been proposed. The extent of mineralization of the target pollutant was also evaluated using Total Organic Carbon (TOC) analysis. .au (M. Ashokkumar). A v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / w a t r e s 0043-1354/$ -see front matter ª w a t e r r e s e a r c h 4 2 ( 2 0 0 8 ) 4 8 7 8 -4 8 8 4
Effects of deposited ions on the photocatalytic activity of TiO 2 –Au nanospheres
NSs, 206 AE 23.7 nm) have been prepared and used as catalysts for the photo degradation of methylene blue (MB) and for the reduction of Cr 6+ to Cr 3+ . TiO 2 NSs are firstly prepared from titanium isopropoxide (TIP) via a solvothermal method. The TiO 2 NSs are then sequentially modified with poly-(sodium-4-styreneulfonate) (PSS) and poly(diallyldimethylammonium chloride) (PDADMAC), which then interact with Au NPs (15 AE 1.3 nm) as seeds. Through reduction of HAuCl 4 by ascorbic acid, core-shell structures of TiO 2 -Au NSs are prepared. Under UV irradiation, TiO 2 -Au NSs provide highly catalytic activity for the degradation of MB and reduction of Cr 6+ within 15 and 60 min, respectively. The TiO 2 -Au NSs relative to commercial TiO 2 (P25) and TiO 2 NSs provide 1.8 and 1.2-fold activity higher for the photo degradation of MB, and 4.3 and 1.8-fold higher for the reduction of Cr 6+ . TiO 2 -Au/Hg and TiO 2 -Au/Ag NSs that are prepared from the deposition of Hg 2+ and Ag + onto TiO 2 -Au NSs, respectively, allow degradation of MB within 10 min, with activities 4.2-and 3.3-fold greater than that of the TiO 2 -Au NSs. The present study reveals that TiO 2 -Au/Hg and TiO 2 -Au/Ag NSs are effective for removal of organic pollutants, while TiO 2 -Au NSs are useful for the reduction of Cr 6+ . † Electronic supplementary information (ESI) available: SEM, EDX, XRD, UV-Vis absorption, effect of oxygen, effect of pH, reusability results. See
Chemical Sciences Journal, 2017
In this study, the Co:La:TiO 2 nanocomposite was prepared by the wet chemical method. Synthesized TiO 2 and Co:La:TiO 2 were characterized by X-Ray Diffractometer, SEM, TEM, UV-vis, FT-IR, Band gap energy and BET. The TiO 2 and Co:La:TiO 2 were used as photocatalyst for the degradation of Methyl Blue. The XRD pattern confirmed the presence of anatase and rutile phase in the catalyst. The particle size was estimated by the Scherrer's and found 68 and 32 nm for TiO 2 and Co:La:TiO 2 respectively. The particle morphology of the photocatalysts was found in nanodiamension. The surface area of the photocatalysts was found 37.52 and 106.68 m 2 /g for TiO 2 and Co:La:TiO 2 respectively. The band gap energy of TiO 2 and Co:La:TiO 2 were 3.2 and 3.0 eV. The photodegradation of Methyl Orange has been found 18% and 88% at 5 pH for TiO 2 and Co:La:TiO 2 respectively. The photodegradation of Methyl Orange has been found 19% and 98.9% at 25 ppm concentration of dye. The photodegradation of Methyl Orange has been found 25% and 96% at 800 mg/L amount of photocatalyst and 180 min illumination of visible light. The photodegradation was following the first order kinetics.