Effect of Cu2O Substrate on Photoinduced Hydrophilicity of TiO2 and ZnO Nanocoatings

Abstract

The effect of a Cu2O substrate on the photoinduced alteration of the hydrophilicity of TiO2 and ZnO surfaces was studied. It was demonstrated that the formation of heterostructures Cu2O/TiO2 and Cu2O/ZnO strongly changed the direction of the photoinduced alteration of surface hydrophilicity: while both TiO2 and ZnO demonstrate surface transition to superhydrophilic state under UV irradiation and no significant alteration of the surface hydrophilicity under visible light irradiation, the formation of Cu2O/TiO2 and Cu2O/ZnO heterostructures resulted in photoinduced decay of the surface hydrophilicity caused by both UV and visible light irradiation. All observed photoinduced changes of the surface hydrophilicity were compared and analyzed in terms of photoinduced alteration of the surface free energy and its polar and dispersive components. Alteration of the photoinduced hydrophilic behavior of TiO2 and ZnO surfaces caused by formation of the corresponding heterostructures with Cu2O are explained within the mechanism of electron transfer and increasing of the electron concentration on the TiO2 and ZnO surfaces.

Effect of the Type of Heterostructures on Photostimulated Alteration of the Surface Hydrophilicity: TiO2/BiVO4 vs. ZnO/BiVO4 Planar Heterostructured Coatings

“…For the zinc oxide sol, 2.5 mL of ethylene glycol (99.5%, LenReactiv, Saint-Petersburg, Russia) and 10 g of zinc acetate dihydrate Zn(OAc) 2 •2H 2 O (99.0%, Vekton, Saint-Petersburg, Russia) were mixed in a round-bottomed flask and heated at 70 • C for 15 min to obtain a uniform transparent mixture. After cooling to room temperature, 150 mL of isopropanol (99.8%, Ecos-1, Moscow, Russia) and 6.4 mL of triethylamine (99.5%, PanReac AppliChem, Darmstadt, Germany) were added to the mixture to promote the hydrolysis of the zinc acetate [24]. To improve the quality of the film, 0.5 mL of glycerol (99.5%, LenReactiv, Saint-Petersburg, Russia) was added dropwise.…”

“…The error of the water contact angle (WCA) measurements was ±1.5 • . The surface free energy (SFE) was calculated by the Owens-Wendt-Rabel-Kaelble (OWRK)/Fowkes approach using the two-liquid method (water contact angle versus methylene iodide contact angle) [24].…”

“…The photoinduced hydrophilic conversion on TiO 2 or ZnO surfaces has been comprehensively studied for TiO 2 /WO 3 [20,21], TiO 2 /CdS [22,23], TiO 2 /ZnO [10], TiO 2 /Cu 2 O, and ZnO/Cu 2 O [24] layered films. The efficiency of photoinduced superhydrophilic conversion on the titanium dioxide surface increased only in the case of TiO 2 /WO 3 films, while CdS, Cu 2 O, and p-Si [25] substrates inhibited the process rate.…”

Unveiling photoinduced electron transfer in cobalt(iii)-R-pyridine complexes anchored to anatase nanocrystals: photoluminescence and magnetic studies

“…The augmentation in photocatalytic reduction stems from two primary factors: (i) Rpy's ability to modify the surface affinity of [Co(tn) 2 (Rpy)Br] 2+ ions with the nano-TiO 2 surface, and (ii) photoexcitation inducing the formation of microdomains in nano-TiO 2 with distinctive hydrophobic/hydrophilic behavior. 56,57 The incorporation of the sixth ligand (Rpy) in [Co(tn) 2 (Rpy) Br] 2+ , characterized by a hydrophobic tail, introduces variations in the surface adherence of the complex ion to the nano-TiO 2 surface. However, it is important to note that the adsorption process is constrained by thermodynamic considerations.…”

Metal Oxide Nanomaterials: From Fundamentals to Applications

“…They found that their ZnO-coated stainless-steel metal fibers had a static underwater oil contact angle of 151.4° ± 0.8° and an underoil water contact angle of 152.7° ± 0.6° and was a highly promising candidate for both water-in-oil and oil-in-water separation in the industry. Maevskaya et al studied the effect of Cu 2 O on the photo-induced alteration of the hydrophilicity of TiO 2 and ZnO surfaces [ 9 ]. The Cu 2 O/TiO 2 and Cu 2 O/ZnO heterostructures showed photo-induced decay of the surface hydrophilicity caused by both UV and visible light irradiation.…”