Visible-Light-Driven Photocatalysts for Self-Cleaning Transparent Surfaces

Abstract

Highly transparent photocatalytic self-cleaning surfaces capable of harvesting near-visible (365−430 nm) photons were synthesized and characterized. This helps to address a current research gap in self-cleaning surfaces, in which photocatalytic coatings that exhibit activity at wavelengths longer than ultraviolet (UV) generally have poor optical transparency, because of broadband scattering and the attenuation of visible light. In this work, the wavelength-dependent photocatalytic activity of Ptmodified TiO 2 (Pt-TiO 2 ) particles was characterized, which exhibited activity for wavelengths up to 430 nm. Pt-TiO 2 nanoparticles were embedded in a mesoporous SiO 2 sol−gel matrix, forming a superhydrophilic surface that allowed for water adsorption and formation of reactive oxide species upon illumination, resulting in the removal of organic surface contaminants. These self-cleaning surfaces only interact strongly with near-visible light (∼365−430 nm), as characterized by photocatalytic self-cleaning tests. Broadband visible transparency was preserved by generating a morphology composed of small clusters of Pt-TiO 2 surrounded by a matrix of SiO 2 , which limited diffuse visible light scattering and attenuation. The wavelength-dependent self-cleaning rate by the films was quantified using stearic acid degradation under both monochromatic and AM1.5G spectral illumination. By varying the film morphology, the average transmittance relative to bare glass can be tuned from ∼93%−99%, and the self-cleaning rate can be adjusted by more than an order of magnitude. Overall, the ability to utilize photocatalysts with tunable visible light activity, while maintaining broadband transparency, can enable the use of photocatalytic self-cleaning surfaces for applications where UV illumination is limited, such as touchscreen displays.

Ceramic ZnO-SnO2-Fe2O3 Powders and Coatings -Effective Photogenerators of Reactive Oxygen Species

“…Therefore, besides the difference in the thickness of photocatalytic layers between thin ceramic coating and powder, the features of crystal structures and morphologies of these ceramics can have an influence on their photocatalytic properties. In spite of small thickness, ceramic coatings demonstrate photocatalytic properties [4,5,14,20,[29][30][31][32], although in some cases the photocatalysis rate is low [31].…”

Self-Cleaning Bending Sensors Based on Semitransparent ZnO Nanostructured Films

“…To this aim, ZnO can well modulate the wettability of the sensor surface and is also featured with good photocatalytic properties, 11,12 which could be beneficial for their photocatalytic properties, similar to semitransparent self-cleaning TiO 2 coatings. 13 A great boost in this technology is pursued by the emerging field of piezocatalysis 14 that leverages piezoelectricity for the efficient conversion of mechanical energy derived from wind or wave motion or waste mechanical vibrations into useful electricity employed for electrochemical reactions, involving, for example, reactive oxygen species (ROS) suitable for water decontamination. 15 To this aim, it would be essential to design a dual-use material, which could combine both sensing and self-cleaning activities by leveraging sunlight, which is an inexpensive source of energy.…”

“…Indeed, self-cleaning surfaces are able to remove surface-attached contaminants by a variety of mechanisms, relying on their superhydrophobic, superhydrophilic, or photocatalytic properties. To this aim, ZnO can well modulate the wettability of the sensor surface and is also featured with good photocatalytic properties, , which could be beneficial for their photocatalytic properties, similar to semitransparent self-cleaning TiO 2 coatings . A great boost in this technology is pursued by the emerging field of piezocatalysis that leverages piezoelectricity for the efficient conversion of mechanical energy derived from wind or wave motion or waste mechanical vibrations into useful electricity employed for electrochemical reactions, involving, for example, reactive oxygen species (ROS) suitable for water decontamination …”

Surface Modification of ZnO Nanorods using Stearic Acid and their Self‐cleaning and Photocatalytic Applications

“…Self‐cleaning is proposed as one of the best techniques to solve these problems. Self‐cleaning removes impurities such as soil, harmful chemicals, and bacteria from any type of surface [32–34] . Coatings for self‐cleaning are used in a wide range of industries, including textile, automotive, optical, marine, aerospace, construction, and medicine [35] .…”

“…Self-cleaning removes impurities such as soil, harmful chemicals, and bacteria from any type of surface. [32][33][34] Coatings for self-cleaning are used in a wide range of industries, including textile, automotive, optical, marine, aerospace, construction, and medicine. [35] In general, self-cleaning of surfaces is based on two mechanisms; surface wettability (hydrophobicity), and photocatalytic degradation of organic compounds.…”