Construction of photocatalytic coating for alleviating the shriveling of postharvest fruit cucumber after simulated transportation.

The shriveling of fruit cucumber was commonly occurred during supply chain, photocatalyst exposed to UV light can endow the coatings with ethylene removal capacity to reduce the respiration of fruit and water loss. The study developed a novel photodynamic technology responsive photocatalytic coating with exceptional ultraviolet (UV) photocatalytic degradation of ethylene ability to decay the shriveling of postharvest fruit cucumber during supply chain. This coating involved the integration of Carbon dots (CDs)-loaded nano ZnO and the skillful selection of pullulan (Pul) and apple pectin (AP) matrix. The CDs/ZnO coatings boasted an impressive array of photocatalytic degradation of ethylene and adhesion properties, including high ethylene removal rates of 32.04 % in 60 min UV light stimulation. The decrease of cell-wall strength, degradation of the cell wall polysaccharides and water loss resulted in cucumber shriveling. Compared with CK sample, after UV-CDs/ZnO coating treatment, the higher firmness and cell wall polysaccharides were found in cucumbers with lower cell wall degrading enzymes activities, weight loss and water movement, which was associated with the decrease of respiration and ethylene accumulation. The UV-CDs/ZnO coatings possessed promising potential for alleviating the shriveling of postharvest fruit cucumber and applications in fruits preservation in the future.

Superhydrophobic and Photocatalytic Synergistic Self-Cleaning Coating Constructed by Hierarchically Structured Flower-like Hollow SiO2@TiO2 Spheres with Oxygen Vacancies.

The self-cleaning coating has both superhydrophobic physical and photocatalytic chemical self-cleaning properties, which has attracted the wide attention of researchers in recent years. First, the flower-like hollow SiO2@TiO2 spheres with oxygen vacancies (rFHSTs) were prepared by the liquid-phase reduction method, in which several different functional components were integrated. Meanwhile, the influence mechanisms of the physical structure and chemical composition on the photocatalytic properties are discussed in detail. The results proved that rFHSTs exhibited the enhanced photoresponse range and photocatalytic degradation performance in visible light because of the synergistic effect of the microstructure (internal cavity, 3D flower-like nanosheet), SiO2/TiO2 heterojunction structure, and oxygen vacancies. After that, superhydrophobic modified rFHSTs were used as fillers to fabricate PVA/PFDTS-rFHSTs composite coatings with both physical and chemical self-cleaning properties. The self-cleaning performances and principles of the composite coating were examined and explored. The results showed that the low surface energy of the hydrophobic chain segment, the inherent particle effect, and the photocatalytic activity of rFHSTs were responsible for the superhydrophobic and photocatalytic effects, finally endowing the composite coating with self-cleaning performance. In short, this study is profound for the development and application of self-cleaning coatings with both physical and chemical performances.

Fabrication of durable self-cleaning photocatalytic coating with long-term effective natural light photocatalytic degradation performance.

The practical application of photocatalytic coating has been greatly challenged in terms of its long-term effective natural light photocatalytic degradation due to its vulnerability and easy contamination caused by poor self-cleaning properties. In this work, photocatalytic coating with self-cleaning properties was prepared by spraying fluorinated dual-scale TiO2 on the inorganic lithium silicate adhesive, enabling excellent durability and long-term effective photocatalytic degradation performance under natural light. The coating exhibits superhydrophobic properties even after abrasion testing, acid and alkali immersion testing, and UV aging, laying a foundation for the practical use. Moreover, the coating can be applied to various substrates and its excellent self-cleaning properties make it resistant to particulate and liquid contamination that may occur in the environment. Besides, we evaluated the photocatalytic stability of the coating by subjecting it to acidic and alkaline environments and high pollution concentrations. Furthermore, benefiting from the synergistic effect of photocatalytic and self-cleaning properties, the coating achieves long-term effective photocatalytic degradation of dye wastewater under natural light, which still has a high removal rate of 95.8% for methylene blue even after 30 cycles of use. Meanwhile, due to the coating's excellent durability, the long-term quality loss rate of the coating still remained below 0.3%, which avoids the risk of secondary environmental pollution caused by nanoparticle leakage. Therefore, these excellent properties enable the coating to have a broad range of application prospects for the treatment of pollutants in water.

Virucidal Properties of Photocatalytic Coating on Glass against a Model Human Coronavirus.

The antimicrobial properties of photocatalysts have long been studied. However, most of the available literature describes their antibacterial properties, while knowledge of their antiviral activity is rather scarce. Since the outset of the coronavirus disease 2019 (COVID-19) pandemic, an increasing body of research has suggested their antiviral potential and highlighted the need for further research in this area. In this study, we investigated the virucidal properties of a commercial TiO2-coated photocatalytic glass against a model human coronavirus. Our findings demonstrate that the TiO2-coated glass consistently inactivates coronaviruses upon contact under daylight illumination, in a time-dependent manner. A 99% drop in virus titer was achieved after 3.9 h. The electron micrographs of virus-covered TiO2-glass showed a reduced number of virions compared to control glass. Morphological alterations of TiO2-exposed viruses included deformation, disruption of the viral envelope, and virion ghosts, endorsing the application of this material in the construction of protective elements to mitigate the transmission of viruses. To the best of our knowledge, this is the first report showing direct visual evidence of human coronaviruses being damaged and morphologically altered following exposure to this photocatalyst. IMPORTANCE Surface contamination is an important contributor to SARS-CoV-2 spread. The use of personal protective elements and physical barriers (i.e., masks, gloves, and indoor glass separators) increases safety and has proven invaluable in preventing contagion. Redesigning these barriers so that the virus cannot remain infectious on them could make a difference in COVID-19 epidemiology. The introduction of additives with virucidal activity could potentiate the protective effects of these barriers to serve not only as physical containment but also as virus killers, reducing surface contamination after hand touch or aerosol deposition. We performed in-depth analysis of the kinetics of photocatalysis-triggered coronavirus inactivation on building glass coated with TiO2. This is the first report showing direct visual evidence (electron microscopy) of coronaviruses being morphologically damaged following exposure to this photocatalyst, demonstrating the high potential of this material to be incorporated into daily-life high-touch surfaces, giving them an added value in decelerating the virus spread.

Preparation and performance of photocatalytic NO degradation superhydrophobic coatings for tunnel.

Due to the semi-closed structure of the tunnel, serious air pollution in tunnels from vehicle exhaust becomes an issue which needed to be addressed. Among the exhaust, nitric oxide (NO) is typically considered as one of the main pollutants. In this paper, a superhydrophobic photocatalytic coating was fabricated by a spraying method by airbrush with a WO3/TiO2 photocatalysis for NO degradation. The water advanced contact angle (WACA) of the coating reached 166.32°, and the WACA was still above 145° after the 30 times abrasion test. The coating exhibited an excellent ability to remove inorganic and organic pollutants. Also, the NO degradation efficiency of this superhydrophobic coating under ultraviolet and visible light sources and humid environments was tested. When the relative humidity reached 98%, the NO degradation efficiency of the coating remained unchanged under visible light irradiation compared with the relative humidity of 45%. In addition, the coating exhibited prominent stability of NO degradation during the cyclic test. Furthermore, the WT coating showed stability and synergy of self-cleaning and photocatalysis toward NO degradation, which ensured the long-term use of the coating. Finally, a synergistic mechanism for self-cleaning and photocatalysis was proposed. This may provide a new idea and support for the application of photocatalytic technology in the degradation of NO in the tunnel.

Structured photocatalytic systems: photocatalytic coatings on low-cost structures for treatment of water contaminated with micropollutants-a short review.

The persistence of many micropollutants in water and wastewater is of great concern to the contemporary scientific community. Several types of advanced techniques such as heterogeneous photocatalysis are being used for the degradation of micropollutants in waters from domestic, industrial, and agricultural activities. Thus, structured photocatalytic systems are a great alternative in the development of photocatalytic reactors and continuous water treatment systems, as they present good autonomy during the treatment process. Many aspects such as type and geometry of the catalytic structure to be developed must be carefully chosen for the proper functioning of the system, as well as the best routes by which the photocatalysts will be immobilized. In this sense, this work brings the main photocatalytic coating techniques in low-cost structures for the treatment of water and wastewater contaminated with micropollutants. The methodologies and synthesis parameters that can influence the final result of the coating were highlighted, as well as the ability to reuse photocatalysts and methods for pretreating the structural surface. The dip-coating technique was the most reported among the current works due to its simplicity and, predominantly, the pretreatment techniques of the structure are still cleaning the surface with water, soap, and also some alcohols.

Efficiency of Novel Photocatalytic Coating and Consolidants for Protection of Valuable Mineral Substrates.

In the process of protection and consolidation of valuable materials, the efficiency is the crucial property that needs to be considered. TiO2/ZnAl layered double hydroxide (LDH) coating and silicate- and carbonate-based consolidants were synthesized and proposed to be used for protection and consolidation of four porous mineral substrates: brick, stone, render and mortar. The photocatalytic efficiency of TiO2/ZnAl LDH coating, as well as consolidation efficiency of two consolidants, both applied on model substrates, were studied. The photocatalytic coating showed significant activity and performed well after the durability tests involving rinsing and freezing/thawing procedures. After treatment with both consolidants, a serious enhancement of consolidation of the used substrates was found. On the other hand, the application of TiO2/ZnAl LDH, as well as consolidants, caused negligible changes in the water vapour permeability values and in appearance of the porous mineral substrates, indicating a high level of compatibility.

Life cycle assessment comparison of photocatalytic coating and air purifier.

This article presents a comparison of 2 very different options for removal of undesirable microorganisms and airborne pollutants from the indoor environment of hospitals, schools, homes, and other enclosed spaces using air purifiers and photocatalytic coatings based on nano titanium dioxide (TiO2 ). Both products were assessed by life cycle assessment (LCA) methodology from cradle-to-grave. The assessment also includes comparison of 2 different nano TiO2 production technologies, one by continuous hydrothermal synthesis and the other by a sulfate process. Results of the study showed a relatively large contribution of photocatalytic coatings to reducing the effects of selected indices in comparison with an air purifier, regardless of which nano TiO2 production method is used. Although the impacts of the sulfate process are significantly lower compared to those of hydrothermal synthesis when viewed in terms of production alone, taken in the context of the entire product life cycle, the net difference becomes less significant. The study has been elaborated within the Sustainable Hydrothermal Manufacturing of Nanomaterials (SHYMAN) project, which aims to develop competitive and sustainable continuous nanoparticle (NP) production technology based on supercritical hydrothermal synthesis. Integr Environ Assess Manag 2016;12:478-485. © 2016 SETAC.