Self-cleaning Materials Research Articles

Preparation of multi band photothermal responsive bio-based superhydrophobic self-healing poly(siloxane-urethane) coating

In order to improve the poor hydrophobicity and single repair conditions of traditional self-healing polyurethane coatings, prepolymers were synthesized with bio-based polyol castor oil (CO), self-made alkyl aryl modified silicone polyols (Si-OH) and isophorone diisocyanate (IPDI), and 4,4'-dithiodianiline (ODD) was used as chain extender containing dynamic disulfide bond, 4-methylumbelliferone (4-MU), as a bio-based end capping agent with reversible ring structure, was polymerized step by step to prepare a photothermal responsive bio-based superhydrophobic self-healing poly(siloxane-urethane) coating (PUSi). In this paper, the effect of the amount of alkyl aryl modified silicone polyol (Si-OH) on the properties of PUSi was studied. The results showed that PUSi with different alkyl aryl modified silicone polyol additions could achieve self-healing under heating, UV irradiation and infrared light irradiation, and the maximum repair efficiency could reach 91% through optical microscope (OM), 3D profilometer and universal testing machine; The contact angle meter proved that the introduction of alkyl aryl modified silicone polyol greatly improved the hydrophobicity of PUSi, and the maximum water contact angle was 162°. The coating has broad application prospects in the fields of self-cleaning fabrics, super hydrophobic surfaces, special protective clothing and so on.

Long-term properties of self-cleaning alkali-activated slag-based mortars with titanium dioxide nanoparticles

Titanium dioxide (TiO2) is considered one of the most efficient photocatalysis to produce self-cleaning cementitious materials. At the same time, alkali activated binders have become one of the most interesting low-carbon alternatives to Portland cement. For this, the addition of titanium dioxide nanoparticles in one-part alkali-activated slag-based (AAS) mortars was analyzed to evaluate the effect on the rheological and mechanical properties, dirt pick-up resistance as well as self-cleaning capability. This paper reports a two-year campaign of outdoor exposure in an industrial environment in Northern Italy to investigate the natural photoactivity of the mortars doped with different TiO2 dosages. The experimental results indicated limited effect of nanoparticles on the rheology and mechanical properties of AAS mortars. It was also highlighted the beneficial effect of TiO2 addition in self-cleaning capability under natural and accelerated conditions and the fundamental role in photocatalytic efficiency of the alkali content.

Functional Fiber Membranes with Antibacterial Properties for Face Masks

Reusable face masks are an important alternative for minimizing costs of disposable and surgical face masks during pandemics. Often complementary to washing, a prolonged lifetime of face masks relies on the incorporation of self-cleaning materials. The development of self-cleaning face mask materials requires the presence of a durable catalyst to deactivate contaminants and microbes after long-term use without reducing filtration efficiency. Herein, we generate self-cleaning fibers by functionalizing silicone-based (polydimethylsiloxane, PDMS) fibrous membranes with a photocatalyst. Coaxial electrospinning is performed to fabricate fibers with a non-crosslinked silicone core within a supporting shell scaffold, followed by thermal crosslinking and removal of the water-soluble shell. Photocatalytic zinc oxide nanoparticles (ZnO NPs) are immobilized on the PDMS fibers by colloid-electrospinning or post-functionalization procedures. The fibers functionalized with ZnO NPs can degrade a photo-sensitive dye and display antibacterial properties against Gram-positive and Gram-negative bacteria (Escherichia coli and Staphylococcus aureus) due to the generation of reactive oxygen species upon irradiation with UV light. Furthermore, a single layer of functionalized fibrous membrane shows an air permeability in the range of 80–180 L/m2s and 65% filtration efficiency against fine particulate matter with a diameter less than 1.0 µm (PM1.0).Graphical abstract

Enhanced self-cleaning capacity of RBP@TiO2 based building coating: Synergetic effect of photocatalysis and photo-induced superhydrophilicity

Building self-cleaning materials are highly demanded due to the incomparable advantages in protecting buildings from pollution. In this paper, recycled brick powder (RBP) was coupled with TiO2 to fabricate an eco-friendly building self-cleaning agent via an in situ hydrolysis-calcination method and applied in building coating. Microstructure and properties of RBP@TiO2 composites were characterized by multiple testing technologies. The self-cleaning capacity of RBP@TiO2 coating was evaluated by photocatalytic decolorization of methylene blue (MB). The results showed that TiO2 was firmly combined with RBP through chemical bonds, and RBP@TiO2 composites exhibited stronger self-cleaning capacity than bare TiO2 due to the enhanced photocatalytic activity and hydrophilicity. Specifically, photocatalytic quantum efficiency of TiO2 was improved by the surface polarization of RBP. And the hydrophilicity was improved due to the enhanced surface roughness, which was caused by the ordered micro-nano structure. Our work clarified the self-cleaning mechanism of RBP@TiO2-based building coating and provided a new utilization path for recycling of RBP.

Transparent Superhydrophobic Coatings of Silica Nanoparticles Using Functionalized Polyurethanes.

Superhydrophobic coatings are essential to prepare water-repellent surfaces, self-cleaning materials, etc. Silica nano-materials are often immobilized to different surfaces for imparting super-hydrophobicity. Direct coating of silica-nanoparticles is often challenging since it can easily be peeled off under different environments. Herein, we reported the use of properly functionalized polyurethanes to facilitate the strong binding of silica-nanoparticles to surfaces. The alkyne terminal polyurethane was synthesized by step-growth polymerization while click-reactions facilitated to post-functionalization using phenyl moiety and were characterized by 1 H, 13 C nuclear magnetic resonance (NMR) spectroscopies, and 1 H spin-lattice relaxation times (T1 s). Upon functionalization, the glass transition temperature (Tg) increased due to enhanced interchain interactions. Moreover, additives like di(propyleneglycol)dibenzoate showed a substantial plasticizing effect to compensate for the increase in Tg, an important parameter for low-temperature applications. NMR signatures the spatial interactions between various protons of grafted silica-nanoparticles and phenyl triazole functionalized polyurethanes, thus indicating the usefulness of polyurethanes to bind silica-nanoparticles. After coating functionalized silica-nanoparticles to leather using functionalized polyurethanes, a contact angle value of more than 157° was observed with retention of grain patterns of leather due to transparency. We anticipate the results to help design varieties of materials with superhydrophobicity where the structural integrity of the surfaces is retained.

A review of plant-mediated synthesis of zinc oxide nanoparticles for self-cleaning textiles

Purpose The textile industry is evolving toward nanotechnology, which provides materials with self-cleaning properties. This paper aims to provide a thorough explanation of the green synthesis and mechanism of ZnO nanoparticles, with prospective applications of zinc oxide nanoparticles (ZnO NPs) in self-cleaning textiles. Design/methodology/approach This review introduces a green mechanism for the synthesis of ZnO NPs using plant extracts, their self-cleaning properties and the mechanisms of physical, chemical and biological self-cleaning actions for textile applications. Findings ZnO NPs are among the several nanoparticles that are beneficial for self-cleaning textiles because of their exceptional physical and chemical properties, although review publications addressing the use of ZnO NPs in textiles for self-cleaning are uncommon. These results indicate that the plant-synthesized ZnO NPs display excellent biological, physical and chemical self-cleaning properties, the mechanism of which involves photocatalysis, surface roughness and interactions between ZnO NPs and bacterial surfaces. Originality/value Nanoformulations of plant-synthesized ZnO have been reviewed to achieve promising self-cleaning textile properties and have not been reviewed earlier.

Transparent and superhydrophobic room temperature vulcanized (RTV) polysiloxane coatings loaded with different hydrophobic silica nanoparticles with self-cleaning characteristics

Superhydrophobic coatings based on room temperature vulcanized (RTV) polysiloxane matrix loaded with organically modified silica (ORMOSIL) nanoparticles were successfully prepared using the cost-effective and scalable one-step spraying coating approach. ORMOSIL nanoparticles were prepared by sol-gel treatment at ambient conditions through the reaction between the commercial hydrophilic silica (R200) and octyl-triethoxysilane (R200.OTS), (1H,1H,2H,2H-nonafluorohexyl)-triethoxysilane (R200.NFS) and a mixture of both (R200.OTS/NFS). The functionalization of the silica was followed by Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). Commercial hydrophobic silica particles functionalized with siloxane (R202) and octyl-silane (R805) were also used for comparison. The presence of 20 % of R202 and R200.NFS resulted in coatings with water contact angle (WCA) higher than 160°, sliding angle <5°, high transparency and an effective self-cleaning behavior. Increasing the amount of nanoparticles increased the superhydrophobic response but the translucence decreased. Coatings containing R200.OTS particles presented high translucence and high WCA, but the sliding angle was also high, which limits their use as self-cleaning material.

Effect of Symmetry and Increasing Hydrophobicity on the Self-Assembly and Function of Benzoylurea Derivatives

A novel series of benzoylurea derivatives containing benzoic acid, m-dibenzoic acid, and benzene 1,3,5-tricarboxylic acid were designed with increasing hydrophobicity. The aggregation behavior of the derivatives was studied by several spectroscopic methods. The porous morphology of the resulting aggregates was examined by polar optical microscopy and field emission scanning electron microscopy. From X-ray single-crystal analysis, it is observed that N,N'-dicyclohexylurea containing compound 3 lost C3 symmetry and adopted a "bowl"-shaped conformation and self-assembles to form a supramolecular honeycomb-like framework that is stabilized by multiple intermolecular hydrogen bonds. However, compound 2 with C2 symmetry had a kink-like conformation and self-assembled to form a sheet-like structure. Discotic compound 3 coated paper, cloth, or glass surfaces, repealed water, and behaved like a self-cleaning material. Discotic compound 3 is also able to separate the oil and water from oil-water emulsion.

Preparation of Superhydrophobic Materials and Establishment of Anticorrosive Coatings on the Tinplate Substrate by Alkylation of Graphene Oxide

Corrosion of structural parts not only reduces the service life of the equipment but also causes safety accidents, so building a long-lasting anti-corrosion coating on its surface is the key to solving this problem. Under the action of alkali catalysis, n-octyltriethoxysilane (OTES), dimethyldimethoxysilane (DMDMS), and perfluorodecyltrimethoxysilane (FTMS) hydrolyzed and polycondensed co-modified graphene oxide (GO), modified to synthesize a self-cleaning superhydrophobic material fluorosilane-modified graphene oxide (FGO). The structure, film morphology, and properties of FGO were systematically characterized. The results showed that the newly synthesized FGO was successfully modified by long-chain fluorocarbon groups and silanes. FGO presented an uneven and rough morphology on the substrate surface, the water contact angle was 151.3°, and the rolling angle was 3.9°, which caused the coating to exhibit excellent self-cleaning function. Meanwhile, the epoxy polymer/fluorosilane-modified graphene oxide (E-FGO) composite coating adhered to the carbon structural steel's surface, and its corrosion resistance was detected by the Tafel curve and EIS impedance. It was found that the current density of the 10 wt% E-FGO coating (Icorr) was the lowest (1.087 × 10-10 A/cm2), which was approximately 3 orders of magnitude lower than that of the unmodified epoxy coating. This was primarily due to the introduction of FGO, which formed a continuous physical barrier in the composite coating and gave the composite coating excellent hydrophobicity. This method might provide new ideas for advances in steel corrosion resistance in the marine sector.

Multi Self-cleaning Properties of Zinc Oxide Nanoparticles/ Polydimethylsiloxane (ZnO/PDMS) Composite on Polyester Textile

Self-cleaning textiles can be divided into three categories, which are the physical, chemical, and biological self-cleaning types. Physical self-cleaning refers to the lotus effect, which relates to the hydrophobic properties of the textile. Chemical self-cleaning is the degradation of color stains, discolored solutions and other organic species that come into contact with textiles. The last is biological self-cleaning, which is the ability to kill bacteria that become attached to the textiles. In this research, the development of all three self-cleaning properties of polyester textile coated with zinc oxide nanoparticles/ polydimethylsiloxane (ZnO/ PDMS) composite was focused. The ZnO nanoparticles were synthesized by a hydrothermal process, which involved blending PDMS with various concentrations of ZnO nanoparticles. The polyester textile was coated with ZnO/ PDMS composite solution via a dip coating technique done with various dipping times. The lotus effect, which depends on hydrophobic properties, was analyzed by water contact angle measurement. The chemical self-cleaning of the polyester textile was examined by photocatalytic methylene blue dye degradation with UV-Vis spectrometry. The inhibition zone of antibacterial activity was tested via disc diffusion technique. From these results, it was found that the polyester textile coated with ZnO/PDMS composite demonstrated all self-cleaning properties, physical, chemical and biological, in a significantly way.

Dispersion of Manganese Dioxide Particles Using Anionic Technol PG and Sodium Cholate in the Preparation for Application as Films on Substrates

Manganese dioxide (MnO2) is widely used in cosmetics and self-cleaning materials because of the high refractive index and photocatalytic activity of this compound. In the present work, the surfaces of MnO2 particles were coated with a commercially available anionic phospholipid mixture, Technol PG, and sodium cholate(SC). These coated particles were readily dispersed in water and subsequently applied as films onto glass substrates by drop-casting.

Promoting Students’ Mental Health through Design and Implementation of Multi-Activity Pods in Educational Institutions Using the WELL Building Standard

The findings of several research studies conducted with university students that aimed to investigate the quantitative relationship between psychological distress, sleep difficulties, and homesickness have shown a significant interrelation among those factors. All the previous studies demonstrated benefits of napping, meditation, relaxation, and sharing feelings and experiences on students’ mental well-being, which could enrich the brain’s educational capacity, a matter that is relevant to a student’s learning level. This study aimed to encourage on-campus students to alleviate their feelings and relax. This process will help students to recharge their energy, in addition to increasing their alertness and focusing abilities, especially since the COVID-19 pandemic has intensified global stresses. In this study, the authors used a systematic review and literature analysis to understand the relationship between mental stresses and student performance. We then used an evidence-based research opinion poll and presented our work at different academic exhibitions for feedback as an approach for developing an experimental conceptual multi-activity unit that can be used across university campuses. The “Reviving Pod” was specifically designed for different activities: napping, meditation, and virtual communication. The designed approach utilizes state-of-the-art technologies (embedded sensors, smart ergonomic seats, contactless technologies, self-cleaning materials, IoT, virtual meetings platforms, mobile applications, etc.). A Reviving Pod can be located variably within a university campus. According to the poll results, we proposed a recreational zone design to accommodate the pods, as well as a diversity of activities that can encourage students to relieve their stresses and reinforce their health, consequently increasing their academic performance and supporting their well-being using the WELL Building Standard to promote better mental health, which is vital for students’ success.

Adsorption and Inactivation of SARS-CoV-2 on the Surface of Anatase TiO2(101)

We investigated the adsorption of severe acute respiratory syndrome corona virus 2 (SARS-CoV-2), the virus responsible for the current pandemic, on the surface of the model catalyst TiO2(101) using atomic force microscopy, transmission electron microscopy, fluorescence microscopy, and X-ray photoelectron spectroscopy, accompanied by density functional theory calculations. Three different methods were employed to inactivate the virus after it was loaded on the surface of TiO2(101): (i) ethanol, (ii) thermal, and (iii) UV treatments. Microscopic studies demonstrate that the denatured spike proteins and other proteins in the virus structure readsorb on the surface of TiO2 under thermal and UV treatments. The interaction of the virus with the surface of TiO2 was different for the thermally and UV treated samples compared to the sample inactivated via ethanol treatment. AFM and TEM results on the UV-treated sample suggested that the adsorbed viral particles undergo damage and photocatalytic oxidation at the surface of TiO2(101) which can affect the structural proteins of SARS-CoV-2 and denature the spike proteins in 30 min. The role of Pd nanoparticles (NPs) was investigated in the interaction between SARS-CoV-2 and TiO2(101). The presence of Pd NPs enhanced the adsorption of the virus due to the possible interaction of the spike protein with the NPs. This study is the first investigation of the interaction of SARS-CoV-2 with the surface of single crystalline TiO2(101) as a potential candidate for virus deactivation applications. Clarification of the interaction of the virus with the surface of semiconductor oxides will aid in obtaining a deeper understanding of the chemical processes involved in photoinactivation of microorganisms, which is important for the design of effective photocatalysts for air purification and self-cleaning materials.

ZnO nanoparticles coated and stearic acid modified superhydrophobic chitosan film for self-cleaning and oil–water separation

The aim of this study was to prepare superhydrophobic chitosan films using a ZnO nanoparticle coating and stearic acid hydrophobic modification. A 1 % concentration of ZnO nanoparticles and a 1 % concentration of stearic acid generated a superhydrophobic film with the largest contact angle (WCA) of 156°, which was attributed to the synergy of micro/nano-level hierarchical structure and low surface energy modification. The superhydrophobic film showed better stability to acid, alkali, heat, and UV irradiation than a neat chitosan film and a reduction in light transmittance of 14.4 % at 354 nm. The superhydrophobic chitosan film also showed excellent self-cleaning and oil–water separation performance. Our findings will expand the application of chitosan films in food packaging, outdoor self-cleaning materials and oil–water separations.

Technological efficiency of mineral modifiers for cement materials with photocatalytic activity

It is known that the efficient kinds of photocatalytic additives for cement materials are “core–shell” compositions synthesized by precipitation of photocatalyst particles on mineral substrates (dispersed carriers). The study aim was to install patterns of influence of 5 mineral modifiers on the technological characteristics of cement systems with finding of the most promising raw materials for dispersed carriers of photocatalytic agents. The increased technological efficiency of silica fume, metakaolin and expanding sulfoaluminate modifier in cement paste, due to the peculiarities of their granulometric composition with high dispersity and defectiveness of particles, was revealed by the research results. It predetermines the prospects of using these mineral additives in the composition of photocatalytically active self-cleaning cement materials.

Fabrication of Transferable and Micro/Nanostructured Superhydrophobic Surfaces Using Demolding and iCVD Processes

Superhydrophobic surfaces possess enormous potential in various applications on account of their versatile functionalities. However, artificial superhydrophobic surfaces with ultralow solid/liquid adhesion often require complicated structure fabrication and surface fluorination processes. Here, we designed a superhydrophobic surface possessed of micro/nanoscale structures by employing facile and low-cost demolding and initiated chemical vapor deposition (iCVD) processes. The achieved micro/nanostructured superhydrophobic surface has a maximum static contact angle of ∼170°, a roll-off angle and contact angle hysteresis below 1°, ultralow solid/liquid adhesion for water droplets, and maintains excellent superhydrophobicity after exposure to strongly corrosive species, like strong acid/base and salt solutions, for 60 h. This reasonability-designed method of creating the superhydrophobic surface could provide valuable guidelines for the manufacture of transferable superhydrophobic surfaces and facilitate potential applications extending from optoelectronic devices to self-cleaning materials, such as solar cells, windows, and electronic displays.

Large-scale structural color on transparent plexiglass by nanosphere lithography combined with reactive-ion etching

Structural color due to unique optical response are of much interest both for their fundamental properties and applications in photonic integrate circuits, optical biomaterials and camouflage. Nanosphere lithography combined with reactive-ion etching demonstrates a feasible strategy to achieve large-scale photonic crystals with structural color. In this work, polymethyl methacrylate (PMMA), namely plexiglass, was firstly used as photonic crystals substrate to fabricate large-area and novel nanopillar arrays via reactive-ion etching monolayer polystyrene (PS) sphere arrays. The height and diameter of plexiglass’ nanopillars can be controlled by adjusting PS size and etching time. In addition, PS sphere arrays exhibited charming structures like chrysanthemum after O2 plasma etching with higher intensity. The nanopillar arrays exhibited the tuned band-gap of such structures with different sizes and tunable resonance peaks from 350 nm to 600 nm. The fabricated nanopillar arrays have potential applications in solar cells, self-cleaning materials, photonic crystals and nonlinear optics.

Dispersion of Titanium Oxide Nanoparticles Using Mixtures of Anionic Technol PG and Sodium Cholate

Titanium dioxide (TiO2) is widely used in cosmetics and self-cleaning materials because of its high refractive index and photocatalytic activity. In the present work, the surfaces of TiO2 nanoparticles were coated with sodium cholate and the commercially available anionic phospholipid mixture Technol PG. These surface-coated TiO2 nanoparticles could be homogeneously dispersed in water and subsequently produced films on glass substrates after drop casting.

A simple solvothermal preparation of Mg-doped anatase TiO2 and its self-cleaning application

Self-cleaning materials have attracted considerable attention for their unique properties and practical applications in energy and environmental areas. Various commercial ceramic products developed based on photo-induced hydrophilic conversion of TiO2 surfaces have also been provided. However, UV light induced and metastable character of anatase TiO2 in medium/high temperature ceramic glaze limited practical applications for self-cleaning photocatalytic materials, which needs further development to improve their efficiency and utilities. In this work, Mg-doped anatase TiO2 was synthesized via a template-free and surfactant-free solvothermal method. The results indicated that MgCl2·6H2O content played key roles in the formation of anatase TiO2. Compared to TiO2-undoped sample, Mg-doped TiO2 sample showed higher photodegradation rate of 99.5 % in 80 min exposed to visible light irradiation. Owing to the introduction of the catalyst, the ceramic glaze showed super-hydrophilicity (water contact angle around 7°) and exhibited excellent stain resistance (e. g. the dried Marker ink on the glaze can immediately float once meeting water after 10 cycles). The glaze after more times recycles could restore super-hydrophilicity is irradiated by visible light for 1 h. This indicates that the introduction of Mg-doped anatase TiO2 demonstrated great practical applications for self-cleaning ceramics toward sunlight.

Fabrication of a Polybutylene Succinate (PBS)/Polybutylene Adipate-Co-Terephthalate (PBAT)-Based Hybrid System Reinforced with Lignin and Zinc Nanoparticles for Potential Biomedical Applications.

Polybutylene adipate-co-terephthalate (PBAT) was used in an effort to improve the properties of polybutylene succinate (PBS). The resultant blend consisting of PBS/PBAT (70/30) was reinforced with lignin at different loadings (5 to 15 wt.%) and zinc (ZnO) nanoparticles (1.5 wt.%). Hot melt extrusion and injection moulding were used to prepare the hybrid composites. The mechanical, thermal, physical, self-cleaning, and antimicrobial properties of the resultant hybrid composites were investigated. The transmission electron microscopy (TEM) results confirmed that ZnO was successfully prepared with average diameters of 80 nm. Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) confirmed that there were interactions between the fillers and the blend. The tensile strength and elongation at the break of the resultant materials decreased with increasing the loadings, while the tensile modulus showed the opposite trend. The melting behaviour of the blend was practically unaffected by incorporating lignin and ZnO nanoparticles. In addition, the incorporation of fillers reduced the thermal stability of the materials. Furthermore, the incorporation of ZnO nanoparticles introduced photocatalytic properties into the polymer blend, rendering it to be a functional self-cleaning material and enhancing its antimicrobial activities.