Green and sustainable self-cleaning flexible SERS base: Utilized for cyclic-detection of residues on apple surface

Advances in flexible SERS substrates has made it possible to approach the ultimate goal of rapid in-situ monitoring of fruit and vegetable safety, but its vulnerability under laser ablation results in low utilization. In order to solve this problem, a 3D framework of TiO2-doped PVDF\PVP polymer was utilized to self-assemble gold-silver core-shell nanorods (Au@Ag NRs) to prepare a flexible SERS substrate with good physical stability and self-cleaning properties. This substrate showed excellent detection limit and recyclability after the detection of three pesticide residues in apple peel. The LOD of methyl-parathion (MP) was as low as 0.037 ng/cm2, with an RSD of 5.61 % for 5 cycle-detection. The recoveries of two additional pesticides thiram (TMTD) and chlorpyrifos (CPF) were 86.32 %-112.47 %. We hoped that this research will contribute to providing a recyclable and facile method for in-situ analysis of fruit and vegetable surface residues and functional manufacture of flexible SERS substrates.

Recent advances in cotton fabric-based photocatalytic composites for the degradation of organic contaminants

Cotton is one of the oldest and most widely used natural fibers in the world. It enables a wide range of applications due to its excellent moisture absorption, thermal insulation, heat resistance, and durability. Benefiting from current developments in textile technology and materials science, people are constantly seeking more comfortable, more beautiful and more versatile cotton fabrics. As the second skin of body, clothing not only provides the basic needs of wear but also increases the protection of body against different environmental stimuli. In this article, a comprehensive review is proposed regarding research activities of systematically summarise the development and research of cotton fabric-based photocatalytic composites for the degradation of organic contaminants in the area of self-cleaning, degradation of gaseous contaminants, pathogenic bacteria or viruses, and chemical warfare agents. Specifically, we begin with a brief exposition of the background and significance of cotton fabric-based photocatalytic composites. Next, a systematical review on cotton fabric-based photocatalytic composites is provided according to their mechanisms and advanced applications. Finally, a simple summary and analysis concludes the current limitations and future directions in these composites for the degradation of organic contaminants.

Robust superhydrophobic cotton fabric based on dual-sized silica particles with self-healing nature

Improving the durability of wear-resistant superhydrophobic surfaces is crucial for their practical use. To tackle this, research is now delving into self-healing superhydrophobic surfaces. In our study, we developed superhydrophobic cotton fabrics by embedding nano-silica particles, micro-silica powder, and polydimethylsiloxane (PDMS) using a dipping method. This innovative design grants the SiO2/PDMS cotton fabric remarkable superhydrophobicity, reflected by a water contact angle of 155°. Moreover, the PDMS was stored in the amorphous areas of cellulose of cotton fabrics, attaching to the fiber surface and playing a role in connecting micro-blocks and nano-particles. This causes a self-diffusion of PDMS molecules in these fabrics, allowing the surface to regain its superhydrophobicity even after abrasion damage. Impressively, this self-healing property can be renewed at least 8 times, showcasing the fabric's resilience. Moreover, these superhydrophobic cotton fabrics exhibit outstanding self-cleaning abilities and repel various substances such as blood, milk, cola, and tea. This resilience, coupled with its simplicity, low cost-effectiveness, and eco-friendliness, makes this coating highly promising for applications across construction, chemical, and medical fields. Our study also delves into understanding the self-healing mechanism of the SiO2/PDMS cotton fabric, offering insights into their long-term performance and potential advancements in this field.

Innovative textiles treated with TiO2-AgNPs with succinic acid as a cross-linking agent for medical uses

Silver and titanium-silver nanoparticles have unique properties that make the textile industry progress through the high quality of textiles. Preparation of AgNPs and TiO2-Ag core-shell nanoparticles in different concentrations (0.01% and 0.1% OWF) and applying it to cotton fabrics (Giza 88 and Giza 94) by using succinic acid 5%/SHP as a cross-linking agent. Ultra-violet visible spectroscopy (UV-Vis), X-ray diffraction (XRD), dynamic light scattering (DLS), zeta potential, transmission electron microscopy (TEM), scanning electron microscopy/energy-dispersive X-ray (SEM-EDX) are tools for AgNPs and TiO2-AgNPs characterization and the treated cotton. The resulting AgNPs and TiO2-AgNPs were added to cotton fabrics at different concentrations. The antimicrobial activities, UV protection, self-cleaning, and the treated fabrics' mechanical characteristics were investigated. Silver nanoparticles and titanium dioxide-silver nanoparticles core-shell were prepared to be used in the treatment of cotton fabrics to improve their UV protection properties, self-cleaning, elongation and strength, as well as the antimicrobial activities to use the produced textiles for medical and laboratory uses and to increase protection for medical workers taking into account the spread of infection. The results demonstrated that a suitable distribution of prepared AgNPs supported the spherical form. Additionally, AgNPs and TiO2-AgNPs have both achieved stability, with values of (- 20.8 mV and - 30 mV, respectively). The synthesized nanoparticles spread and penetrated textiles' surfaces with efficiency. The findings demonstrated the superior UV protection value (UPF 50+) and self-cleaning capabilities of AgNPs and TiO2-AgNPs. In the treatment with 0.01% AgNPs and TiO2-AgNPs, the tensile strength dropped, but the mechanical characteristics were enhanced by raising the concentration to 0.1%. The results of this investigation demonstrated that the cotton fabric treated with TiO2-AgNPs exhibited superior general characteristics when compared to the sample treated only with AgNPs.

Stability enhancement of perovskite solar cells using multifunctional inorganic materials with UV protective, self cleaning, and high wear resistance properties

Organometal halide perovskite solar cells have reached a high power conversion efficiency of up to 25.8% but suffered from poor long-term stability against environmental factors such as ultraviolet irradiation and humidity of the environment. Herein, two different multifunctional transparent coatings containing AZO and ZnO porous UV light absorbers were employed on the front of the PSCs. This strategy is designed to improve the long-term stability of PSCs against UV irradiation. Moreover, the provided coatings exhibit two additional roles, including self-cleaning and high wear resistance. In this regard, AZO coating showed higher wear resistance compared to the ZnO coating. The photocatalytic self-cleaning properties of these prepared coatings make them stable against environmental pollutants. Furthermore, appropriate mechanical properties such as high hardness and low coefficient of friction that leads to high resistance against wear are other features of these coatings. The devices with AZO/Glass/FTO/meso-TiO2/Perovskite/spiro/Au and ZnO/Glass/FTO/meso-TiO2/Perovskite/spiro/Au configurations maintained 40% and 30% of their initial performance for 100 h during 11 days (9 h per day) against the UV light with the high intensity of 50 mW cm-2 which is due to higher absorption of AZO compared with ZnO in the ultraviolet region. Since AZO has a higher light transmission in the visible region in comparison to ZnO, perovskite cells with AZO protective layers have higher efficiency than perovskite cells with ZnO layers. It is worth noting that the mentioned features make these coatings usable for cover glass in all types of solar cells.

CFD study of self-cleaning system of multi-stage tangential roller threshing unit for precise buckwheat breeding

Buckwheat is a globally recognized, nutritionally rich crop with robust adaptability, serving as a multi-purpose plant for its health benefits. Achieving precise and mechanized plot seed harvesting is a critical step in obtaining accurate results in breeding experiments. However, plot breeding requires no seed retention, no mixing, and ensures no accumulation of seed in the threshing unit. A self-cleaning technology was developed to prevent seed retention, mixing, and accumulation in the multistage tangential cylinder threshing unit. The newly designed cleaning system has five air inlets and a centrifugal fan for pneumatic cleaning. CFD simulations were conducted for each inlet position, coupled with four varying inlet velocities and the rotation speed of the main threshing cylinder. During the post-processing stage of the CFD modeling, a line consisting of fifty points was drawn beneath the threshing drums, and the air velocity at these points was recorded. The optimal configuration of inlet position, inlet air velocity, and main threshing drum rotation speed for efficient cleaning was identified based on the ratio of points beneath the drums where the airflow speed surpassed the suspension speed of buckwheat to the points where the airflow speed was lower than the suspension speed of buckwheat. The optimal configuration for "inlet_1" was identified based on the suspension velocity of buckwheat grain, with an inlet velocity of 4 m/s and a main threshing drum speed of 450 rpm.

In-situ assessment of the performance of oil-water separation by superhydrophobic coated cotton under extreme conditions

The present study aims to address the issue of oil in water pollution by application of a superhydrophobic cotton fabric. The superhydrophobic cotton fabric with a water contact angle of 158 ± 2°, is developed by a solution immersion technique using zirconium dioxide (ZrO2) nanoparticles and hexadecyltrimethoxysilane. The synthesis parameters such as concentration, curing temperature, and immersion time were optimized using Box-Behnken design method. With mechanical durability, chemical resilience and thermal stability, the coated fabric can separate different oil-water mixtures with an efficiency of 99.9 %. The coated fabric can also be reused for 50 separation cycles in acidic and neutral medium. Besides, droplet dynamic behavior of oil-water mixture has also been studied to ascertain the effect of mixture impact velocities on separation performance. Additionally, coated fabric possesses self-cleaning feature, which makes it viable for muddy oil-water separation. Prepared coated fabric holds tremendous potential for industrial use and oil-water separation in extreme conditions.

Preparation of mixed matrix self-cleaning membrane incorporated by Z-scheme heterostructure via robust engineering in terms of dimension for decreasing cake fouling in a cross-flow reactor

Reducing irreversible fouling in polymer membranes by integrating photocatalytic and membrane processes as the self-cleaning photocatalytic membrane is a promising candidate for improving membrane filtration performance. In this study, mixed matrix photocatalytic membranes were prepared from the combination of different morphologies ZnO-g-C3N4 heterostructure in the polymer matrix by the phase-separation method. To investigate the self-cleaning and performance properties of mixed matrix photocatalytic membranes prepared from different morphologies heterostructures, the photocatalytic membrane reactor with a visible-light source was applied. Nanoflower/nanosheet (NF/NS) ZnO-g-C3N4 photocatalytic membrane showed good self-cleaning performance owing to the high photocatalytic performance of NF/NS ZnO-g-C3N4 heterostructure by the reduction of irreversible membrane fouling, thus improving the antifouling and filtration performance of the membrane. Also, the morphology and the uniform distribution of the NF/NS ZnO-g-C3N4 heterostructure in the membrane matrix caused good hydrophilic properties, high porosity, and a more symmetrical structure in the (NF/NS) ZnO-g-C3N4 photocatalytic membrane (F4). For the F4 membrane, the permeability and rejection values increased from 40.35 L m-2 h-1 and 90.9% in the dark environment to 84.37 L m-2 h-1 and 97.4% under visible-light for dye pollutants. Accordingly, F4 had the best filtration and self-cleaning performance, which can be used as a promising visible-light photocatalytic membrane in wastewater treatment processes.

A comprehensive review on anticorrosive/antifouling superhydrophobic coatings: Fabrication, assessment, applications, challenges and future perspectives

Superhydrophobicity (SHP) is an incredible phenomenon of extreme water repellency of surfaces ubiquitous in nature (E.g. lotus leaves, butterfly wings, taro leaves, mosquito eyes, water-strider legs, etc). Historically, surface exhibiting water contact angle (WCA) > 150° and contact angle hysteresis <10° is considered as SHP. The SHP surfaces garnered considerable attention in recent years due to their applications in anti-corrosion, anti-fouling, self-cleaning, oil-water separation, viscous drag reduction, anti-icing, etc. As corrosion and marine biofouling are global problems, there has been focused efforts in combating these issues using innovative environmentally friendly coatings designs taking cues from natural SHP surfaces. Over the last two decades, though significant progress has been made on the fabrication of various SHP surfaces, the practical adaptation of these surfaces for various applications is hampered, mainly because of the high cost, non-scalability, lack of simplicity, non-adaptability for a wide range of substrates, poor mechanical robustness and chemical inertness. Despite the extensive research, the exact mechanism of corrosion/anti-fouling of such coatings also remains elusive. The current focus of research in recent years has been on the development of facile, eco-friendly, cost-effective, mechanically robust chemically inert, and scalable methods to prepare durable SHP coating on a variety of surfaces. Although there are some general reviews on SHP surfaces, there is no comprehensive review focusing on SHP on metallic and alloy surfaces with corrosion-resistant and antifouling properties. This review is aimed at filling this gap. This review provides a pedagogical description with the necessary background, key concepts, genesis, classical models of superhydrophobicity, rational design of SHP, coatings characterization, testing approaches, mechanisms, and novel fabrication approaches currently being explored for anticorrosion and antifouling, both from a fundamental and practical perspective. The review also provides a summary of important experimental studies with key findings, and detailed descriptions of the evaluation of surface morphologies, chemical properties, mechanical, chemical, corrosion, and antifouling properties. The recent developments in the fabrication of SHP -Cr-Mo steel, Ti, and Al are presented, along with the latest understanding of the mechanism of anticorrosion and antifouling properties of the coating also discussed. In addition, different promising applications of SHP surfaces in diverse disciplines are discussed. The last part of the review highlights the challenges and future directions. The review is an ideal material for researchers practicing in the field of coatings and also serves as an excellent reference for freshers who intend to begin research on this topic.

A laser-processed micro/nanostructures surface and its photothermal de-icing and self-cleaning performance

Micro/nanostructures have garnered significant attention and widespread applications in areas such as photocatalysis, coated fabrics, microchips, and sensors. However, high-resolution and multifunctional micro/nanostructures fabrication remains a great challenge. In this work, a novel self-assembly-femtosecond laser processing for the regular micro squares and nano bumps surface on steel substrates is proposed, and a great potential in the field of anti-icing/de-icing and self-cleaning is demonstrated. The surface tension gradient-driven liquid-air self-assembly provides a silica microsphere monolayer, while the post-femtosecond laser process can give precise micro/nano decoration. We systematically explore the impact of laser repetition frequency, scanning speed, and laser incident power on the size and shape of micro/nano decorations that have been studied. The different performances of self-cleaning effects, ice adhesion, and the photothermal de-icing capability due to the change in surface wettability have been demonstrated. This research shows a new pathway for the creation of smart micro/nanostructures surface which possess stable super hydrophilic and highly adhesive superhydrophobic properties, as well as high abrasion resistance. The discovery achieves a suitable blend of multiple functions on the surface of a single material, which can be applied to various surface engineering fields.

Self-cleaning foulant attachment on near-infrared responsive photocatalytic membrane for continuous dynamic removing antibiotics in sewage effluent environment

Bifunctional photocatalytic nanofiltration (PNF) membrane has become a reliable frontier technique for removing refractory organic micropollutants. However, the active mitigated fouling mechanism from the microscopic perspective during its long-term operation of purifying real micro-polluted water is rarely studied. Herein, with an integrated use of QSense Explorer and confocal laser scanning microscope techniques, self-cleaning foulant attachment on an activated and customized near-infrared responsive polymeric PNF (termed as nPNF) membrane with good service performance for continuous dynamic removing antibiotics in sewage effluent environment was firstly elucidated. Time-dependent changes in dissipation oscillation frequency, sensed mass and the visualized foulant spatial distribution all indicated that there were only sporadic foulant attachment, an extremely low fouling layer thickness and irreversible fouling rate on/of the activated nPNF membrane top surface, thereby endowing it with excellent self-cleaning characteristic. This is probably because the reactive oxygen species (mainly •O2- and •OH) concurrently destroys the integrity of fouling layer and its internal adhesion structure, transforming part of the irreversible fouling on nPNF membrane surface into reversible one that is easy to wash off. These new horizons provided useful insight on the fate of selected antibiotics in the to-be-removed stage and self-cleaning foulant attachment of PNF membrane.

Super-wetting and self-cleaning polyvinyl alcohol/sodium alginate nanofiber membrane decorated with MIL-88A(Fe) for efficient oil/water emulsion separation and dye degradation

Membrane separation is considered an effective approach to water purification. Nevertheless, membrane fouling dramatically decreases the separation efficiency and lifetime of membranes, thus limiting its further development and application. Herein, a multifunctional self-cleaning MIL-88A(Fe) decorated polyvinyl alcohol/sodium alginate (MIL-88A(Fe)@PVA-SA) nanofiber membrane was prepared by electrospinning and in-situ growth methods for the separation of oil/water emulsions and photo-Fenton degradation of dyes. The membrane possesses superhydrophilicity with a water contact angle (WCA) of 0° and superoleophobicity with underwater oil contact angle (UCA) of 161.7°, and exhibits superior separation efficiency (>99.5 %) and permeation flux (1140-2455 L/m2/h) for different oil/water emulsions. Moreover, the membrane exhibited an outstanding photo-Fenton performance under visible light, with degradation efficiencies (~99.9 %) towards methylene blue (MB) and reactive red 24 (RR24) within 90 min. Importantly, the membrane can be easily regenerated by simple rinsing and photo-Fenton self-cleaning treatment. In this study, MIL-88A(Fe)@PVA-SA nanofiber membrane has a promising application in dye removal and oil/water separation, providing a new idea to develop novel membrane materials.

Construction of type-II scheme SnO@HfC photocatalyst for bisphenol A degradation via peroxymonosulfate activation; DFT and self-cleaning analysis

In this study, novel stannous oxide@hafnium carbide (SnO@HfC) nanocomposite was successfully manufactured by an appropriate hydrothermal scheme which was utilized for the photocatalytic degradation of BPA by stimulation of peroxymonosulfate (PMS) and self-cleaning application. Numerous methods were applied for the characterization of photocatalyst and demonstrated the successful preparation of SnO@HfC nanocomposite. The crystal structures, band structures and density of states for SnO and HfC were explored by DFT analysis. The amazing PMS stimulation performance of SnO@HfC nanocomposite originated from the establishment of a heterojunction, which led to the enhancement of the light response aptitude and the electron conduction competence of the composite. BPA was degraded by 0.75 g/L PMS and SnO@HfC at neutral pH during the period of 60 min. In order to identify active groups in the reaction procedure, quenching experiments and electron paramagnetic resonance (EPR) approaches were also used. In the subsequent active species scavenging assays, where sulfate radicals, hydroxyl radicals, holes, and superoxide radicals were engaged in the degradation of BPA. While, liquid phase mass spectrometry (LC-MS) was used to pinpoint the intermediate metabolites in the course of degradation. SnO@HfC/PMS/light system delivered excellent TOC removal efficiency and less ions leaching. The SnO@HfC nanocomposite proved good durability and reusability in continuous cycle tests along with excellent self-cleaning function on the glass substrate. The SnO@HfC nanocomposite performs admirably in terms of self-cleaning application. The SnO@HfC nanocomposite is expected to be used in the future for the treatment of wastewater that contains pharmaceuticals due to its superior stability and reusability after five consecutive cycles.

From clean spaces to crime scenes: Exploring trace DNA recovery from titania-coated self-cleaning substrates

Titanium dioxide (titania, TiO2) is frequently used as a coating for a variety of self-cleaning products, such as antifogging vehicle mirrors, ceramic tiles, and glass windows because of its distinct physiochemical features. When exposed to light TiO2 causes photocatalytic decomposition of organic contaminants, potentially compromising DNA integrity. The impact of TiO2-coated commercial glasses, Bioclean® and SaniTise™, on trace DNA persistence, recovery, and profiling was investigated. DNA in saliva and touch samples deposited on self-cleaning glass slides exposed to indoor fluorescent light for up to seven days was more degraded than control samples indicating some degree of fluorescent light-induced photocatalytic activity of the self-cleaning surfaces. When exposed to sunlight, DNA yields from saliva and touch samples deposited on the titania-coated substrates decreased rapidly, with a corresponding increase in DNA degradation. After three days no DNA samples applied to self-cleaning glass and exposed to natural sunlight yielded STR profiles. These results suggest that the photocatalytic activation of TiO2 is the likely mechanism of action underlying the extreme DNA degradation on the Bioclean® and SaniTise™ glasses. Consequently, rapid sample collection and use may be warranted in casework scenarios involving TiO2-coated materials.

Regulable preparation of silk fibroin composite cryogel by dual-directional crosslink for achieving self-cleaning, superelasticity and multifunctional water purification

Recently, the cryogel as a special type of hydrogel was widely used in the field of medicine due to its porous structure and good biocompatibilit. However, great challenges existed for its irregular pore size and incompressible property, limiting its application in other fields. In this study, a novel silk fibroin-based cryogel (named SF@PVA/CS) with regulable pore size, excellent elasticity and durability was constructed using a green dual-directional crosslink strategy. The SF@PVA/CS was prepared by using silk fibroin (SF) as bone scaffold, and chitosan (CS) and polyvinyl alcohol (PVA) as polymer hydrogel which was introduced into the inner bone scaffold of SF. Such a brand-new cryogel possessed three-dimensional dual network structure, which can overcome the shortcoming of unregulatable pore size and incompressibility of traditional cryogel. Additionally, the developed SF@PVA/CS membrane was used for water purification for the first time, which exhibited superior selective permeation, excellent anti-fouling and brilliant self-cleaning property, and it can achieve the purification of both oil/water emulsion and methylene blue solution. This study expanded the application of SF-based cryogel, providing a novel routine for designing new-type composite cryogel and widening the application of dual-directional crosslink strategy developed in this study for facilitating the purification of wastewater.

Robust self-cleaning membrane with superhydrophilicity and underwater superoleophobicity for oil-in-water separation

The discharge of oily wastewater has increased dramatically and will bring serious environmental problems. In this work, a self-cleaning and anti-fouling g-C₃N₄/TiO₂/PVDF composite membrane was fabricated via the layer-by-layer approach. The surface of as-prepared composite membrane displayed a superhydrophilic and underwater superoleophobic behavior under irradiation with visible light. Also, upon irradiation with visible light, the fabricated g-C₃N₄/TiO₂/PVDF composite membrane displayed enhanced permeation flux and improved oil removal efficiency as a result of the generation of hydroxyl free radicals during the photocatalytic filtration process. Significantly, irradiation with visible light remarkably improved reusability of the composite membrane by initiating photocatalytic decomposition of deposited oil foulants, which enabled removal of over 99.75% of oils, thus reaching a nearly 100% flux recovery ratio. Furthermore, the g-C₃N₄/TiO₂/PVDF composite membrane exhibited great anti-fouling behavior in photocatalysis-assisted filtration. The mechanistic study revealed that underwater superhydrophobicity and the generation of free hydroxyl radicals jointly contributed to membrane anti-fouling. The greatest advantages of this g-C₃N₄/TiO₂/PVDF composite membrane are that not only does it degrades the oil pollutants, but it also makes the membrane less vulnerable to fouling.

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.

A review of self-cleaning photocatalytic surface: Effect of surface characteristics on photocatalytic activity for NO

Self-cleaning surface has attracted much attention in the field of photocatalytic degradation of NO due to its dirt pickup resistance and self-cleaning effect under the action of rainwater. In this review, the factors affecting NO degradation efficiency were analyzed in terms of photocatalyst characteristics and environmental conditions combined with the photocatalytic degradation mechanism. The feasibility of photocatalytic degradation of NO on superhydrophilic, superhydrophobic and superamphiphobic surfaces was discussed. Furthermore, the effect of special surface characteristics of self-cleaning on photocatalytic NO was highlighted and the improvement of the long-term effect using three self-cleaning surfaces on photocatalytic NO was evaluated and summarized. Finally, the conclusion and outlook were proposed related to the self-cleaning surface for photocatalytic degradation of NO. In future research, the comprehensive effects of the characteristics of photocatalytic materials, self-cleaning characteristics and environmental factors on the photocatalytic degradation of NO and the actual application effects of such self-cleaning photocatalytic surfaces should be further clarified in combination with the engineering. It is believed that this review can provide some theoretical basis and support for the development of self-cleaning surfaces in the field of photocatalytic degradation of NO.

Removing of cationic dyes using self-cleaning membranes-based PVC/nano-cellulose combined with titanium aluminate

This research used the phase inversion approach to construct polyvinyl chloride nanocellulose@titanium aluminate nanocomposite membranes (PVC/NC@TALCM) to adsorb and filter dye from wastewater. FTIR, XRD, and SEM were used to determine the adsorptive nanocomposite membrane that had been synthesized. The thermal and electrical properties measurements were carried out using a static system. The influence of several adsorbent dosages, pH, and dye concentrations on the nanocomposite membrane's adsorption ability was investigated. Using a dead-end filtration system, the PVC-NC@TALCM was evaluated as a pressure filtration membrane system. It was found that 98.6% of MB dye was removed by PVC-NC@TALCM membrane, which was loaded with 5% titanium aluminate at pH 10. The kinetic adsorption studies indicated that the adsorption of MB onto the PVC-NC@TALCM nanocomposite membrane obeys pseudo-second-order that indicates the chemosorption process. The isotherm data were described using Freundlich and Langmuir models, and the Freundlich isotherms were shown to be more closely match the experimental data than the Langmuir model. Finally, the PVC-NC@TALCM nanocomposite membrane was economical, environmentally friendly, and self-cleaning.

Self-cleaning and photocatalytic properties of eco-friendly clay-based facing bricks from industrial and natural wastes

In this study, self-cleaning and photocatalytic performance of clay-based facing bricks produced using two different wastes (red mud: RM, hazelnut shell: HS) under visible light by an organic pollutant, methylene blue (MB), were discussed. The results revealed that the incorporation of waste into the samples improved the photocatalytic activity for certain ratios and also provided the desired physical properties according to the relevant standards. In terms of self-cleaning performance, the best results were obtained from the samples containing 5% RM (RM5HS) and 10% RM (RM10HS) combined with 10% of HS by weight. While RM10HS with an apparent reaction rate of 2.99 × 10^-1 h^-1 achieved total removal efficiency of 89.74%, RM5HS with an apparent reaction rate of 2.82 × 10^-1 h^-1 was able to remove 91.21% of initial concentration of MB dye.

Friction force-based measurements for simultaneous determination of the wetting properties and stability of superhydrophobic surfaces

HYPOTHESIS

Contact angle and sliding angle measurements are widely used to characterize superhydrophobic surfaces because of the simplicity and accessibility of the technique. We hypothesize that dynamic friction measurements, with increasing pre-loads, between a water drop and a superhydrophobic surface is more accurate because this technique is less influenced by local surface inhomogeneities and temporal surface changes.

EXPERIMENTS

A water drop, held by a ring probe which is connected to a dual-axis force sensor, is sheared against a superhydrophobic surface while maintaining a constant preload. From this force-based technique, static and kinetic friction forces measurements are used to characterize the wetting properties of the superhydrophobic surfaces. Furthermore, by applying increased pre-loads to the water drop while shearing, the critical load at which the drop transitions from the Cassie-Baxter to Wenzel state is also measured.

FINDINGS

The force-based technique predicts sliding angles with reduced standard deviations (between 56 and 64%) compared to conventional optical-based measurements. Kinetic friction force measurements show a higher accuracy (between 35 and 80%) compared to static friction force measurements in characterizing the wetting properties of superhydrophobic surfaces. The critical loads for the Cassie-Baxter to Wenzel state transition allows for stability characterization between seemingly similar superhydrophobic surfaces.

Construction of Self-Assembly Based Tunable Absorber: Lightweight, Hydrophobic and Self-Cleaning Properties

Although multifunctional aerogels are expected to be used in applications such as portable electronic devices, it is still a great challenge to confer multifunctionality to aerogels while maintaining their inherent microstructure. Herein, a simple method is proposed to prepare multifunctional NiCo/C aerogels with excellent electromagnetic wave absorption properties, superhydrophobicity, and self-cleaning by water-induced NiCo-MOF self-assembly. Specifically, the impedance matching of the three-dimensional (3D) structure and the interfacial polarization provided by CoNi/C as well as the defect-induced dipole polarization are the primary contributors to the broadband absorption. As a result, the prepared NiCo/C aerogels have a broadband width of 6.22 GHz at 1.9 mm. Due to the presence of hydrophobic functional groups, CoNi/C aerogels improve the stability in humid environments and obtain hydrophobicity with large contact angles > 140°. This multifunctional aerogel has promising applications in electromagnetic wave absorption, resistance to water or humid environments.

Sodium alginate/chitosan-coated TiO2NPs hybrid fiber with photocatalytic self-cleaning property, UV resistance and enhanced tensile strength

SA/CS-coated TiO₂NPs hybrid fibers with photocatalytic self-cleaning properties, UV resistance and enhanced tensile strength were successfully prepared by adding CS-coated TiO₂NPs to SA matrix. The FTIR and TEM results demonstrate the successful preparation of CS-coated TiO₂NPs core-shell structured composite particles. SEM and Tyndall effect results showed that the core-shell particles were uniformly dispersed in the SA matrix. When the content of Core-shell particles increased from 0.1 to 0.3 wt%, the tensile strength of SA/CS-coated TiO₂NPs hybrid fibers increased from 26.89 to 64.45 % compared with SA/TiO₂NPs hybrid fibers. The SA/CS-coated TiO₂NPs hybrid fiber (0.3 wt%) exhibits excellent photocatalytic degradation performance, achieving a 90 % degradation rate for the RhB solution. And the fibers also exhibit outstanding photocatalytic degradation performance towards various dyes and stains commonly encountered in daily life, including methyl orange, malachite green, Congo red, coffee and mulberry juice. The UV transmittance of the SA/CS-coated TiO₂NPs hybrid fibers decreased significantly from 90 % to 75 % with the increase in core-shell particle addition, and correspondingly, the UV absorption capacity increased. The SA/CS-coated TiO₂NPs hybrid fibers prepared lay the groundwork for potential applications in various fields, including textiles, automotive engineering, electronics and medicine.

Electronic structure and optical properties of Br- and Cl-doped rutile TiO2 for application in self-cleaning and photovoltaic panel's coatings: first-principle calculations

Development of novel self-cleaning technologies, especially those based on semiconductor photocatalysis system, is one of the most important research problems in environmental cleanup. Titanium dioxide (TiO₂) is a well-known semiconductor photocatalyst that has a strong photocatalytic activity in the ultra-violet part of the spectrum while its photocatalytic efficiency is very limited within the visible range due to its large band gap. In the field of photocatalytic materials, doping is an efficient method to increase the spectral response and promote charge separation. However, the type of dopant is not the only important factor, but also its position in the material lattice. In the present study, we have carried out first-principle calculations based on density functional theory to explore how particular doping configuration, such as Br or Cl doping at an O site, may influence the electronic structure and the charge density distribution within rutile TiO₂. Furthermore, optical properties such as the absorption coefficient, the transmittance, and reflectance spectra have also been derived from the calculated complex dielectric function and examined to see whether this doping configuration has any effect on the use of the material as a self-cleaning coating on photovoltaic panels.

A high-sensitivity high-resolution intravascular photoacoustic catheter through mode cleaning in a graded-index fiber

Intravascular photoacoustic imaging has been developed to evaluate the possibility of plaque rupture in atherosclerosis by high spatial resolution imaging of lipid. However, the detection sensitivity and spatial resolution are compromised by the poor focusing caused by a multimode fiber. In this work, we report an intravascular photoacoustic catheter with mode self-cleaning in a graded-index fiber to improve the beam quality and the sensitivity for lipid detection. Compared with the higher-order modes in a step-index multimode fiber, the lower-order modes generated by the self-cleaning effect in the graded-index fiber greatly enhanced the photoacoustic spatial resolution and detection sensitivity. The dominant ringing artifact caused by laser absorption of the ultrasound transducer was further reduced by using stripe suppression. A lipid plaque mimicking phantom was imaged for evaluation. Lipid particles with a small diameter of 75.7 µm were clearly observed.

Flexible biomimetic materials with excellent photothermal performance and superhydrophobicity

Although thousands of superhydrophobic composites have been reported, it is still a challenge to develop eco-friendly superhydrophobic materials by a simple and low-cost strategy. Here, a paper-based superhydrophobic material was prepared by carbon fiber powders and polydimethylsiloxane through a facile spraying method. This obtained material has excellent liquid resistance and self-cleaning properties, whose contact angle reaches 155°. In addition, it possesses excellent photothermal conversion characteristics with a stable surface temperature of 73.4 °C and good water evaporation performance with an evaporation rate up to 1.08 kg/(m2·h) under one solar intensity (100 mW/cm2). Also, it has outstanding self-deicing performance, whose deicing time is 120 s earlier than that of the untreated surface under one solar intensity. An adaptability test shows this strategy of functional coatings can also be applied to other fiber substrates (coating paper, kraft paper, non-woven fabric, paulownia veneer, etc.). Overall, this superhydrophobic material has a promising application prospect in many fields such as waterproof packaging, deicing materials, water evaporation materials, etc.

Silicon carbide catalytic ceramic membranes with nano-wire structure for enhanced anti-fouling performance

Membrane fouling is a critical challenge for current ceramic membranes, which suffer from low flux and insufficient removal. Development of self-cleaning catalytic ceramic membranes is promising to address this challenge. Herein, we design heterogeneous silicon carbide ceramic membranes featuring a novel structure of g-C₃N₄-decorated β-SiC nano-wire catalytic functional layer, which enables enhanced anti-fouling self-cleaning performance. At chemical harsh (alkaline or especially acidic) conditions, the nano-wire membrane exhibits catalysis-enhanced removal performance for organic contaminants. Unlike conventional particle-packing membrane structure, such a nano-wire network membrane structure has not only high porosity (56.1%), but exceptional water permeance (110 L·m^-2·h^-1·bar^-1) and removal (100%) of organic substance under simulated sunlight, outperforming state-of-the-art organic membranes and ceramic membranes. Superoxide radical (∙O₂^-) was experimentally confirmed to be major reactive species responsible for self-cleaning function. We also propose a catalytic mechanism model with radical formation pathway, enabled by the as-formed g-C₃N₄@β-SiC heterojunction structure with reduced electron-hole recombination. This work would provide new insights into not only rational design of next-generation ceramic membranes with self-cleaning function but also more applications of efficient treatment of refractory wastewaters containing degradable organic substances by using such membranes.

Highly efficient removal of organic contaminant with wide concentration range by a novel self-cleaning hydrogel: Mechanism, degradation pathway and DFT calculation

A novel carbon nitride based self-cleaning hydrogel photocatalyst (KI-PCN gel, potassium and iodine co-doped carbon nitride confined in alginate) has been successfully constructed by a facile method. Fabricated photocatalyst showed enhanced synergistic adsorption-photocatalytic degradation property on a high concentration of methylene blue (HMB) because of enhanced carrier separation efficiency and improved light adsorption capacity of KI-PCN. As expected, the KI-PCN gel showed the highest apparent rate constant value ₍K_app =0.0310 min^-1), which was about 38.8 and 5.8 times as that of blank hydrogel (K_app=0.0008 min^-1) and PCN gel (K_app=0.0053 min^-1), respectively. Meanwhile, KI-PCN gel can continuously adsorb low concentration of MB (LMB), and the MB-adsorbed KI-PCN gel can self-clean under light irradiation. The bench-scale experiments simulating real river showed that KI-PCN gel can effectively and continuously remove LMB (0.1-20 ppm), indicating the possibility for the removal of contaminants in natural rivers. Furthermore, the possible degradation pathways were proposed by combining the density functional calculations (DFT) and intermediates identified by liquid chromatography-mass spectrometry (LC-MS). This work proposed a new perspective to acquire a novel self-cleaning and easily recyclable photocatalyst for treatment of wide concentration range organic wastewater as well as remediation of natural waterbody.

Wodyetia bifurcate structured carbon fabrics with durable superhydrophobicity for high-efficiency oil-water separation

The superhydrophobic fiber-based membranes with features of high separation efficiency and low energy consumption for oil-water separation remains a formidable challenge. In this paper, a robust and durable superhydrophobic cotton-derived carbon fabric (CDCF) with wodyetia bifurcate-like structure is fabricated via in situ cobalt-nickel basic carbonate (CNC) deposition and 1 H, 1 H, 2 H, 2 H-perfluorooctyltriethoxysilane (POTS) coating. The combined action of rough surface structure and low surface energy makes CDCF/CNC/POTS with superhydrophobicity/superoleophilicity, anti-wetting, and self-cleaning performance. Intriguingly, the CDCF/CNC/POTS can keep its superhydrophobicity under of the water droplet impact pressure of 781 Pa. In addition to its robust dynamic superhydrophobicity, CDCF/CNC/POTS can also maintain its non-wetting property under harsh environmental conditions such as mechanical abrasion treatment, acidic, alkaline and salt solutions, and ultraviolet radiation. Importantly, the CDCF/CNC/POTS can separate various oil-water mixtures and emulsions under gravity with ultrahigh oil-water mixtures permeate flux (∼19,126 L/m²h), high surfactant-stabilized emulsion permeate flux (∼821 L/m²h), and high separation efficiency (> 98.60 %). Moreover, remarkable recyclability endow the CDCF/CNC/POTS with promising application in treating oily wastewater. This work may benefit the low-cost mass production of cotton-based carbon fabrics for developing eco-friendly high-efficiency separators.

Crosslinked biomimetic coating modified stainless-steel-mesh enables completely self-cleaning separation of crude oil/water mixtures

The development of high-flux, durable and completely self-cleaning membranes is highly desired for separation of massive oil/water mixtures. Herein, differently crosslinked poly(2-methacryloyloxylethyl phosphorylcholine) (PMPC) brush grafted stainless steel mesh (SSM) membranes (SSM/PMPCs) were fabricated by integrating of mussel inspired universal adhesion and crosslinking chemistry with surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (SI-ARGET-ATRP). The durability and self-cleaning performance of the prepared SSM membranes were evaluated by separating sticky crude oil/water mixtures in a continuous recycling dead-end filtration device. The water filtration flux driven by gravity reached 60,000 L⋅m^-2⋅h^-1 with a separation efficiency of over 99.98%. Furthermore, zero-flux-decline was observed during a 5 h continuous filtration when assisted by mechanical stirring. More significantly, such a completely self-cleaning separation of the well crosslinked SSM/PMPC2 membrane under optimized flux and stirring conditions had been operated cumulatively for 190 h in 30 days without any additional cleaning. These significant advances are more promising for practical applications in crude oil-contaminated water treatments and massive oil/water mixture separation.

Mouthpart adaptations of antlion larvae facilitate prey handling and fluid feeding in sandy habitats

Antlion larvae are fluid-feeding ambush predators that feed on arthropods trapped in their funnel-shaped pits built in sandy habitats; however, details are lacking about their feeding mechanism. Here we tested the hypothesis that the antlion, Myrmeleon crudelis, has adaptations that facilitate fluid feeding in sandy habitats. We measured contact angles of water droplets and used the capillary-rise technique to assess mouthpart wettability. A structural organization was discovered that provides a hydrophobic-hydrophilic wetting dichotomy that would simultaneously support self-cleaning and fluid uptake and is enabled by antiparallel movements of the maxillae. The mouthparts also are augmented by their mechanical properties, including maxillae and mandible tips that might be heavily sclerotized, as determined by confocal microscopy, which likely facilitate piercing prey. Our findings provide insight on how antlion larvae have overcome the challenges of fluid feeding in sandy habitats, which likely contributed to their success and widespread distribution.

Photocatalytic nanohybrid membranes for highly efficient wastewater treatment: A comprehensive review

Wastewater is inevitably generated from human activities as part of the life cycle chain that potentially damages the environment. The integration of photocatalytic reaction and membrane separation for wastewater treatment has gained great attention in recent studies. However, there are still many technical limitations for its application such as toxic metal release, catalyst deactivation, fouling/biofouling, polymer disintegration, and separation performance decline. Different types, combinations, and modifications of photocatalysts material combined with membranes such as semiconductor metal oxides, binary/ternary hybrid metal oxides, elemental doped semiconductors, and metal-organic frameworks (MOFs) for improving the performance and compatibility are presented and discussed. The strategies of incorporating photocatalysts into membrane matrix for pursuing the most stable membrane integrity, high photocatalytic efficiency, and excellent perm-selectivity performance in the very recent studies were discussed. This review also outlines the performance enhancement of photocatalytic membranes (PMs) in wastewater treatment and its potential for water reclamation. Photocatalysts enhanced membrane separation by inducing anti-fouling and self-cleaning properties as well as antibacterial activity. Based on the reviewed study, PMs are possible to achieve complete removal of emerging contaminants and ∼99% reduction of bacterial colony that leading on the zero liquid discharge (ZLD). However, the intensive exposure of photo-induced radicals potentially damages the polymeric membrane. Therefore, future studies should be focused on fabricating chemically stable host-membrane material. Moreover, the light source and the membrane module design for the practical application by considering the hydrodynamic and cost-efficiency should be a concern for technology diffusion to the industrial-scale application.

Dye decomposition and air de-pollution performance of TiO2/SiO2 and N-TiO2/SiO2 photocatalysts coated on Portland cement mortar substates

In this study, the newly synthesized TiO₂ and N doped TiO₂ clusters were added to silica sol to synthesize N-TiO₂/SiO₂ composites via the sol-gel method. Afterwards, the prepared sols were applied by brushing on portland cement. Doping with nitrogen significantly increased the absorption of TiO₂ towards the visible region, thus, increasing the photocatalytic activity. SEM characterization of the treated samples showed that the clusters were distributed in form of aggregates on the samples' surface. The self-cleaning and air de-polluting performances were assessed through methylene blue degradation and the oxidation of nitrogen oxide, resulting in methylene blue (MB) removal of 85% and 78% after 60 min of irradiation for SN10TiO₂ and STiO₂, respectively. Regarding air de-pollution performance, the newly synthesized photocatalysts showed the ability of NOx reduction. However, their efficiency was somewhat lower, in which 23.81% of NO has been oxidized by the sample SN10TiO₂, while SP25 showed a total NO conversion of 38.98%. The powdered xerogels of the newly synthesized nanoparticles revealed high photocatalytic efficiency concerning NO oxidation, resulting in a higher performance compared to those obtained by the xerogel containing P25.

Large-scale preparation of a versatile bioinspired sponge with physic-mechanochemical robustness for multitasking separation

Developing novel biomaterials integrating robustness and multitasking separation performance are of importance. However, those were limited in application due to the expensive, time-consuming and complex fabrication process. In this work, with the inspiration from high porosity and surface area of natural materials, the porous superhydrophobic melamine sponges (SMS) coated hydrophobic TiO₂ and epoxy copolymer were fabricated via a facile, inexpensive, eco-friendly and large-scale strategy. The SMS showed excellent superhydrophobic property, and could well resist the harsh mechanical damage, chemical corrosion, extreme temperature, and irradiation of UV without losing antiwetting ability. Besides, it displayed selective oil absorbing ability, recyclability, and self-cleaning ability. Moreover, the SMS displayed superior multitasking performance for continuous oil/water separation, surfactant-stabilized O/W emulsions separation (separation efficiency above 99%), and bacterial/fungus containing filtration (filtration efficiency over 60% for S. aureus, 90% for E. coli and C. albicans). With the multifaceted features, the SMS is a promising sponge material for treatment of industry oily or bacterial/fungus-containing wastewater in practical application.

Defective MOFs-based electrocatalytic self-cleaning membrane for wastewater reclamation: Enhanced antibiotics removal, membrane fouling control and mechanisms

In order to resolve the poor antibiotics rejection and serious fouling of ultrafiltration (UF) membrane during municipal wastewater reclamation, a novel anodic membrane (defective UiO-66 (D-UiO-66)/Graphite/Polyvinylidene fluoride (PVDF)) with high pure water flux (596.1 L•h ^- 1•m ^- 2•bar^-1) was fabricated by incorporating defective zirconium based metal-organic framework (D-UiO-66) and conductive graphite particles into PVDF matrix and applied in the coupling of electro-oxidation and membrane filtration process. Compared to the other anodic membranes (i.e., Graphite/PVDF and UiO-66/Graphite/PVDF), D-UiO-66/Graphite/PVDF possesses superior anti-fouling and self-cleaning abilities (flux recovery=100%, model foulant: bovine serum albumin) in both intermittent and continuous supply of electric field under current density of 0.01 mA/cm²; moreover, efficient antibiotics (tetracycline, norfloxacin, tylosin and sulfamethoxazole) removal (> 96.6%) and bactericidal efficiency against E. coli and S. aureus (100%) were achieved simultaneously without the addition of chemical reagents due to the higher electrocatalytic activity of anodic membrane for oxidation of pollutants by •OH and •O₂^- free radicals. Three degradation pathways of antibiotics were proposed and the self-cleaning mechanism of membrane was dominated by the synergy of the partial mineralization and the reduced fouling potential of foulants after oxidation as revealed by the increase in hydrophilicity, and decrease in negative charge and molecular weight. The fabricated membrane also presents excellent electrochemical stability, separation and self-cleaning performance for treatment of municipal secondary effluent during long-term filtration with low electric energy consumption, which is promising in wastewater reclamation.

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.

Effect of dust and methods of cleaning on the performance of solar PV module for different climate regions: Comprehensive review

Recent achievement and progress in solar PV play a significant role in controlling climate change. This study reviewed comprehensively electrical characteristics, life cycle of dust, optical characteristics, and different cleaning techniques related to the effect of dust on the performance of PV modules throughout different climate regions of the world. The power maximum power point (MPP) and curve of PV module under the effect of irradiance and temperature were presented. The effect of dust (shading) on the electrical efficiency of PV module was discussed based on soft, partial, and complete (soiling) shading. The physical properties of dust around the globe such as PM₁₀ concentration, dust loading (mgm^-2), and fine dust particles concentration were covered and discussed. Reasons behind the accumulation of dust based on, location and installation factors, dust type, and environmental factors. Environmental reasons causing dust and dust removal in accordance with the life cycle of dust was covered in detail. All the reasons that cause the generation, accumulation and removal of dust during its life cycle were explained. All forces responsible for the adhesion phase of the dust life cycle were presented. The effect of dust on PV module transmittance and electrical parameters module were discussed in detail based on physical properties of the dust at its location and installation conditions. Self-cleaning super hydrophobic surfaces based on methods such as solvents, vapor-assisted coating, powder coating, and polymerization were discussed. All cleaning technologies, including self-cleaning technologies, based on the material coating used, and the manufacturing of PV cells was compared. The future prospective for PV technologies and cleaning methods were also covered.

Fabrication of silver vanadate quantum dots/reduced graphene oxide/graphitic carbon nitride Z-scheme heterostructure modified polyvinylidene fluoride self-cleaning membrane for enhancing photocatalysis and mechanism insight

The enhancement of the self-cleaning ability of photocatalytic membranes and their degradation efficiency over tetracycline (TC) still remains a challenge. In this study, an alternative silver vanadate quantum dots (AgVO₃ QDs) doped reduced graphene oxide (RGO) and graphitic carbon nitride (C₃N₄) nanocomposites modified polyvinylidene fluoride (PVDF) membrane (AgVO₃/RGO/C₃N₄-PVDF) was successfully fabricated to enhance the photocatalytic activity. The AgVO₃/RGO/C₃N₄ nanocomposites were functioned as the active component for the photocatalytic membrane. The unique Z-scheme heterostructure of AgVO₃/RGO/C₃N₄ and the porous PVDF framework synergistically enhanced the separation and transport efficiency of photogenerated carriers and facilitated the interaction between the photocatalyst and the pollutant. As a result, the degradation efficiency of TC for the AgVO₃/RGO/C₃N₄-PVDF reached 88.53% within 120 min, which was higher than those of the binary component membranes (64.8% for RGO/C₃N₄-PVDF and 79.18% AgVO₃/C₃N₄-PVDF). In addition, AgVO₃/RGO/C₃N₄-PVDF exhibited high permeability (1977 L·m^-2·h^-1·bar^-1) and excellent antifouling activity. Under visible-light irradiation, the flux recovery rate (FRR) increased from 92.4% to 99.1%. Furthermore, AgVO₃/RGO/C₃N₄-PVDF could reject 97.4% of Escherichia coli (E. coli) owning to its self-cleaning capacity, and eliminated the E. coli under visible-light irradiation trough the photogeneration of h⁺. This study highlights a highly efficient photocatalytic membrane based on a Z-scheme heterostructure, which may have a great potential application in practical wastewater treatment.

Honeycomb-like cobalt hydroxide nanosheets induced basalt fiber fabrics with robust and durable superhydrophobicity for anti-icing and oil-water separation

The fiber-based membranes with superhydrophobic/superoleophilic features are highly desirable for oil-water separation applications. Herein, a superhydrophobic/superoleophilic basalt fiber fabric is constructed by using a general strategy of surface KMnO₄ pre-oxidation, honeycomb-like cobalt hydroxide nanosheets in-situ deposition, and hydrophobization. The influence of morphology change on wettability and roughness of the fabric surface were investigated. Benefiting from the dual-scale micro-/nanostructures, the obtained composite fabric has outstanding superhydrophobicity (water contact angle > 161°) and sustains non-wettability against multifarious food liquids. Meanwhile, the fabric displays substantial superhydrophobic durability during sandpaper abrasion, tape-peeling, and bending treatment. Moreover, the fabric also demonstrates excellent anti-wetting, self-cleaning and anti-icing performance. With these properties, the fabric has outstanding separation efficiencies (> 99.31%) and recyclability for various oil-water mixtures and emulsions under gravity. Therefore, this work provides an idea for development of superhydrophobic fabrics with potential application in the rapid treatment of oily wastewater.

Annealing temperature variation and its influence on the self-cleaning properties of TiO2 thin films

Titanium dioxide (TiO2) is an important material in science and engineering because of its basic and synthetic properties. Nevertheless, there is a dearth of reports in the open literature focusing on its ability to self-clean under temperature changes. In this study, we used the spin coating technique to produce TiO2 thin films to evaluate its self-cleaning ability after annealing at different temperatures. The TiO2 sol was obtained through an endothermal sol-gel process, and the gel was coated on a glass substrate using a spin coater. The deposited films were then annealed at 400 °C, 600 °C, and 800 °C for 1 h. The influence of annealing temperature variation on the self-cleaning properties of the thin film was characterized using X-ray diffraction, scanning electron microscope; Fourier transformed infrared spectrometric analysis and UV-vis spectrophotometer. A test to ascertain self-cleaning was conducted using the degradation of methylene blue, and the different films were tested for durability. The durability test confirmed the connection between solid coating and substrate at all annealing temperatures. Thin films annealed at 600 °C revealed the best self-cleaning properties. The morphological analysis revealed snowflake shapes uniformly distributed over the substrate at 400 °C, and agglomeration improved as the annealing temperature increased. Structural analysis showed an increase in crystallinity with an increase in annealing temperature for both rutile and anatase phases. At three different temperatures, the chemical bond and the absorption band pattern followed the same path, although the peak intensity declined with temperature rise. Finally, the optical bandgap of the thin coated TiO2 declined from 3.39 eV to 3.20 eV as the binding temperature increased from 400 to 800 °C.

Superhydrophobic and deacidified cellulose/CaCO3-derived granular coating toward historic paper preservation

Deacidification and surface self-cleaning are of great significance for the long-term preservation of historic literature. Herein, a superhydrophobic self-cleaning coating, derived from nanocellulose coated with CaCO₃ particles is constructed via chemical vapor deposition (CVD) for the first time for the preservation of historic paper. The static contact angle of superhydrophobic paper reached more than 150° and the minimum sliding angle was 6.4°. Deacidification effect was achieved with a desired pH value in the range from 7.50 to 7.77 and the maximum alkali storage was up to 1.235 mol/kg. It is found that the low-cost CaCO₃ nanoparticles can not only remove the acid substances, but also gave the paper function of self-cleaning, which is very great significant for the protection of paper-based relics.

Bioinspired micro/nano structured aluminum with multifaceted applications

Inspired by many biological systems such as lotus leaves, insect wings and rose petals, great attention has been devoted to the study and fabrication of artificial superhydrophobic surfaces with multiple functionalities. In the present study, a simple and ecological synthesis route has been employed for large scale fabrication of self-assembled, sustainable nanostructures on unprocessed and micro imprinted aluminum surfaces named 'Nano' and 'Hierarchy'. The processed samples show extreme wettability ranging from superhydrophilicity to superhydrophobicity depending on post-processing conditions. The densely packed ellipsoidal nanostructures exhibited superhydrophobicity with excellent water, bacterial and dust repellency when modified by low surface energy material 1H,1H,2H,2H-perfluorooctyltriethoxysilane (FOTES), characterized by a static contact angle of 163 ± 1° and contact angle hysteresis (CAH) ~3°. These coated surfaces show significant corrosion resistance with current density of 6 nA/cm² which is 40 times lower than unprocessed counterpart and retain chemical stability after prolonged immersion in corrosive media. These surfaces show excellent self-cleaning ability with significantly low water consumption (< 0.1 µl/mm²-mg) and prevent biofouling which ensures its applicability in biological environment and marine components. The nanostructured superhydrophilic aluminum shows maximum antibacterial activity due to disruption of cell membrane. This work can offer a simple strategy to large scale fabrication of multifunctional biomimetic metallic surfaces.

Hollow heterostructure design enables self-cleaning surface for enhanced polysulfides conversion in advanced lithium-sulfur batteries

Constructing interpenetrating heterointerface with reasonable interface energy barriers to improve electron/ion transport and accelerate the deposition/decomposition of lithium sulfide (Li₂S) is an effective method to improve the electrochemical performance of lithium-sulfur (Li-S) batteries. Herein, NiCoO₂/NiCoP heterostructures with hollow nanocage morphology are prepared for efficient multifunctional Li-S batteries. The hollow nanocage structure exposes abundant active sites, traps lithium polysulfides and inhibits the shuttle effect. The NiCoO₂/NiCoP heterostructure, combing strong adsorption capacity of NiCoO₂ and excellent catalytic ability of NiCoP, facilitates the process of anchoring-diffusion-transformation of polysulfides. The successful construction of heterostructures reduces the reaction barrier, accelerating the lithium ion (Li⁺) diffusion rate and thus effectively enhancing the redox reaction kinetics. More importantly, NiCoO₂/NiCoP heterostructure plays a role in self-cleaning that minimizes solid sulfur species accumulation to maintain surface clean during long cycling for a continuously catalysis of the polysulfides conversion reactions. With the merit of these features, the NiCoO₂/NiCoP modified separator exhibits excellent cycling stability with a low capacity decay of 0.043% per cycle up to 1000 cycles at 2 C. The design of NiCoO₂/NiCoP hollow nanocage heterostructures offers a new option for high-performance electrochemical energy storage devices.

Bioinspired engineering protein nanofibrils-based multilayered self-cleaning membranes for universal water purification

Proteinaceous materials are promising for membranes due to greater mechanical strength, in-built functionalities, amphiphilicity and high molecular loading capacity. Herein, a novel strategy of functionalization of silk nanofibrils with metal oxyhydroxide and fabrication of ultrafast permeable multi-layered and self-cleaning membrane was demonstrated. Typically, 1.9 µm thick multilayered membrane efficiently purifies macromolecules, dyes, pharmaceutical, surfactants and oil-water emulsion contaminated wastewater with rejection rate > 89% with the flux rate > 883 Lm²h^-1. Further, the potential of the multilayered membrane was tested for series of different feed concentrations of fluoride and As (V) to validate the commercial applicability of the multilayered membranes for industry wastewater. Notably, even at higher concentration of 10-30 mgL^-1, >96% for fluoride and >87% for As (V) rejection was obtained. Furthermore, the functionalized multilayered membrane exhibited outstanding performance for fluoride removal in real water streams, where, it purifies approximately 4710 L.m^-2 in two consecutive cycles, before the quality of the effluents no longer meets WHO criteria. However, the remarkable separation efficiency principally attributed to adsorption sites on the surface of the membrane. Thus, various regeneration strategies were established based on the nature of pollutants. More importantly, photocatalytic Fenton-like reaction assisted self-cleaning property of the multilayered membrane is demonstrated for regeneration of organic fouled membrane. Overall, the present multilayered membrane exhibits superior performance in purifying organic, inorganic contaminated water and oil-water emulsion with excellent recyclability; hence, envisaged its application for Universal water purification.

Multifunctional nanofibrous membranes with sunlight-driven self-cleaning performance for complex oily wastewater remediation

Developing multifunctional, efficient and durable membrane for long-term usage for treating complex oily wastewater is highly desirable but still a challenge due to the severe membrane fouling. Herein, a hierarchical structured superhydrophilic/underwater superoleophobic nanofibrous with antifouling and visible-light-induced self-cleaning performance was manufactured by a facile combination of electrospun silver/β-cyclodextrin/polyacrylonitrile (Ag/β-CD/PAN) nanofibers and then the in-situ growth of a zinc oxide (ZnO) layer. The formed micro/nano sized hierarchical structure greatly increased the roughness and improved the underwater superoleophobic ability of the membrane. Therefore, the resultant ZnO/Ag/β-CD/PAN membrane displays splendid separation performance for oil/dye/water complex emulsions and high flux recovery (>90%). Meanwhile, the permeation flux of a variety of oil/water emulsions was higher than 619 L m^-2h^-1 with a separation efficiency above 99.7% under the action of gravity. Furthermore, the as-fabricated membrane exhibits excellent stability towards different harsh conditions (e. g. corrosive solution, high temperature, UV irradiation and ultrasound washing). The robust mechanical and chemical stability, outstanding separation capabilities as well as excellent flux recovery capabilities makes the self-cleaning membrane a good candidate for the remediation of complex oily wastewater.

Blow-spun nanofibrous composite Self-cleaning membrane for enhanced purification of oily wastewater

Membrane separation is one of the most effective strategies for water treatment. However, problems such as poor emulsion separation performance, single function and easy membrane fouling limit its application in dealing with complex wastewater. The synergistic treatment technology of adsorption and visible light catalysis is an efficient and environment-friendly method to degrade organic pollutants. Here, we report a simple method to fabricate Zeolitic Imidazolate Framework-8/Graphene oxide/Polyacrylonitrile (ZIF-8/GO/PAN) nanofibrous membranes and their multifunctional treatment capacity for complex wastewater. The construction of superhydrophilic and underwater superoleophobic surface structure has achieved excellent emulsion separation performance (with a maximum flux of 6779.66 L m^-2h^-1), visible light photocatalytic degradation (with an efficiency of 96.5% in 90 min) and antibacterial properties. Moreover, the fibrous membrane also shows good biosafety, and will not have toxic effects on aquatic organisms. These excellent performances endow this membrane with great potential in complex wastewater purification.

Photocatalytic, self-cleaning and antibacterial properties of Cu(II) doped TiO2

In the study, sol-gel based TiO₂ nanoparticles (NPs) were doped by Cu(II), and the surface of cotton fabric was coated with Cu-doped TiO₂ NPs to develop self-cleaning and antibacterial properties. Coffee stains were introduced on the modified cotton fabric and under suntest illumination; a decrease in the color of coffee stain was followed over time via K/S value to determine self-cleaning performance. The photocurrent in a photoelectrocatalytic reactor was measured to evaluate the photocatalytic effect of Cu(II) doping. TiO₂ NPs showed self-cleaning and antibacterial effects under UV-illuminated conditions. However, no effects were observed under dark (non-illuminated) conditions. The modified textiles with Cu(II) doped TiO₂ NPs showed antibacterial activity against E. coli under light and dark conditions. Under the 2 h illumination period, fluctuating color changes were observed on the raw cotton fabric, and stains remained on the fabric while 78% and 100% color removals were achieved in the cotton fabrics coated by Cu doped TiO₂ NPs in 1 h and 2 h, respectively.

Silver-based nanocomposite for fabricating high performance value-added cotton

Cotton is one of the most important cellulose fibers, but the absence of antimicrobial capacity along with the self-cleaning, UV protection and electric conductivity often frustrates its wider applications in many fields. Nanotechnology has provided new insights into the development of functional nanomaterials with unique chemical and physical properties. Silver has been effectively incorporated into the cotton fabrics as the antimicrobial agents due to the strong inhibitory and antimicrobial effects on a broad spectrum of bacteria, fungi and virus with low toxicity to human being. In this review, a variety of strategies have been summarized to load silver on cotton fabrics in situ or ex situ and to fabricate high performance value-added cotton fabrics with self-cleaning, UV protection, electric conductivity and antimicrobial capability depending on the synthesis of silver coating or silver-based nanocomposite coating.

Eco-friendly and superhydrophobic nano-starch based coatings for self-cleaning application and oil-water separation

High-performance nano-based superhydrophobic coatings have attracted tremendous attention in a wide range of sectors. As a biodegradable and low-cost natural polymer, starch nanoparticles (SNPs) exhibit significant potential for use in many advanced materials. However, nano-starch based superhydrophobic coatings have not yet been reported. Herein, SNPs/polydimethylsiloxane composites were applied to fabricate these coatings using an environmentally friendly approach. The coating exhibited superhydrophobic (water contact angle >152.0° and sliding angle <9.0°) and self-cleaning properties owing to the hierarchical micro and nanostructures formed by coralloid SNP aggregates combined with the low surface energy of the PDMS covering. Meanwhile, the strong adhesion of PDMS and chemical bonding of SNPs with PDMS endowed the coatings with mechanical and chemical robustness. The excellent oil-water separation abilities of the coating were also comprehensively confirmed. This coating shows the potential application in the development of eco-friendly self-cleaning materials and oily wastewater treatment.

Hydrophilic and underwater superoleophobic porous graphitic carbon nitride (g-C3N4) membranes with photo-Fenton self-cleaning ability for efficient oil/water separation

Due to the great fouling resistance property, (super)hydrophilic/underwater superoleophobic membranes are prevalent candidates for oil-polluted wastewater treatment. Even so, membrane fouling inevitably occurs during long-term operation. Therefore, it is of great significance to construct anti-fouling membranes with robust flux recovery. Herein, a polyvinyl pyrrolidone (PVP) coated porous potassium-doped g-C₃N₄ (PKCN) membrane was fabricated for the first time by vacuum filtration. The as-prepared membrane displays enhanced hydrophilicity and underwater superoleophobicity. The permeability of the membrane increased significantly after sonication treatment, which is attributed to the increased pore volume and small nanosheets size that shorten the transport pathway of water molecules. Importantly, owing to the high photo-Fenton activity, the PKCN membrane exhibits fast (within 15 min) and excellent flux recovery (96.5%) after the photo-Fenton cleaning process. Furthermore, after 10 repeated usages, the PKCN membrane still keeps stable permeability and excellent purification efficiency. This work opens a door for developing self-cleaning membranes with the superior anti-fouling ability for effective oil/water separation.