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In this review, several cost-effective thin-film coating methods, which include dip-coating, spin-coating, spray-coating, blade-coating, and roll-coating, are presented. Each method has its own set of advantages and disadvantages depending on the proposed application. Not all of them are appropriate for large-scale production due to their certain limitations. That is why the coating method should be selected based on the type and size of the substrate, including the thickness and surface roughness of the required thin films. The sol–gel method offers several benefits, such as simplicity in fabrication, excellent film uniformity, the capacity to cover surfaces of any size and over vast areas, and a low processing temperature. Nevertheless, these coating methods are somewhat economical and well managed in low-budget laboratories. Moreover, these methods offer thin films with good homogeneity and low-surface roughness. Furthermore, some other thin-film deposition methods, for instance, physical vapor deposition (PVD) and chemical vapor deposition (CVD), are also discussed. Since CVD is not restricted to line-of-sight deposition, a characteristic shared by sputtering, evaporation, and other PVD methods, many manufacturing methods favor it. However, these techniques require sophisticated equipment and cleanroom facilities. We aim to provide the pros and cons of thin-film coating methods and let the readers decide the suitable coating technique for their specific application.

Zinc oxide layers on soda-lime glass substrates were fabricated using the sol-gel method and the dip-coating technique. Zinc acetate dihydrate was applied as the precursor, while diethanolamine as the stabilizing agent. This study aimed to determine what effect has the duration of the sol aging process on the properties of fabricated ZnO films. Investigations were carried out with the sol that was aged during the period from 2 to 64 days. The sol was studied using the dynamic light scattering method to determine its distribution of molecule size. The properties of ZnO layers were studied using the following methods: scanning electron microscopy, atomic force microscopy, transmission and reflection spectroscopy in the UV-Vis range, and the goniometric method for determination of the water contact angle. Furthermore, photocatalytic properties of ZnO layers were studied by the observation and quantification of the methylene blue dye degradation in an aqueous solution under UV illumination. Our studies showed that ZnO layers have grain structure, and their physical–chemical properties depend on the duration of aging. The strongest photocatalytic activity was observed for layers produced from the sol that was aged over 30 days. These layers have also the greatest porosity (37.1%) and the largest water contact angle (68.53°). Our studies have also shown that there are two absorption bands in studied ZnO layers, and values of optical energy band gaps determined from positions of maxima in reflectance characteristics are equal to those determined using the Tauc method. Optical energy band gaps of the ZnO layer fabricated from the sol aged over 30 days are EgI = 4.485 eV and EgII = 3.300 eV for the first and second bands, respectively. This layer also showed the highest photocatalytic activity, causing the pollution to degrade 79.5% after 120 min of UV irradiation. We believe that ZnO layers presented here, thanks to their attractive photocatalytic properties, may find application in environmental protection for the degradation of organic pollutants.

In this work, a racetrack ring resonator (RTRR) integrated with a multimode interferometer (MMI) structure based on a silica–titania (SiO2:TiO2) platform is projected for refractive index sensing application. The typical ring resonator structure requires a gap of ~100 nm to 200 nm between the bus waveguide (WG) and the ring structure which makes it challenging to fabricate a precise device. Thus, the device proposed in this paper can be considered a “gapless” ring resonator structure in which the coupling of light between the ring and bus WG can be achieved via an MMI coupler. A minor change in the refractive index in the vicinity of the MMI structure can trigger a shift in the resonance wavelength of the device. Thus, this simple and fascinating structure can be employed as a refractive index sensor. The device’s sensitivity is ~142.5 nm/RIU in the refractive index range of 1.33 to 1.36 with a figure of merit (FOM) of 78.3. This simple device structure can potentially be fabricated via a low-cost and highly efficient sol–gel process and dip-coating method combined with the nanoimprint lithography (NIL) method.

The presented review summarizes recent studies in the field of electro conductive textiles as an essential part of lightweight and flexible textile-based electronics (so called e-textiles), with the main focus on a relatively simple and low-cost dip-coating technique that can easily be integrated into an existing textile finishing plant. Herein, numerous electro conductive compounds are discussed, including intrinsically conductive polymers, carbon-based materials, metal, and metal-based nanomaterials, as well as their combinations, with their advantages and drawbacks in contributing to the sectors of healthcare, military, security, fitness, entertainment, environmental, and fashion, for applications such as energy harvesting, energy storage, real-time health and human motion monitoring, personal thermal management, Electromagnetic Interference (EMI) shielding, wireless communication, light emitting, tracking, etc. The greatest challenge is related to the wash and wear durability of the conductive compounds and their unreduced performance during the textiles’ lifetimes, which includes the action of water, high temperature, detergents, mechanical forces, repeated bending, rubbing, sweat, etc. Besides electrical conductivity, the applied compounds also influence the physical-mechanical, optical, morphological, and comfort properties of textiles, depending on the type and concentration of the compound, the number of applied layers, the process parameters, as well as additional protective coatings. Finally, the sustainability and end-of-life of e-textiles are critically discussed in terms of the circular economy and eco-design, since these aspects are mainly neglected, although e-textile’ waste could become a huge problem in the future when their mass production starts.

In this study, undoped zinc oxide and cobalt-doped thin films were deposited on glass substrates using a sol–gel dip-coating technic. The effect of gamma irradiation on structural, morphological, and optical properties of the samples was investigated. Different analyses including X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Raman spectroscopy, UV–Vis spectrophotometry, and photoluminescence spectroscopy (PL) were applied to evaluate the physical changes due to gamma irradiation of the 60 Co gamma-ray source. Furthermore, the sensing performance of the samples toward ethylene glycol vapor was investigated before and after irradiation. The results revealed that under low and relatively long-term gamma irradiation, tangible effects on various physical properties (especially optical and sensing characteristics) can be observed. According to our data, in undoped zinc oxide, a higher sensitivity is observed (with an increase of 2.5 times), whereas in cobalt doped, the sensitivity is reduced (with a 1.8 times reduction). Highlights ZnO and ZnO:Co thin films have been prepared by the sol-gel dip coating method. Physical properties were examined by exposing to gamma irradiation for 40 days. Gamma irradiation effectively affected the optical properties of the samples. Ethylene glycol sensing of ZnO is increased by 2.5 times after irradiation.

This paper presents a review on dip-coating for fibrous materials, mainly concentrated on the mechanism, recently developed dip-coating methods and novel functional applications. The emphasis has been made here, to present theoretical basis of dip-coating-induced film deposition, especially, the reported works to predict the thickness based on various processing parameters. Different modified dip-coating techniques to fabricate deposited films for fibrous substrate have also been gathered. The scope of reviewed dip-coating methods are not only conventional solution and sol–gel-based dip-coating, but also recently developed vacuum-assisted, spin-assisted, photo-assisted and multi-layered dip-coating methods. An overview of reported and potential applications for coated fibrous materials has also been given, which mainly including self-cleaning, oil–water separation, conductive textiles, fibrous-based energy storage devices, and photonic crystals, etc. This review is intended to give readers a good horizon for the present status concerning variety of studies and applications related to dip-coating. An effort has been made here to report the important contributions in the area of dip-coating for fibrous substrate, and critical points regarding future research directions are outlined in the summary. Graphical Abstract

This article presents the microstructure (SEM) and corrosion behavior of ZnAl12Mg3Si0.3 (ZAMS) coatings obtained by the double hot-dip method on Sebisty steel with increased strength. On the basis of chemical composition studies in micro-areas (EDS) and phase composition studies (XRD), structural components of the coating and corrosion products formed on the coating surface after exposure to the neutral salt spray (NSS) test (EN ISO 9227) were identified. The presence of the Fe(Al,Si,Zn)3 intermetallic phase was found in the Fe-Al intermetallic layer, while in the outer layer, dendrites rich in Al and Zn were identified. In these dendrites, the eutectics of Zn/MgZn2 and precipitates of the MgZn2 phase and Si were located. The NSS test showed better corrosion resistance of ZAMS coatings compared to conventional zinc hot-dip coatings. The increase in corrosion resistance is due to the formation of favorable corrosion products: simonkolleite—Zn5(OH)8Cl2·H2O and hydrozincite—Zn5(OH)6(CO3)2, and the presence of the MgZn2 phase in the coating, which is more anodic than other structural components.

Traditional antifouling agents usually have a certain toxic effect on marine environments and non-target organisms. In this study, Dictyophora indusiata polysaccharide (DIP) was applied as a natural antifouling surface modifier to prepare the surface coating for marine antifouling. Three DIP coatings were prepared: D. indusiata spore polysaccharide (DISP), D. indusiata volva polysaccharide (DIVP), and D. indusiata embryonic body polysaccharide (DIEP). The antifouling, tribological, and anticorrosion behavior of the coatings were examined. Results revealed that the three kinds of DIP coatings had excellent antifouling properties, which could effectively prevent the adhesion of Chlorella and the attachment of water-based and oily stains on the surface. Additionally, the coatings showed great mechanical stability and could maintain an extremely low coefficient of friction (COF < 0.05) after continuous wear. The drag reduction rate of the coated surfaces reached 5%, showing a powerful lubrication performance. Furthermore, the DIP coatings presented an outstanding corrosion resistance, where the equivalent circuit impedances were 4–9 orders of magnitude higher than the control groups. This research showed a promising prospect of surface coating fabrication with DIP for marine devices to achieve the purpose of antifouling and drag reduction.

Developing flame-retardant, environment-friendly, sustainable functional textiles is highly desirable. Alginate fibers, typically as the calcium alginate, whose raw material is extracted from natural brown seaweed, possess excellent intrinsic flame retardancy, biocompatibility, and hydrophilicity. To overcome the problem of water-absorption-induced deformation of alginate fibers, superhydrophobic alginate fabrics were prepared by a one-step dip-coating process in hexadecyltrimethoxysilane (HDTMS) alcosol. Alginate fabrics treated with 3 wt% HDTMS alcosol exhibited excellent water repellence with an average contact angle of 158.2° and a sliding angle less than 10°. The surface morphology and chemical composition of alginate textiles treated with various HDTMS concentrations were thoroughly characterized. The mechanism of the one-step dip-coating strategy was explored. Superhydrophobic surface treatment improves the deformation resistance of alginate fabrics in water, which reveals no obvious change for 7 days with a swelling absorbency of 124.1%. Salt resistance of treated alginate fabrics was also enhanced. Due to the intrinsic flame retardancy of calcium alginate, the treated alginate fabrics possessed outstanding fire-proof behaviour with a limiting oxygen index value of 28.0. Notably, a decorative flower fabricated from treated fabrics showed good water resistance and flame retardancy, which broadens the application of alginate textile in the field of environment-friendly flame-retardant functional textiles.Graphic abstract

Superhydrophobic material involves the fabrication of appropriate roughness and low surface energy. Studies concerning enhancing the attachment between substrates and low surface energy material have been reported. Hence, it might also be feasible to make low surface energy material as an interface binder to enhance the attachment. In our work, the simple dip-coating method was used to fabricate polybenzoxazine (PBZ)/SiO 2 -coating cotton (PBZSC) fabric for rapid oil–water separation. The surface morphology and wettability of the PBZSC fabric as well as the properties of the separation were explored using various methods. These results demonstrated that PBZSC fabric not only had excellent thermal properties, but also maintained excellent superhydrophobicity (WCA > 150°) under various harsh conditions which was mainly attributed to higher surface roughness contributed by SiO 2 and lower surface energy, heat resistance as well as acid and alkali resistance from PBZ resin, respectively. More importantly, the separation conducted by the PBZSC fabric not only showed great recycle property, but also separated a series of oil and water mixtures with up to 96% separation efficiency. Therefore, it is anticipated that this low-cost PBZSC fabric will be readily and widely utilized in designing multifunctional membrane for large-area oil-spill cleanup without using fluoropolymers or silicones. Graphical abstract