Durability and corrosion behaviors of superhydrophobic amorphous coatings: a contrastive investigation

Superhydrophobic surfaces can be derived from roughening hydrophobic materials. However, the superhydrophobic surfaces with various micro/nano morphologies present variations of chemical and mechanical durability, which limits their practical applications. Very little actually is known about comparing durability and corrosion resistance of concave and convex superhydrophobic surface structures systematically. In this paper, two kinds of superhydrophobic AlNiTi amorphous coatings with concave and convex surfaces were obtained by chemical etching and hydrothermal methods, respectively. Benefiting from nanoscale sheet structure, the convex superhydrophobic coating displays higher water-repellence (contact angle = 157.6°), better self-cleaning performance and corrosion resistance. The corrosion current density of the convex superhydrophobic surface is approximately one order of magnitude smaller than the concave superhydrophobic surface. Besides, the long-term chemical stability and mechanical durability of both superhydrophobic surfaces were also investigated. The formation and damage mechanisms of these two kinds of superhydrophobic surfaces were proposed. It is hoped that these investigations could provide clear guidance for the real-world applications of superhydrophobic amorphous coatings.

Ionic Liquid-Assisted Fast Synthesis of Carbon Dots with Strong Fluorescence and Their Tunable Multicolor Emission

Conventional synthesis of carbon dots (CDs) mostly involves a hydrothermal or solvent-thermal reaction which needs relatively high temperature and pressure. In this work, ionic liquid is used to assist in fast synthesizing CDs with an ultrahigh photoluminescent quantum yield (98.5%) by heating at a low temperature (≤100 °C) and at atmospheric pressure. In addition, through this approach, tunable multicolor emissive CDs can be successfully achieved and used for preparing high-performance white light-emitting diodes. Theoretical computation proves that the activity of synthesis reaction can be significantly enhanced by ionic liquids. Density functional theory calculation reveals that the size and graphite nitrogen ratios of CDs have an effect on bandgap reduction, resulting in a redshift of the emission, which is in good agreement with the experimental results. This simple and promising approach for fast synthesis of tunable emissive CDs using ionic liquid affords the facilitation of CDs-based luminescent materials for fast manufacturing of functional devices.

Insights into the impact of polydopamine modification on permeability and anti-fouling performance of forward osmosis membrane

Forward osmosis (FO) has drawn wide attention as a promising method to address world-wide water crisis due to the advantages of low-energy consumption and easy separation operation. Unfortunately, the trade-off between permeability and selectivity as well as membrane fouling hindered the application of forward osmosis. Surface modification is a feasible method to address these issues. However, there is a lack of systematic evaluation about the effect of modification position on FO performance due to the asymmetric structure of thin film composite (TFC) FO membrane. To provide new insights into the design of FO membrane with satisfied permeability and fouling resistance, novel TFC FO membranes were fabricated by introducing polydopamine (PDA) on the support layer (TFC-I) or active layer (TFC-S), respectively. The surface morphology, chemical composition and wettability of the fabricated membrane were studied. It was found that the surface wettability of the modified membrane was improved greatly compared to pristine TFC membrane (TFC-C). Moreover, TFC-S membrane displayed a rougher surface than that of TFC-I membrane. As a result, a superior TFC-S membrane with a water flux of 60.95 ± 3.15 L m^-2h^-1 in AL-DS mode was obtained, which was 72.61% and 17.87% higher than that of TFC-C and TFC-I membrane, respectively. In addition, the TFC-S membrane also presented an excellent fouling resistance and membrane regeneration performance during the three organic fouling cycle experiments. The results indicated that the introduction of PDA as a surface coating for TFC membranes modification guaranteed the high-performance and fouling resistance. Especially, the PDA coating on the support layer surface resulted in an enhancement in permeability, while both the permeability and anti-fouling performance were significantly improved with the PDA coating on the polyamide active layer surface. This study provides new insights into the development of modification TFC-FO membranes for practical applications in water treatment.

Promising Polymeric Drug Carriers for Local Delivery: The Case of in situ Gels

BACKGROUND

At present, the controlled local drug delivery is a very promising approach compared to systemic administration, since it mostly targets the affected tissue. In fact, various drug carriers for local delivery have been prepared with improved therapeutic efficacy.

OBJECTIVE

in situ polymer gels are drug delivery systems that not only present liquid characteristics before their administration in body, but once they are administered, form gels due to gelation. Their gelation mechanism is due to factors such as pH alteration, temperature change, ion activation or ultraviolet irradiation. in situ gels offer various advantages compared to conventional formulations due to their ability to release drugs in a sustainable and controllable manner. Most importantly, in situ gels can be used in local drug delivery applications for various diseases.

METHODS

This review includes the basic knowledge and theory of in situ gels as well as their various applications according to their administration route.

RESULTS

Various natural, semisynthetic, and synthetic polymers can produce in situ polymeric gels. For example, natural polysaccharides such as alginic acid, chitosan, gellan gum, carrageenan etc. have been utilized as in situ gels for topical delivery. Besides the polysaccharides, poloxamers, poly(Nisopropylacrylamide), poly(ethyleneoxide)/ (lactic-co-glycolic acid), and thermosensitive liposome systems can be applied as in situ gels. In most cases, in situ polymeric gels could be applied via various administration routes such as oral, vaginal, ocular, intranasal and injectable.

CONCLUSION

To conclude, it can be revealed that in situ gels could be a promising alternative carrier for both chronic and immediate diseases.

Design and fabrication of polydopamine based superhydrophobic fabrics for efficient oil-water separation

In this work, we prepare a PDMS-SiO2-PDA@fabric with high water contact angle (WCA = 155°). Combining dopamine self-polymerization and a sol-gel method, SiO2 is in situ grown on a PDA-modified fabric surface to synergistically construct micro-nano rough structures. Finally, a superhydrophobic fabric is successfully obtained after coating the fabric with a layer of PDMS. The prepared fabric can maintain superhydrophobicity after immersion in various solvents (pH = 1, 3, 5, 7, 9, 11, 13, DMF, ethanol, THF, n-hexane) for 24 h and strong ultraviolet irradiation for 60 min. Thanks to the highly reactive PDA clusters, the stronger interfacial bond between the fabric and SiO2 enables it to withstand 180 min of washing and 159.22 N tensile stress, showing strong adhesion strength. In addition, the modified fabric has excellent self-cleaning properties and is resistant to contamination such as milk, coffee and tea. More importantly, the prepared fabric can selectively repel water and adsorb oil, achieving above 90% oil-water separation efficiency even after 8 cycles.

Superhydrophobic Poly(l-lactic acid) Membranes with Fish-Scale Hierarchical Microstructures and Their Potential Application in Oil-Water Separation

In this work, superhydrophobic poly(l-lactic acid) (PLLA) hierarchical membranes exhibiting excellent oil-removal performance, which is of great importance in curbing the oil-pollution environment, were fabricated by a simple solvent-evaporation-induced precipitation method. PLLA membranes with hierarchical micro/nanostructures (fish scales, fibrous sheets, and petal-like morphology) can be conveniently prepared by adjusting the preparation parameters including PLLA concentration, precipitation temperature, type of solvent and nonsolvent, and the addition of nano-SiO₂. The results show that the water contact angle of the fish-scale-structured PLLA membrane was 138.6°, revealing that water repellency was significantly improved compared to that of the solvent-casting PLLA membrane (∼72.8°). Moreover, the PLLA/SiO₂ nanocomposite membrane with a dense hierarchical micro/nanostructure had a water contact angle greater than 167.1°, which has great potential in oil-water separation.

Reversible Thermochromic Superhydrophobic BiVO4 Hybrid Pigments Coatings with Self-Cleaning Performance and Environmental Stability Based on Kaolinite

The inferior acid resistance and high cost of BiVO₄ pigments seriously hinder their wide applications in some fields. Inspired by the superhydrophobic properties of some plants and insects in nature, the reversible thermochromic superhydrophobic coatings with self-cleaning performance and environmental stability were successfully designed by combining with the surface roughness of kaolinite/BiVO₄ hybrid pigments (Kaol/BiVO₄-HP) and the modification with hexadecyltrimethoxysilane (HDTMS). When the concentration of HDTMS was 4.58 mmol/L, the yellow superhydrophobic coatings exhibited excellent self-cleaning properties and chemical and environmental stability. Furthermore, the superhydrophobic Kaol/BiVO₄-HP coatings exhibited the reversible thermochromic behavior with the change of the external temperatures from room temperature to 270 °C. Interestingly, this facile strategy also can be used to fabricate a series of superhydrophobic clay mineral/BiVO₄-HP coatings based on the different clay minerals, and there was no relationship between the superhydrophobic properties of the coatings and the morphologies of clay minerals, which was different from the reported color superhydrophobic coatings prepared with Maya-like blue pigments. Thus, the low-cost and thermochromic superhydrophobic clay mineral/BiVO₄-HP coatings presented a promising application in temperature sensors and switches with the excellent weather resistance to record and monitor the temperature changes.

Continuous Movement Mechanism of Oil Droplets Adhered on Surfaces with Different Wettability in the Flow Field

In this aticle, the continuous movement patterns and characteristic parameters of oil droplets on surfaces with different wettability immersed in a laminar flow field were observed, and the change rules of the geometric parameters of oil droplets under different experimental conditions were obtained. Then, the factors influencing the continuous moving behaviors of the oil droplets were analyzed, and the continuous movement velocity of the oil droplets under different experimental conditions was demonstrated. On this basis, the change law of the continuous movement velocity of oil droplets with the flow velocity was discussed. In addition, the coupling effect of the oil drops' height, surface properties, and water flow velocity on the continuous movement of oil droplets was studied, and the critical conditions for the continuous movement were obtained. According to the critical conditions, the mathematical model which described the law of continuous motion of the oil droplets adhered on surfaces with different wettability in the laminar flow field was established. The quantitative relationships among the average continuous moving velocity of oil droplets, physical properties, geometric parameters, water flow velocity, and surface wettability were obtained, which defined the necessary conditions for the uniform and accelerated movement of oil droplets, providing an important basis for choices of suitable surface wettability and flow field conditions in practical engineering applications.

A review of smart electrospun fibers toward textiles

Electrospinning as a versatile technology has attracted a large amount of attention in the past few decades due to the facile way to produce micro- and nano-scale fibers featuring flexibility, large specific surface area and high porosity. Stimuli-responsive polymers are a class of smart materials that are capable of sensing surround environment and interacting with them. Therefore, the combination of electrospinning and smart materials could have a great deal of benefits over the development of smart fibers. In this review, it offers a comprehensive understanding of smart electrospun fibers toward textile applications. Firstly, the definition of smart fibers and the differences between interactive fibers and passive interactive fibers are briefly introduced. Then some interactive fibers made from temperature-, pH-, light-, electric field/electricity-, magnetic field-, multi-responsive polymers, as well as some polymers featuring piezoelectric and triboelectric effect which are suitable flexible electrics, are emphasized with their applications in the form of electrospun fibers. Afterwards, some passive and hybrid smart electrospun fibers are introduced. Finally, associated challenges and perspectives are summarized and discussed.

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Understanding of passive smart electrospun fibers and interactive smart electrospun fibers.

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The recent progress in flexible electronics from electrospun fibers.

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The recent progress in stimuli-responsive polymers applied in interactive smart electrospun fibers.

Recent Progress in Polymer-Based Building Materials

With the development of human society, the requirements for building materials are becoming higher. The development of polymer materials and their application in the field of architecture have greatly enhanced and broadened the functions of building materials. With the development of material science and technology, many functional materials have been developed. Polymer materials have many excellent properties compared with inorganic materials, and they can also be improved to enhance functional properties by blending or adding various additives (such as flame retardants, antistatic agents, and antioxidants). In this paper, polymer-based building materials are introduced with three classes according to the applications, that is, substrates, coatings, and binders, and their recent signs of progress in the preparations and applications are carefully demonstrated.

Structural design toward functional materials by electrospinning: A review

Electrospinning as one of the most versatile technologies have attracted a lot of scientists’ interests in past decades due to its great diversity of fabricating nanofibers featuring high aspect ratio, large specific surface area, flexibility, structural abundance, and surface functionality. Remarkable progress has been made in terms of the versatile structures of electrospun fibers and great functionalities to enable a broad spectrum of applications. In this article, the electrospun fibers with different structures and their applications are reviewed. First, several kinds of electrospun fibers with different structures are presented. Then the applications of various structural electrospun fibers in different fields, including catalysis, drug release, batteries, and supercapacitors, are reviewed. Finally, the application prospect and main challenges of electrospun fibers are discussed. We hope that this review will provide readers with a comprehensive understanding of the structural design and applications of electrospun fibers in different fields.

Sterically Stabilized Polyionic Complex Nanogels of Chitosan Lysate and PEG-b-Polyglutamic Acid Copolymer for the Delivery of Irinotecan Active Metabolite (SN-38)

BACKGROUND

Poly Ionic Complex (PIC) nanogels are promising delivery systems with numerous attractions such as simple, fast, and organic solvent-free particle formation and mild drug loading conditions. Among polyelectrolytes, poly (L-amino acid) copolymers, such as poly (ethylene glycol)-block-poly (L-glutamic acid) copolymers (PEG-b-PGlu) are interesting biocompatible and biodegradable candidates bearing carboxylic acid functional groups.

OBJECTIVE

Aiming to solubilize and to preserve short-acting irinotecan active metabolite (SN38), sterically stabilized PIC nanogels were prepared through electrostatic charge neutralization between PEG-b-PGlu and chitosan lysate, a polycationic natural polymer obtained through digestion of chitosan by hydrogen peroxide oxidation and is soluble in a wide range of pH.

METHODS

Synthesis of PEG-b-PGlu was accomplished by N-carboxy anhydride polymerization of γ -benzyl L-glutamic acid, which is initiated by methoxy PEG-NH2 and successive debenzylation reaction.

RESULTS

The resulting block copolymer was characterized by FTIR, ¹H-NMR, and Size Exclusion Chromatography (SEC). Self-assembling properties of the PIC nanogels were investigated by pyrene assay, Dynamic Light Scattering (DLS), and Transmission Electron Microscopy (TEM), indicating the formation of homogeneous spherical particles with a mean size of 28 nm at the PEGb- PGlu concentrations/LMWC weight ratio of 5:1. Upon direct loading of SN38, the drug solubility enhanced more than 4×10³ folds with a mean loading efficiency of 89% and the drug loading of 30%. PIC nanogels exhibited zeta potential of +1 mV, acceptable biocompatibility, and superior cytotoxicity in murine colorectal carcinoma (CT26 cell line) compared to free drug.

CONCLUSION

In addition, the PIC nanogels provided SN38 protection against hydrolytic degradation in physiologic conditions. Conclusively, the well-tuned PIC nanogels are suggested as a potentially biocompatible nanocarrier for SN38 delivery.

Superlyophilic Shape Memory Porous Sponge for Smart Liquid Permeation

Recently, smart liquid permeation has aroused much attention. However, existing strategies to achieve such a goal are often based on reversibly controlling hydrophobicity/hydrophilicity on static porous structures, which are unsuitable for oils with low surface tension, and meanwhile they cannot realize tunable permeation flux since the pore sizes are constant. Herein, we report a superlyophilic shape memory porous sponge (SSMS) that can demonstrate tunable pore size from about 28 nm to 900 μm as the material's shape is changed. Based on the controllability in pore size, not only ON/OFF penetration but also precisely tunable permeation flux can be obtained for both water and oil. Furthermore, by using the SSMS, an application in accurate release of small-molecule rhodamine B was also demonstrated. This work reports a material with tunable pore size for controllable liquid permeation, which provides some ideas for designing smart superwetting permeation materials.

A Contrastive Investigation on the Anticorrosive Performance of Stearic Acid and Fluoroalkylsilane-Modified Superhydrophobic Surface in Salt, Alkali, and Acid Solution

Stearic acid and fluoroalkylsilane are widely used in chemical modification to fabricate superhydrophobic surfaces in corrosion-resistant exploration. However, extensive works have just explored their anticorrosive performance in salt solution. Very rare work has focused on comparing their corrosion-resistant performance in corrosive solution (salt, alkali, and acid) systematically. In this study, two kinds of superhydrophobic surfaces were obtained on laser-processed rough IN304 surface after the stearic acid and FAS modification processes, respectively. The investigation and comparison of anticorrosion performance in salt, alkali, and acid electrolyte were carried out via potentiodynamic polarization and electrochemical impedance spectroscopy measurements. The promotion mechanism or impairing mechanism was further proposed based on the results of surface wettability, surface morphology, and X-ray photoelectron spectroscopy. Besides, the long-term anticorrosion performance and the stability of surface wettability were also investigated. It is hoped that these research findings could provide an explicit guidance of suitable anticorrosion methods selection for metals in different kinds of corrosive solution (salt, alkali, and acid), which will further raise the promising prospect of functional surfaces for practical applications in industry.

Metal sensing-carbon dots loaded TiO2-nanocomposite for photocatalytic bacterial deactivation and application in aquaculture

Nowadays, bioactive nanomaterials have been attracted the researcher's enthusiasm in various fields. Herein, Diplocyclos palmatus leaf extract-derived green-fluorescence carbon dots (DP-CDs) were prepared using the hydrothermal method. Due to the strong fluorescence stability, the prepared DP-CDs were coated on filter-paper to make a fluorometric sensor-strip for Fe3+ detection. After, a bandgap-narrowed DP-CDs/TiO2 nanocomposite (DCTN) was prepared using the methanolic extract of D. palmatus. The prepared DCTN exhibited improved photocatalytic bacterial deactivation under sunlight irradiation. The DCTN-photocatalysis slaughtered V. harveyi cells by the production of reactive oxygen species, which prompting oxidative stress, damaging the cell membrane and cellular constituents. These results suggest the plausible mode of bactericidal action of DCTN-photocatalysis under sunlight. Further, the DCTN has shown potent anti-biofilm activity against V. harveyi, and thereby, DCTN extended the survival of V. harveyi-infected shrimps during the in vivo trial with Litopenaeus vannamei. Notably, this is the first report for the disinfection of V. harveyi-mediated acute-hepatopancreatic necrosis disease (AHPND) using nanocomposite. The reduced internal-colonization of V. harveyi on the hepatopancreas as well as the rescue action of the pathognomonic effect in the experimental animals demonstrated the anti-infection potential of DCTN against V. harveyi-mediated AHPND in aquaculture.

Chewable Tablets of Acacia catechu Extract, an Alternative to Betel (Paan) for Mouth Ulcers: Formulation and In vitro Evaluation

OBJECTIVE

The objective of the current research work was to prepare chewable tablets having Acacia catechu extract useful for mouth ulcers using a 3² factorial design.

METHODS

Acacia catechu heartwood extract was prepared using a reported method with some modifications. The extract was characterized using TLC against the catechin marker. Then, drug-excipient interaction studies were carried out. The mixture of drug and excipients was evaluated for pre-compression parameters. With the application of 3² factorial design, chewable tablets were prepared using direct compression technique. Prepared tablets were evaluated for post-compression parameters.

RESULTS

In vitro drug release study of the developed formulations was investigated both in intact and crushed form of tablets. Based on the in vitro performance, the best formulations were selected (F6, F7 & F8 from intact and F1, F5 & F9 from the crushed group) and subjected to various kinetic models and evaluated for Chewing Difficulty Index (CDI).

CONCLUSION

The overall results revealed that the formulated chewable tablets complied with the standards and exhibited the satisfactory performance in terms of drug release, chewing difficulty index and other related parameters.

Robust superhydrophobic polyurea@cellulose nanocrystal coating

A multifunctional superhydrophobic PU@CNC composite coating with self-cleaning properties and mechanical durability was fabricated using a facile spraying method.