Chitosan extraction from Amanita phalloides: yield, crystallinity, degree of deacetylation, azo dye removal and antibacterial properties.

Chitosan, a biopolymer obtained from chitin, is known for its remarkable adsorption abilities for dyes, drugs, and fats, and its diverse array of antibacterial characteristics. This study explores the extraction and characterization of chitosan from the mycelium of Amanita phalloides. The moisture content, ash content, water binding capacity, fat binding capacity, and degree of deacetylation of the extracted chitosan were determined. The chitosan exhibited a high yield of 70%, crystallinity of 49.07%, a degree of deacetylation of 86%, and potent antimicrobial properties against both Gram-negative and Gram-positive bacteria. The study also examined the adsorption capabilities of chitosan to remove methylene blue (MB) dye by analysing specific factors like pH, reaction time, and MB concentration using the response surface model. The highest degree of MB dye removal was 91.6% at a pH of 6, a reaction time of around 60 min and an initial dye concentration of 16 ppm. This experimental design can be applied for chitosan adsorption of other organic compounds such as dyes, proteins, drugs, and fats.

Galvanostatic Electroshock Synthesis of Low Loading Au-Pt Nanoalloys onto Gas Diffusion Electrodes as Multifunctional Electrocatalysts for a Glycerol-Fed Electrolyzer.

Water electrolysis is increasingly considered a viable solution for meeting the world's growing energy demands and mitigating environmental issues. An inventive strategy to mitigate the energy requirements involves substituting the energy-intensive oxygen evolution reaction (OER) with biomass-derived glycerol electrooxidation. Nonetheless, the synthesis of electrocatalysts for controlling the selectivity towards added-value chemicals at the anode and efficient H2 generation at the cathode remains a critical bottleneck. Herein, we implemented a galvanostatic electroshock synthesis approach to control the reduction kinetics of Au(III) and Pt(IV) to grow ultra-low amount of gold-platinum alloys on a gas diffusion electrode (12-26 µgmetal cm‒2) for glycerol-fed hydroxide anion exchange membrane based electrolyzer. The symmetric GDE-Au100-xPtx||GDE-Au100-xPtx systems showed a notable improvement in electrolyzer performance (GDE-Au64Pt36 = 201 mA cm-2) as compared to monometallic versions (GDE-Au100Pt0 = 18 mA cm-2, GDE-Au0Pt100 = 81 mA cm-2). Chromatography (HPLC) analysis underscores the critical importance of bulk electrolysis methodology (galvanostatic vs potentiostatic) for the efficient conversion of glycerol into high-value-added products. Regarding the electrical energy required to produce 1 kg of H2 for such an electrolyzer fed at the anode with glycerol, our results confirm a drastic decrease by a factor of at least two compared with conventional water electrolysis.

Antibacterial and Antifungal Activities of Cimbopogon winterianus and Origanum syriacum Extracts and Essential Oils against Uropathogenic Bacteria and Foodborne Fungal Isolates.

This study focused on testing the antibacterial and antifungal activity of Origanum syriacum (O. syriacum) and Cimbopogon winterianus (C. winterianus) extracts and their essential oils (EOs). The bacteria were isolated from urine samples and identified by a VITEK assay, and the fungi were isolated from spoiled food samples and further identified by MALDI-TOF. The susceptibility of the microbial isolates was assessed by determining the bacteriostatic and bactericidal/fungicidal effects by the minimum inhibitory concentration (MIC) and minimum bactericidal/fungicidal concentration (MBC/MFC) broth microdilution assay and time-kill test. The antibiofilm activities were assessed by the antibiofilm screening assays. The bacterial isolates included three Gram-negative isolates (Escherichia coli, Klebsiella pneumonia, and Citrobacter freundii) and two Gram-positive isolates (Staphylococcus aureus and Streptococcus intermedius). The fungal isolates included Candida albicans and Aspergillus niger. The O. syriacum and C. winterianus extracts exhibited bacteriostatic and fungistatic activities (MIC 1.25-2.5 mg/mL for the bacterial isolates and 2.5-5 mg/mL for the fungal isolates). However, their EOs exhibited bactericidal (MBC 5-20%) and fungicidal (MFC 1.25-10%) activities, meaning that the EOs had a better antimicrobial potential than the extracts. The antibiofilm activities of the mentioned extracts and their EOs were relatively weak. The O. syriacum extract inhibited S. aureus, S. intermedius, and K. pneumonia biofilms at a concentration of 0.3125 mg/mL and C. albicans and A. niger biofilms at 0.625 mg/mL. No antibiofilm activity was recorded for C. winterianus extract. In addition, the packaging of grapes with C. winterianus extract preserved them for about 40 days. The results reflect the significant antimicrobial activity of O. syriacum and C. winterianus extracts and their EOs, thus suggesting their potential in food packaging and preservation.

Enhancing Wastewater Depollution: Sustainable Biosorption Using Chemically Modified Chitosan Derivatives for Efficient Removal of Heavy Metals and Dyes.

Driven by concerns over polluted industrial wastewater, particularly heavy metals and dyes, this study explores biosorption using chemically cross-link chitosan derivatives as a sustainable and cost-effective depollution method. Chitosan cross-linking employs either water-soluble polymers and agents like glutaraldehyde or copolymerization of hydrophilic monomers with a cross-linker. Chemical cross-linking of polymers has emerged as a promising approach to enhance the wet-strength properties of materials. The chitosan thus extracted, as powder or gel, was used to adsorb heavy metals (lead (Pb2+) and copper (Cu2+)) and dyes (methylene blue (MB) and crystal violet (CV)). Extensive analysis of the physicochemical properties of both the powder and hydrogel adsorbents was conducted using a range of analytical techniques, including Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), and scanning electron microscopy (SEM), as well as 1H and 13C nuclear magnetic resonance (NMR). To gain a comprehensive understanding of the sorption process, the effect of contact time, pH, concentration, and temperature was investigated. The adsorption capacity of chitosan powder for Cu(II), Pb(II), methylene blue (MB), and crystal violet (CV) was subsequently determined as follows: 99, 75, 98, and 80%, respectively. In addition, the adsorption capacity of chitosan hydrogel for Cu(II), Pb(II), MB, and CV was as follows: 85, 95, 85, and 98%, respectively. The experimental data obtained were analyzed using the Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models. The isotherm study revealed that the adsorption equilibrium is well fitted to the Freundlich isotherm (R2 = 0.998), and the sorption capacity of both chitosan powder and hydrogel was found to be exceptionally high (approximately 98%) with the adsorbent favoring multilayer adsorption. Besides, Dubinin has given an indication that the sorption process was dominated by Van der Waals physical forces at all studied temperatures.

Ammodaucus Leucotrichus Seed Extract as a Potential Therapy in Animal Models of Rheumatoid Arthritis Induced by Complete Freund Adjuvant and Chicken Cartilage Collagen.

This study assessed the efficacy of an Ammodaucus leucotrichus seed extract to treat rheumatoid arthritis in rat models of this disease. Rheumatoid arthritis was induced in rats using two methods: immunization with 100 µL of Complete Freund Adjuvant (CFA) and immunization with 100 µL of a 3 mg/ml solution of type II collagen (CII) from chicken cartilage. The therapeutic potential of the extract was assessed at different doses (150, 300, and 600 mg/kg/day for 21 days in the CII-induced arthritis model and for 14 days in the CFA-induced arthritis model) and compared with methotrexate (MTX; 0.2 mg/kg for the same periods), a commonly used drug for rheumatoid arthritis treatment in humans. In both models (CII-induced arthritis and CFA-induced arthritis), walking distance, step length, intra-step distance and footprint area were improved following treatment with the A. leucotrichus seed extract (all concentrations) and MTX compared with untreated animals. Both treatments increased the serum concentration of glutathione and reduced that of complement C3, malondialdehyde and myeloperoxidase. Radiographic data and histological analysis indicated that cartilage destruction was reduced already with the lowest dose of the extract (100 mg/kg/dose) in both models. These results show the substantial antiarthritic potential of the A. leucotrichus seed extract, even at the lowest dose, suggesting that it may be a promising alternative therapy for rheumatoid arthritis and joint inflammation. They also emphasize its efficacy at various doses, providing impetus for more research on this extract as a potential therapeutic agent for arthritis.

Exploring the potential of a Ephedra alata leaf extract: Phytochemical analysis, antioxidant activity, antibacterial properties, and green synthesis of ZnO nanoparticles for photocatalytic degradation of methylene blue.

Ephedra alata leaf extracts have therapeutic properties and contain various natural compounds known as phytochemicals. This study assessed the phytochemical content and antioxidant effects of a Ephedra alata leaf extract, as well as zinc oxide (ZnO) nanoparticle production. The extract contained phenolic acids, including vanillic acid, chlorogenic acid, gallic acid, p-coumaric acid, vanillin and rutin. Its total phenolic content and total flavonoid content were 48.7 ± 0.9 mg.g-1 and 1.7 ± 0.4 mg.g-1, respectively. The extract displayed a DPPH inhibition rate of 70.5%, total antioxidant activity of 49.5 ± 3.4 mg.g-1, and significant antimicrobial activity toward Gram-positive and negative bacteria. The synthesized ZnO nanoparticles had spherical shape, crystallite size of 25 nm, particle size between 5 and 30 nm, and bandgap energy of 3.3 eV. In specific conditions (90 min contact time, pH 7, and 25°C), these nanoparticles efficiently photodegraded 87% of methylene blue, suggesting potential applications for sustainable water treatment and pollution control.

Exploring the Therapeutic Potential of Ammodaucus leucotrichus Seed Extracts: A Multi-Faceted Analysis of Phytochemical Composition, Anti-Inflammatory Efficacy, Predictive Anti-Arthritic Properties, and Molecular Docking Insights.

Ammodaucus leucotrichus exhibits promising pharmacological activity, hinting at anti-inflammatory and anti-arthritic effects. This study investigated seed extracts from Ammodaucus leucotrichus using methanol and n-hexane, focusing on anti-inflammatory and anti-arthritic properties. The methanol extract outperformed the n-hexane extract and diclofenac, a reference anti-inflammatory drug, in trypsin inhibition (85% vs. 30% and 64.67% at 125 µg/mL). For trypsin inhibition, the IC50 values were 82.97 µg/mL (methanol), 202.70 µg/mL (n-hexane), and 97.04 µg/mL (diclofenac). Additionally, the n-hexane extract surpassed the methanol extract and diclofenac in BSA (bovine serum albumin) denaturation inhibition (90.4% vs. 22.0% and 51.4% at 62.5 µg/mL). The BSA denaturation IC50 values were 14.30 µg/mL (n-hexane), 5408 µg/mL (methanol), and 42.30 µg/mL (diclofenac). Gas chromatography-mass spectrometry (GC-MS) revealed 59 and 58 secondary metabolites in the methanol and n-hexane extracts, respectively. The higher therapeutic activity of the methanol extract was attributed to hydroxyacetic acid hydrazide, absent in the n-hexane extract. In silico docking studies identified 28 compounds with negative binding energies, indicating potential trypsin inhibition. The 2-hydroxyacetohydrazide displayed superior inhibitory effects compared to diclofenac. Further mechanistic studies are crucial to validate 2-hydroxyacetohydrazide as a potential drug candidate for rheumatoid arthritis treatment.

Cymbopogon winterianus (Java Citronella Plant): A Multi-Faceted Approach for Food Preservation, Insecticidal Effects, and Bread Application.

Certain plants like Rosemarinus officinalis, Lavandula angustifolia and Origanum vulgare have been used in the food industry for centuries. Cymbopogon winterianus (Java Citronella plant) is one of the most significant plants. The objective of this study is to screen for secondary metabolites by phytochemical screening, evaluate the antioxidant contents of extracts and investigate the use of the Java Citronella plant in food preservation and as an insecticide. Java Citronella powder was added to bread and evaluated for its moisture content, and a visual and sensory analysis was performed. Sitophilus granarius (L.) weevils were exposed to Java Citronella essential oil (JCEO). The phytochemical screening revealed that the extracts were abundant in secondary metabolites. The JCEO had a yield of 0.75%. The aqueous extract had a higher total phenolic content of 49.043 ± 0.217 mg GAE/g than the ethanolic extract, which was 24.478 ± 1.956 mg GAE/g. The aqueous extract had a total flavonoids content 27,725.25 ± 54.96 µg RE/g higher than the ethanolic extract, with 24,263 ± 74 µg RE/g. The ethanolic extract had stronger antioxidant activity, with anIC50 = 196.116 µg/mL higher than the aqueous extract at 420 µg/mL. The 2% Java Citronella powder in the bread was preferred by consumers, and had a shelf life of 6 days. JCEO killed all the weevils with a high dose of 10% after 48 h. The Java Citronella showed insecticidal and food preservative activity. The results should help in future research to enhance the applications of Java Citronella in various domains, from food technology to insecticides.

TiO2/PDA Multilayer Nanocomposites with Exceptionally Sharp Large-Scale Interfaces and Nitrogen Doping Gradient.

The evolving field of photocatalysis requires the development of new functional materials, particularly those suitable for large-scale commercial systems. One particularly promising approach is the creation of hybrid organic/inorganic materials. Despite being extensively studied, materials such as polydopamine (PDA) and titanium oxide continue to show significant promise for use in such applications. Nitrogen-doped titanium oxide and free-standing PDA films obtained at the air/water interface are particularly interesting. This study introduces a straightforward and reproducible approach for synthesizing a novel class of large-scale multilayer nanocomposites. The method involves the alternate layering of high-quality materials at the air/water interface combined with precise atomic layer deposition techniques, resulting in a gradient nitrogen doping of titanium oxide layers with exceptionally sharp oxide/polymer interfaces. The analysis confirmed the presence of nitrogen in the interstitial and substitutional sites of the TiO2 lattice while maintaining the 2D-like structure of the PDA films. These chemical and structural characteristics translate into a reduction of the band gap by over 0.63 eV and an increase in the photogenerated current by over 60% compared with pure amorphous TiO2. Furthermore, the nanocomposites demonstrate excellent stability during the 1 h continuous photocurrent generation test.

Ag-BN/HNT-TiO2 nanofibers produced by electrospinning as catalysts to remove acetaminophen.

In this study, we present a novel approach to enhancing the degradation of acetaminophen (ACT) using nanostructured hybrid nanofibers. The hybrid nanofibers were produced by employing both sol-gel and electrospinning methodologies, integrating precise quantities of silver (Ag) and boron nitride (BN) nanosheets into titanium oxide (TiO2) nanofibers and halloysite nanotubes (HNT). We extensively examined the morphology, structure, and optical properties of these materials by employing scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy in our analysis. In the case of the HNT-TiO2 composite, the introduction of Ag nanoparticles at concentrations of 0.5%, 1.5%, and 3% led to a significant improvement in photocatalytic activity. Under visible light exposure for 4 h, the photocatalytic activity increased from 63% (HNT-TiO2) to 78.92%, 91.21%, and 92.90%, respectively. This enhancement can be attributed to the role of Ag nanoparticles as co-catalysts, facilitating the separation of electrons and holes generated during the photocatalytic process. Furthermore, BN nanosheets served as co-catalysts, capitalizing on their distinct attributes, including exceptional thermal conductivity, chemical stability, and electrical insulation. The incorporation of BN nanosheets into the Ag (3%)/HNT-TiO2 composite at a concentration of 5% resulted in a remarkable increase in ACT degradation efficiency. The degradation efficiency improved from 59.47% to an impressive 99.29% within a 2-h irradiation period due to the presence of BN nanosheets. Toxicity and scavenging assays revealed that OH•-, O2•-, and h+ were the major contributors to ACT degradation. Moreover, across five consecutive cycles, the Ag-BN/HNT-TiO2 composite exhibited consistent and stable performance, underscoring the significant contributions of Ag and BN in augmenting the photocatalytic capabilities of the composite. Overall, our findings suggest that this novel hybrid nanofiber composite holds great promise for practical applications in environmental remediation due to its improved photocatalytic activity and stability.

Fabrication of cellulose nanocrystals/carboxymethyl cellulose/zeolite membranes for methylene blue dye removal: understanding factors, adsorption kinetics, and thermodynamic isotherms.

This study introduces environmentally-friendly nanocellulose-based membranes for AZO dye (methylene blue, MB) removal from wastewater. These membranes, made of cellulose nanocrystals (CNCs), carboxymethyl cellulose (CMC), zeolite, and citric acid, aim to offer eco-friendly water treatment solutions. CNCs, obtained from sugarcane bagasse, act as the foundational material for the membranes. The study aims to investigate both the composition of the membranes (CMC/CNC/zeolite/citric acid) and the critical adsorption factors (initial MB concentration, contact time, temperature, and pH) that impact the removal of the dye. After systematic experimentation, the optimal membrane composition is identified as 60% CNC, 15% CMC, 20% zeolites, and 5% citric acid. This composition achieved a 79.9% dye removal efficiency and a 38.3 mg/g adsorption capacity at pH 7. The optimized membrane exhibited enhanced MB dye removal under specific conditions, including a 50 mg adsorbent mass, 50 ppm dye concentration, 50 mL solution volume, 120-min contact time, and a temperature of 25°C. Increasing pH from neutral to alkaline enhances MB dye removal efficiency from 79.9% to 94.5%, with the adsorption capacity rising from 38.3 mg/g to 76.5 mg/g. The study extended to study the MB adsorption mechanisms, revealing the chemisorption of MB dye with pseudo-second-order kinetics. Chemical thermodynamic experiments determine the Freundlich isotherm as the apt model for MB dye adsorption on the membrane surface. In conclusion, this study successfully develops nanocellulose-based membranes for efficient AZO dye removal, contributing to sustainable water treatment technologies and environmental preservation efforts.

A Comprehensive Review on Modification of Titanium Dioxide-Based Catalysts in Advanced Oxidation Processes for Water Treatment.

It has become necessary to develop effective strategies to prevent and reduce water pollution as a result of the increase in dangerous pollutants in water reservoirs. Consequently, there is a need to design new catalyst materials to promote the efficiency of advanced oxidation processes (AOPs) in the field of wastewater treatment plant to ensure the mineralization of trace organic contaminants. A notable approach gaining attention involves the coupling of sulfate radicals-based AOPs to photocatalysis or electrocatalysis processes, aiming to achieve the complete removal of refractory contaminants into water and carbon dioxide. Titanium dioxide as metal oxide has received great attention for its catalytic application in water purification. TiO2 catalysts offer a multitude of advantages in AOPs. They are characterized by their high photocatalytic activity under both ultraviolet and visible light, making them environmentally friendly due to the absence of toxic byproducts during oxidation. Their versatility is remarkable, finding utility in various AOPs, from photocatalysis to photo-Fenton processes. TiO2's durability ensures long-lasting catalytic activity, which is crucial for continuous treatment processes, and their cost-effectiveness is particularly advantageous. Furthermore, their chemical stability allows it to withstand varying pH conditions. However, the large band gap energy and low electrical conductivity hinder the catalytic reaction effectiveness. This review aims to examine various approaches to enhance the catalytic performance of titanium dioxide, with the objective of enabling more efficient water purification methods.

Exploring Hydrogen Sources in Catalytic Transfer Hydrogenation: A Review of Unsaturated Compound Reduction.

Catalytic transfer hydrogenation has emerged as a pivotal chemical process with transformative potential in various industries. This review highlights the significance of catalytic transfer hydrogenation, a reaction that facilitates the transfer of hydrogen from one molecule to another, using a distinct molecule as the hydrogen source in the presence of a catalyst. Unlike conventional direct hydrogenation, catalytic transfer hydrogenation offers numerous advantages, such as enhanced safety, cost-effective hydrogen donors, byproduct recyclability, catalyst accessibility, and the potential for catalytic asymmetric transfer hydrogenation, particularly with chiral ligands. Moreover, the diverse range of hydrogen donor molecules utilized in this reaction have been explored, shedding light on their unique properties and their impact on catalytic systems and the mechanism elucidation of some reactions. Alcohols such as methanol and isopropanol are prominent hydrogen donors, demonstrating remarkable efficacy in various reductions. Formic acid offers irreversible hydrogenation, preventing the occurrence of reverse reactions, and is extensively utilized in chiral compound synthesis. Unconventional donors such as 1,4-cyclohexadiene and glycerol have shown a good efficiency in reducing unsaturated compounds, with glycerol additionally serving as a green solvent in some transformations. The compatibility of these donors with various catalysts, substrates, and reaction conditions were all discussed. Furthermore, this paper outlines future trends which include the utilization of biomass-derived hydrogen donors, the exploration of hydrogen storage materials such as metal-organic frameworks (MOFs), catalyst development for enhanced activity and recyclability, and the utilization of eco-friendly solvents such as glycerol and ionic liquids. Innovative heating methods, diverse base materials, and continued research into catalyst-hydrogen donor interactions are aimed to shape the future of catalytic transfer hydrogenation, enhancing its selectivity and efficiency across various industries and applications.

Corrigendum: Challenge of material haemocompatibility for microfluidic blood-contacting applications.

[This corrects the article DOI: 10.3389/fbioe.2023.1249753.].

Challenge of material haemocompatibility for microfluidic blood-contacting applications.

Biological applications of microfluidics technology is beginning to expand beyond the original focus of diagnostics, analytics and organ-on-chip devices. There is a growing interest in the development of microfluidic devices for therapeutic treatments, such as extra-corporeal haemodialysis and oxygenation. However, the great potential in this area comes with great challenges. Haemocompatibility of materials has long been a concern for blood-contacting medical devices, and microfluidic devices are no exception. The small channel size, high surface area to volume ratio and dynamic conditions integral to microchannels contribute to the blood-material interactions. This review will begin by describing features of microfluidic technology with a focus on blood-contacting applications. Material haemocompatibility will be discussed in the context of interactions with blood components, from the initial absorption of plasma proteins to the activation of cells and factors, and the contribution of these interactions to the coagulation cascade and thrombogenesis. Reference will be made to the testing requirements for medical devices in contact with blood, set out by International Standards in ISO 10993-4. Finally, we will review the techniques for improving microfluidic channel haemocompatibility through material surface modifications-including bioactive and biopassive coatings-and future directions.

Enhancing Water Treatment Performance of Porous Polysulfone Hollow Fiber Membranes through Atomic Layer Deposition.

Polysulfone (PSF) is one of the most used polymers for water treatment membranes, but its intrinsic hydrophobicity can be detrimental to the membranes' performances. By modifying a membrane's surface, it is possible to adapt its physicochemical properties and thus tune the membrane's hydrophilicity or porosity, which can achieve improved permeability and antifouling efficiency. Atomic layer deposition (ALD) stands as a distinctive technology offering exceedingly even and uniform layers of coatings, like oxides that cover the surfaces of objects with three-dimensional (3D) shapes, porous structures, and particles. In the context of this study, the focus was on titanium dioxide (TiO2), zinc oxide (ZnO), and alumina (Al2O3), which were deposited on polysulfone hollow fiber (HF) membranes via ALD using TiCl4, diethyl zinc (DEZ), and trimethylamine (TMA), respectively, and H2O as precursors. The morphology and mechanical properties of membranes were changed without damaging their performances. The deposition was confirmed mainly by energy-dispersive X-ray spectroscopy (EDX). All depositions offered great performances with a maintained permeability and BSA retention and a 20 to 40° lower water contact angle (WCA) than the raw PSF HF membrane. The deposition of TiO2 offered the best results, showing an enhancement of 50% for the water permeability and 20% for the fouling resistance of the PSF HF membranes.

CaCu3Ti4O12 Perovskite Materials for Advanced Oxidation Processes for Water Treatment.

The many pollutants detected in water represent a global environmental issue. Emerging and persistent organic pollutants are particularly difficult to remove using traditional treatment methods. Electro-oxidation and sulfate-radical-based advanced oxidation processes are innovative removal methods for these contaminants. These approaches rely on the generation of hydroxyl and sulfate radicals during electro-oxidation and sulfate activation, respectively. In addition, hybrid activation, in which these methods are combined, is interesting because of the synergistic effect of hydroxyl and sulfate radicals. Hybrid activation effectiveness in pollutant removal can be influenced by various factors, particularly the materials used for the anode. This review focuses on various organic pollutants. However, it focuses more on pharmaceutical pollutants, particularly paracetamol, as this is the most frequently detected emerging pollutant. It then discusses electro-oxidation, photocatalysis and sulfate radicals, highlighting their unique advantages and their performance for water treatment. It focuses on perovskite oxides as an anode material, with a particular interest in calcium copper titanate (CCTO), due to its unique properties. The review describes different CCTO synthesis techniques, modifications, and applications for water remediation.

Control of Intermolecular Interactions toward the Production of Free-Standing Interfacial Polydopamine Films.

Aggregation of the polydopamine (PDA) molecular building blocks at the air/water interface leads to obtaining large surface nanometric-thin films. This mechanism follows two possible pathways, namely, covalent or non-covalent self-assembly, which result in a different degree of structure order and, consequently, different structural properties. Control of this mechanism could be vital for applications that require true self-support PDA free-standing films, for example, electrochemical sensing or membrane technology. Here, we are considering the impact of boric acid (BA) and Cu2+ ions on the mentioned mechanism exclusively for the free-standing films from the air/water interface. We have employed and refined our own spectroscopic reflectometry method to achieve an exceptionally high real-time control over the thickness growth. It turned out that BA and Cu2+ ions significantly impact the film growth process. Reduction of the nanoparticles size and their number was examined via UV-vis spectroscopy and transmission electron microscopy, showing a colossal reduction in the mean diameter of nanoparticles in the case of BA and a moderate reduction in the case of Cu2+. This modification is leading to significant enhancement of the process efficiency through moderation of the topological properties of the films, as revealed by atomic force microscopy. Next, applying infrared, Raman, and X-ray photoelectron spectroscopy, we presented small amounts of metal (B or Cu) in the final structure of PDA and simultaneously their vital role in the oxidation mechanism and cross-linking through covalent or non-covalent bonds. Therefore, we revealed the possibility of synthesizing films via the expected self-assembly mechanism which has hitherto been out of control. Moreover, modification of mechanical properties toward exceptionally elastic films through the BA-assisted synthesis pathway was shown by achieving Young's modulus value up to 24.1 ± 5.6 and 18.3 ± 6.4 GPa, using nanoindentation and Brillouin light scattering, respectively.

Halloysite-TiO2 Nanocomposites for Water Treatment: A Review.

Halloysite nanotubes (HNTs) are clay minerals with a tubular structure that can be used for many different applications in place of carbon nanotubes. Indeed, HNTs display low/non-toxicity, are biocompatible, and can be easily prepared. Moreover, the aluminum and silica groups present on HNTs' inner and outer surfaces facilitate the interaction with various functional agents, such as alkalis, organosilanes, polymers, surfactants, and nanomaterials. This allows the deposition of different materials, for instance, metal and non-metal oxides, on different substrate types. This review article first briefly presents HNTs' general structure and the various applications described in the last 20 years (e.g., drug delivery, medical implants, and energy storage). Then, it discusses in detail HNT applications for water purification (inorganic and organic pollutants). It focuses particularly on HNT-TiO2 composites that are considered very promising photocatalysts due to their high specific surface area and adsorption capacity, large pore volume, good stability, and mechanical features.