Polyelectrolyte Coatings—A Viable Approach for Cultural Heritage Protection

The continuous degradation of cultural heritage artifacts (due to different factors, including the rising air pollution, climate change or excessive biological activity, among others) requires the continuous development of protection strategies, technologies and materials. In this regard, polyelectrolytes have offered effective ways to fight against degradation but also to conserve the cultural heritage objects. In this review, we highlight the key developments in the creation and use of polyelectrolytes for the preservation, consolidation and cleaning of the cultural heritage artifacts (with particular focus on stone, metal and artifacts of organic nature, such as paper, leather, wood or textile). The state of the art in this area is presented, as well as future development perspectives

Iron-Modified Titanate Nanorods for Oxidation of Aqueous Ammonia Using Combined Treatment with Ozone and Solar Light Irradiation

Sodium titanate nanorods were synthesized by a hydrothermal method and subsequently modified with an iron precursor. For comparison, Fe2O3 nanocubes were also obtained through a similar hydrothermal treatment. Pristine, Fe-modified nanorods and Fe2O3 nanocubes were suspended in diluted ammonia solutions (20 ppm) and exposed to ozone and simulated light irradiation. Ammonia abatement, together with the resulting nitrogen-containing products (NO3−), was monitored by ion chromatography measurements. The generation of reactive oxygen species (·OH and O2−) in the investigated materials and their photoelectrochemical behaviour were also investigated. Morphological and structural characterizations (SEM, XRD, XRF, UV–Vis, H2-TPR, NH3-TPD, PL, PZC) of the studied catalysts were correlated with their activity for ammonia degradation with ozone- and photo-assisted oxidation. An increase in ammonia conversion and a decreasing amount of NO3− were achieved by combining the above-mentioned processes

Synergistic Antioxidant Activity and Enhanced Stability of Curcumin Encapsulated in Vegetal Oil-Based Microemulsion and Gel Microemulsions

Curcumin, due to its antioxidant, antibacterial, anti-inflammatory, and antitumoral activity, has attracted huge attention in applications in many fields such as pharmacy, medicine, nutrition, cosmetics, and biotechnology. The stability of curcumin-based products and preservation of antioxidant properties are still challenges in practical applications. Stability and antioxidant properties were studied for curcumin encapsulated in O/W microemulsion systems and three related gel microemulsions. Only biodegradable and biocompatible ingredients were used for carriers: grape seed oil as oily phase, Tween 80, and Plurol® Diisostearique CG as a surfactant mix, and ethanol as a co-solvent. For the gel microemulsions, water-soluble polymers, namely Carbopol® 980 NF, chitosan, and sodium hyaluronate were used. The influence of UVC irradiation and heat treatment on the degradation kinetics of curcumin in the formulations was studied. Because of the antioxidant character of the microemulsion oily phase, the possibility of a synergistic effect between grape seed oil and curcumin was explored. In this study, the high efficiency of the studied drug delivery systems to ensure protection from external degradative factors was confirmed. Also, the influence of the encapsulation in microemulsion and derived gel microemulsion systems on the antioxidant capacity curcumin was studied, and a synergistic effect with vegetal oil was demonstrated

Iron-Modified Titanate Nanorods for Oxidation of Aqueous Ammonia Using Combined Treatment with Ozone and Solar Light Irradiation

Sodium titanate nanorods were synthesized by a hydrothermal method and subsequently modified with an iron precursor. For comparison, Fe2O3 nanocubes were also obtained through a similar hydrothermal treatment. Pristine, Fe-modified nanorods and Fe2O3 nanocubes were suspended in diluted ammonia solutions (20 ppm) and exposed to ozone and simulated light irradiation. Ammonia abatement, together with the resulting nitrogen-containing products (NO3−), was monitored by ion chromatography measurements. The generation of reactive oxygen species (·OH and O2−) in the investigated materials and their photoelectrochemical behaviour were also investigated. Morphological and structural characterizations (SEM, XRD, XRF, UV–Vis, H2-TPR, NH3-TPD, PL, PZC) of the studied catalysts were correlated with their activity for ammonia degradation with ozone- and photo-assisted oxidation. An increase in ammonia conversion and a decreasing amount of NO3− were achieved by combining the above-mentioned processes

Mesoporous Silica Nanoreservoirs Loaded with 1-H Benzotriazole for Active Anticorrosion Protection

In recent years, scientists are paying increased attention to the development of intelligent nanocontainers in applications such as biomedical, catalysis, and anticorrosion [1]. Preparation of anticorrosion coatings containing smart nanocontainers loaded with corrosion inhibitors, which can be initiated when the barrier coatings are damaged, favor the long-term function, as uncontrolled loss by leaching is inhibited [2]. The aim of the present study is to optimize the amount of an organic inhibitor (1-H benzotriazole (BTA)) that can be in situ encapsulated in a mesoporous silica nanocontainer, prepared by an original sol-gel formulation. Materials and methods: For the synthesis of silica mesoporous, nanoparticles loaded with BTA were used with three silica co-precursors: tetraethylorthosilicate (TEOS), phenyltriethoxysilane (PTES), and octyltriethoxysilane (OTES), at a 5/1/1 gravimetric ratio. The synthesis was carried out in the presence of a solvent (ethanol) and of a surfactant (Igepal CA-630). The pH of the sol–gel system was adjusted to ~9 by dripping an aqueous solution of NH4OH (25%). Prior to the addition to the sol–gel reaction system, BTA was completely dissolved in ethanol. Various amounts of BTA were loaded to the sol–gel systems: 0.25; 0.5; 0.75; 1; 1.25; 1.5; and 2 g (corresponding to 0.09; 0.18; 0.27; 0.35; 0.44; 0.53; and 0.70% grav. of the total amount of sol–gel mixture, respectively). Furthermore, a similar set of samples was prepared in the presence of a constant amount of rhodamine B, dissolved in ethanol. This second set was obtained in order to perform a visual evaluation of the encapsulation efficiency. Particles dimensions, size distributions, and particles charging in the final dispersions were evaluated by the dynamic light scattering (DLS) technique and Zeta potential measurements. Surface morphology was observed by SEM. The structural characteristics of the silica mesoporous particles were investigated by N2 adsorption–desorption analysis on the calcined samples. Results: During the in situ synthesis of silica nanoparticles, the aromatic molecules of the corrosion inhibitor BTA were linked via a hydrophobic interaction with the phenyl groups from the silica pores formed by the hydrophobic functions of silica co-precursors, i.e., PTES and OTES. In addition, the corrosion inhibitor was trapped inside the surfactant micelles of Igepal and encapsulated together inside the silica pores formed by the surfactant. Moreover, it was observed that only a small amount of BTA can be encapsulated in the absence of the surfactant. Conclusions: An optimized method was developed to obtain mesoporous silica nanoparticles loaded with 1-H Benzotriazole (BTA) as a corrosion inhibitor. The optimal range of the BTA concentration was found to be between 0.18 and 0.35%

The Effect of Different Coupling Agents on Nano-ZnO Materials Obtained via the Sol–Gel Process

Hybrid nanomaterials based on zinc oxide were synthesized via the sol–gel method, using different silane coupling agents: (3-glycidyloxypropyl)trimethoxysilane (GPTMS), phenyltriethoxysilane (PhTES), octyltriethoxysilane (OTES), and octadecyltriethoxysilane (ODTES). Morphological properties and the silane precursor type effect on the particle size were investigated using dynamic light scattering (DLS), environmental scanning electron microscopy (ESEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and X-ray diffraction (XRD). The bonding characteristics of modified ZnO materials were investigated using Fourier transform infrared spectroscopy (FTIR). The final solutions were deposited on metallic substrate (aluminum) in order to realize coatings with various wettability and roughness. The morphological studies, obtained by ESEM and TEM analysis, showed that the sizes of the ZnO nanoparticles are changed as function of silane precursor used in synthesis. The thermal stability of modified ZnO materials showed that the degradation of the alkyl groups takes place in the 300–500 °C range. Water wettability study revealed a contact angle of 142 ± 5° for the surface covered with ZnO material modified with ODTES and showed that the water contact angle increases as the alkyl chain from the silica precursor increases. These modified ZnO materials, therefore, can be easily incorporated in coatings for various applications such as anti-corrosion and anti-icing

Antimicrobial Activities of Hydrophobically Modified Poly(Acrylate) Films and Their Complexes with Different Chain Length Cationic Surfactants

Multilayer films from hydrophobically modified poly(acrylic acid) (HMPA) and their complexes with cationic surfactants were successfully prepared using the layer-by-layer (LbL) method. Alkyl trimethylammonium bromide derivatives with various lengths of the hydrophobic chain (C10–C18) were used to interact with the HMPA polymer, generating highly hydrophobic domains in the films and contributing to the antimicrobial properties of the prepared coating. The antimicrobial efficiency against common pathogens such as Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans was investigated in relationship with the morphology and composition of the thin films. The wettability and roughness of the multilayered systems were evaluated using atomic force microscopy (AFM) and contact angle measurements. The effects of the microbial exposure on the surface properties of the prepared films were investigated in order to assess the stability of the HMPA-deposited multilayers and the durability of the antimicrobial activity. The hydrophobically modified films exhibited antimicrobial activity against the studied pathogens. The best efficiency was registered in the case of S. aureus, which showed an inhibition of growth up to 100% after 2 h. C. albicans proved to be less sensitive to the effect of the multilayers deposited from HMPA–surfactant complexes. These results suggest that HMPA and HMPA–surfactant complex LbL multilayer films can be used as promising materials in antimicrobial surface coatings with increased resistance to pathogens during exposure