We highlight the development of nanocontainer-based active materials started in 2006 at the Max Planck Institute of Colloids and Interfaces under the supervision of Prof. Helmuth Möhwald. The active ...materials encapsulated in the nanocontainers with controlled shell permeability have been first applied for self-healing coatings with controlled release of the corrosion inhibitor. The nanocontainers have been added to the paint formulation matrix at 5–10 wt % concentration, which resulted in attaining a coating-autonomous self-healing ability. This research idea has attracted the attention of many scientists around the world (>1500 publications during the last 10 years) and has already been transferred to the commercialization level. The current trend in nanocontainer-based active systems is devoted to the multifunctionality of the capsules which can combine self-healing, antibacterial, thermal, and other functionalities into one host matrix. This article summarizes the previous research done in the area of nanocontainer-based active materials together with future perspectives of capsule-based materials with antifouling or thermoregulating activity.
The release properties and reloading ability of polyelectrolyte‐modified halloysite nanotubes, polyelectrolyte‐modified SiO2 nanoparticles, and polyelectrolyte capsules are studied. Three containers ...are distinguished by keeping the low‐molecular‐weight corrosion inhibitor benzotriazole in a hollow lumen inside or within the polyelectrolyte matrix and allowing release in either one direction or into all space dimensions. Polyelectrolyte shells, which modify the outer surface of the nanocontainers, are fabricated by using layer‐by‐layer assembly of poly(diallyldimethylammonium chloride)/poly(styrene sulfonate), poly(allylamine hydrochloride)/poly(styrene sulfonate), and poly(allylamine hydrochloride)/poly(methacrylic acid) polyelectrolyte bilayers. All nanocontainers reveal an increase of the benzotriazole release in aqueous solution at alkaline or acidic pH. The highest reloading efficiency (up to 80 %) is observed for halloysite‐based nanocontainers; however, after five reloading cycles the efficiency decreases to 20 %. The application of appropriate nanocontainers depends on the demands required from feedback‐active anticorrosion coatings. For coatings where the immediate release of the inhibitor is necessary, SiO2‐based or halloysite‐based nanocontainers with a shell consisting of weak polyelectrolytes are preferable. When continuous, gradual release is required, halloysite‐based nanocontainers with a shell consisting of one weak and one or two strong polyelectrolytes are preferable.
Nanocontainers with surfaces modified with polyelectrolyte shells (see figure) are fabricated using a layer‐by‐layer method and are tested at various pHs for the release of benzotriazole. When immediate release is necessary, SiO2‐based or halloysite‐based nanocontainers with a shell of weak polyelectrolytes are preferable. When continuous, gradual release is required, halloysite‐based nanocontainers with a shell of one weak and one or two strong polyelectrolytes are preferable.
A novel approach to the emulsion encapsulation was developed by combining the advantages of direct encapsulation of a liquid colloidal core with the accuracy and multifunctionality of layer-by-layer ...polyelectrolyte deposition. Experimental data obtained for the model oil-in-water emulsion confirm unambiguously the alternating PE assembly in the capsule shell as well as the maintenance of the liquid colloidal core. Two different mechanisms of capsule destruction upon interaction with the solid substrate were observed and qualitatively explained. The proposed method can be easily generalized to the preparation of oil-filled capsules in various oil/water/polyelectrolyte systems important in the field of pharmacy, medicine, and food industry.
In this review, the recent achievements in the synthesis of inorganic nanomaterials inside the spatially confined volume of individual micro‐ and submicroreactors (emulsions, micelles, organized thin ...films, polyelectrolyte capsules, etc.) are presented. The advantages and shortcomings of each type of microreactor are discussed. Particular attention is paid to polyelectrolyte capsules as confined microreactors with controlled shell permeability and the possibility of shell engineering on the nanolevel, thus tailoring different functionalities. Nanomaterials synthesized inside a confined multifunctional microreactor have several advantages: i) absence of particle aggregates, ii) amorphous or metastable crystal phases, and iii) unique composite inorganic/inorganic and inorganic/organic structures.
Recent achievements in the synthesis of inorganic nanomaterials inside the spatially confined volume of individual micro‐ and submicroreactors (emulsions, micelles, organized thin films, polyelectrolyte capsules; see Figure) are presented. Particular attention is paid to polyelectrolyte capsules as confined microreactors with controlled permeability of the shell and shell engineering on the nanolevel for the tailoring of different functionalities.
The self‐healing anticorrosion effect of layer‐by‐layer (LbL) assembled nanoreservoirs (polyelectrolyte‐coated nanoparticles) embedded in a hybrid coating deposited onto an Al alloy is investigated ...(see figure). The corrosion inhibitor, benzotriazole, is entrapped in the polyelectrolyte at the LbL assembly step; its release is initiated by local pH changes near the corrosion‐damaged zones in the alloy. The nanoreservoirs increase long‐term corrosion protection of the substrate and provide effective inhibitor storage and its prolonged release on demand.
Thermal dark matter models with particle χ masses below the electroweak scale can provide an explanation for the observed relic dark matter density. This would imply the existence of a new feeble ...interaction between the dark and ordinary matter. We report on a new search for the sub-GeV χ production through the interaction mediated by a new vector boson, called the dark photon A^{'}, in collisions of 100 GeV electrons with the active target of the NA64 experiment at the CERN SPS. With 9.37×10^{11} electrons on target collected during 2016-2022 runs NA64 probes for the first time the well-motivated region of parameter space of benchmark thermal scalar and fermionic dark matter models. No evidence for dark matter production has been found. This allows us to set the most sensitive limits on the A^{'} couplings to photons for masses m_{A^{'}}≲0.35 GeV, and to exclude scalar and Majorana dark matter with the χ-A^{'} coupling α_{D}≤0.1 for masses 0.001≲m_{χ}≲0.1 GeV and 3m_{χ}≤m_{A^{'}}.
•Ultrasound accelerates synthesis of nanofibrillar cellulose/polystyrene composite.•High biodegradability of nanofibrillar cellulose/polystyrene composite.•High mechanic strength of nanofibrillar ...cellulose/polystyrene composite.
A new method of the synthesis of nanofibrillar cellulose/polystyrene composite based on ultrasonic treatment of styrene emulsion in cellulose-water solution was elaborated. A new approach does not require additional heating and proposes a significantly faster synthesis (15 min, 45 °C) of the target composite compared to the methods described previously. A comprehensive analysis did not reveal any significant differences between mechanical, physical and biodegradable properties of the composite obtained by ultrasonic method and that one obtained by conventional thermal method, which requires much higher temperature (above 75 °C) and reaction duration (from 3 h).
We report the formation and ultraviolet (UV) photodetection of single-crystalline spherical ZnO particles by pulsed laser irradiation of commercial ZnO nanoparticles in water. The phase and ...microstructure analysis before and after laser irradiation reveals a crystal size increase and shape transformation from irregular to spherical. Time-dependent laser irradiation confirmed that fusion is the reason for nanoparticle growth up to single-crystalline spherical particles. After rapid cooling, they maintain size and shape and possess unique optical and electrical properties. Because of the single-crystalline feature and smooth surfaces, high and selective sensing of ultraviolet light is observed.
The observation of morphological details down to the nanometer range of the outer surface of micro-, submicro- and nanoparticles in a high-resolution scanning electron microscope (SEM) was extended ...with in-depth observation by enabling the transmission mode in the SEM, i.e. TSEM. The micro- and nanocapsules characterized in this study were fabricated as depots for protective agents to be embedded in innovative self-healing coatings. By combining the two imaging modes (upper and in-depth observation) complementing each other a better characterisation by a more comprehensive interpretation of the "consistency" of the challenging specimens, e.g. including details "hidden" beyond the surface or the real specimen shape at all, has been attained. Furthermore, the preparation of the quasi electron transparent samples onto thin supporting foils enables also elemental imaging by energy dispersive X-ray spectroscopy (EDX) with high spatial resolution. Valuable information on the elemental distribution in individual micro-, submicro- and even nanocapsules completes the "3D" high resolution morphological characterization at the same multimodal SEM/TSEM/EDX system.
PDF
