Bioinspired nanovalves with selective permeability and pH sensitivity

Study on Preparation and Performance of Acid pH-Responsive Intelligent Self-Healing Coating

In this paper, microcapsules with acidic pH stimulus responsiveness were prepared through a one-step in situ polymerization method and a layer-by-layer assembly method. The effects of factors such as chitosan (CS) concentration, polymerization time, polymerization process temperature, and the number of polymerization layers on the performance of microcapsules were explored, and microcapsules with optimal performance were prepared and added to the epoxy coating. The morphology and structure of the microcapsules were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and zeta potential testing. The thermal stability and sustained release properties of the microcapsules were studied through thermogravimetric analysis and sustained release curve testing. Through scratch experiments, immersion experiments, salt spray experiments, and electrochemical impedance spectroscopy tests, the impact of the added amount of microcapsules on the self-healing performance and anti-corrosion performance of the coating in complex environments was explored. The results show that the optimal preparation process of acidic pH-responsive microcapsules requires that the concentration of chitosan is 2 mg/mL, the polymerization time of the polyelectrolyte layer is 8 h, the heating temperature during the polymerization process is 75 °C, and the number of polyelectrolyte layers is three. The prepared acidic pH-responsive microcapsules have good morphology, pH sensitivity, and thermal stability. The average particle size is approximately 203 μm, the drug loading rate reaches 59.74%, and the encapsulation rate reaches 63.99%. The optimal added amount of the acidic pH-responsive microcapsule coating is 15 wt%. The coating has a dual-trigger mechanism underlying it stimulus response capability and has an obvious stimulus response to acidic pH. It can inhibit corrosion in non-scratch areas, and its anti-corrosion ability is significantly stronger than that of epoxy coatings and ordinary self-healing coatings. The coating has a stronger repair effect and anti-corrosion ability when the environmental pH becomes acidic.

Self-Healing Abilities of Shape-Memory Epoxy-Contained Polycaprolactone Microspheres Filled with Cerium(III) Nitrate Coated on Aluminum 2024-T3

The shape-memory epoxy (SME) mixed with 10 wt % polycaprolactone (PCL) microspheres containing 5% cerium(III) nitrate (Ce(NO₃)₃) (PCL5Ce) was coated on an aluminum plate 2024-T3 to investigate the self-healing property. The coating was scratched and heated at 80 °C for 30 min to activate the self-healing mechanism and compare with a nonscratched coating. Surface morphology was investigated by scanning electron microscopy. The scratch was completely healed by the PCL5Ce via a thermally assisted self-healing process. Based on electrochemical impedance spectroscopy, the postheated scratched coating had shown impedance values close to the nonscratched coating, which indicated that corrosion resistivity was restored. Ce(NO₃)₃ content at the scratched area was analyzed by focused ion beam-scanning electron microscopy. The scratch width was healed and filled with Ce(NO₃)₃. Therefore, PCL5Ce is capable of being used as an enhancing additive for the self-healing performance in SME coating.

Optimization of analytical assay performance of antibody-gated indicator-releasing mesoporous silica particles

An in-depth study of the chemical tuning modes of antibody-gated indicator delivery (gAID) systems revealed the importance of size matching, localisation of grafting and loading sequence for obtaining high-performance small-molecule sensor materials.

Nanocontainer-Based Active Systems: From Self-Healing Coatings to Thermal Energy Storage

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.

Mussel-Inspired Self-Healing Coatings Based on Polydopamine-Coated Nanocontainers for Corrosion Protection

The mussel-inspired properties of dopamine have attracted immense scientific interest for surface modification of nanoparticles due to the high potential of dopamine functional groups to increase the adhesion of nanoparticles to flat surfaces. Here, we report for the first time a novel type of inhibitor-loaded nanocontainer using polydopamine (PDA) as a pH-sensitive gatekeeper for mesoporous silica nanoparticles (MSNs). The encapsulated inhibitor (benzotriazole) was loaded into MSNs at neutral pH, demonstrating fast release in an acidic environment. The self-healing effect of water-borne alkyd coatings doped with nanocontainers was achieved by both on-demand release of benzotriazole during the corrosion process and formation of the complexes between the dopamine functional groups and iron oxides, thus providing dual self-healing protection for the mild steel substrate. The coatings were characterized by electrochemical impedance spectroscopy, visual observations, and confocal Raman microscopy. In all cases, the coatings with embedded benzotriazole-loaded MSNs with PDA-decorated outer surfaces demonstrated superior self-healing effects on the damaged areas. We anticipate that dopamine-based multifunctional gatekeepers can find application potential not only in intelligent self-healing anticorrosive coatings but also in drug delivery, antimicrobial protection, and other fields.

Nanocontainer-based self-healing coatings: current progress and future perspectives

Nanocontainers add more functionalities to the standard coating formulations.

Two-shell structured PMAA@CeO2 nanocontainers loaded with 2-mercaptobenzothiazole for corrosion protection of damaged epoxy coated AA 2024-T3

In this work, novel two-shell structured inhibitor-loaded poly(methacrylic acid)@cerium oxide (PMAA@CeO₂) nanocontainers were synthesised and characterized. The purpose of the nanocontainers is to increase the corrosion protection provided by an epoxy coating applied to an aerospace alloy (AA 2024-T3). The (PMAA@CeO₂) nanocontainers with diameters of 550 nm were synthesised by a four-step process with the method of distillation precipitation polymerization for the synthesis of the inner PMAA layer, and the sol-gel method for the development of the outer CeO₂ layer. The loaded nanocontainers were characterized by scanning and transmission electron microscopies. The corrosion protection properties of the epoxy coated AA 2024-T3 with 2-mercaptobenzothiazole (2-MBT) loaded PMAA@CeO₂ nanocontainers were evaluated with and without artificial scribes by electrochemical impedance spectroscopy (EIS). The results indicated that the epoxy coating containing the 2-MBT-loaded nanocontainers provided enhanced protection of the AA 2024-T3 substrate.

Selective Fluorogenic Sensing of As(III) Using Aptamer-Capped Nanomaterials

Organic-inorganic hybrid nanomaterials offer extremely valuable tools for monitoring many types of analytes in solution. Within this framework, aptamer-based nanomaterials for heavy metal detection are still very scarce. Herein, a novel sensing nanoprobe for the selective and sensitive detection of As(III) based on the combination of aptamers with mesoporous silica nanoparticles has been developed. The efficiency of the sensor is demonstrated in environmental conditions, showing a great potential in As(III) monitoring assays.

Cooperative self-healing performance of shape memory polyurethane and Alodine-containing microcapsules

In this study, a method to prepare self-healing coatings by incorporating Alodine-containing microcapsules as fillers in Shape Memory Polyurethane (SMPU) was presented.

Gated Molecular Transport in Highly Ordered Heterogeneous Nanochannel Array Electrode

In biology, all protein channels share a common feature of containing narrow pore regions with hydrophobic functional groups and selectivity filter regions abundant with charged residues, which work together to account for fast and selective mass transport in and out of cells. In this work, an ultrathin layer of polydimethylsiloxane (PDMS) was evaporated on the top orifices of charged silica nanochannels (2-3 nm in diameter and 60 nm in length) vertically attached to the electrode surface, and the resulting structure is designated as heterogeneous silica nanochannels (HSNs). As evidenced by voltammetric studies, the transport of ionic species in these HSNs was controlled by both hydrophobic rejection and electrostatic force arising from the top PDMS layer and from the bottom silica nanochannels, respectively. Anionic species encountered both hydrophobic rejection and electrostatic repulsion forces, and thus, their transport was strongly prohibited, while the transport of cationic species was permitted once the electrostatic attraction exceeded the hydrophobic rejection. Moreover, the magnitude of hydrophobic force could be regulated by the PDMS layer thickness, and that of the electrostatic force can be modulated by the salt concentration, solution pH, or applied voltage. It was demonstrated that the HSNs could be activated from an OFF state (no ion can transport) to an ON state (only cation transport occurs) by decreasing the salt concentration, increasing the solution pH, or applying negative voltages.

Cationic surfactant assisted synthesis of poly o-methoxy aniline (PoMA) hollow spheres and their self healing performance

Hollow microspheres of poly(o-methoxy aniline) (PoMA) were prepared in a solution of cetyltrimethylammonium bromide (CTAB) using ammonium persulfate (APS) as oxidant.

Ultrathin Silica Membranes with Highly Ordered and Perpendicular Nanochannels for Precise and Fast Molecular Separation

Membranes with the ability of molecular/ionic separation offer potential in many processes ranging from molecular purification/sensing, to nanofluidics and to mimicking biological membranes. In this work, we report the preparation of a perforative free-standing ultrathin silica membrane consisting of straight and parallel nanochannels with a uniform size (∼2.3 nm) for precise and fast molecular separation. Due to its small and uniform channel size, the membrane exhibits a precise selectivity toward molecules based on size and charge, which can be tuned by ionic strength, pH or surface modification. Furthermore, the ultrasmall thickness (10-120 nm), vertically aligned channels, and high porosity (4.0 × 10(12) pores cm(-2)) give rise to a significantly high molecular transport rate. In addition, the membrane also displays excellent stability and can be consecutively reused for a month after washing or calcination. More importantly, the membrane fabrication is convenient, inexpensive, and does not rely on sophisticated facilities or conditions, providing potential applications in both separation science and micro/nanofluidic chip technologies.