Mesoporous Silica Nanocontainers Research Articles

Improved anti-corrosion and self-healing performance of epoxy coatings reinforced by chitosan encapsulated mesoporous silica nanocontainers

In this work, corrosion inhibitor of 1H-Benzotriazole (BTA) was loaded into hollow mesoporous silica nanocontainers (HMSNs-BTA). Then, chitosan (CS) was coated on the surface of the HMSNs (HMSNs-BTA@CS) to realize pH-controlled release of BTA. The prepared HMSN-BTA@CS was used to enhance the corrosion resistance of epoxy coating. The results show that the pH-controlled release of BTA endows the coating with self-healing ability. After 60 days immersion in salt solution, the low-frequency impedance modulus of HMSNs-BTA@CS reinforced epoxy coating still reaches 3.74 × 108 Ω cm2. This is caused by the healing effect of BTA and the good dispersion of the nanofillers in epoxy coating.

Smart nanoarchitectonics of epoxy coating: Preparation, release behavior and self-healing performance based on mesoporous silica nano-containers loaded with DMTD inhibitors

Self-healing coatings doped by nano-containers loaded with inhibitors have shown remarkable anti-corrosion efficiency and durability in extending metal life and slowing down coating failure. However, low loading capacity of corrosion inhibitors in nano-containers is a problem plaguing the further development and application of smart coatings. In this study, mesoporous silica with large pore sizes (MSN) was synthesized using the soft template method which significantly increased the loading capacity of the corrosion inhibitor, and a smart self-healing composite coating was designed, which could protect carbon steel from corrosion and provide durable protection for it. Specifically, the composite coating (EP/DMTD@MSN-PAA) was prepared by incorporating mesoporous silica nano-containers embedded with 2,5-dimercapto-1,3,4-thiadiazole (DMTD) molecules into the epoxy resin coating. The results of BET test showed that the prepared MSNs had high specific surface area (734.97 m2/g) and large pore volume (0.85 cm3/g). The thermogravimetric (TG) analysis showed 35.7% of loading amount of corrosion inhibitors in the nano-materials. Response release experiments showed that the DMTD@MSN-PAA had of acid-response release characteristics. When pH value of the system decreased from 7 to 3, the release amount of the DMTD molecules increased from 40.3% to 93.7%. The contact angle test showed that the epoxy resin (EP) coating had a contact angle value of 57.7°, while those of the composite coatings doped with 1 wt%, 3 wt% and 6 wt% DMTD@MSN-PAA (EP/DMTD@MSN-PAA) were 65.1°, 75.2° and 67.2°, respectively. These results indicated that the composite coatings had better hydrophobicity compared to the EP coating, and were conducive to prolonging the coating service time. The anti-corrosion performances of both the EP and the composite coatings with different doping amounts of DMTD@MSN-PAA were evaluated by EIS measurements. The Rct value of the EP coating decreased from 190.3 to 25.1 Ω · cm2 within the time of 48 h of immersion in 3.5 wt% NaCl solution, while ones of the EP/DMTD@MSN-PAA coatings doped with 1 wt%, 3 wt% and 6 wt% of DMTD@MSN-PAA increased from 303.1, 720.7.7, 523.4–1426.4, 2113.8, 1066.3 Ω · cm2, respectively. In addition, the corrosion resistance of the EP and composite coatings were further evaluated by etching experiments. The results showed that after 35 d of immersion, compared with that of the EP coating, surface corrosion degree of the composite coatings was lower, and the scaling off speed of the coatings slowed down, which further proved that the composite coating had strong corrosion resistance and special self-healing characteristics.

Antibacterial Bionanocomposites Based on Drug-Templated Bifunctional Mesoporous Silica Nanocontainers.

The creation of antibacterial nanocomposites that provide prolonged release of encapsulated drugs is of great interest for various fields of medicine (dentistry, tissue regeneration, etc.). This article demonstrates the possibility of creating such nanocomposites based on sodium alginate and drug-templated mesoporous silica nanocontainers (MSNs) loaded with two bioactive substances. Herein, we thoroughly study all stages of the process, starting with the synthesis of MSNs using antiseptic micelles containing the hydrophobic drug quercetin and ending with assessing the activity of the resulting composites against various microorganisms. The main emphasis is on studying the quercetin solubilization in antiseptic micelles as well as establishing the relationship between the conditions of MSN synthesis and micelle morphology and capacity. The effect of medium pH on the release rate of encapsulated drugs is also evaluated. It was shown that the MSNs contained large amounts of encapsulated drugs and that the rate of drug unloading depended on the medium pH. The incorporation of such MSNs into the alginate matrix allowed for a prolonged release of the drugs.

Epoxy composite coating with excellent anti-corrosion and self-healing properties based on mesoporous silica nano-containers

Anti-corrosion coating containing smart nano-containers loaded with inhibitors played an increasingly important role in extending the coating lifetime and slowing down metal corrosion. Whereas, the low loading capacity of the inhibitors in the nano-container limits its applications. In this work, mesoporous silica (SiO2) nano-materials with large pore diameter were prepared and designed as the nano-containers loaded by 2-amino-5-mercapto-1,3,4-thiadiazole (AMT) inhibitors. The prepared nano-containers not only achieved acid-responsive release ability but also greatly increased the loading capacity of the inhibitors. The results showed that the loading capacity of the AMT inhibitors reached 36% and the release amount of them from the SiO2-based nano-containers increased as the gradually decreased pH value of the system. When the pH was 3, 5 and 7, the release amount of the AMT inhibitors was 92.3%, 73.6% and 50.2%, respectively, indicating that the strong acidic system could exacerbate the metal damage, whereas the increasing release amount of the inhibitors could effectively slow down the metal corrosion. The experiments about the release process of the inhibitors from the nano-container ensured that the epoxy composite coating doped by the above-mentioned nano-containers could exhibit self-healing function under different acidic conditions. In addition, the prepared epoxy composite coating (EP/AMT@MSN-PAA) showed an increasing Rct value with the immersion time (that varied from 3105 Ω·cm2 to 4509 Ω·cm2 when the immersion time lasted from 0 h to 48 h). Compared to the blank epoxy coating (EP), the Rct value significantly decreased from 2876 Ω·cm2 to 658 Ω·cm2 with the time, which indicated that the epoxy composite coating had wonderful anti-corrosion performance and excellent self-healing function in harsh environments.

Electrochemiluminescence Sensor with Controlled-Release Triggering Electrostatic Attraction Elimination Mechanism for Trenbolone Trace Detection.

A controlled-release strategy can meet the needs of sensitive environmental monitoring for pollutants through a self-on/off mode. In this work, an electrochemiluminescence (ECL) biosensor with controlled-release triggering electrostatic attraction elimination and biomolecular stimulated response strategies was constructed to detect environmental steroid hormones sensitively. The blocked pores on the aminated mesoporous silica nanocontainers were opened by specific binding between the trenbolone (TB) antigen and the antibody. The released l-cysteine counteracted the negative charge on the MnO2 NF surface through the redox reaction between -SH and MnO2, making the electrostatic interaction between the MnO2 NFs and the Ru(dcbpy)32+ disappear. Ru(dcbpy)32+ released an ECL signal on the electrode, thus completing the controlled-release triggering electrostatic attraction elimination strategy. In addition, with the TB antibody as the target and the competition strategy between the TB antigen and the standard substance, the constructed controlled-release ECL biosensor was used to detect the TB standard substance. Moreover, MnO2 NFs as the substrate of the ECL biosensor increased the active specific surface area of the electrode, effectively catalyzing the production of OH• and O2•-, thus endowing the ECL biosensor with coreactant-catalytic enhancement characteristic and further improving its ECL performance. This sensitive signal response brought about a low limit of detection of 2.53 fg/mL for the constructed ECL biosensor, which contributed a feasible idea for efficient trace analysis of pollutants in the environment.

Characterization and Behaviour of Silica Engineered Nanocontainers in Low and High Ionic Strength Media.

Mesoporous silica engineered nanomaterials are of interest to the industry due to their drug-carrier ability. Advances in coating technology include using mesoporous silica nanocontainers (SiNC) loaded with organic molecules as additives in protective coatings. The SiNC loaded with the biocide 4,5-dichloro-2-octyl-4-isothiazolin-3-one (DCOIT), i.e., SiNC-DCOIT, is proposed as an additive for antifouling marine paints. As the instability of nanomaterials in ionic-rich media has been reported and related to shifting key properties and its environmental fate, this study aims at understanding the behaviour of SiNC and SiNC-DCOIT in aqueous media with distinct ionic strengths. Both nanomaterials were dispersed in (i) low- (ultrapure water-UP) and (ii) high- ionic strength media-artificial seawater (ASW) and f/2 medium enriched in ASW (f/2 medium). The morphology, size and zeta potential (ζP) of both engineering nanomaterials were evaluated at different timepoints and concentrations. Results showed that both nanomaterials were unstable in aqueous suspensions, with the initial ζP values in UP below -30 mV and the particle size varying from 148 to 235 nm and 153 to 173 nm for SiNC and SiNC-DCOIT, respectively. In UP, aggregation occurs over time, regardless of the concentration. Additionally, the formation of larger complexes was associated with modifications in the ζP values towards the threshold of stable nanoparticles. In ASW, SiNC and SiNC-DCOIT formed aggregates (<300 nm) independently of the time or concentration, while larger and heterogeneous nanostructures (>300 nm) were detected in the f/2 medium. The pattern of aggregation detected may increase engineering nanomaterial sedimentation rates and enhance the risks towards dwelling organisms.

Towards weathering and corrosion resistant, self-warning and self-healing epoxy coatings with tannic acid loaded nanocontainers

In this work, an active protective epoxy coating with weathering resistant, corrosion-warning, and self-healing properties was developed by incorporating tannic acid (TA) loaded mesoporous silica (MSN-TA) nanocontainers. The introduction of MSN-TA nanocontainers could alleviate the coating degradation via scavenging the radicals generated during UV irradiation. Compared with the blank coating, the coating containing 5 wt.% MSN-TA nanocontainers exhibited much less degradation in surface morphology, wettability and glossiness, and maintained a good barrier property after 384 h of accelerated weathering. Once the coating was damaged, the released TA could react with the Fe3+ ions to form a chelate that endowed the coating scratch with a visible black coloration, i.e. triggering a self-warning capability to indicate the initial onset of corrosion. In addition, the generated chelate could inhibit extensive corrosion propagation, offering a significant self-healing effect demonstrated by the stabilized impedance modulus values during 28 days of immersion in NaCl solution.

PH-responsive mesoporous silica nanocontainers based on Zn-BTA complexes as stoppers for controllable release of corrosion inhibitors and application in epoxy coatings

A classical strategy of constructing pH-sensitive release system is to encapsulate mesoporous nanoparticles with insoluble complexes such as copper-benzotriazole (Cu-BTA) complex. In this paper, a new capping material, Zn-BTA complex, was adopted to overcome the promoting effect of Cu2+ ions from the decomposition of Cu-BTA complexes on corrosion of mild steel. Mesoporous silica nanoparticles (MSNs) were synthesized, loaded with BTA and then capped with Zn-BTA complexes as stoppers to form MSN-BTA@Zn nanocontainers. The releasing behaviors of BTA at various pH values were investigated, and it was found that MSN-BTA@Zn could achieve on-command release of BTA in response to decrease of pH caused by anodic reaction of corrosion. MSN-BTA@Zn nanocontainers were introduced to epoxy resin to construct stimuli-responsive coating on mild steel substrate. The composite coating with artificial defects shows a distinct stimuli-responsive performance in 3.5 % NaCl, and the incorporation of MSN-BTA@Zn has no impact on the adhesion of the coating to the substrate. The formation of zinc hydroxide compounds in the cathodic zone of galvanic cell makes contribution to the enhancement of corrosion resistance for the coating.

Highly Efficient Signal On/Off Electrochemiluminescence Gel Aptasensor Based on a Controlled Release Strategy for the Sensitive Detection of Prostate Specific Antigen.

The controlled release strategy can make the constructed sensor have the function of self-on/off, which has an obvious effect on improving the sensitivity in immunoassays. Metal organic gels (MOGs) are the most noteworthy. They are materials with ultrahigh surface area, highly dispersed atomical metal sites, and well-defined porosity and can be used as an efficient luminophore to cause the developed sensor to have good hydrophilicity and adjustability, thus further improving the detection sensitivity. In this work, a novel on/off electrochemiluminescence (ECL) gel aptasensor was constructed using the Cys-[Ru(dcbpy)3]2+ gel as a luminophore, ZnS quantum dots (QDs) as quenchers, and aminated mesoporous silica nanocontainers (SiO2-NH2) as carriers of controlled release for prostate specific antigen (PSA) detection. Specifically, the ssDNA and PSA aptamer made up clamp-like molecules to block holes of the SiO2-NH2 after encapsulating the quencher ZnS QDs. Because of the specific binding between the PSA antigen and aptamer, the clamp-like molecules of ssDNA and the PSA aptamer were disassembled. Finally, the release of ZnS QDs was triggered, thereby realizing a self-off mode of the ECL signals under a co-reactant-free environment by ECL resonance energy transfer (ECL-RET) between the Cys-[Ru(dcbpy)3]2+ and ZnS QDs. In addition, the quenching mechanism was confirmed by molecular orbitals from the theoretical calculation level. The detection limit of the gel aptasensor for PSA was as low as 1.01 fg/mL, showing excellent sensitivity and accuracy. These strategies provided a feasible idea for PSA and even other tumor marker immunoassays.

PVCL-grafted mesoporous silica nanocontainers for thermo-responsive controlled release and their antifungal activity study

Herein, thermo-responsive nanocontainers depended on mesoporous silica nanoparticles (MSN) functionalized with two copolymers: poly(3-methacryloxypropyltrimethoxysilane) “PMPS, source of condensation with silica” and poly(N-vinylcaprolactam) “PVCL” were synthesized by a facile one-step approach, characterized then evaluated as antifungal materials. Taking advantage of the polymer gatekeeper strategy, the loading or release processes of anidulafungin (AFG) as a model antifungal drug were adjusted by the stimuli-responsiveness of PVCL. Upon temperature treatment at various conditions, the loaded AFG was released with a killing effect against four strains of fungi, as reported by filter-paper and hole-plate technique. This kind of stimuli-sensitive nanocontainers can be a potential platform for biomedical applications.

Controllable construction of mesoporous silica/2D-COF nanocomposites reinforced epoxy coatings with excellent self-repairing and long-lasting anticorrosion performances

Endowing epoxy coatings with long-term anticorrosion performance is extremely important and urgent for its application in extreme marine environment. We prepared a new composite nanofiller to realize this purpose. Mesoporous silica nanocontainers (MSNs) are prepared by sol-gel method. The corrosion inhibitor (BTA) is loaded in the MSNs to give the self-healing ability of the nanofiller. To realize controllable release of BTA, chitosan (CS) is coated on the surface of the MSNs-CS. To improve the dispersion ability of the MSNs-CS nanofillers in epoxy coatings, the fillers are loaded on the surface of 2D nanoflakes of TpPa. The results show that the coated CS can act as a pH response valve to control the release of the loaded BTA. The TpPa can not only improve the dispersion ability of MSNs in epoxy coatings, but also it can act as physical barrier to prevent the diffusion of corrosive media. The controllable release of BTA gives the coatings self-healing ability. After 90 days of immersion, results show that the low-frequency impedance modulus of MSNs-CS/TpPa-1 wt% reaches 7.68 × 109 Ω cm2, and the low-frequency impedance modulus of MSNs-1 wt% and COF-1 wt% are only 6.74 × 107 Ω cm2 and 1.24× 107 Ω cm2, respectively. In the abrasion resistance test, the averaged friction coefficient of MSNs-CS/TpPa-1 wt% is as low as about 0.35 and has the smallest wear area of 125 μm2. It proves that it has good anti-wear performance. This work provides a new nanofiller to enhance the long-term protection performance of epoxy coatings.

Corrosion resistance and mechanisms of smart micro-arc oxidation/epoxy resin coatings on AZ31 Mg alloy: Strategic positioning of nanocontainers

Smart micro-arc oxidation (MAO)/epoxy resin (EP) composite coatings were formed on AZ31 magnesium (Mg) alloy. Mesoporous silica nanocontainers (MSN) encapsulated with sodium benzoate (SB) corrosion inhibitors were strategically incorporated in the MAO micropores and in the top EP layer. The influence of the strategic positioning of the nanocontainers on the corrosion protective performance of coating was investigated. The experimental results and analysis indicated that the superior corrosion resistance of the hybrid coating is ascribed to the protection mechanisms of the nanocontainers. This involves two phenomena: (1) the presence of the nanocontainers in the MAO micropores decreased the distance between MSN@SB and the substrate, demonstrating a low admittance value (∼ 5.18 × 10−8 Ω−1), and thus exhibiting significant corrosion inhibition and self-healing function; and (2) the addition of nanocontainers in the top EP layer densified the coating via sealing of the inherent defects, and hence the coating maintained higher resistance even after 90 days of immersion (1.13 × 1010 Ω cm2). However, the possibility of corrosion inhibitors located away from the substrate transport to the substrate is reduced, reducing its effective utilization rate. This work demonstrates the importance of the positioning of nanocontainers in the coating for enhanced corrosion resistance, and thereby providing a novel perspective for the design of smart protective coatings through regulating the distribution of nanocontainers in the coatings.

Triggered drug release of surface cyclic peptide gatekeepers with endothelial cell targeting sequence conjugated to mesoporous nanocontainers

• The sequence targeting tumor endothelial cell is introduced to the peptide gatekeeper. • The release of entrapped drugs is completely inhibited in the absence of stimuli. • The structure of peptide gatekeeper was converted by addition of bioreductant. • The entrapped drugs in nanocontainers are released on-demand. Peptides have been used to develop drug delivery vehicles because of their ability to selectively target desired cells and respond to various biomolecules. In this study, a WIFPWIQL sequence with the capability of selectively targeting angiogenic endothelial cells was introduced to prepare a cyclized peptide gatekeeper on the surface of mesoporous silica nanocontainers (MSNs). In the absence of any stimulus, the WIFPWIQL-containing peptide gatekeeper, cyclized by a cystine unit, inhibited the release of drugs encapsulated within the MSNs. In the presence of a bioreductant, the disulfide bond of the cystine unit was decomposed to yield thiol units, and the peptide gatekeeper was converted into a linear structure. The encapsulated drugs in the MSNs were released responsively.

Rapid and eco-friendly one-step synthesis of dodecylamine-encapsulated mesoporous silica nanocontainers

Incorporating nanoreservoirs loaded with corrosion inhibitors is the most attractive approach for developing extrinsic self-healing anti-corrosion coatings. This work reports a rapid and eco-friendly one-step synthesis of dodecylamine-encapsulated mesoporous silica nanocontainers. The nanocontainers were characterized by X-ray diffraction, electron microscopy and thermogravimetric analysis. The as-synthesized nanocontainers were amorphous with short-range ordered mesoporous channels. Thermogravimetric study confirmed the inhibitor loading to be ∼13.6%. The nanocontainers (1 wt%) were further dispersed in 0.1 mol/L NaCl solution, and the release behaviour was systematically studied as a function of pH (acidic, basic and neutral) by electrochemical impedance spectroscopy at different durations. The release was more pronounced at acidic pH ranges. The inhibitor-loaded nanocontainers provided significantly higher impedance values in acidic environment revealing sustained inhibitor release and enhanced corrosion protection for the carbon steel electrode. The study also reports detailed thermogravimetric results on the effect of different washing procedures in determining the inhibitor percentage loading.

Superoxide-Responsive Cargo Release of Mesoporous Silica Nanocontainers with Thioketal Linker

Superoxide-Responsive Cargo Release of Mesoporous Silica Nanocontainers with Thioketal Linker

Difunctional Silicon Dioxide Combined with Graphene Oxide Nanocomposite to Enhance the Anticorrosion Performance of Epoxy Coatings.

The nanocomposite BTA-SiO2-GO was fabricated for the purpose of metal corrosion protection. Herein, the BTA-loaded mesoporous silica nanocontainers were prepared through a facile one-step synthetic method. Subsequently, graphene oxide (GO) was combined with the resultant BTA-SiO2 compound because GO had a superior barrier property and impermeability. We must note that the double functional groups exist on SiO2. Benzotriazole (BTA), as an inhibitor, can be loaded into the nanocontainer and GO can also be modified by it, resulting in excellent dispersion in epoxy coatings, which were conducive to enhancing its anticorrosion performance. In this way, the nanocomposite endows the coating system with both self-healing and physical barrier abilities. The EIS results indicated that the impedance value of the BTA-SiO2-GO composite coatings was up to 1.2 × 109 Ω cm2, which indicated excellent corrosion resistant properties.

Anti-corrosive Polystyrene Coatings Modified with Tannic Acid on Zinc and Steel Substrates

Polystyrene (PS) polymer layers were prepared and studied as anti-corrosive barrier layers on both carbon steel and zinc substrates. To increase the corrosion resistance of the coatings, two different approaches were considered: (i) the use of mesoporous silica-nanocontainers impregnated with a corrosion inhibitor (tannic acid) introduced into the polystyrene matrix and (ii) direct impregnation of polystyrene coatings with the same corrosion inhibitor. The impregnated nanocontainers were characterized by Transmission Electron Microscopy. The thickness and the adhesion of the coatings were measured, and their corrosion behavior was investigated by Electrochemical Impedance Spectroscopy. Results showed that the used inhibitor slightly decreased adhesion, but significantly increased the corrosion resistance of the coatings. The direct introduction of tannic acid into the polymer matrix offers higher corrosion resistance than in the case of polystyrene coatings doped with impregnated silica nanocontainers.

Rapid and Ecofriendly One-Step Synthesis of Dodecylamine Encapsulated Mesoporous Silica Nanocontainers

Rapid and Ecofriendly One-Step Synthesis of Dodecylamine Encapsulated Mesoporous Silica Nanocontainers

Durable and long-lasting transparent anticorrosive films for copper substrates using mesoporous silica nanocontainers loaded with corrosion inhibitor

We have developed functional films capable of retaining anticorrosive properties even after severe mechanical damage which directly exposes the metal surface to corrosive environments. It was found that functional films prepared by simply dispersing mesoporous silica-nanocontainers loaded with a corrosion inhibitor, tolyltriazole, in a commercially available aqueous polyurethane solution could effectively prevent the corrosion of copper substrates. Even after cutting of the films and submersion in aqueous sodium chloride, no serious oxidation of the damaged areas was observed for up to four months. The transparency of the resulting polyurethane films remained almost unchanged with or without the addition of MPS-NCs/TTA.

NIR-Controlled Treatment of Multidrug-Resistant Tumor Cells by Mesoporous Silica Capsules Containing Gold Nanorods and Doxorubicin.

Multidrug resistance (MDR) is identified as a major impediment to the efficient chemotherapy of cancer, and considerable endeavors have been devoted to reverse MDR containing structuring varieties of multifunctional nanocarriers. Here, a specially light-activated hollow mesoporous silica nanocontainer with an in situ-synthesized Au nanorod (AuNR) core and a surface-modified hairpin structure DNA gatekeeper is reported for treating MDR tumor cells. In this system, the AuNR only fills part of the space in hollow mesoporous silica due to its controllable size, and the remaining space is used to load enough DOX. By controlling the near-infrared (NIR) laser intensity and exposure duration, the configuration of hairpin-structured DNA (Tm = 51.4 °C) can change reversibly and then trigger the controllable intracellular release of DOX, leading to a significantly enhanced chemotherapeutic efficacy and adjustable photothermal treatment for multidrug-resistant cancer cells. The in vitro experiments showed that this system could effectively overcome the MDR of HepG2-adm cells (a MDR cell line of human hepatocarcinoma cells) by the increased concentration of DOX intracellularly and the photothermal conversion of AuNRs, even at a low concentration (e.g., 30 μg mL-1). Therefore, this NIR-triggered chemo-photothermal synergistic treatment system can be used as a promising efficient strategy in reversing the multidrug resistance for cancer therapy.