Structure and Bottom-up Formation Mechanism of Multisheet Silica-Based Nanoparticles Formed in an Epoxy Matrix through an In Situ Process

Assessment of metabolic responses following silica nanoparticles in zebrafish models using 1H NMR analysis

Silica nanoparticles (SNPs) are widely explored as drug carriers, gene delivery vehicles, and as nanoparticles intended for bone and tissue engineering. SNPs are highly evident through various clinical trials for a wide range of biomedical applications. SNPs are biocompatible and promising nanoparticles for next-generation therapeutics. However, despite the well-established importance of SNPs, metabolomics methods for the SNPs remain elusive which renders its maximal clinical translation. We applied 1H nuclear magnetic resonance (1H NMR) spectroscopy to investigate the metabolomics profile in Zebrafish (Danio rerio) exposed to SNPs. Zebrafish were exposed to the SNPs (10.0, 25.0, and 50.0 μg/mL) for 72 h and whole-body samples were subjected for targeted profiling. Pattern recognition of 1H NMR spectral data depicted alterations in the metabolomic profiles between control and SNPs exposed zebrafish. We found that tryptophane, lysine, methionine, phenylalanine, tyrosine, sn-glycero-3-phosphocholine (G3PC), and o-phosphocholine were decreased. The metabolic expression of niacinamide, nicotinamide adenine dinucleotide (NAD+), citrate, adenosine triphosphate (ATP), and xanthine were increased in zebrafish with SNPs treatment. We are report for the first time on metabolite alterations and phenotypic expression in zebrafish via 1H NMR. These results demonstrate that SNPs can adversely affect the significant metabolic pathways involved in energy, amino acids, cellular membrane, lipids, and fatty acid metabolisms. Metabolomics profiling may be able to detect metabolic dysregulation in SNPs-treated zebrafish and establish a foundation for further toxicological studies.

Fluorescent and visual sensing of sodium dodecylbenzene sulfonate with an aminosilane self-condensation promoting and electrostatic attraction effect-based ratiometric probe

BACKGROUND

Increasing attention has been paid to sodium dodecylbenzene sulfonate (SDBS) detection because it could cause damage to human body and environmental water. For example, SDBS must not be detected on tableware surface according to national standard of China (GB 14934-2016). However, there is no report heretofore addressing SDBS sensing on surfaces. More importantly, the interferents often affect the sensing performance of analytical approaches. Hence, there is an urgent need to establish a method with good anti-interference ability for SDBS detection both on tableware surfaces and in water.

RESULTS

Inspired by a finding that SDBS could cause the generation of white turbidity in (3-aminopropyl)trimethoxysilane (APTMS, an aminosilane) aqueous solution, APTMS modified Mn doped ZnS quantum dots (QDs) and fluorescent (FL) whitening agent (FWA) were constructed as a ratiometric probe for FL and visual sensing of SDBS. The modified QDs aggregated and settled in presence of SDBS, which was likely to be connected to the stimulatory effect of SDBS on the APTMS self-condensation and the electrostatic attraction. The FL emission from the QDs at 605 nm then decreased dramatically, whereas that at 425 nm was virtually constant owing to FWA. SDBS sensing could be achieved by calculating the ratio change of their FL intensities. The detection limits of FL and visual methods were found to be 0.011 and 10 μg/L, respectively, making it one of the most sensitive approaches in literature. Finally, it was successfully utilized for SDBS detection on tableware surfaces and in water.

SIGNIFICANCE

Herein, the specific interaction between SDBS and APTMS was reported and the reaction mechanisms were explored for the first time. The proposed probe based on the effect described above provided a promising potential for SDBS analysis owing to high sensitivity, selectivity, anti-interference ability, and stability (in 20 days).

Sol-Gel Approach for Fabricating Silica/Epoxy Nanocomposites

This review focuses on the opportunities provided by sol-gel chemistry for the production of silica/epoxy nanocomposites, with significant representative examples of the "extra situ" approach and an updated description of the "in situ" strategy. The "extra situ" strategy enables the creation of nanocomposites containing highly engineered nanoparticles. The "in situ" approach is a very promising synthesis route that allows us to produce, in a much easier and eco-friendly manner, properly flame-retarded silica/epoxy nanocomposites endowed with very interesting properties. The review highlights the recently proposed mechanism of nanoparticles formation, which is expected to help to design the synthesis strategies of nanocomposites, changing their composition (both for the nanoparticle and matrix nature) and with in situ-generated nanoparticles possibly more complex than the ones obtained, until today, through this route.

Hybrid Hemp Particles as Functional Fillers for the Manufacturing of Hydrophobic and Anti-icing Epoxy Composite Coatings

The development of hydrophobic composite coatings is of great interest for several applications in the aerospace industry. Functionalized microparticles can be obtained from waste fabrics and employed as fillers to prepare sustainable hydrophobic epoxy-based coatings. Following a waste-to-wealth approach, a novel hydrophobic epoxy-based composite including hemp microparticles (HMPs) functionalized with waterglass solution, 3-aminopropyl triethoxysilane, polypropylene-graft-maleic anhydride, and either hexadecyltrimethoxysilane or 1H,1H,2H,2H-perfluorooctyltriethoxysilane is presented. The resulting epoxy coatings based on hydrophobic HMPs were cast on aeronautical carbon fiber-reinforced panels to improve their anti-icing performance. Wettability and anti-icing behavior of the prepared composites were investigated at 25 °C and -30 °C (complete icing time), respectively. Samples cast with the composite coating can achieve up to 30 °C higher water contact angle and doubled icing time than aeronautical panels treated with unfilled epoxy resin. A low content (2 wt %) of tailored HMPs causes an increase of ∼26% in the glass transition temperature of the coatings compared to pristine resin, confirming the good interaction between the hemp filler and epoxy matrix at the interphase. Finally, atomic force microscopy reveals that the HMPs can induce the formation of a hierarchical structure on the surface of casted panels. This rough morphology, combined with the silane activity, allows the preparation of aeronautical substrates with enhanced hydrophobicity, anti-icing capability, and thermal stability.

Polyacrylonitrile Fibers with a Gradient Silica Distribution as Precursors of Carbon-Silicon-Carbide Fibers

This study presents preparing and characterization of polyacrylonitrile (PAN) fibers containing various content of tetraethoxysilane (TEOS) incorporated via mutual spinning solution or emulsion using wet and mechanotropic spinning methods. It was shown that the presence of TEOS in dopes does not affect their rheological properties. The coagulation kinetics of complex PAN solution was investigated by optical methods on the solution drop. It was shown that during the interdiffusion process phase separation occurs and TEOS droplets form and move in the middle of the dope's drop. Mechanotropic spinning induces the TEOS droplets to move to the fiber periphery. The morphology and structure of the fibers obtained were investigated by scanning and transmission electron microscopy, as well as X-ray diffraction methods. It was shown that during fiber spinning stages the transformation of the TEOS drops into solid silica particles takes place as a result of hydrolytic polycondensation. This process can be characterized as the sol-gel synthesis. The formation of nano-sized (3-30 nm) silica particles proceeds without particles aggregation, but in a mode of the distribution gradient along the fiber cross-section leading to the accumulation of the silica particles either in the fiber center (wet spinning) or in the fiber periphery (mechanotropic spinning). The prepared composite fibers were carbonized and according to XRD analysis of carbon fibers, the clear peaks corresponding to SiC were observed. These findings indicate the useful role of TEOS as a precursor agent for both, silica in PAN fibers and silicon carbide in carbon fibers that has potential applications in some advanced materials with high thermal properties.

N-Containing Hybrid Composites Coatings for Enhanced Fire-Retardant Properties of Cotton Fabric Using One-Pot Sol-Gel Process

In this report, a unique methodology/process steps were followed using Sol-gel-based concept to deposit thin flame-retardant coatings on cotton fabric. Surface microstructure and compositional analysis of the coated cotton were carried out using scanning electronic microscope (SEM), which explored significant coverage of the fabric. The obtained samples were further analyzed through rupturing mechanism test and color check. Compositional investigation of the coated samples was carried through Attenuated total reflection Fourier transform infrared (ATR-FTIR) and energy-dispersive X-rays spectroscopy (EDS) analysis. Thermal analyses were carried out through Thermogravimetric analysis (TGA) and Vertical flame tests (VFT), which suggested higher resistance of the coatings obtained for 5 h and zero heat-treatment time on the cotton fabric. A 28.86% char residue was obtained for the same sample (ET-5h-RT) coupled with higher degradation temperature and excellent combustion properties.

Synthesis of Mesoporous Silica Adsorbent Modified with Mercapto-Amine Groups for Selective Adsorption of Cu2+ Ion from Aqueous Solution

In a sol-gel co-condensation, a mesoporous silica hybrid integrated with (3-mercaptopropyl)trimethoxysilane (TMPSH) was prepared and then reacted with allylamine via a post-surface functionalization approach. Approximately 15 mol% of TMSPSH was introduced into the mesoporous silica pore walls along with tetraethyl orthosilicate. The mercapto ligands in the prepared mesoporous silica pore walls were then reacted with allylamine (AM) to form the mercapto-amine-modified mesoporous silica adsorbent (MSH@MA). The MSH@MA NPs demonstrate highly selective adsorption of copper (Cu²⁺) ions (~190 mg/g) with a fast equilibrium adsorption time (30 min). The prepared adsorbent shows at least a five times more efficient recyclable stability. The MSH@MA NPs adsorbent is useful for selective adsorption of Cu²⁺ ions.

Effect of the Coupling Agent (3-Aminopropyl) Triethoxysilane on the Structure and Fire Behavior of Solvent-Free One-Pot Synthesized Silica-Epoxy Nanocomposites

Uniformly distributed silica/epoxy nanocomposites (2 and 6 wt.% silica content) were obtained through a “solvent-free one-pot” process. The inorganic phases were obtained through “in situ” sol-gel chemistry from two precursors, tetraethyl orthosilicate (TEOS) and (3-aminopropyl)-triethoxysilane (APTES). APTES acts as a coupling agent. Surprisingly when changing TEOS/APTES molar ratio (from 2.32 to 1.25), two opposite trends of glass transformation temperature (Tg) were observed for silica loading, i.e., at lower content, a decreased Tg (for 2 wt.% silica) and at higher content an increased Tg (for 6 wt.% silica) was observed. High-Resolution Transmission Electron Microscopy (HRTEM) showed the formation of multi-sheet silica-based nanoparticles with decreasing size at a lower TEOS/APTES molar ratio. Based on a recently proposed mechanism, the experimental results can be explained by the formation of a co-continuous hybrid network due to reorganization of the epoxy matrix around two different “in situ” sol-gel derived silicatic phases, i.e., micelles formed mainly by APTES and multi-sheet silica nanoparticles. Moreover, the concentration of APTES affected the size distribution of the multi-sheet silica-based nanoparticles, leading to the formation of structures that became smaller at a higher content. Flammability and forced-combustion tests proved that the nanocomposites exhibited excellent fire retardancy.

Solvent-Free One-Pot Synthesis of Epoxy Nanocomposites Containing Mg(OH)2 Nanocrystal-Nanoparticle Formation Mechanism

Epoxy nanocomposites containing Mg(OH)₂ nanocrystals (MgNCs, 5.3 wt %) were produced via an eco-friendly "solvent-free one-pot" process. X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and thermogravimetric analysis (TGA) confirm the presence of well-dispersed MgNCs. HRTEM reveals the presence also of multisheet-silica-based nanoparticles and a tendency of MgNCs to intergrow, leading to complex nanometric structures with an intersheet size of ∼0.43 nm, which is in agreement with the lattice spacing of the Mg(OH)₂ (001) planes. The synthesis of MgNCs was designed on the basis of a mechanism initially proposed for the preparation of multisheet-silica-based/epoxy nanocomposites. The successful "in situ" generation of MgNCs in the epoxy via a "solvent-free one-pot" process confirms the validity of the earlier disclosed mechanism and thus opens up possibilities of new NCs with different fillers and polymer matrix. The condition would be the availability of a nanoparticle precursor soluble in the hydrophobic resin, giving the desired phase through hydrolysis and polycondensation.