Preparation of the cellulose/silica hybrid containing cationic group by sol–gel crosslinking process and its dyeing properties

Self-Assembled Nanodot Actuator with Changeable Fluorescence by π-π Stacking Force Based on a Four-Armed Foldable Phthalocyanine Molecule and Its Supersensitive Molecular Recognition

Designing intelligent molecules and smart nanomaterials as molecular machines is becoming increasingly important in the nanoscience fields. Herein, we report a nanodot actuator with changeable fluorescence by π-π stacking force based on a four-armed foldable phthalocyanine molecule. The assembled nanodot possessed a three-dimensional molecular space structure and multiple supramolecular interactions. The arms of the nanodot could fold and open intelligently in response to environmental molecular stimuli such as natural plant mimosa, which could lead to multiple variable fluorescence emissions. The nanodot was highly sensitive to the biomolecule thyroxine at the molecular level. The accurate molecular recognition and the changeable fluorescence conversion of the nanodot were attributed to multiple supramolecular interactions, including photoinduced electron transfer (PET), intramolecular fluorescence resonance energy transfer (FRET), and π-π stacking of the nanodots, resulting in an intelligent "nanodot machine with folding arms". The self-assembled nanodot actuators with changeable fluorescence have potential applications in advanced intelligent material fields.

Dopamine-Dyed and Functionally Finished Silk with Rapid Oxidation Polymerization

Nowadays, more and more attention has been paid to ecological environment problems, and the dyeing and finishing field is no exception. Environmentally friendly dyeing and finishing methods have been extensively studied. Inspired by the bioadhesive force of marine mussels, dopamine (DA) was applied as a dyestuff and investigated in textile dyeing. In this work, dopamine was dyed on silk with a rapid oxidation polymerization in the presence of metal ions (Fe3+) and sodium perborate oxidant (Ox). The polydopamine (PDA) was rapidly deposited on silk fabric and the dyeing process was optimized as follows: the concentration of DA was 2 g·L-1, and that of Fe3+ was 2 mmol·L-1; the total reaction time was 50 min and reacted at 50 °C; 9 mmol·L-1 Ox was added at 20 min. The K/S value of the treated silk fabric reached 11.46. The color fastness of dyed fabric to light fastness reached Level 4. The SEM and AFM tests showed that the particles attached to the fabric surface and increased the roughness. The XPS test further proved that polydopamine (PDA) was deposited on the fabric. The treated fabric also had a good anti-UV property with a UPF >30 and UVA <4%. The water contact angle of treated fabric attained 142.6°, showing better hydrophobicity, and the weft breaking strength was also improved. This environmentally friendly dyeing and finishing method can be applied and extended to other fabrics.

Hybrid composite membranes of chitosan/sulfonated polyaniline/silica as polymer electrolyte membrane for fuel cells

A series of novel ionic cross-linked chitosan (CS) based hybrid nanocomposites were prepared by using polyaniline/nano silica (PAni/SiO₂) as inorganic filler and sulfuric acid as an ionic cross-linking agent. The CS-PAni/SiO₂ nanocomposites show enhanced mechanical properties and improved oxidative stabilities. These nanocomposites can be effectively used as environmental friendly proton exchange membranes. Incorporation of PAni/SiO₂ into CS matrix enhances water uptake and facilitates the phase separation which enables the formation of hydrophilic domains and improves the proton transport. Moreover, the doped polyaniline also provides some additional pathways for proton conduction. The membrane containing 3wt% loading of PAni/SiO₂ in chitosan (CS-PAni/SiO₂-3) exhibits high proton conductivity at 80°C (8.39×10^-3Scm^-1) in fully hydrated state due to its excellent water retention properties. Moreover, methanol permeability of the ionic cross-linked CS-PAni/SiO₂ nanocomposite membranes significantly reduces with the addition of PAni/SiO₂ nano particles. The CS-PAni/SiO₂-3 composite membrane displays the best overall performance as a polymer electrolyte membrane.

Bacterial cellulose composites loaded with SiO2 nanoparticles: Dynamic-mechanical and thermal properties

The aim of this paper was to prepare composites of bacterial cellulose (BC) filled with silica (SiO₂) nanoparticles to evaluate the influence of the SiO₂ contents (3, 5 and 7wt%) on the thermo-mechanical properties of the composites. BC hydro-gel was immersed in an aqueous solution of silanol derived from tetraethoxysilane (TEOS), the silanol was then converted into SiO₂ in the BC matrix by pressing at 120°C and 2MPa. The BC/SiO₂ translucent sheets were examined by dynamic-mechanical analysis (DMA), thermo gravimetric analysis (TGA), and scanning electron microscopy (SEM). The temperature dependence of the storage modulus, loss modulus and tan delta was determined by DMA. In general, the results revealed that the increment of storage modulus and thermal stability increased concomitantly with the augmentation of SiO₂ content. Therefore, it could be concluded that the mechanical properties of the composites were improved by using high amounts of nano silica. This would be a high aspect ratio of BC capable of connecting the BC matrix and SiO₂, thereby enhancing a large contact surface and resulting in excellent coherence. A decrease of the storage modulus was consistent with increasing temperature, resulting from softening of the composites. The storage modulus of the composites increased in the order: BC/S7>BC/S5>BC/S3, while the loss modulus and tan delta decreased. On the other hand, the thermal stabilities of all BC/SiO₂ composites were remarkably enhanced as compared to the pristine BC. TGA curves showed that the temperature of decomposition of the pure BC gradually shifted from about 260°C to about 370°C as silica content increased. SEM observations illustrated that the nano-scale SiO₂ was embedded between the voids and nano-fibrils of the BC matrix. Overall, the results indicated that the successful synthesis and superior properties of BC/SiO₂ advocate its effectiveness for various applications.

Surface functionalization of viscose and polyester fabrics toward antibacterial and coloration properties

Nanoparticles have been increasingly used to improve the properties of textile fabrics. Viscose and polyester fabrics are treated with SiO(2) nanoparticle by another technique than the conventional sol-gel method in presence of binder (acrylate based copolymer). The effect of the content of SiO(2) nanoparticle on the physical properties of the treated fabrics such as moisture regain, tensile strength and elongation % were investigated. Furthermore, the antibacterial activity and coloration properties of pretreated fabrics were evaluated. Characterizations of pretreated samples by infrared spectroscopy and scanning electron microscopy were also conducted. The results show that the physical and coloration properties of pretreated samples were improved. The treated viscose fabric showed outstanding antibacterial performance against both Escherichia coli (G-) and Staphylococcus aureus (G+). Excellent durability of the treatment to repeated home laundering toward antibacterial and coloration properties was obtained in presence of binder.

Design and properties of biopolymer–silica hybrid materials: The example of pectin-based biodegradable hydrogels

The association of natural polymers with silica is a fruitful strategy to design novel hybrid structures with potential applications in the fields of biotechnology, medicine, and environmental sciences. Here we illustrate the principles of formation, the structure, and the properties of such biohybrid systems by the specific example of silica–pectin porous materials. The influence of the silica source, i.e., aqueous silicates and tetraethoxysilane (TEOS), was more specifically addressed. The alkoxide precursor may be associated with the polysaccharide in a wide range of concentrations. In contrast, the high initial viscosity and fast condensation rate of silicates limits the range of accessible compositions. Owing to weak interactions between the mineral and organic components, silicification does not improve the thermal stability of the polymer but has a strong impact on the water stability of the materials, which depends on the silica source. It is shown that the stability of the silica–pectin hybrid materials during enzymatic degradation is optimum for low carbohydrate content and high silica content, independently of the inorganic precursor.