Using Laminar Nanoclays for Phycocyanin and Phycoerythrin Stabilization as New Natural Hybrid Pigments from Microalgae Extraction

C-Phycocyanin (PC) and B-phycoerythrin (PE) are light-harvesting water-soluble phycobiliproteins from microalgae that belong mainly to the cyanobaceria and rhodhophytes families. Different methods have been developed for PC and PE extraction and purification from microalgae, and offer a high potential for their use as additives in sectors such as food and cosmetics. However, the main limitations of using these dyes are the sensitivity of their environmental factors, such as light fastness, temperature, and pH. We successfully employed safe lamellar nanoclays such as montmorillonite (M) and Laponite (L) for phycobiliproteins stabilization, as we did before with other natural dyes. We obtained a wide color gamut from blues to pink by combining four different factors under synthesis conditions: three dye concentrations; two laminar nanoclay sizes; a two nanoclay surface modifiers combination with cetylpyridinium bromide (CPB) and a coupling agent (3-Aminopropyl) triethoxysilane. The experimental conditions were defined according to a multilevel factorial design of experiment (DOE) to study the factors interacting in the final hybrid pigment characteristics. In both M and L, the d001 distance (nm) increased due to PC and PE adsorption. The best conditions to increase the basal space depend on the nanoclay structure, and it is better to use the surfactant for M, and silane modification for L. In addition, optical and thermal PE and PC properties significantly improved. We show the optimal synthesis conditions to increase PC and PE adsorption using the high dye concentration, with surfactant and silane depending on the nanoclay. The hybrid pigments from these phycobiliproteins offer the opportunity to perform several industrial applications, including in polymer additives, cosmetics, and packaging.

Silane Modification of Mesoporous Materials for the Optimization of Antiviral Drug Adsorption and Release Capabilities in Vaginal Media

Three different functionalities have been incorporated into mesoporous materials by means of a coupling reaction with the siloxanes 3-glycidoxypropyl-trimethoxysilane (GLYMO), 3-methacryloxypropyl-trimethoxysilane (MEMO), and 3-mercaptopropyl-trimethoxysilane (MPTMS). The disposition of the different functional groups, as well as the interaction mechanism, with the mesoporous substrate has been identified. The amount of the antiviral drug acyclovir (ACV) adsorbed depends not only on the available surface area but also on the chemical or physicochemical interactions between functionalities. The drug adsorption isotherm of the materials functionalized with GLYMO and MPTMS follow mechanisms dependent on the different surface coverage and the possibilities to establish physicochemical interactions between the drug molecule and the functionalities. On the contrary, when functionalizing with MEMO, the dominant adsorption mechanism is characteristic of chemically bonded adsorbates. The ACV release kinetics is best fitted to the Weibull model in all the functionalized materials. When the MTPMS is used as a functionalizing agent, the drug diffusion occurs at low kinetics and homogeneously along the mesoporous channels.

ZnO-Impregnated Polyacrylonitrile Nanofiber Filters against Various Phases of Air Pollutants

The incorporation of metal oxide nanoparticles (NPs) in fiber filters is an effective approach to enhance the specific surface area and surface roughness of the fiber, hence improving their efficiency for fine dust capture and other gas treatment or biological applications. Nevertheless, uneven distribution of NPs limits their practical applications. In this study, a commercial silane coupling agent (3-methacryloxypropyltrimethoxysilane) was used to improve the dispersion of zinc oxide (ZnO) NPs in thin polyacrylonitrile fibers. Scanning electron microscopy (SEM) revealed that the fibers incorporating the silane-modified NPs exhibited better distribution of NPs than those prepared with pristine ZnO NPs. The silane modification enhanced the specific surface area, surface roughness, and fiber porosity. In particular, the nanofiber filter incorporating 12 wt% ZnO NPs modified with 0.5 g silane per g of ZnO NPs maintained a filtration efficiency of 99.76% with a low pressure drop of 44 Pa, excellent antibacterial activity, and could decompose organic methylene blue dye with an efficiency of 85.11% under visible light.

Halloysite and Laponite Hybrid Pigments Synthesis with Copper Chlorophyll

Sustainable and green materials have been studied in dye and pigment productions to reduce their environment impacts from being produced and applied. Although natural dyes are an excellent choice to move from agrowaste, some improvements must be made before they are applied given their poor fastness. One way of improving natural dye properties is their adsorption into nanoclay structures to give hybrid pigments. This work used tubular halloysite and laminar laponite to adsorb and stabilize natural copper chlorophyll. With a statistical design of experiments, we observed interactions between synthesis factors, such as pH, ionic strength, and surfactant or silane modification. Cool hybrid pigments with high TSR (%) values and a wide color range were obtained by using dispersions with only distilled water at room temperature. Successful chlorophyll adsorption on both nanoclay surfaces took place by XRD and DTA analyses. The maximum natural dye absorption for both nanoclay types took place under acid conditions, pH 3–4, and in the presence of mordant. The TSR (%) improved by the silane pH interaction, and halloysite hybrid pigments obtained higher TSR values than the laponite ones. Finally, a wide chromatic green color range was obtained with the surfactant modification in both nanoclays, and the color fastening was also improved in the hybrid pigments application. The samples generated with 10% of hybrid pigments from both nanoclays and an Epoxy bioresin, show higher colorfastness than the sample with the natural chlorophyll, due to the nanoclays–dye interaction and protection.

Electrophoretic deposition of non-conductive halloysite nanotubes onto glass fabrics with improved interlaminar properties of glass/epoxy composites

This study achieved a homogeneous hierarchical distribution of non-conductive halloysite nanotubes (HNTs) on unidirectional glass fabrics using electrophoretic deposition (EPD). Silane modification was successfully applied to HNTs and glass fabrics. The HNTs and glass fabrics were covalently bonded by condensation polymerization between the carboxyl and amino groups during the EPD process. The HNT-grafted glass fabrics were fabricated into glass fiber-reinforced polymers (GFRPs) using vacuum-assisted resin transfer molding. These results demonstrate an effective enhancement in the through-thickness of HNT-grafted GFRPs. The enhanced mechanical properties of the hierarchically and covalently distributed HNTs were attributed to the excellent interfacial bonding and nanobridging of the HNTs.