New natural organic–inorganic pH indicators: Synthesis and characterization of pro-ecological hybrid pigments based on anthraquinone dyes and mineral supports

Synthesis of Berberis aristate rhizome extract stabilized magnesium nanoparticles using green chemistry: rhizome characterization, in vitro antimicrobial and anti-inflammatory activity

In the present study, magnesium nanoparticles (Mg NPs) were synthesized utilizing an aqueous extract of Berberis aristate rhizome and evaluated for antimicrobial and anti-inflammatory activity. Technofunctional properties of rhizome powder were evaluated and during thermal stability evaluation four stages of decomposition with a maximum delta Y value of 76.04 % was observed. Optimization of Mg NPs was carried out by employing eight different concentrations (C1-C8)   and the C4 showed maximum absorbance at 330 nm confirming the NPs synthesis. The Mg NPs showed the particle size of 62 nm, zeta potential of -24.7 mV and hexagonal mprphology. Potential inhibition against S. aureus and E. coli (76.78 ± 0.05% and 74.62 ± 0.17%)and anti-inflammatory activity ranging from 42.43 ± 0.07-82.92 ± 0.04% was observed for Mg NPs. Therefore, green synthesis of Mg NPs is a promising approach for the development ofbiological active NPs to cure microbial infections.

Structure and morphology of red pigments based on sepiolite

Sepiolite is an important raw fibrous material. A method to prepare red pigments based on sepiolite through the thermal treatment of sepiolite with sulfur and sodium sulfide hydrate is reported. Sepiolite was heated until 800 °C in order to remove zeolitic water, the first coordinated water, the second coordinated water, and structural hydroxyls. Several [S/Na2S]molar ratios in the range 0.5-7 were employed. The properties of these pigments were studied by different analytical techniques, such as colorimetric analysis, thermal analysis, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction and scanning electron microscopy. The samples with [S/Na2S] = 0.5 and 1, corresponding to high contents of sodium sulfide in the synthesis procedure, exhibit high values of the colorimetric parameter CIE a* and a maximum reflectance in the visible zone belonging to red, based on the red colour of the samples. Under the reducing conditions of the synthesis, sulfur forms polysulfides of the general formula [Sx]2-. The sodium sulfide reacts with the excess S to form polysulfides as well. From the polysulfides, the radical anions of the general formula [Sx/2]˙- originate and they are identified as the chromophore groups responsible for the color in the sulfur-based pigment analogues of ultramarines. The red colour of the samples could be mainly attributed to the presence of S4 and S4˙- identified by FTIR.

Enhancing the accuracy, speed, and efficiency of kafirin-PEO electrospun bio-nanocomposite pH indicators with red beetroot extract using image processing

Intelligent electrospun pH indicators were produced from bio-nanocomposite kafirin-polyethylene oxide (PEO) containing red beetroot extract. The aim was to evaluate the performance and stability of the electrospun pH indicators via image processing. Red beetroot extract was added to a mixture of kafirin and PEO at various concentrations. The mixtures were electrospun, and infrared Fourier transform spectroscopy confirmed the presence of kafirin, PEO, and red beetroot extract in the resulting pH indicator. The results showed that the pH indicators had high stability and reversibility at different temperatures, pHs, and environmental conditions. The results showed that the color of the indicators was significantly reversible after pH changes, with highly desirable reversibility observed at pH values of 1, 3, 4, 5, 7, 9, and 10. The findings proved that the red beetroot extract loaded bio-nanocomposite pH indicator accompanied by evaluation of color characteristics through image processing technique, can serve as a time-efficient, accurate tool for detecting and tracking pH changes caused by food spoilage.

Functionalization of bamboo fibers with lawsone dye (Lawsonia inermis) to produce bioinspired hybrid color composite with antibacterial activity

There is great interest in using eco-friendly functional colorants with antibacterial activity to produce colorful textile and plastic products. In this study, we designed, produced, and analyzed a novel multifunctional hybrid color composite colorant with antimicrobial properties, prepared from plant-based products. The new functional color composite was prepared by stabilizing lawsone dye onto amino-silanized cellulose from bamboo fibers. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy were performed to examine the possible interactions between the lawsone dye and silanized bamboo fibers. The color performance, morphology, chemical stability, and thermal stability of the prepared color composite were evaluated using scanning electron microscopy (SEM), UV-Vis spectrophotometry, and thermogravimetric analysis (TGA). The results were compared to those for pure lawsone dye. Modification of amino-silanized bamboo fibers with lawsone dye led to the formation of a light brown colorant that is more resistant to organic solvents (e.g. acetone, ethanol) and elevated temperatures than raw natural dye. Importantly, the designed bamboo fiber/lawsone system (BF-APTES-L) benefits from the synergistic combination of lawsone and bamboo fibers, showing strong antibacterial activity compared to the control sample of bamboo-as evidenced by noticeably inhibited growth of E. coli, S. aureus, and B. subtilis.

Preparation of Hybrid Nanopigments with Excellent Environmental Stability, Antibacterial and Antioxidant Properties Based on Monascus Red and Sepiolite by One-Step Grinding Process

This study is focused on the preparation, characterization, and multifunctional properties of intelligent hybrid nanopigments. The hybrid nanopigments with excellent environmental stability and antibacterial and antioxidant properties were fabricated based on natural Monascus red, surfactant, and sepiolite via a facile one-step grinding process. The density functional theory calculations demonstrated that the surfactants loaded on sepiolite were in favor of enhancing the electrostatic, coordination, and hydrogen bonding interactions between Monascus red and sepiolite. Thus, the obtained hybrid nanopigments exhibited excellent antibacterial and antioxidant properties, with an inhibition effect on Gram-positive bacteria that was superior to that of Gram-negative bacteria. In addition, the scavenging activity on DPPH and hydroxyl free radicals as well as the reducing power of hybrid nanopigments were higher than those of hybrid nanopigments prepared without the addition of the surfactant. Inspired by nature, gas-sensitive reversible alochroic superamphiphobic coatings with excellent thermal and chemical stability were successfully designed by combining hybrid nanopigments and fluorinated polysiloxane. Therefore, intelligent multifunctional hybrid nanopigments have great application foreground in related fields.

Novel pH-sensitive catechol dyes synthesised by a three component one-pot reaction

The synthesis and characterisation of new dyes based on indolizines bearing catechol groups in their structure is presented. The preparation was carried out through a simple three component one-pot reaction promoted by CuNPs/C, between pyridine-2-carbaldehyde, an aromatic alkyne and a tetrahydroisoquinoline (THIQ) functionalized with catechol groups. The products were isolated in 30%-34% yield, which was considered more than acceptable considering that the catechol hydroxyl groups were not protected prior to reaction. In view of the colour developed by the products and their response to the acidic and basic conditions of the medium, product 3aa was studied by UV-Vis and NMR spectroscopies at different pH values. We concluded that product 3aa suffered two deprotonations at pK_a of 4.4 and 9.5, giving three species in a pH range between 2-12, with colours varying from light red to deep orange. The reversibility of the process observed for 3aa at different pH values, together with its changes in colour, make this new family of products attractive candidates to use them as pH indicators.

Fibrous Clays in Dermopharmaceutical and Cosmetic Applications: Traditional and Emerging Perspectives

Functionalization of natural clay minerals for high value-added pharmaceutical and cosmetic applications receives significant research attention worldwide attributable to a rising demand and ongoing search for green, efficient, economically sustainable and ecofriendly geomaterials. Fibrous clays, i.e. palygorskite and sepiolite, are naturally-occurring hydrated magnesium aluminum silicate clay minerals with 2:1 layer-chain microstructure and one-dimensional nanofibrous morphology. Due to their unique structural, textural and compatibility features, over the past decade, fibrous clays and their organic modified derivatives are increasingly used in the dermopharmaceutical and cosmetic fields as excipients, active agents or nanocarriers to develop novel skin delivery systems or to modify drug release profile for enhanced health effects. This comprehensive review presents the up-to-date information on fibrous clays used in topically-applied products for therapeutic and cosmetic purposes with the focus on their performance-related structural characteristics and the underlying mechanisms. The recent advancement of fibrous clay-based skin delivery systems was summarized in wide range of applications including pelotherapy, wound healing, antimicrobial action, coloration and UV protection. An overview of the commonly used topically-applied dosage forms (powders, hydrogels, films, peloids and Pickering emulsion) as well as the toxicological aspects was also included, which might provide guidance to the design and development of fibrous clay-based skin delivery systems.

Structure and Stability Characterization of Natural Lake Pigments Made from Plant Extracts and Their Potential Application in Polymer Composites for Packaging Materials

Natural dyes were extracted from various plant sources and converted into lake pigments based on aluminum and tin. Three different plants (weld, Persian berries, and Brazilwood) were chosen as representative sources of natural dyes. High-performance liquid chromatography (HPLC) and triple-quadrupole mass spectrometry (QqQ MS) were used to identify dyestuffs in the raw extracts. The natural dyes and lake pigments were further characterized by optical and scanning electron microscopy (SEM), UV-Vis spectrophotometry, and thermogravimetric analysis (TGA). The stabilization of the studied plant extracts onto aluminum and tin salts led to the formation of natural lake pigments characterized by different color shades. The natural lake pigments showed improved thermal and chemical stability, which was confirmed by their higher degradation temperatures and lower solubility in chemical agents compared to natural dyes extracted from plants. This improvement can be attributed to electrostatic attraction due to the process of chelation. Ethylene-norbornene (EN) composites colored with the lake pigments exhibited uniform color and improved resistance to long-term UV exposure aging. After 300 h of UV exposure, the aging factor of the neat EN copolymer reduced to 0.3, indicating an advanced aging process of polymer compared to colored samples. Prolonged UV exposure deteriorated the mechanical properties of EN by approximately 57%, compared to about 43% with the application of BW/Al lake pigment. Natural lake pigments could be used as effective substitutes for commercial colorants in plastics for packaging applications.