Search Results (329)

Nanostructure-based coloration has been investigated extensively to overcome the limitations of conventional pigments and dyes. In this study, we focused on the dynamic coloration of plasmonic structures via the photothermal deformation of a metal semi-shell. However, identifying the optimal structure using this method typically requires considerable computational time. To address the high computational cost of structural optimization in dynamic plasmonic coloration, we propose an efficient method for estimating the optimal nanostructure geometry. The color gamut area was found to be influenced by both the nanosphere density and the thickness of the metal semi-shell. The optical response of deformed semi-shells, resulting from laser-induced local heating, was simulated across a range of semi-shell shapes. From these simulations, an empirical correlation was identified that links nanoparticle diameter, density, and semi-shell thickness. This correlation enables the rapid estimation of optimal parameters, thereby reducing computational demands and supporting the efficient fabrication of dynamic plasmonic color materials. Full article

Annually, more than 10,000 synthetic dyes are produced worldwide, generating around 280,000 tons of waste, posing risks to human and aquatic life, and potentially creating even more toxic products than the dyes themselves. This study aims to immobilize organic dyes, forming hybrid pigments using ZnO as support obtained through starch combustion. ZnO was obtained by starch (sago) combustion and characterized by XRD, SEM and the BET method. It was then used for the adsorption of orange and green textile dyes, evaluating the adsorbent dosage, initial dye concentration, contact time, and selectivity with copper ions. The removal studies indicated up to 100% removal of both dyes at low concentrations. The co-adsorption system showed excellent performance, with removal percentages exceeding 90% for both textile dyes and Cu (II) ions. Hybrid pigments were assessed for solvent resistance and durability under extended white light exposure. ZnO immobilized the dyes, showing resistance to organic solvents and good stability under prolonged white light exposure. Full article

This study presents a theoretical model for the thermoelastic response in transmission-mode photoacoustic systems that feature a two-layer structure. The model incorporates volumetric optical absorption in both layers and is based on classical heat conduction theory, hyperbolic generalized heat conduction theory, and fractional heat conduction models including inertial memory in Generalizations of the Cattaneo Equation (GCEI, GCEII, and GCEIII). To validate the model, comparisons were made with the existing literature models. Using the proposed model, the thermoelastic photoacoustic response of a two-layer system composed of a 3D-printed porous polyamide (PA12) substrate coated with a thin, highly absorptive protective dye layer is analyzed. We obtain that the thickness and thermal conduction in properties of the coating are very important in influencing the thermoelastic component and should not be overlooked. Furthermore, the thermoelastic component is affected by the selected fractional model—whether it is subdiffusion or superdiffusion—along with the value of the order of the fractional derivative, as well as the optical absorption coefficient of the layer being investigated. Additionally, it is concluded that the phase has a greater impact than the amplitude when selecting the appropriate theoretical heat conduction model. Full article

Dyed wool samples and lake pigments prepared from the same dyestuffs were exposed to light over the course of 14 months. Brazilwood or sappanwood, cochineal, madder, and weld were used for both wools and pigments, with the addition of dyer’s broom, indigo, and tannin-containing black dyes for the wools and eosin for the pigments. The wools were dyed within the MODHT European project on historic tapestries (2002–2005), using recipes derived from fifteenth- to seventeenth-century sources. The pigments were prepared according to European recipes of the same period, or using late nineteenth-century French or English recipes. Colour measurements made throughout the experiment allowed for overall colour difference (ΔE₀₀) to be tracked and half-lives to be calculated for some of the colour changes. Alterations in the samples’ hue and chroma were also monitored, and spectral information was collected. The results showed that, for both textiles and pigments, madder is the most stable red dye, followed by cochineal, and then brazilwood. Eosin was the most fugitive sample examined. Comparisons of textile and lake samples derived from the same dyestuff, whether red or yellow, indicate that the colourants are more stable when used as textile dyes than in analogous lake pigments. Full article

Betalains are nitrogen-containing, water-soluble, and non-toxic natural pigments found in various plant species. Among these, Celosia argentea (Amaranthaceae) has garnered attention as a significant source, accumulating substantial quantities of both red–purple betacyanins and yellow–orange betaxanthins. Impressively, betalain concentrations in C. argentea inflorescences can reach up to 14.91 mg/g dry weight (DW), a level comparable to that reported in red beetroot. Beyond harvesting from inflorescences, betalains can also be produced using cell culture systems, which can yield even higher amounts, up to 42.08 mg/g DW. Beyond their role as vibrant natural colorants, betalains exhibit impressive health-promoting properties, most notably potent antioxidant activities. For instance, C. argentea inflorescence extracts demonstrate approximately 84.07% 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 88.70% 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging. Extracts derived from cell cultures show even higher scavenging capacities, reaching up to 99.28% for ABTS and 99.63% for DPPH, rivaling the antioxidant standard (ascorbic acid). Further research indicates additional potential benefits, including anti-inflammatory, antimicrobial, anticancer, antidiabetic, and hepatoprotective properties. This diverse bioactivity underpins their value across various industries. Betalains serve as natural colorants and functional ingredients in food and beverages, offer sustainable alternatives for textile dyeing, and hold therapeutic promise in cosmetics and pharmaceuticals. This review critically examines existing research on betalain production in C. argentea. Recognizing that research specific to C. argentea is less extensive compared with that on species such as Beta vulgaris and Hylocereus polyrhizus, this review analyzes its biosynthetic pathways, diverse biological properties, and wide-ranging applications. This is achieved by integrating available C. argentea-specific data with relevant insights drawn from these more broadly studied betalain sources. Furthermore, the review discusses perspectives on future research directions aimed at optimizing yield and exploring the full potential of betalains, specifically within C. argentea. Full article

In 1900, Francis Herbert Jennison’s book The Manufacture of Lake Pigments from Artificial Colours was published in London. In the early 20th century, the technical literature focussing on synthetic dyes mainly dealt with their use for dyeing. Conversely, the literature on lake pigment manufacture is less comprehensive, and Jennison’s publication was the first monograph on this topic. His book comprises descriptions of the dyes, substrates, and various methods for lake making. Practical examples complete the work: sixteen colour plates with original samples of lake pigments showcase the practical effect on colour of the different dyes and preparation methods. Herein, we present an overview of the context of Jennison’s research and delve into a selection of formulations. Green lake pigment plates were sampled and analysed by liquid chromatography coupled with spectroscopic and spectrometric detectors and by X-ray fluorescence spectroscopy to correlate the chemical composition with the recipes reported in the book. Seldom or no longer used and unexplored historical dyes were detected, along with polyphenolic compounds possibly used as precipitating agents in lake pigment formulations. Moreover, the examination of two different editions of the Jennison manuscript (i.e., the English and German books) revealed different chemical profiles corresponding to the same lake pigment formulation. This emphasizes the significance of Jennison’s book, confirming how understanding of early formulations is needed to elucidate the later ones. Full article

Bio-based polyamide 56 (PA56) is a new sustainable material in the polyamide family. In this study, dyes suitable for PA56 fibers were experimentally screened from natural plants rich in pigments. The results showed that the preferred natural dyes for PA56 fabric are turmeric for a yellow hue, madder for a red hue, catechu for a brown hue, and indigo for a blue hue. A green hue was achieved by the two-bath dyeing method using indigo and turmeric, respectively. For a dyability comparison with conventional PA6 and PA66, PA56, PA6, and PA66 fabrics were woven under identical conditions and dyed with turmeric, madder, catechu, and commercial indigo extracts. PA56 fabric exhibited the best dye uptake and the fastest dyeing rate (PA56 > PA6 > PA66). The reason for the excellent dyeability of PA56 fibers was analyzed in terms of differential scanning calorimetry measurement and molecular dynamics simulations. The results showed that the lowest crystallinity was exhibited by PA56 (PA56 < PA6 < PA66); in addition, PA56 displayed the largest fractional free volume (PA56 > PA6 > PA66). These structural characteristics contribute to the excellent dyeability of PA56 fibers. Therefore, PA56 fibers are promising materials, as they are derived from a sustainable source and have superior dyeing properties compared to PA6 and PA66 fibers. Full article

Thermochromic materials have attracted interest in textile applications, particularly in printing and dyeing processes. However, their thermochromic properties and impact on fabric comfort remain underexplored. This study aimed to investigate the thermochromic properties of printed fabrics with green-to-brown transitions and evaluates their comfort attributes. In the present study, a thermochromic dye paste was applied to nylon/cotton medium-weight fabric via screen printing process. The brown pigment paste was applied first, followed by the thermochromic olive green dye. The printed fabrics were tested for thermochromism, morphology, Fourier Transform Infrared Spectroscopy (FTIR), and comfort properties. Comfort properties were assessed via air permeability, water vapour permeability, and moisture management tests. The results show reversible colour changes from green (25 °C) to brown (40 °C), with increasing lightness (L*) and shifting green–red coordinates (−a*). The scanning electron microscopy (SEM) confirmed uniform dye dispersion, and the FTIR validated the presence of thermochromic pigments. The printed fabrics showed a reduction in air permeability from 40.2 mm/s to 0 mm/s, while water vapour permeability decreased by 62.50% compared to the pristine fabric due to the coating layers. The overall moisture management properties of the printed fabric remained similar to those of the unprinted fabric, with a grade of 1. These findings highlight the potential of thermochromic textiles for adaptive camouflage, particularly in military uniforms, contributing to the advancement of intelligent textiles with enhanced thermal responsiveness. Full article

Bacterial pigments have gained significant attention across multiple industries due to their natural hues and unique functional properties. Beyond coloration, some of these pigments exhibit antibacterial activity, making them particularly valuable in the textile industry as sustainable alternatives to synthetic antimicrobial treatments. Bacteria produce a vast array of pigments through diverse biosynthetic pathways, which reflect their metabolic adaptability and ecological roles. These pathways are influenced by environmental factors such as pH, temperature, and nutrient availability. Key pigments, including carotenoids, melanin, violacein, and prodigiosin, are synthesised through distinct mechanisms, often involving tightly regulated enzymatic reactions. For example, carotenoid biosynthesis relies on isoprenoid precursors, while melanin formation involves the oxidation of aromatic amino acids. Understanding these pathways provides insights into bacterial survival strategies, stress responses, and interactions with their environment. This review examines the dyeing potential of bacterial pigments on natural and synthetic fabrics, highlighting advancements in environmentally friendly extraction methods to minimise the ecological impact. Additionally, it explores safety, biocompatibility, and industrial challenges associated with bacterial pigment applications. Finally, future perspectives on integrating these pigments into various industries are discussed, emphasising their potential as bio-based solutions for sustainable and functional materials. Full article

Historically, natural pigments have been used to color textiles, food, and cosmetics, but the rise of synthetic dyes in the 19th century reduced their use. Recently, interest in plant-based pigments has surged due to health and environmental concerns. Among Thailand’s ethnic groups, the Karen use plant colorants extensively, but their practices remain understudied. In this study, we document the knowledge of plant colorants of the Karen community in Chiang Mai province, assess the color stability of the plant colorants, and evaluate their cytotoxicity in HepG2 cells. Interviews with 113 informants revealed 52 plant species used for dyeing, primarily through hot water extraction. The most common color was brown, and Strobilanthes cusia had the highest color use value (0.93). The study identified 10 color shades, with blue showing the highest consensus. Color stability was tested at room and elevated temperatures, which showed that colorants from Oroxylum indicum were the most stable, and those of Strobilanthes cusia had the lowest toxicity (CC₅₀ = 994.1 µg/mL), while Artocarpus lacucha had the highest toxicity (CC₅₀ = 63.96 µg/mL). Oroxylum indicum, which has excellent color stability and moderate cytotoxicity (CC₅₀ = 294.4 µg/mL), is recommended as a promising natural colorant. This study provides valuable insights into preserving traditional knowledge in Karen communities. Full article

This report discusses the synthesis of a biosourced divanillin derivative obtained by Knoevenagel condensation. The compound was fully characterized by proton (¹H), carbon (¹³C), heteronuclear single quantum coherence (HSQC), homonuclear correlation spectroscopy (COSY), and heteronuclear multiple bond correlation (HMBC) NMR, as well as high-resolution mass spectroscopy (HRMS). We also investigated the optical properties through UV-visible spectroscopy and Fourier-transform infrared (FTIR) spectroscopy. At last, the thermal properties of this divanillin derivative were evaluated by thermogravimetric analysis (TGA) as well as differential scanning calorimetry (DSC). Full article

Sulfamic acid (SA) is extensively utilised in industry as a component in the production of flameproof materials, a catalyst for swift and highly efficient synthesis, in dye and pigment manufacturing processes, or as herbicide. Under ambient conditions, this compound exists as a solid in zwitterionc form, undergoing pressure-induced isosymmetric polymorphic phase transition (IPT), starting at approximately 10.0 GPa. In this work, multiple computational approaches were used to predict and describe this transition. While geometry optimisation at an increased pressure using periodic DFT-level calculations have not resulted in the anticipated IPT, the comparison of the experimental and theoretical Raman spectra confirmed this transformation. Thermodynamic calculations enabled the comparison of the stability of the modelled phases and explained the experimental observations. Ab initio molecular dynamics simulations revealed the mechanisms behind the observed transition. This work presents a complex methodology that can be successfully used to predict the IPT of molecular crystals. Full article

Phycobiliproteins and pigments derived from cyanobacteria hold significant potential for diverse applications in the food, pharmaceutical, and chemical industries. The filamentous cyanobacterium Anabaena cylindrica serves as a valuable resource for extracting these compounds. This study develops a simplified, safe, and cost-effective extraction method that eliminates toxic solvents and minimizes processing steps. This makes the method applicable for all users and allows the easy integration of the extraction into biorefinery concepts in which the biomass is to be used as a fertilizer, for example. Utilizing salts such as ammonium sulfate and calcium chloride (15 gL⁻¹ each) enables the effective extraction of phycocyanin (PC) and allophycocyanin, achieving a PC concentration of 192.34 $\mathrm{mg}{\mathrm{g}}_{\mathrm{CDW}}^{-1}$ and 209.44 $\mathrm{mg}{\mathrm{g}}_{\mathrm{CDW}}^{-1}$, respectively. Ethanol was introduced as a less toxic alternative to methanol for pigment extraction, increasing chlorophyll a and carotenoid recovery by 21% and 37%, respectively. Full article

Nanopigments consisting of organic/inorganic hybrid composites represent a convenient alternative for pigments, combining the qualities of organic dyes with those of inorganic materials. We obtained Maya blue pigments from methylene blue and modified bentonites, using Ulva lactuca aqueous extract. Structural modifications of bentonites during the synthesis of nanopigments were evidenced by the interplanar distance and the basal peak position in X-ray diffraction patterns. The presence of methylene blue in Maya blue nanopigments was also confirmed by UV-vis and FTIR spectra. The adsorption study revealed a higher adsorption capacity in the presence of Ulva lactuca extract compared to water, and two adsorption models, Langmuir and Freundlich, were applied for studying the adsorption of methylene blue onto bentonite. The stability and seed germination effect of the resulting nanopigments were assessed. Accordingly, it was found that the nanopigments obtained in Ulva lactuca extract had superior redox stability compared to those obtained in water or methylene blue solution. The ability of bentonite-based nanopigments to be used in seed treatment is another interesting feature that can be exploited. Full article

Structural color-generating materials are expected to replace pigments and dyes as a new type of color-developing materials with good light stability and bright colors. Due to the relatively high refractive index of Cu₂O microspheres, they have strong Mie scattering in the visible region. Herein, various sizes of Cu₂O microspheres were synthesized by a two-step reduction method, and the Cu₂O spheres were firmly bonded to the fabrics by using the PVA binder. Four different fabrics (cotton, silk, polyester, and nylon fabrics) were evaluated to investigate the physical properties and color fastness. It turns out that the tensile and tearing properties of the Cu₂O structured fabrics decreased to a certain extent, and the bursting properties of fabrics increased, except for the cotton structured fabrics. Meanwhile, all the structural colored fabrics showed excellent color fastness to shearing, rubbing, and washing. This study provides experimental data for developing the application of structural colors on different fabrics. Full article