Color Pigments Research Articles

Nanostructure-free crescent-shaped microparticles as full-color reflective pigments

Structural colors provide a promising visualization with high color saturation, iridescent characteristics, and fade resistance. However, pragmatic uses are frequently impeded by complex manufacturing processes for sophisticated nanostructures. Here, we report a facile emulsion-templating strategy to produce crescent-shaped microparticles as structural color pigments. The micro-crescents exhibit brilliant colors under directional light originating from total internal reflections and optical interferences in the absence of periodic nanostructures while being transparent under ambient light. The colors are finely tunable by adjusting the size of the micro-crescents, which can be further mixed to enrich the variety. Importantly, the pre-defined convex surface secures high stability of colors and enables structural coloration on target surfaces through direct deposition as inks. We anticipate this class of nanostructure-free structural colorants is pragmatic as invisible inks in particular for anti-counterfeiting patches and color cosmetics with distinctive impressions due to low-cost, scalable manufacturing, unique optical properties, and versatility.

A novel high reflective glass-ceramic ink with Bi2Ti2O7 nanocrystals used for the photovoltaic glass backplane

Photovoltaic glass ink is a kind of ink used for the photovoltaic glass backplane to enhance the photoelectric conversion efficiency of solar cells. In this work, a novel kind of photovoltaic glass-ceramic ink, with Bi2Ti2O7 nanocrystals precipitated from the low-melting glass for the first time in the short sintering process, was successfully designed and prepared to further improve the reflectance of near-infrared light. Bi2Ti2O7 nanocrystals fill the gap between TiO2 color pigments to a certain extent, which reduce the diffraction of light and greatly improve the reflectivity of the photovoltaic glass backplane to near-infrared light. In the near-infrared wavelength range (780–2500 nm), the average reflectance of photovoltaic glass ink with Bi2Ti2O7 nanocrystals is 20.6% higher than that without Bi2Ti2O7 nanocrystals. The maximum reflectance of photovoltaic glass-ceramic ink is 86.18%. Our research and findings have provided an important reference point for future development of photovoltaic glass inks.

Contribution of the TGFβ signaling pathway to pigmentation in sea cucumber (Apostichopus japonicus)

Pigmentation mediated by the transforming growth factor β (TGFβ) signaling pathway is a key trait for understanding environmental adaptability and species stability. In this study, TGFβ signaling pathway members and their expression patterns in different color morphs of the sea cucumber Apostichopus japonicus were evaluated. Using a bioinformatics approach, 22 protein sequences of TGFβ signaling pathway members in A. japonicus were classified, including 14 that were identified for the first time in the species, including 7 ligands, 6 receptors, and 1 R-Smad. We further evaluated mRNA expression data for different color morphs and pigmentation periods. These results support the hypothesis that both subfamilies of the TGFβ superfamily, i.e., the TGFβ/activin/Nodal and BMP/GDF/AMH subfamilies, are involved in the regulation of pigmentation in A. japonicus. The former subfamily was complete and contributes to the different color morphs. The BMP/GDF/AMH subfamily was incomplete. BMP2/4-induced differentiation of white adipocytes was regulated by the BMP2/4–ACVR2A–Smad1 signaling pathway. These findings provide insight into the TGFβ family in early chordate evolution as well as the molecular basis of color variation in an economically valuable species.

Unifying colors by primes

RGB and CYMK are two major coloring schemes currently available for light colors and pigment colors, respectively. Both systems use letter-based color codes that require a large range of values to represent different colors. The problem is that these two systems are hard to use for manipulating any operations involving combinations of colors, and they lack the capacity for inter-changeability or unification. Based on prime number theory and Goldbach’s conjecture, this study presents a universal color system (C235) using a number-based structure to encode, compute and unify all colors on a color wheel. The proposed C235 system offers a unified representation for the efficient encoding and effective manipulation of color. It can be applied to designing a high-rate LCD system and colorizing objects with multiple attributes and DNA codons, opening the door to manipulating colors and lights for even broader applications.

Antibacterial assay of cyanobacteria in invitro conditions and its valuable applications

Cyanobacteria are aquatic and photosynthetic they survive in fresh water ponds and sewage water. Since these cyanobacteria are quite small and unicellular, they often grow in large colonies more enough to see by naked eye. Cyanobacteria they produce bluish green colour pigments as they are phycocyanin, phycobiliproteins and carotenoids. It may surprise you to know that cyanobacteria are still around they are one of the largest and most important groups of bacteria on earth. The cyanobacterial ethanolic extracts of Oscillatoria formosa, Oscillatoria subbrevis, Oscillatoria princeps, Oscillatoria sancta and Oscillatoria fischeri showed effective antibacterial activity against pathogenic microorganisms like Streptococcus pyogenes, Streptococcus pneumoniae, Clostridium perfringes, Salmonella typhi and Vibrio cholerae. Cyanobacteria like Oscillatoria curviceps, Lyngbya majuscula and Spirulina subsalsa are rich source of bioactive compounds with antibacterial, antifungal, antialgal and antiviral properties. Some cyanobacteria like Synechococcus elongatus have ability to accumulate polyhydroxyalkanoates which may be used as bioplastics. In addition to these applications the Cyanobacteria are also useful in agricultural practices like Nostoc commune and Anabaena aequalis as biofertilizers. Some eukaryotic green algae like Chlorella vulgaris, Botryococcus braunii and Schizochytrium limacinum produce more oil content for ecofriendly production of more biodiesel.

Dual-energy CT evaluation of 3D printed materials for radiotherapy applications

Objective. There is a continuous increase in 3D printing applications in several fields including medical imaging and radiotherapy. Although there are numerous advantages of using 3D printing for the development of customized phantoms, bolus, quality assurance devices and other clinical applications, material properties are not well known and printer settings can affect considerably the properties (e.g. density, isotropy and homogeneity) of the printed parts. This study aims to evaluate several materials and printer properties to identify a range of tissue-mimicking materials. Approach. Dual-energy CT was used to obtain the effective atomic number (Z eff) and relative electron density (RED) for thirty-one different materials including different colours of the same filament from the same manufacturer and the same type of filament from different manufacturers. In addition, a custom bone equivalent filament was developed and evaluated since a high-density filament with a composition similar to bone is not commercially available. Printing settings such as infill density, infill pattern, layer height and nozzle size were also evaluated. Main results. Large differences were observed for HU (288), RED (>10%) and Z eff (>50%) for different colours of the same filament due to the colour pigment. Results show a wide HU variation (−714 to 1104), RED (0.277 to 1.480) and Z eff (5.22 to 12.39) between the printed samples with some materials being comparable to commercial tissue-mimicking materials and good substitutes to a range of materials from lung to bone. Printer settings can result in directional dependency and significantly affect the homogeneity of the samples. Significance. The use of DECT to extract RED, and Z eff allows for quantitative imaging and dosimetry using 3D printed materials equivalent to certified tissue-mimicking tissues.

A Review of the Biological Properties of Purple Corn (Zea mays L.)

In the food and beverage industries, replacing synthetic colorants with plant-based colorants has become popular in recent times. Purple corn (Zea mays L.) is an important source of natural colorants due to its range in color from orange to purple. The whole plant of purple corn has a high amount of anthocyanin content. Anthocyanin is the water-soluble pigment found in various fruits and vegetables. The color pigments are chiefly found in the pericarp or kernels, in addition to corn cobs. Purple corn is rich in various health-promoting compounds, mainly anthocyanins such as cyanidin-3-O-glucoside, perlagonidin-3-O-glucoside, peonidin 3-O-glucoside, and their malonylated forms. This review emphasized recent updates regarding the in vitro and in vivo biological properties of extracts and compounds from purple corn. Purple corn color extracts possess a variety of biological properties, including antioxidant, anti-inflammatory, anticancer, anti-diabetic, anti-obesity, etc. The results of in vitro and in vivo studies of the biological properties of purple corn could lead to the development of different health-promoting products in the near future.

Tuning of Optical Stopband Wavelength and Effective Bandwidth of Gel-Immobilized Colloidal Photonic Crystal Films.

We show that both the optical stopband wavelength and effective bandwidth of films of gel-immobilized loosely packed colloidal photonic crystals can be controlled over a wide range. When the gelation reagent of the charge-stabilized colloidal crystals was photopolymerized under ultraviolet light using different upper- and bottom-light intensities, it resulted in a gel-immobilized colloidal crystal film with a broadened Bragg reflection peak. Moreover, the width of the Bragg peak increased from 30 to 190 nm as the difference between the light intensities increased. Films with wider Bragg peaks exhibited a brighter reflection color because of the superposition of the shifted Bragg reflections. Furthermore, the Bragg wavelength could be varied over a wide range (500-650 nm) while maintaining the same broadened effective bandwidth by varying the swelling solvent concentration. These findings will expand the applicability of colloidal crystals for use in photonic devices and color pigments.

Structural color printing and evaluation based on 3D printing

PurposeThe purpose of this study is to modify the FDM 3D printer to print with polystyrene (PS) microspheres as the printing material, thus enabling bottom-up structural color printing and evaluating structural color printing.Design/methodology/approachThis study chose a range of different heated bed temperatures to determine a suitable temperature for accelerating the self-assembly of photonic crystals and printing structural colors on various substrates. In addition, this study enhanced the structural color by doping PS microspheres with different contents of Acid Black 210 dye and evaluated the color-enhanced structural color by eye and spectrophotometer under different light sources.FindingsThe results show that the modified 3D printer can be used for structural color printing, and 50°C is determined as the heated bed temperature. There are significant differences in structural colors when printing under different color backgrounds and material substrates, and corresponding suitable substrates should be selected according to the application. The doping of PS microspheres with varying contents of dye results in different color levels of structural color. As with pigment colors, the visual perception of structural color varies when viewed under different light sources.Originality/valueThis paper proposes to print structural colors low-costly, analyze structural colors under substrate and light source conditions, and expand the structural color gamut by enhancing structural colors, which has positive implications for further research on structural colors as printing colors.

A Greener Facile Approach to Develop Durable Multifunctional Cellulosic Pigment Prints Using β-CD, ZnO-NPs and Several Bioactive Guest Molecules

In the present work, β-CD, ZnO-NPs, and several eco-friendly bioactive guests, namely, cinnamon oil, lemon oil, lavender oil, and vanillin along with environmentally benign pigment paste constituents were applied to cotton, viscose, cotton/viscose, and cotton/linen cellulosic substrates to develop durable multi-functional pigment prints in a single step using the pad-dry-thermofixation method. The developed one-step pigment coloration and multi-functionalization method resulted in a remarkable improvement in antibacterial efficacy, UV-protection ability, aroma property along with a noticeable increase in depth of the obtained pigment prints, making them very useful for a wide range of potential applications. The extent of enhancement in the above-mentioned functional and coloration properties is governed by type of cellulosic substrate, presence of β-CD/ZnO-NPs, type of bioactive agent as well as kind of pigment colorant. Among the used bioactive agents, lavender oil proved to be the best for attaining multi-functional and pigment coloration properties, keeping other parameters constant. The obtained results also demonstrated that increasing washing cycles up to 15 washes resulted in a slight decrease in the imparted functional and coloration properties, regardless of the used cellulosic substrate. Both SEM images and EDX spectra confirmed the surface modification and ZnO-NPs immobilization onto the selected fabric surfaces. Mode of interactions among the different printing paste constituents and the cellulosic substrates were also suggested.

A Future with Engineering Stone Made from Silica-Rich Iron Ore Tailings from Vale

Among the many initiatives being developed to recover and reuse mineral waste at Vale mining sites, the new business solution presented here uses silica-rich tailings as a substitute for primary silica to produce engineering stone products like kitchens countertop, bathroom vanities and floor tiles in a booming, multi-billion dollar industry. Engineering stone is an alternative to natural stone like granite. It is manufactured from approximately 93% primary silica, 7% resin, colour pigments and selected aesthetic additives, with the recipes varying depending on desired colour and aesthetic properties. Using primary (typically white) silica allows engineering stone manufactures to produce products with a wide colour range, so when used, residual (darker) iron ore in tailings can somewhat decrease colour control. Through innovative technological advances combined with a skilled and highly motivated workforce, Vale has been able to systematically improve separation efficiency of its concentration/beneficiation processes (primarily aimed at maximizing the recovery of iron ore). Fortuitous laws governing mass balances have ensured that increased recovery of iron ore in one stream has meant an associated increase in silica content of the other stream (tailings), in some strategic process streams as high as 90-96% SiO2. Such a systematic increase in the silica content (becoming whiter) has meant an increase in the colour control Vale silica-rich tailings can deliver the industry. Since 2014 Vale has been working closely with leaders in the engineering stone manufacturing industry to develop recipes. This collaboration is delivering engineering stone that not only meet EN 14617 industry standards for resistance to stain, strength and impact but also have colour ranges able to satisfy market needs.

π-Extended benzo[1,2:4,5]di[7]annulene bis(dicarboximide)s - a new class of non-alternant polycyclic aromatic dicarboximides.

Aromatic dicarboximides are a class of molecules represented by the well-known rylene bis(dicarboximide)s, in particular perylene or naphthalene bis(dicarboximide)s, which show pronounced optoelectronic properties and are applied as color pigments, fluorescent dyes and organic semiconductors. Herein we extend the family of aromatic bis(dicarboximide)s and report the synthesis of the first series of non-alternant aromatic dicarboximides by twofold Pd-catalyzed [5 + 2] annulation. Characterization by UV/vis spectroscopy and cyclic voltammetry (CV) measurements give insight into the optoelectronic characteristics of the hitherto unexplored substance class of heptagon-containing imides. Theoretical studies by nucleus independent chemical shift (NICS) XY-scans and anisotropy of the induced current density (ACID) plots demonstrate the influence of both the non-alternant carbon framework and the imide moieties on aromaticity of the synthesized bisimides.

Fungal Azaphilone Pigments as Promising Natural Colorants

Abstract—Microscopic fungi form and excrete numerous and diverse secondary metabolites, including pigments of various colors, which may be used as an alternative to chemical and plant colorants used in industry. Azaphilone compounds, first discovered in fungi of the genus Monascus, are among the promising classes of fungal pigments. The review analyzes the publications on formation of azaphilone-type pigments in Monascus fungi, as well as in Talaromyces and Aspergillus сavernicola. Brief information is provided concerning the antimicrobial, antitumor, anti-inflammatory, and hypolipidemic activities of azaphilone pigments. is given. Possible strategies for increasing the efficiency of the production process and directed synthesis of yellow, orange, and red pigments and their derivatives are discussed. In general, the review provides for assessment of the role of azaphilone pigments, as well as of the prospects and ways to expand their production for use as natural dyes in various fields.

Tuning the Color of Photonic Glass Pigments by Thermal Annealing.

Thermal or solvent annealing is commonly employed to enhance phase separation and remove defects in block copolymer (BCP) films, leading to well-resolved nanostructures. Annealing is of particular importance for photonic BCP materials, where large, well-ordered lamellar domains are required to generate strong reflections at visible wavelengths. However, such strategies have not been considered for porous BCP systems, such as inverse photonic glasses, where the structure (and thus the optical response) is no longer defined solely by the chemical compatibility of the blocks, but by the size and arrangement of voids within the BCP matrix. In this study, a demonstration of how the concept of "thermal annealing" can be applied to bottlebrush block copolymer (BBCP) microparticles with a photonic glass architecture is presented, enabling their coloration to be tuned from blue to red. By comparing biocompatible BBCPs with similar composition, but different thermal behavior, it is shown that this process is driven by both a temperature-induced softening of the BBCP matrix (i.e., polymer mobility) and the absence of microphase separation (enabling diffusion-induced swelling of the pores). Last, this concept is applied toward the production of a thermochromic patterned hydrogel, exemplifying the potential of such responsive biocompatible photonic-glass pigments toward smart labeling or anticounterfeiting applications.

Evaluation of color and stability of ethyl-linked anthocyanin-flavanol pigments in model wine solutions using combined chemical analysis and 3D molecular simulations

Ethyl-linked anthocyanin-flavanol pigments are one of the most important condensation products formed during the red winemaking and ageing period. They have great contribution to the color characteristics and stability of aged red wines. In this study, the color characteristics and stability of ethyl-linked anthocyanin-flavanol pigments and their precursor anthocyanins were evaluated by combined spectrophotometry and 3D molecular simulations. In model wine solutions, the condensation reactions between three anthocyanins and (-)-epicatechin, mediated by acetaldehyde, were conducted to produce ethyl-linked anthocyanin-flavanol pigments. The color was assessed by the CIELab method, and the concentration changes were analyzed by HPLC-DAD. On the other hand, the stability of these pigmented compounds was also calculated by the three 3D molecular simulation methods, that is molecular mechanics, molecular dynamics, and quantum chemistry simulation. The results obtained from CIELab analysis indicated that the formation of ethyl-linked anthocyanin-flavanol pigments resulted in a decrease of L*, a*, b* and C* values, and conversely, a rising of h* value. The 3D molecular simulations revealed that the stability of anthocyanins was as follows: Mv-3-O-glu > Pn-3-O-glu > Cy-3-O-glu. The cis or trans ethyl-linked anthocyanin-flavanol pigments were much more stable than their precursor anthocyanins. Among the pigments, ethyl-linked malvidin-3-O-glucoside-flavanol was more stable than ethyl-linked cyanidin-3-O-glucoside-flavanol and ethyl-linked peonidin-3-O-glucoside-flavanol.

Thermal stabilities of lycopene and β-carotene in tomato pulp and pink grapefruit juice

Thermal stabilities of lycopene and β-carotene in tomato pulp and pink grapefruit juice were studied at 80, 95 and 110 °C. Lycopene and β-carotene degradations in both products followed to first-order reaction kinetics, but biphasic curves were obtained for β-carotene degradation. Stabilities of both pigments are highly affected by processing temperatures. For example, t 1/2 values for lycopene degradation decreased from 7.4 at 80 °C to 4.0 h at 110 °C in tomato pulp, and from 32.1 to 5.9 h in pink grapefruit juice, respectively. Similar decreases in t 1/2 values (46.8–27.3 h in tomato pulp and 113.6 to 11.7 h in grapefruit juice, respectively) were obtained for β-carotene degradations. Lycopene and β-carotene degradations in tomato pulp were not very sensitive to temperature elevations (E a = 22.7 and 20.2 kJ/mol, respectively), but very sensitive in pink grapefruit juice (E a = 63.8 and 85.3 kJ/mol, respectively). High correlations were found between a*, b*and h° values, and lycopene concentrations ( r = 0.659–0.978) and β-carotene concentrations ( r = 0.647–0.997). • Both pigments showed much higher thermostability in grapefruit juice than tomato pulp. • Both pigments were more sensitive to temperature changes in grapefruit juice than tomato pulp. • High correlations were found between colour values and pigment contents in both products. • Changes in red colour of both products can be followed by measuring a* and h° values. • Changes in yellow colour can be tracked by measuring h° values in tomato pulp.

Synthesis and near-infrared reflection performance of (Cr,V)-ZrSiO4 jewel green pigments

Novel (Cr,V)-ZrSiO4 jewel green pigments were synthesized by in situ mineralization at 900?C. The effects of Cr/Si molar ratio were investigated via DTA-TG, XRD, FE-SEM, TEM, UV-Vis-NIR, colorimeter and etc. The obtained results referred that the colour of pigment exhibits blue to jewel green, and then to dark green as the Cr/Si molar ratio increases from 0 to 0.4. When the Cr/Si molar ratio is 0.2, the (Cr,V)-ZrSiO4 pigment exhibits a jewel green hue (L* = 56.69, a* = ?18.52, b* = ?9.28), showing good rendering performance. In addition, the obtained pigment shows good thermal stability in the base glaze synthesized at 1200?C and near-infrared reflection performance. The results of this study show great potential for using the pigments for heat insulation.

The molecular regulators, pathways, and environmental impacts of white flowers

White flowers are an important element of natural beauty, although they are thought of colorless. Anthocyanins are the major compounds responsible for a variety of pigments in flowers. White flowers surely lack pigmented anthocyanins and other compounds, but there are regulatory mechanisms that hinder the deposition of color pigments in white flowers. Moreover, there are also some compounds that deposit to instigate white appearance and the genetic regulators control the biosynthesis and deposition of such compounds. Experts have shown that fluctuation in the equilibrium of FLS and DFR genes determines the degree of accumulation of anthocyanins and flavonols in the flowers, leading to different color patterns. The gene suppression techniques to suppress certain flavonoid pathway genes, such as CHS, or the insertion of DNA transposable elements into CHS produce white flower color in a number of species. Although pigments find wide application in the everyday life, white color does possess special importance in nature. Land plants use white flowers for reproductive viability during cold early spring to conserve energy and reduce nutrient costs, particularly in low density pollinations. Moreover, white fruit skins deposit specific amounts of anthocyanins and phenols with significant health benefits. This review, thus, deciphers the regulatory mechanisms for the absence of pigments in the white flowers and the deposition of special compounds causing white appearance and the benefits of white color in nature.

Picturing Political Power: Eighteenth-Century Korean Portraits in San Francisco's Asian Art Museum

Picturing Political Power: Eighteenth-Century Korean Portraits in San Francisco's Asian Art Museum

Multi-Analytical Characterization of Rupestrian Precolonial Paintings of Inhuma, Piauí, Brazil

The chemical-mineralogical characterization of rupestrian paintings in red, white, black and yellow colors, which decorate the rocky walls from the archaeological sites of Ema and Furna dos Índios (Inhuma, Piauí, Brazil) was performed. The chemical analyses were performed in situ by the non-invasive analytical technique X-ray fluorescence spectrometry (XRF) as well as in laboratory using a non-destructive approach, without previous sample preparation, and Raman microscopy, and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS) techniques. The results, when together, allowed unequivocal identification of the main substances responsible for the color pigments, namely, hematite (red pigment), gypsum (white pigment), amorphous carbon from charcoal (black pigment) and goethite (yellow pigment).