Black Bioinks from Superstructured Carbonized Lignin Particles

A renewable source of carbon black is introduced by the processing of lignin from agro-forestry residues. Lignin side streams are converted into spherical particles by direct aerosolization followed by carbonization. The obtained submicron black carbon is combined with cellulose nanofibers, which act as a binder and rheology modifier, resulting in a new type of colloidal bioink. The bioinks are tested in handwriting and direct ink writing. After consolidation, the black bioinks display total light reflectance (%R) at least three times lower than commercial black inks (reduction from 12 to 4%R). A loading of up to 20% of nanofibers positively affects the cohesion of the dried bioink (1 to 16 MPa), with no significant reduction in light reflectance. This is a result of the superstructuring of the ink components, which disrupts particle packing, intensifies colloidal interactions, introduces light absorption, and non-reflective multiple scattering.     

A rapid estimation of pigment content in virgin olive oils by a solvent-free method

In this work, a fast method was proposed for estimating the virgin olive oils (VOOs) carotenoids and chlorophylls concentration using color measurement. The pigment content by conventional spectrophotometry method and CIELAB color (L*, a*, and b*) at different degree of sample thickness (from 5 to 50 mm) of one hundred VOOs were measured. Oil carotenoids and chlorophylls content were correlated with the color parameters for the different oil thickness studied to design the prediction models of the new method. The best regression coefficients (R²) were obtained for multiple linear regression model using the three independent variables (L*, a*, and b*) together measured at 5 mm of oil thickness. The R² were 0.9679, 0.9515, and 0.9644 for predicting carotenoids, chlorophylls, and total pigments, respectively. External validation of these prediction models was satisfactory (relative error < 0.1). Therefore, this new solvent-free colorimetric method is a useful method for determination of carotenoids and chlorophylls content in VOOs. Practical applications: The simple colorimetric method developed in this study offers a fast and accurate alternative to current methods published in the literature to estimate the pigment content in VOOs. It is a rapid (less than 1 min) and cheap method, with the advantage of ease of operation, no sample pretreatment and solvent-free, thus environmentally friendly. This methodology can potentially be used by trained “nonprofessional analytical skilled” people in small laboratories or olive oil mills with limited technical facilities. Therefore, the technique is highly plausible as an alternative to determine the pigment content in VOOs. Finally, future works with this methodology could be carried out to online control of VOOs pigments content in the oil extraction process.     

Robust Full-Spectral Color Tuning of Photonic Colloids

Creation of color through photonic morphologies manufactured by molecular self-assembly is a promising approach, but the complexity and lack of robustness of the fabrication processes have limited their technical exploitation. Here, it is shown that photonic spheres with full-color tuning across the entire visible spectrum can be readily and reliably achieved by the emulsification of solutions containing a block copolymer (BCP) and two swelling additives. Solvent diffusion out of the emulsion droplets gives rise to 20–150 µm-sized spheres with an onion-like lamellar morphology. Controlling the lamellar thickness by differential swelling with the two additives enables color tuning of the Bragg interference-based reflection band across the entire visible spectrum. By studying five different systems, a set of important principles for manufacturing photonic colloids is established. Two swelling additives are required, one of which must exhibit strong interactions with one of the BCP blocks. The additives should be chosen to enhance the dielectric contrast, and the formation kinetics of the spheres must be sufficiently slow to enable the emergence of the photonic morphology. The proposed approach is versatile and robust and allows the scalable production of photonic pigments with possible future applications in inks for cosmetics and arts, coatings, and displays.     

Facile fabrication of cool yellow pigment with enhanced NIR reflectance by tailoring oxygen defects and its application in energy-saving building

Intensity of absorption tail at long wavelength side of absorption edge is affected by concentration of oxygen vacancy (O_v), which determines chromaticity, near-infrared (NIR) reflectance and application value of cool pigments. In this work, a feasible strategy is proposed to restrain the generation of O_v by lattice distortion to enhance color and NIR reflectance. Compression lattice is formed by introducing smaller ions of Ti⁴⁺ or Zr⁴⁺ into Tb site in SrTbO₃ host. This results in significant reduction of concentration of O_v. Compared to SrTbO₃, color component L* of SrTb_0.6Zr_0.4O₃ increases from 69.09 to 87.30. Moreover, NIR and solar reflectance are remarkably enhanced, reaching 18.3% and 19.3%, respectively. In addition, 11.6 °C and 5.6 °C decreases in temperature were observed for inner surface of roof and indoor room of simulation house. The strategy proposed in this work will contribute to developing color-cool pigments with suitable properties and high solar regulation ability.