A Comparative Study on Color Stability of Anthocyanin Hybrid Pigments Derived from 1D and 2D Clay Minerals

Abstract

Anthocyanin extracted from the fresh blue berry fruits was loaded onto different clay minerals including one-dimensional tubular halloysite and fibrous sepiolite, and two-dimensional lamellar kaolinite and montmorillonite to fabricate reversible allochroic hybrid pigments. The effect of the possible interaction mechanism between anthocyanin and clay minerals on the color stability of hybrid pigments was investigated. Due to the difference in the structures and properties of clay minerals, natural anthocyanin was inclined to be absorbed on the surface and intercalated into the interlayer of 2:1 type layered montmorillonite, while it was mainly anchored on the surface of 1:1 type kaolinite and halloysite. By contrast, it was simultaneously loaded on the surface and confined into the nanochannels and/or grooves of 2:1 type chain-layered sepiolite. Interestingly, the resulting hybrid pigments presented good thermal stability and resistance to chemical reagents, as well as reversible gas-sensitive allochroic behavior in HCl or NH3 gases, especially anthocyanin/sepiolite hybrid pigments due to the shielding effect of the well-defined nanochannels and grooves of sepiolite. Based on this color-change behavior, a simple pH test paper was also prepared with obvious color change at different pH values by coating the filter paper with anthocyanin/sepiolite hybrid pigments.

Saponite-anthocyanin derivatives: The role of organoclays in pigment photostability

“…Li et al, 2019 have reported the acid/base reversible allochroic hybrid pigments prepared by incorporation of ACN on sepiolite, halloysite, kaolinite and montmorillonite. Their comparative study has demonstrated the influence of the clay compositions on color properties, the nanochannels of Sep were claimed to be responsible for the optimum vivid color properties, thermal stability, and chemical corrosion resistance (Li et al, 2019b). Palygorskite was also studied to provide enhancement in ACN stability (Li et al, 2019a).…”

Fabrication of Eco-Friendly Betanin Hybrid Materials Based on Palygorskite and Halloysite

“…Subsequently, the grinding and heating treatment are applied to promote the physical and chemical interaction between betanin and clay minerals [ 39 , 48 ]. Among them, the application of heating treatment helps to remove the water molecules partially located in the clay minerals, resulted in facilitating the fixation of betanin molecules on clay minerals and improving their stability [ 1 , 8 , 9 , 35 , 39 ]. The natural Pal and Hal are white and light yellow ( Table S1 ), respectively, and hybrid materials present pink color after incorporation of betanin, which indicates that betanin has been successfully loaded on the clay minerals [ 13 , 35 , 39 ].…”

“…Clay minerals have high specific surface area, cation exchange capacity and excellent adsorption properties [ 29 , 30 , 31 , 32 ]. In addition, different clay minerals have different morphologies, structures, chemical compositions, and properties [ 33 , 34 , 35 ]. Therefore, the eco-friendly natural clay minerals have become the focus of the relevant researches on the loading of natural pigments in the last few years, and the interaction between clay minerals and natural pigments is explored and guide to improve the properties of natural pigments.…”

“…Interestingly, the surface charge of Hal is the result of the interaction between the negatively charged outer layer (siloxane groups) and the positively charged inner surface (aluminol groups) in the range of pH 2–8 [ 46 , 47 ]. At present, our group has successfully synthesized a series of acid/base reversible allochroic anthocyanin/clay minerals hybrid pigments based on anthocyanin natural molecules and clay minerals (Pal, Hal, sepiolite, kaolinite, and montmorillonite) [ 35 , 39 ]. However, the studies on the natural anionic pigments and clay minerals are rarely reported.…”

Anthocyanin Hybrid Nanopigments from Pomegranate Waste: Colour, Thermomechanical Stability and Environmental Impact of Polyester-Based Bionanocomposites

“…The development of stabilization strategies to improve the colour stability of ACNs such as the addition of co-pigments, formation of supramolecular complexes and encapsulation systems, and protection with natural clay minerals were proposed by Li et al [19]. In this sense, it has been proved that colour stabilization can be achieved by using hybridization of clay nanostructures [20][21][22]. A number of recent studies have focused on the adsorption of ACNs to obtain dye/clay hybrid pigments with improved colour fastness and stability which include reports of stable hybrid pigments prepared from ACNs and several clay minerals that undergo reversible pH-dependent colour changes [23][24][25].…”