Photostability enhancement of anionic natural dye by intercalation into hydrotalcite

Abstract

The aim of this study is the improvement of the photostability of several natural anionic dyes, carmine (CM), carthamus yellow (CY), and annatto dye (ANA), by complexation with hydrotalcite. The composite of the dyes and hydrotalcite is prepared by the coprecipitation method. CM is successfully intercalated in the hydrotalcite layer when the amount of introduced CM is large. The photostability of CM in CM/HT composites is superior to the CM adsorbed on silica surface. The effect of the stability enhancement is larger when the amount of introduced CM exceeds 0.23 g/g-host, or when the layer charge density of the hydrotalcite is larger. CY is also stabilized by complexation with hydrotalcite, whereas ANA is not stabilized by complexation with hydrotalcite. The photostability of an anionic natural dye can be improved by intercalation into the hydrotalcite layer, if the dye has a hydrophilic nature and a rather planar structure. The intercalated dye is stabilized by the protection from the attack of the atmospheric oxygen. In addition, contribution of the electrostatic interaction between the positively charged hydrotalcite layer and the intercalated anionic dye is also proposed.

Preparation of an anion dye intercalated into layered double hydroxides and its controllable luminescence properties

“…5), larger than ANS in ethanol solution (370 nm) but less than solid ANS (406 nm). This indicates that the J-type aggregate of ANS may exist in the galleries of LDH [35].…”

A combination of three surface modifiers for the optimal generation and application of natural hybrid nanopigments in a biodegradable resin

“…Test duration was 1,000 h, and measurements were taken in different time intervals. Previous works have checked organic dye stabilisation in nanoclay structures by changes in absorption curves [27]. We calculated the colour difference (∆E ab *), and also standardised the calculated values by natural dye content (g) in each sample (∆E ab */g.dye).…”

Intercalation of anionic organic ultraviolet ray absorbers into layered zinc hydroxide nitrate

“…According to the literature [26], the frequency difference (dm) between asymmetric and symmetric C-O bonds of the carboxylate group (dm = m as À m s ) gives information about the coordination to the matrix layer. In this case a monodentade coordination is the most likely alternative [24,26].…”