• Energy Research

Pigments are the main components of cosmetics, which determine both toxicity and consumer color characteristics. Zn-Al layered double hydroxides intercalated with anionic food dyes are promising pigments. The best sources of dyes for intercalation are natural ones. The most promising are spices. Natural dyes from spices are often biologically active substances. The parameters of samples of Zn-Al (Zn:Al=3:1) hydroxides intercalated with natural food dyes, synthesized in the medium of aqueous tinctures of saffron and safflower, were studied. The crystal structure of the samples was studied by X-ray phase analysis; color characteristics were studied by spectroscopy and calculation of parameters in the CIE L*a*b system. The possibility of synthesizing Zn-Al colored layered double hydroxides intercalated with natural dyes in the medium of saffron and safflower tinctures was shown. X-ray phase analysis showed that both pigment samples were layered double hydroxides with the α-Zn(OH)2 structure. For the pigment intercalated with saffron dye, the phenomenon of partial decomposition of Zn-Al LDH to ZnO during synthesis was revealed. The color characteristics of the samples were studied. Zn-Al LDH pigment synthesized in a saffron tincture had a bright yellow color determined by intercalated saffron carotenoids (crocin and crocetin). It was suggested that safflower dye flavonoids were partially hydrolyzed (red ones - cartamine and cartamidine, and yellow - Safflor Yellow A), which led to the formation of a dark orange-brown color of the sample. The prospects of using Zn-Al LDH intercalated with saffron food dyes as a cosmetic pigment were shown

Pigments are the main components of cosmetics, which determine both toxicity and consumer color characteristics. Zn-Al layered double hydroxides intercalated with anionic food dyes are promising pigments. The best sources of dyes for intercalation are natural ones. The most promising are spices. Natural dyes from spices are often biologically active substances. The parameters of samples of Zn-Al (Zn:Al=3:1) hydroxides intercalated with natural food dyes, synthesized in the medium of aqueous tinctures of saffron and safflower, were studied. The crystal structure of the samples was studied by X-ray phase analysis; color characteristics were studied by spectroscopy and calculation of parameters in the CIE L*a*b system. The possibility of synthesizing Zn-Al colored layered double hydroxides intercalated with natural dyes in the medium of saffron and safflower tinctures was shown. X-ray phase analysis showed that both pigment samples were layered double hydroxides with the α-Zn(OH)2 structure. For the pigment intercalated with saffron dye, the phenomenon of partial decomposition of Zn-Al LDH to ZnO during synthesis was revealed. The color characteristics of the samples were studied. Zn-Al LDH pigment synthesized in a saffron tincture had a bright yellow color determined by intercalated saffron carotenoids (crocin and crocetin). It was suggested that safflower dye flavonoids were partially hydrolyzed (red ones - cartamine and cartamidine, and yellow - Safflor Yellow A), which led to the formation of a dark orange-brown color of the sample. The prospects of using Zn-Al LDH intercalated with saffron food dyes as a cosmetic pigment were shown

Electrochromic coating is the basis of smart windows with variable optical characteristics. Nevertheless, despite the obvious advantages of using smart windows in construction, their cost is high.We have considered the coatings obtained by the cathodic template method, which are more economical in production. The presented studies are devoted to tests at cyclic temperature loads – repeated cooling and heating. The paper shows the influence of the medium and the method of heat supply (removal) to an electrochromic electrode based on a composite Ni(OH)2-PVA coating as well as the effect of surface preparation before its application.As a medium for cyclic temperature loads, we used air or a working electrolyte – 0.1 M KOH. As a preliminary preparation of the transparent electrically conductive base, we used electrochemical etching of a part of the layer of the electrically conductive transparent coating of tin oxide doped with fluorine in a solution of 1 M HCl.The result of a series of experiments was the discovery of a strong influence of temperature cyclic loads on the final characteristics of electrochromic films. The electrochromic film on the sample, which was subjected to cyclic temperature changes in air and on the substrate without etching, almost completely lost its electrochromic characteristics and adhesion. The sample, which was subjected to thermal stress in an alkali solution, lost its uniformity during coloring.On the other hand, both films, which were deposited on etched substrates, had generally better characteristics than samples deposited without etching and subjected to thermal stress in the air and in alkali. In this case, the sample, which was obtained on the substrate with pretreatment by etching and subjected to temperature cycling in alkali, had even slightly better characteristics than the reference sample

Electrochromic coating is the basis of smart windows with variable optical characteristics. Nevertheless, despite the obvious advantages of using smart windows in construction, their cost is high.We have considered the coatings obtained by the cathodic template method, which are more economical in production. The presented studies are devoted to tests at cyclic temperature loads – repeated cooling and heating. The paper shows the influence of the medium and the method of heat supply (removal) to an electrochromic electrode based on a composite Ni(OH)2-PVA coating as well as the effect of surface preparation before its application.As a medium for cyclic temperature loads, we used air or a working electrolyte – 0.1 M KOH. As a preliminary preparation of the transparent electrically conductive base, we used electrochemical etching of a part of the layer of the electrically conductive transparent coating of tin oxide doped with fluorine in a solution of 1 M HCl.The result of a series of experiments was the discovery of a strong influence of temperature cyclic loads on the final characteristics of electrochromic films. The electrochromic film on the sample, which was subjected to cyclic temperature changes in air and on the substrate without etching, almost completely lost its electrochromic characteristics and adhesion. The sample, which was subjected to thermal stress in an alkali solution, lost its uniformity during coloring.On the other hand, both films, which were deposited on etched substrates, had generally better characteristics than samples deposited without etching and subjected to thermal stress in the air and in alkali. In this case, the sample, which was obtained on the substrate with pretreatment by etching and subjected to temperature cycling in alkali, had even slightly better characteristics than the reference sample

Layered double hydroxides, especially Zn-Al, are valuable matrices for intercalation with various functional anions: dyes, medicines, food additives, etc. For the purposeful development and optimization of the technology for the synthesis of Zn-Al hydroxides intercalated with functional anions, the phase composition and crystal structure of Zn-Al nitrate layered double hydroxide samples (Zn:Al=4:1) synthesized at solution flow rates of 0.8 and 1.6 l/h, pH=7, 8, 9, 10 and t=10, 20, 30, 40, 50 and 60 °С were studied. XRD showed that all samples synthesized at different temperatures, pH, and solution flow rates were Zn-Al layered double hydroxides with an α-Zn(OH)2 crystal lattice of medium crystallinity, with an admixture of an oxide phase with a ZnO lattice. Three sections of the dependence of the crystallite size of the sample on the synthesis temperature were distinguished: 10–20 °C, 30–50 °C, and 60 °C, within which an increase in temperature led to an increase in crystallinity. A hypothesis was put forward about a change in the mechanism or kinetics of LDH formation at temperatures of 30 °C and 60 °C. An increase in the pH of the synthesis and the flow rate of solutions led to an increase in crystallinity. A retrospective comparative analysis of the phase composition and crystal structure of Zn-Al-nitrate and Zn-Al-tripolyphosphate (tartrazine or Orange Yellow S) LDH samples was carried out. It was found that the use of large and multi-charged functional anions caused significant adsorption on precipitate nuclei and difficult intercalation. As a result, low crystallinity was formed (Tartrazine anion) or a significant part of LDH was decomposed to oxide (tripolyphosphate and Orange Yellow S anions).

Layered double hydroxides, especially Zn-Al, are valuable matrices for intercalation with various functional anions: dyes, medicines, food additives, etc. For the purposeful development and optimization of the technology for the synthesis of Zn-Al hydroxides intercalated with functional anions, the phase composition and crystal structure of Zn-Al nitrate layered double hydroxide samples (Zn:Al=4:1) synthesized at solution flow rates of 0.8 and 1.6 l/h, pH=7, 8, 9, 10 and t=10, 20, 30, 40, 50 and 60 °С were studied. XRD showed that all samples synthesized at different temperatures, pH, and solution flow rates were Zn-Al layered double hydroxides with an α-Zn(OH)2 crystal lattice of medium crystallinity, with an admixture of an oxide phase with a ZnO lattice. Three sections of the dependence of the crystallite size of the sample on the synthesis temperature were distinguished: 10–20 °C, 30–50 °C, and 60 °C, within which an increase in temperature led to an increase in crystallinity. A hypothesis was put forward about a change in the mechanism or kinetics of LDH formation at temperatures of 30 °C and 60 °C. An increase in the pH of the synthesis and the flow rate of solutions led to an increase in crystallinity. A retrospective comparative analysis of the phase composition and crystal structure of Zn-Al-nitrate and Zn-Al-tripolyphosphate (tartrazine or Orange Yellow S) LDH samples was carried out. It was found that the use of large and multi-charged functional anions caused significant adsorption on precipitate nuclei and difficult intercalation. As a result, low crystallinity was formed (Tartrazine anion) or a significant part of LDH was decomposed to oxide (tripolyphosphate and Orange Yellow S anions).

Layered double hydroxides, especially Zn-Al, are valuable bases for intercalating various functional anions: dyes, drugs, food additives, etc. For purposeful development and optimization of the synthesis technology of functional materials based on Zn-Al layered double hydroxides, the technological parameters of Zn-Al nitrate layered double hydroxide samples (Zn:Al=4:1) synthesized at solution flow rates of 0.8 and 1.6 l/h, pH=7, 8, 9, 10 and t=10, 20, 30, 40, 50 and 60 °C were determined. The yield values of the samples were determined by the gravimetric method. The sedimentation rate was studied by measuring the normalized thickness of the precipitate layer (relative to the initial layer thickness) during 30 minutes of settling. It was found that with an increase in the synthesis pH, the yield increased from 74.68 % to 83.54 %. Increasing the flow rate of the solutions led to a decrease in yield. On the yield-synthesis temperature dependence, two sections of 10–20 °C and 30–60 °C were identified, within which an increase in temperature led to a decrease in yield. It is shown that with increasing synthesis pH, as well as the solution flow rate, the sedimentation rate increased significantly. At pH=10, almost complete sedimentation of the sample occurred within the first 5 minutes. The obtained data indicate that the pH of the zero charges of the Zn-Al-NO3 layered double hydroxide particles was close to 10. It was found that increasing the temperature reduced the sedimentation rate. An abnormally low sedimentation rate at a synthesis temperature of 30 °C and an abnormally high sedimentation rate at 50 °C were detected. The obtained data confirm the previously stated hypothesis regarding the change of the mechanism or kinetics of the formation of layered double hydroxides at temperatures of 30 °C and 50 °C