Leuco Dye Research Articles

Remarkable responsive behaviors of iso-aminobenzopyranoxanthenes: protonation effect, photochromism and piezochromism

The iso-cis/trans-aminobenzopyranoxanthenes (iso-cis/trans-ABPXs), as one of popular leuco dyes, were investigated in solution or crystal phase. The introduction of benzo-pentacyclic-ester group in iso-cis/trans-ABPXs leads to remarkable multi-stimuli responsive behaviors, including protonation effect, photochromism and piezochromism with notable color changes. The iso-cis/trans-ABPXs show different in the responsive sensitivity and the iso-cis-ABPX is highly sensitive to environmental stimuli relative to the trans-form, which can be explained by their different C-H⋯O interaction and/or C-O bond length. Interestingly, as the ultraviolet light irradiation time increasing, the iso-cis/trans-ABPXs solution gradually becomes transparent and orange precipitates are achieved, which is identified as iso-ABPXs±. Multi-stimuli responsive behaviors on the iso-cis/trans-ABPXs provide a comprehensive insight into the chromogenic mechanisms of this type of materials, suggesting that they may be potential candidate materials for sensors and indicators.

Antioxidant properties of citric acid interfere with the uricase-based measurement of circulating uric acid

BackgroundCirculating uric acid (UA) is an important biomarker, not only in the detection and management of gout, but also in assessing the risk of related comorbidity. The impact of collection methods on clinical UA measurements has been the subject of limited study. After observing significant differences between UA concentrations of blood samples obtained by different collection tubes, we began examining the effects of exogenous tube components on measured UA concentrations. We aimed to: (1) demonstrate the variability in uricase-based UA measurements attributable to different collection methods and (2) identify factors influencing this variability. MethodsBlood samples from human subjects were collected using Serum Separator Tubes (SST tubes), Acid Citrate Dextrose (ACD) tubes, and Sodium Citrate (SC) tubes. Circulating UA concentrations were measured by chemistry analyzers utilizing the uricase method. Absorbance assays were run in order to determine the effects of citric acid, sodium citrate, and dextrose on measured absorbance in the presence of leuco crystal violet dye, hydrogen peroxide, and peroxidase. Statistical analyses—including Student’s T tests and ANOVA—were used to compare results. ResultsUA concentrations of blood samples collected in ACD tubes were significantly lower than those collected in SST tubes (P < 0.01). Samples collected in SC tubes trended towards lower UA measurements than samples collected in SST tubes, although this difference did not reach statistical significance (P = 0.06). Blood samples spiked with separate concentrations of sodium citrate (3.2 and 22.0 g/L), citric acid (8.0 g/L), and dextrose (24.5 g/L) demonstrated significantly lower UA measurements compared to controls (P < 0.01). Absorbance assays demonstrated that increasing concentrations of citric acid and sodium citrate—in the presence of leuco crystal violet, hydrogen peroxide, and peroxidase—decreased the amount of oxidized dye in the uricase method of UA measurement in a dose-dependent manner (P < 0.01). In contrast, dextrose did not significantly alter the amount of oxidized dye available. DiscussionOur results indicate that citric acid obstructs accurate uricase-based UA measurement, providing falsely low values. Citric acid, a known antioxidant, scavenges hydrogen peroxide, a key intermediate using the uricase method. By scavenging hydrogen peroxide, citric acid decreases the amount of oxidized leuco dye leading to falsely low UA measurements. Therefore, collection tubes, like ACD and SC tubes, which contain concentrations of citric acid or its conjugate base sodium citrate should not be used to measure circulating UA levels when utilizing uricase-based measurement methods.

Using advanced thermochromic technologies in the built environment: Recent development and potential to decrease the energy consumption and fight urban overheating

Construction materials play a crucial role in the thermal behaviour of the urban space as well as the building energy consumption and indoor environmental quality. Recently, there has been growing interest in optical construction materials/coatings as an effective method to minimise energy use, improve indoor and outdoor thermal comfort and fight urban overheating. Thermochromic materials as one of the advanced optical materials that change their optical properties/colour as a function of the ambient temperature can present lower/higher surface temperature than conventional materials during the warm/cold periods. Although pilot applications of thermochromic materials in the built environment shown a tremendous energy conservation potential, the serious optical degradation they exhibited, restricts seriously their use. Recent development in the field of thermochromic materials including quantum dots, plasmonics, photonic crystals, conjugated polymers, Schiff bases, liquid crystals, and nano optical filters for Leuco dyes present fascinating and impressive characteristics, enhance significantly the potential of thermochromic materials and opens new opportunities for the development and use of advanced cutting-edge optical materials. The present paper aims to offer a comprehensive overview of the recent developments on advanced thermochromic materials and on their energy conservation potential.

On the Discoloration of Methylene Blue by Visible Light.

The discoloration of methylene blue in aqueous solution was studied under illumination by a fluorescent lamp, LEDs of red, green, and blue light, and a UV-A black light bulb. Overall results showed that methylene blue was discolored with and without the presence of any photoactive semiconductor. Outcomes depended on the combination substrate-light source employed. Photosensitization was assumed as the discoloration mechanism followed upon visible light irradiation. Fluorescence spectroscopy and high-performance liquid chromatography were used to investigate the possible intermediates formed in the irradiated solutions. The detailed nature of formed species was not stablished, but it was proved that the dye molecule photo-bleached and partially defragmented in several intermediates including leuco dyes, demethylated phenothiazine dyes, and probably humic substances. Since the fluorescence intermediates found were similar for most of the irradiated solutions, it was assumed that comparable reactive species were responsible for the discoloration of the molecule in solution. Results proved the misconception of discoloration experiments found in the literature when employing visible light near the absorption region of the dye.

Inflammatory conditions affect the acetaminophen-induced liver injury in a novel 3D model of human multicellular microtissues

To introduce and evaluate a novel deformable 3-dimensional (3D) dosimetry system (Presage-Def/Optical-CT) and its application toward investigating the accuracy of dose deformation in a commercial deformable image registration (DIR) package.Presage-Def is a new dosimetry material consisting of an elastic polyurethane matrix doped with radiochromic leuco dye. Radiologic and mechanical properties were characterized using standard techniques. Dose-tracking feasibility was evaluated by comparing dose distributions between dosimeters irradiated with and without 27% lateral compression. A checkerboard plan of 5-mm square fields enabled precise measurement of true deformation using 3D dosimetry. Predicted deformation was determined from a commercial DIR algorithm.Presage-Def exhibited a linear dose response with sensitivity of 0.0032 ΔOD/(Gy∙cm). Mass density is 1.02 g/cm3, and effective atomic number is within 1.5% of water over a broad (0.03-10 MeV) energy range, indicating good water-equivalence. Elastic characteristics were close to that of liver tissue, with Young's modulus of 13.5-887 kPa over a stress range of 0.233-303 kPa, and Poisson's ratio of 0.475 (SE, 0.036). The Presage-Def/Optical-CT system successfully imaged the nondeformed and deformed dose distributions, with isotropic resolution of 1 mm. Comparison with the predicted deformed 3D dose distribution identified inaccuracies in the commercial DIR algorithm. Although external contours were accurately deformed (submillimeter accuracy), volumetric dose deformation was poor. Checkerboard field positioning and dimension errors of up to 9 and 14 mm, respectively, were identified, and the 3D DIR-deformed dose γ passing rate was only γ3%/3 mm = 60.0%.The Presage-Def/Optical-CT system shows strong potential for comprehensive investigation of DIR algorithm accuracy. Substantial errors in a commercial DIR were found in the conditions evaluated. This work highlights the critical importance of careful validation of DIR algorithms before clinical implementation.

Thermochromic ink–paper interactions and their role in biodegradation of UV curable prints

In this study, biodegradability aspects of UV thermochromic leuco dye print on three different paper materials (synthetic, recycled, and bulky) were studied using the soil burial test under anaerobic conditions. Biodegradation of UV curable thermochromic prints were evaluated for changes by visual examination, microbial growth assay, weight loss measurements, Fourier transform infrared spectroscopy, scanning electron microscopy and colorimetric measurements. Results showed a better absorption of ink into the bulky paper structure, followed by recycled paper. Synthetic paper is not absorbent. The ink binder altogether with classic pigment and microcapsules penetrates into the structure of bulky paper. Recycled paper absorbs ink binder mostly with classic pigment. Better adsorption of binder into the bulky paper structure results in thinner layer of ink binder on the paper surface. On non-absorbent synthetic paper, microcapsules are covered with thicker layer of ink binder. In the case of bulky paper, the highest rate of biodegradation was observed, resulting in a higher number of bacteria, higher weight loss, higher changes in colour (destruction of almost all microcapsules) and almost complete reduction in thermochromic effect of the prints. Results show that microcapsules, which penetrate into the structure of bulky paper, are promoting the rate of bulky paper biodegradation. The opposite behaviour was noticed for the penetration of classic pigment into the structure of recycled paper, which resulted in remarkable reduction of recycled paper biodegradation rate. The thicker layer of ink binder (containing classic pigment) on the surface of microcapsules on recycled paper resulted in slower rate of microcapsules degradation and smaller colour change of the print. The thickest layer of ink binder and classic pigment on synthetic paper surface causes the slowest rate of biodegradation of print.

Self‐Assembled Ionic Composites of Negatively Charged Zn(salen) Complexes and Triphenylmethane Derived Polycations as Recyclable Catalysts for the Addition of Carbon Dioxide to Epoxides

AbstractThe design and synthesis of a novel type of self‐assembled ionic composite composed of negatively charged Zn(salen) complexes and triphenylmethane derived polycations is reported. These composites were applied as easily recyclable catalysts for carbon dioxide addition to epoxides. The composites functioned as bifunctional catalysts which could be easily separated and recycled by precipitation from the reaction mixture upon addition of tetrachloromethane. The same batch of the catalyst could be employed for, at least, five runs with its catalytic properties improving as it was reused. A fully heterogeneous system was also prepared by cross‐linking leuco dye with para‐dibromoxylene and adding to it calculated amounts of Zn(salen) complex. The heterogeneous system was catalytically competent in the reaction between styrene oxide and carbon dioxide and its activity also increased on its reuse.

Colorimetric analysis of thermochromic samples in different forms employing a digital camera

The calibrated and characterised digital camera was used for the recording of a dynamic colour change of thermally treated three-component leuco dye based thermochromic samples in various forms – bulk system, dry pigment, water- and solvent-based ink formulations, and their dry layers coated on different paper substrates. The study has proved that the proposed approach enables to examine the thermochromic behaviour through the individual stages of the thermochromic coating preparation process. The measured path in CIELAB colour space and derived characteristics of the dynamic colour change were obtained with higher time-temperature resolution than with previously employed methods, enabling to observe even the less distinct features. The most significant differences were related to the length and complexity of the colour path. Dry layers of the water-based thermochromic ink coated on papers had higher values of the total length of the path and the total colour contrast than the layers of the solvent-based ink. The colour of water-based coatings had higher chroma and also it was less influenced by paper substrate. When compared to the bulk thermochromic system, the dry pigment and dry ink layers on paper substrates exhibited a larger width of a hysteresis loop at the decolouration limit, mainly due to the decrease of the temperature at which the colouration starts on cooling.

Solventless triarylmethane synthesis via hydroxyalkylation of anisole with benzaldehyde by modified heteropoly acid on mesocellular foam silica (MCF)

Triarylmethane (TRAM) compounds have wide applications such as leuco dyes for sensing tumors and other biological activities. Hydroxyalkylation of arenes with benzaldehyde results in formation of triarylmethane compounds. In the present study, 20 (wt.%) Cs2.5H0.5PW12O40 (Cs-DTP) supported on mesocellular foam (MCF) silica was prepared, characterized and tested for its activity in hydroxyalkylation reaction of anisole with benzaldehyde. Its activity was compared with commercial catalysts like Amberlyst-15, montmorillonite clay K-10, H3PW12O40 and unsupported Cs2.5H0.5PW12O40.The prepared catalyst showed the best activity compared to others with advantage of separation of catalyst and reusability. Reaction parameters were studied in detail and kinetic study was carried out for the said reaction. 20 (wt. %) Cs-DTP/MCF was found to be the best, robust and reusable catalyst. Reaction mechanism and kinetics were also studied. The results are new.

Microencapsulation of Three-Component Thermochromic System for Reversible Color Change and Thermal Energy Storage

In this study, poly(methyl methacrylate)/thermochromic system (PMMA/TS) and poly(methyl methacrylate-comethacrylic acid)/thermochromic system (P(MMA-co-MA)/TS) microcapsules were prepared by using emulsion polymerization method. The thermochromic system was consisting of crystal violet lactone (CVL) as a leuco dye, bisphenol-A (BPA) as a color developer, and 1-tetradecanol (TD) as a solvent. Microcapsules with different ratio of core/shell were synthesized to examine the effect of core/shell ratio on the properties of microcapsules. Phase transition temperatures and enthalpies, morphology, and particle size distributions of the microcapsules were analyzed using differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and particle size analyzer instruments, respectively. FT-IR spectroscopy was used to prove the presence of the thermochromic system in the microcapsules. UV-Vis absorption bands of the thermochromic system (TS) and microencapsulated thermochromic system (MTS) at both below and above the melting temperature of the solvent were obtained by using a UV-Vis spectrophotometer. The visible color change depending on temperature was monitored for each microcapsule individually by using a digital camera. Spherical morphology and unimodal particle size distribution of the microcapsules were determined by means of SEM photographs and particle size distribution curve analysis. The mean particle sizes of the produced microcapsules varied in a range of 16.0-35.2 μm. The digital camera photographs and the UV-Vis absorbance curves proved that color changed between dark blue and light blue depending upon the temperature change. Meanwhile, the produced microcapsules were proven for an excellent heat storage capacity for thermal energy storage owing to phase changing of the tetradecanol solvent used in the thermochromic system. The melting enthalpy of the microcapsules ranged from 145.5 J/g to 193.4 J/g.

Multistimuli-Responsive Camouflage Swimmers

Multistimuli-responsive camouflaging and autonomously propelled swimmers are presented. These bioinspired artificial swimmers are capable of color changing in response to a variety of environmental stimuli such as temperature, pH, and light. By multiplexing different stimuli-responsive materials on a single swimmer, a vast library of independently addressable colors can be achieved. Unlike other color-changing robots, our color-changing swimmers can move autonomously in solution and are decoupled from tethered supports. The utilized leuco dyes, pH indicators, and phosphorescent powders display excellent reversibility and prolonged color retention. Finally, we design camouflage patterns which render the swimmers invisible against virtually any background, while revealing the swimmer upon changing the environmental conditions. By mimicking animal camouflage strategies these artificial swimmers present a significant step toward realizing multienvironmental stimuli-responsive color-changing strategies for the...

Structural Modifications of Surfactant-Assisted Alumina and Their Effectiveness for the Removal of Dyes

The current study focuses on the development of the modified surface of the alumina by anionic surfactant sodium dodecyl sulfate. The synthesized Surfactant Modified Alumina (SMA) effectively associated with dye molecules and amended their properties. The triphenylmethane (CBB) and thiazine dyes (MB) were selected as a simulated dye wastewater system. The removal was carried out by adsorption method under the optimized amount of adsorbent dosage, the concentration of adsorbate, contact time and temperature. The adsorption isotherm models like Langmuir, Freundlich and Dubinin Radushkevish were employed. The mechanism of the interaction represents the decolorized leuco dye molecules were formed after adsorption. Moreover, the thermodynamic parameters like (∆S°), (∆H°) and (∆G°) were calculated represents the endothermic and spontaneous nature of the adsorption process. The pH at the point of zero charges (pHPZC) was determined. The photocatalytic degradation of respective dye systems was also observed. The surface morphology of (SMA) was determined by FTIR and SEM techniques. Whereas the pseudo-second-order kinetics model was followed in the present system. The Pearson Correlation Coefficient was conjointly applied. The removal efficiency was ascertained to be 99.50% for CBB(R-250) and 95.70% for (MB).

Customizable, Flexible Pressure, and Temperature Step Sensors with Human Skinlike Color

Durability and multifunctionality are very important factors for human skinlike tactile sensors for measuring physical stimuli if they provide reasonable pressure measurement range and sensitivity. Here, we propose a step tactile sensor with a simple processing unit, showing high repeatability and mechanical stability without drifting caused by thermal and geometrical noise. The proposed sensor, similar to a switch mechanism, detects the applied pressure discretely and has a wide pressure range of 2 kPa to 1.2 MPa according to its geometry. The developed tactile sensor can be designed and fabricated in various morphologies to detect a wide range of tactile stimuli, which help in customizing the sensor as per user demand for practical applications such as a prosthesis arm or hand. It is also easy to extend the sensor size to cover a large area owing to the simple fabrication process by using a 3D printer. Furthermore, with the addition of a flexible exterior layer of leuco dyes and the polydimethylsiloxane mixture, the color of a step tactile sensor not only resembles that of human skin color but also changes its color depending on the temperature changes as human skin does. Thus, the function of a pressure and temperature indicator in a flexible step sensor finds practical applications in various fields, including but not limited to prosthetic applications for the customized and comfortable usage.

Fabrication and characterization of reversible thermochromic wood veneers

Leuco dyes are widely used as functional materials for their thermosensitive chromogenic nature. The influences of thermochromic compounds and impregnation processing conditions on thermochromic wood veneer properties were investigated in this paper. The thermochromic compounds included thermochromic dye (ODB-2), color developer (bisphenol A) and solvent (1-tetradecanol). To achieve the maximum color change, the optimum mixing ratio of ODB-2 to bisphenol A to 1-tetradecanol was 1:2:60. Juglans mandshurica veneers were ultrasonically impregnated with reversible thermochromic compound suspensions. Analysis of variance showed that the influences of impregnation parameters on veneer color change were significant at the 0.05 level. The optimum thermochromic wood veneer can be obtained by impregnating with a thermochromic compound suspension for 2.0 min at 65 °C. In this paper, the thermochromic properties of wood veneers were evaluated, and functional thermochromic veneers exhibited excellent properties and thermostability.

Solvents interactions with thermochromic print

In this study, the interactions between different solvents (benzene, acetone, cyclohexanone, various alcohols and water) and thermochromic printing ink were investigated. Thermochromic printing ink was printed on metal surface. Components of thermochromic printing inks are polymeric microcapsules and classic yellow offset printing ink. Below its activation temperature, dye and developer within the microcapsules form a blue coloured complex. Therefore, thermochromic print is green. By heating above the activation temperature, blue colour of the complex turns into the leuco dye colourless state and the green colour of the prints turns into the yellow colour of the classic offset pigment. The results of the interaction with various solvents show that the thermochromic print is stable in all tested solvents except in ethanol, acetone and cyclohexanone. In ethanol, the green colour of the print becomes yellow. SEM analysis shows that microcapsules are dissolved. In acetone and cyclohexanone, the green colour of the print turns into blue, and the microcapsules become significantly more visible. Thus, the yellow pigment interacts with examined ketones. Based on the obtained interactions it can be concluded that the microcapsules have more polar nature than the classical pigment particles. Solvent-thermocromic print interactions were analysed using Hansen solubility parameters that rank the solvents based on their estimated interaction capabilities.

Colorimetric description of thermochromic printing inks

The dynamic colour of three commercial reversible thermochromic inks were studied. Thermochromic printing inks change their colour according to a change in temperature. The two types of thermochromic inks are based on leuco dyes and liquid crystals. The thermochromic effect achieved by liquid crystals is quite different from the effect achieved with leuco dyes. Leuco dyes change from a coloured to a colourless state, or from one colour shade to another due to structural changes inside leuco dye molecules under assistance of developer. Liquid crystal inks change colour continuously throughout the spectrum, producing iridescent colours starting from red and shifting to blue part of the spectrum with temperature. The colour change results from the way light interacts with special arrangement of liquid crystal molecules to produce coloured reflection by interference, and with the variation of this structure with temperature. In this paper we will present differences between two types of thermochromic printing inks giving careful colorimetric characterization.

Detection of therapeutic radiation in three-dimensions.

For over the last twenty years there has been a multitude of sophisticated three-dimensional radiation delivery procedures developed which requires a corresponding verification of the impact on patients. This article reviews the state of the art in the development of chemical detectors used to characterize the three-dimensional shape of therapeutic radiation. These detectors are composed of polyurethane, radical initiator and a leuco dye, which is radiolytically oxidized to a dye absorbing at 630 nm.

A Thermochromic Leuco Dye Coated Glove for the Prevention of Frostbite in Cold Environments

A Thermochromic Leuco Dye Coated Glove for the Prevention of Frostbite in Cold Environments

Biodegradation of thermochromic offset prints

In this study, biodegradability aspect of thermochromic leuco dye print on two different paper materials were studied using the soil burial test under anaerobic conditions. Printed paper samples were evaluated for changes by visual examination, weight loss measurements, FTIR spectroscopy, SEM, microscopic images, and colorimetric measurements. SEM micrographs indicated that microcapsules on non- absorbent synthetic paper are covered with thicker layer of ink binder, which was also confirmed by the IR spectra. Therefore, the microcapsules on SEM micrograph aren’t visible. SEM analysis shows significant penetration of the binder in the structure of absorbent recycled paper, making the microcapsules more visible even though they are covered with a thinner layer of a binder. Colour degradation of the print on the recycled paper is significant – the colour changes from green to yellow – green. The SEM micrograph shows certain deformation of the microcapsules for the print on recycled paper. Lower degradation was noticed for the print on synthetic paper for which the obtained SEM micrograph indicates destruction of the binder and possible interactions of bacteria with microcapsule at a place of resulting cracks. FTIR spectra show that vegetable oil in ink vehicle was oxidized on all prints during biodegradation test.

Radiochromic Hydrogel Dosimeters

Radiochromic hydrogel dosimeters are a useful tool for the verification of 3D dose distributions using optical CT scanners which are lower cost and with higher spatial resolution in a limited time than MRI scanners. In this paper, recent development of radiochromic micelle gel and genipin-gelatin gel dosimeters are described. They have the advantage of water equivalency, low or no diffusion property, and lower toxicity. Micelle gels consist of leuco dye, surfactant, radical initiator (halocarbons), and gelling agent. The dose sensitivities are affected by the concentration of each component and the temperature during irradiation. In non-diffusing genipin-gelatin gels, radiation induced bleaching is observed. The dose sensitivity is strongly affected by the concentration of genipin and sulfuric acid and by the blending time with gelatin. Higher dose sensitivity and standardization of the dose evaluation procedure will be the future issue.