Range Of Color Change Research Articles

Synthesis and structural determination of thermochromic compound

Thermochromic materials are extensively utilized in various fields, such as healthcare, textiles, and military applications. The exceptional thermal properties of these materials are attributed to the thermochromic substances they contain. Lactone-based thermochromic compounds, known for their high sensitivity, broad color change range, and durability, have been extensively researched and developed. In this article, a thermochromic compound, crystal violet lactone (CVL), chemically identified as 3,3-bis(4-dimethylaminophenyl)-6-dimethylaminophthalide, was prepared through two steps by the reaction of N,N-dimethylaniline, m-dimethylaminobenzoic acid, and p-dimethylamino-benzaldehyde in acid condition. CVL exists in white powder, melting point 180 - 183 oC, yield 61.6%. The product structure was determined by modern physical methods such as IR, 1D NMR, 2D NMR, and MS spectra.

Mobile phone-assisted imprinted nanozyme for bicolor colorimetric visual detection of erythromycin in river water and milk samples

The residues of erythromycin (ERY) may have negative impacts on the ecological environment, health, and food safety. How to detect ERY effectively and visually is a challenging issue. Herein, we synthesized a molecularly imprinted polymer based nanozymes for selective detection of erythromycin (ERY-MIPNs) at neutral pH, and developed a mobile phone-assisted bicolor colorimetric detection system. This system produced a wide range of color changes from blue to pinkish purple as the ERY concentration increased, making it easy to capture the visualization result. Also, the system showed good sensitivity to ERY ranging from 15 to 135 μM, with a detection limit of 1.78 μM. In addition, the system worked well in the detection of ERY in river water and milk, with the recoveries of 95.57% ∼ 103.20%. These data suggests that this strategy is of considerable potential for practical applications and it provides a new idea for visual detection with portable measurement.

Effect of concentration of Er3+ on up‐conversion luminescence in NaYF4 containing oxy‐fluoride glass‐ceramics

AbstractThe color of micro‐structured glass can be tuned by adjusting the cross‐relaxation between Er3+ ions through the mechanism of up‐conversion, although the range of color change is very limited. Here, we report the simple and reproducible synthesis of transparent oxy‐fluoride glass‐ceramics co‐doped with Yb3+/Er3+ by melting and secondary heat treatment. By adjusting the doping content of Er3+ ions from 0.2 to 10 mol%, followed by the secondary heat treatment, the intensity of up‐conversion luminescence under 980 nm laser excitation was increased by more than 100 times, and the glass‐ceramics showed an Er3+ doping content‐depended color change of the up‐conversion luminescence from green light to red light. The elemental analysis with TEM–EDS mapping and the measurement of the lifetime of up‐conversion luminescence suggest that changes in the cross‐relaxation between Er3+ ions is the principal mechanism behind the color change of up‐conversion luminescence. As a result, the red emission due to the electronic transition of 4F9/2 is much greater than that of the green emission (4S3/2). Therefore, we present a simple and reproducible strategy to achieve an efficient up‐conversion luminescence from glass‐ceramics with a broad range of color tunability and high color purity.

Study on preparation, characterization and application of mixed-colorants thermochromic microcapsules

In order to expand the color-change range and make the discoloration temperature suitable for the daily textiles, a new formulation of mixed-colorants thermochromic core material is designed, in which crystal violet lactone (CVL) is the basic color former, bisphenol A (BPA) is the developer, especially the solvent-based dye and dodecyl dedecanoate are used as the extended dye and the solvent, respectively. Scanning electron microscope (SEM), differential scanning calorimeter (DSC) and thermogravimetric analyzer (TGA) were applied to study the morphology, encapsulation rate, non-isothermal crystallization behavior and thermal stability of the mixed-colorant thermochromic microcapsules (MCTMs) prepared by in-situ polymerization. The results show that MCTMs have good sphericity, uniform particle size, good thermal stability and the encapsulation rate can reach 86.73%. Under the non-isothermal conditions, the encapsulation of formaldehyde-melamine resin wall material can slightly reduce the crystallization rate of the solvent, but does not affect the relative crystallinity, thermal properties and discoloration sensitivity of the core materials. With the variety of ambient temperatures in the range of 20–35 °C, the printed cotton fabrics with MCTMs could change color reversibly between different tones with good reliability and durability, and exhibit more gorgeous colors than the common thermochromic materials.

Multicolor Electrochromic Display and Patterned Device Based on Hollow-SiO2-Supported WO3 Photonic Crystals.

Electrochromic photonic crystals (PCs) have been intensively studied in the field of display, sensors, and intelligent materials due to their tunable brilliant structural colors. The mostly studied electrochromic PCs are based on the tunable lattice parameter after electrifying; namely, the electrochromic process is caused by the structural change of PCs. Besides the lattice parameter, the refractive index is another key factor to determine the structural color of PCs. Here, a kind of hollow-SiO2-supported WO3 (H-SiO2/WO3) PCs is designed, where the refractive index of the WO3 portion is changeable under charging. Benefiting from the support effect and tunable thickness of H-SiO2, large-area PC samples with good surface morphology and bright multicolor output are prepared. The reflection peaks of these composite PCs can shift by 30-90 nm, and their corresponding colors changed obviously after the voltage was applied. After being pixelated by laser-marking, the H-SiO2/WO3 PCs can dynamically display different numeric and alphabetic patterns in an electric-driven writing and erasing process. Not only does this composite PC structure broaden the color change range of WO3-based materials but also avoids the structural change in the electrochromic process. This work provides more possibilities for electrochromic PCs in the field of color-changing pattern displays.

Research progress in conductive polymer-based electrochromic fabrics

Conductive polymer-based electrochromic fabrics show promising applications in new intelligent displays, flexible smart wearables, and military camouflage, thanks to their flexibility, light weight, high degree of controllability, and wide range of color change. However, despite these advantages, electrochromic textiles that rely on conductive polymers face several limitations, such as discomfort during use, instability in structure, and issues with the continuous production technology of electrochromic fibers. These factors hinder their further development. To address these limitations and promote the industrialization of conductive polymer-based electrochromic fabrics, this paper provides a comprehensive analysis that covers various aspects of electrochromic devices, including device structure, color-change mechanisms, electrochromic materials, application of electrochromic textiles, and the advantages and disadvantages of commonly used conductive polymers in electrochromic fabrics. By exploring these aspects, a better understanding of the structure and performance of conductive polymer-based electrochromic fabrics can be achieved, leading to a more effective promotion of their industrialization. Moreover, progress in the research of conductive polymer-based electrochromic fabrics is systematically reviewed from the structural design perspective, both domestically and internationally. Finally, the challenges that conductive polymer-based electrochromic fabrics currently face are discussed, and their future development trends are presented.

Mechanochromic photonic fibers composed of strain responsive colloidal crystals and spandex yarns

Mechanochromic photonic fibers can realize a visual dynamic color response to external stimuli, and are widely used in colorimetric sensing, smart display, and medical care. At present, colloidal crystals-based mechanochromic photonic fibers with a core-sheath structure have been successfully prepared by electrophoretic deposition and dip-coating. However, problems such as the complicated preparation process and the limited range of color change are still unsolved and hinder the applications of mechanochromic photonic fibers. Here, a mechanochromic photonic fiber with a wide color shift range is prepared by a simple and effective strategy. The fiber is fabricated by coating elastic rubber containing a non-close-packed array of silica particles onto spandex yarn. The obtained photonic fiber displays a structural color that can be controlled by adjusting the diameter and volume fraction of silica particles. Under stretching, the fiber shifts from red to blue with a color change range of 127 nm. More importantly, it achieves reversible color change in the visible range under mechanical strain. These mechanochromic photonic fibers based on colloidal crystals and spandex yarns are promising for smart wearables, display textiles, and visual sensors.

Synthesis and electrochromic properties of all donor polymers containing fused thienothiophene derivatives with high contrast and color efficiency

Synthesis of high-performance electrochromic polymers is still one of the research highlights in electrochromic field. In this work, four solution-processable electrochromic polymers based on fused thienothiophene derivative (tris(thienothiophene) (TTT)) or indacenodithieno[3,2-b]thiophene (IDTT)) and 3,4-dialkyloxythiophene derivative (3,4-ethylenedioxythiophene (EDOT) or 3,4-propylenedioxythiophene (ProDOT)) are successfully synthesized via direct arylation random polymerization (DArP) with a low reaction temperature to decrease the β-coupling. H Nuclear magnetic resonance (HNMR), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), Cyclic voltamogram (CV), and spectroelectrochemistry are applied to characterize these four polymers. These four polymers present colored-to-highly transmissive electrochromic performance, while the IDTT-based polymers give red-to-transmissive color change range and TTT-based polymers can change from blue to highly transmissive. All these four polymers present high optical contrast (>45%), fast switching response, good stability, and high coloration efficiency. Two electrochromic devices fabricated based on these prepared polymers confirm the excellent electrochromic performance of these polymers in devices.

Construction of novel luminescent thermometers based on dual-emission centers of rare-earth and bismuth ions.

Optical thermometry based on fluorescence intensity ratio (FIR) technology has several advantages for industrial and medical applications such as remote signaling, non-invasiveness, and excellent spatial resolution. Here, an approach to the construction of luminescent thermometers is proposed based on high-temperature solid-state reactions through doping of rare earth (RE) elements (e.g., samarium (Sm3+) or europium (Eu3+)) into Ca2Y0.97Bi0.03SbO6 (CYBS) phosphors. The tuning of the CYBS:Eu3+ and CYBS:Sm3+ ratios in the phosphors provided a wide range of color changes from purplish blue to red and from purplish blue to pink, respectively. The superiority of optical thermometer is validated by higher values of absolute sensitivity (Sa) and relative sensitivity (Sr). As such, both phosphors exhibit excellent temperature sensing performance with Sa/Sr values (at 483K) of 4.945×10-2/0.968×10-2K-1 (CYBS:0.05Eu3+) and 2.964×10-2/0.864×10-2K-1 (CYBS:0.05Sm3+). Thus, RE-doped CYBS materials with color tuning properties and superior temperature sensing performance are recommended for the construction of novel luminescent optical thermometers.

Range of color changes of beech wood in the steaming process

Changes in color were evaluated for beech wood Fagus sylvatica L., caused by a steaming process using either a mixture of saturated steam and air or saturated water steam in the temperature range: t = 95 °C to 125 °C for a duration of T = 3 h to 12 h. The initially light white-gray color of beech wood with a yellow tint darkened during the thermal treatment process. It changed to a pale pink-brown and then to dark brown color. According to the visible changes in the color of beech wood obtained by the thermal treatment process with the human eye, , a color scale was proposed as a means to categorize the severity of treatment. The color ranged from a pale pink-brown color to a dark brown-red color depending on the value of the total color difference ∆E*.

Comparison of Color Change to pH Range and Acid-Base Titration Indicator Precision Test of Multiple Ethanol Extracts

Natural indicators using anthocyanin compounds can be an alternative to synthetic indicators on acid-base titration because anthocyanin is an organic compound that is unstable with changes in pH. The extraction was carried out with ethanol because the compounds of anthocyanin were polar. This study was to ensure an ethanol extract of some plants could be used as an acid-base indicator that had a pH range of color change and the value of the equality parameter was not significantly different from the phenolphthalein indicator. The research method is to collect research journals on making natural indicators from ethanol extracts of various plants compared to phenolphthalein indicators so that secondary data from these journals can be processed statistically. Research results and conclusions: Based on the results of statistical data processing using the t-test there was no difference in the average pH of the phenolphthalein indicator with the average pH of ethanol extracts of adam air leaves (Rheo discolor), white frangipani flowers and Clitoria teratea L., with a significance value > 0.05 and the equality test (precision) had the requirements of good equality.
 HIGHLIGHTS
 
 Natural indicators are needed as a substitute for synthetic indicators in determining acid-base titrations; one of them is anthocyanin dye
 Research journals on making natural indicators from ethanol extracts of various plants compared to phenolphthalein indicators so that secondary data from these journals can be processed statistically
 There was no significant difference between the average pH of the phenolphthalein indicator and the average pH of the ethanol extract of Adam's Eve Leaves, ethanol extracts of white Cambodia flowers and ethanol extracts of Telang flowers in producing color changes
 
 GRAPHICAL ABSTRACT

Multifunctional colorimetric cellulose acetate membrane incorporated with Perilla frutescens (L.) Britt. anthocyanins and chamomile essential oil

A colorimetric cellulose acetate (CA) membrane incorporated with Perilla frutescens (L.) Britt. anthocyanins (PFA) and chamomile essential oil (CO) is developed via electrospinning technique for food freshness monitoring and shelf-life extending. The moieties of PFA and CO are well-dispersed in fiber matrix by hydrogen bonds and their incorporation increases the fiber size but with no obvious influence on the fiber morphology at incorporation levels. The presence of CO enhances membrane hydrophobicity. The target membrane of CA-PFA6-CO15 (PFA6%, CO15%) has a wide color change range of pH 2–12 which is high sensitive and reversible towards external pH-stimuli. The membrane has good antibacterial activity against E. coli and S. aureus besides antioxidant activity. The release of bioactive moieties is predominantly controlled by Fickian diffusion. The target membrane can simultaneously monitor pork freshness in real-time and double the shelf-life at 25 °C, indicating its potential application in active and intelligent food packaging.

Copper(II) complexes containing mixed- chelate ligand, solvatochromism and density functional theory studies

This study presents an experimental and computational study on ligand L (N,N-diisopropyl-N'-pyridine-2-yl(methyl)ethane-1,2-diamine) and the mixed chelate copper(II) complexes of [Cu(L)(Cl-acac)](ClO4), 1 and [Cu(LH)(Cl-acac)(ClO4)]ClO4, 2 , in which Cl-acac stands for 3-chloroacetylacetone. The ligand L and complexes were characterized by elemental analysis, IR, molar conductivity measurements and single crystal X-ray analysis. The ligand L in [Cu(L)(Cl-acac)](ClO4), 1 acts as a tridentate ligand, while in 2 it serves as bidentate ligand due to protonation of one of the coordinating atoms. The geometry around the copper(II) is distorted trigonal bipyramidal in 1 but 2 is almost square pyramidal. The square pyramidal geometry of compound 2 made it a good solvatochromic probe with the color change range from green to blue in 14 organic solvents. Its solvatochromism was studied in 14 organic solvents, which showed a positive trend with increasing donor power of the solvents. A multi-parametric equation was used to describe the solvent effect on the d–d transition of the complex using SPSS/PC software. Statistical analysis using stepwise multiple linear regression (SMLR) showed that the solvent donor number (DN) model plays a significant role in the observed salvochromism. The positive solvatochromism is due to the coordination of the solvent molecules with different donor power to the axial positions of the copper(II) ion by replacing the weakly coordinated perchlorate ion. To study the electronic structure of the complex and examine the proposed mechanism the density functional theory (DFT) and time dependent DFT calculations were used, respectively. The computational results in three solvents with different donor numbers support the proposed solvatochromism mechanism.

In situ polymerization of PEDOT:PSS films based on EMI-TFSI and the analysis of electrochromic performance

Abstract In this report, PEDOT composite films were prepared by in situ electrochemical polymerization. 1-Ethyl-3-methylimidazole bis(trifluoromethylsulfonyl)imide (EMI-TFSI) was used as an ionic liquid dopant for PEDOT:PSS films. Subsequently, these PEDOT:PSS/EMI-TFSI films were compared with PEDOT:PSS films based on their morphology, structure, electrochromic properties, and optical properties at different deposition voltages and deposition times. It was observed that the addition of EMI-TFSI enhanced all the aforementioned properties of the films. PEDOT:PSS/EMI-TFSI films were seen to have a larger ion diffusion coefficient (1.38 × 10−20 cm2·s−1), a wider color change range (43.48%), a shorter response time (coloring response time = 1.2 s; fade response time = 2 s), and a higher coloring efficiency (189.86 cm2·C−1) when compared with normal PEDOT:PSS films. The introduction of EMI-TFSI in the films ultimately resulted in superior electrochemical and optical properties along with higher stability.

Fluorescent color analysis of ascorbic acid by ratiometric fluorescent paper utilizing hybrid carbon dots-silica coated quantum dots

Monitoring the concentration of ascorbic acid (AA) in biological samples is essential to food quality and healthcare. Various fluorescence methods widely reported for the detection of AA are usually based on “turn-on” or “turn-off” principle. However, few ratiometric fluorescent sensors were reported for AA determination. Additionally, the application of ratiometric fluorescence probe is usually limited by the narrow range of color changes and insensitivity color change of the AA concentration. Herein, a novel ratiometric fluorescent test paper to achieve the continuous color changes from red to blue was developed for the fluorometric qualitative and quantitative determination of AA. The nanoprobe consists of blue-emitting carbon dots (C-dots) and red-emitting silica coated quantum dots (QDs@SiO2) with certain ratiometric fluorescence intensity of blue to red. The fluorescence of blue-emitting CDs (peaking at 450 nm) is quenched by Fe3+, then the blue fluorescence is restored consecutively with the gradual increasing of AA concentration due to the reduction from Fe3+ to Fe2+ by using AA. While the fluorescence of red-emitting QD@SiO2 (peaking at 630 nm) works as a stable internal standard. Therefore, a distinguish color transition from red to blue can be observed by naked eyes intuitively with the increasing of AA concentration. By calculating the ratiometric fluorescent intensity at 450 nm and 630 nm or observing the color of the mixture solution by naked eyes, the concentration of AA can be detected easily and accurately. Under optimized conditions, the fluorescent intensity ratio (I450/I630) shows linear relationship with the concentration of AA from 0 to 70 μM with the detection limit as low as 3.17 μM. Finally, a ratiometric fluorescent sensor paper was further developed for AA detection with satisfactory results in fruit juice. The method proposed here gives the wide applications of fluorescent test paper in food and biological assays.

Study on the bio-inspired electrochromic device enabled via dielectric elastomer actuator

Abstract As a promising research field, electrochromic devices have attracted researcher's attention because of their dynamic display capabilities, high brightness, and convenience of electric signals. Among all the electrochromic modes, the use of electroactive actuators to produce color change is one of the important means. In view of the characteristics of dielectric elastomer (DE) materials such as rapid response and large deformation under electric signal, dielectric elastomer actuators (DEAs) were prepared and explored for their applications in biomedicine, aerospace, intelligent robotics and other fields. In this paper, inspired by the skin of chameleons, a kind of electrochromic device enabled via dielectric elastomer actuator (EDDEA) is prepared by integrating the stretchable photonic crystals (SPCs) with DEAs. The SPCs can achieve color changes in visible light range and maintain stable performance during multiple working cycles. The prepared EDDEA can produce strain under an electric field, which in turn causes color changes. In addition, the EDDEA can be used to display and measure the strain range of the DEA during actuating process under the excitation of electric field. The results demonstrate that the prepared EDDEA is a fully flexible, highly integrated electrochromic device, which can produce a wide range of color change under electric field. Meanwhile, this device provides potential application value in the strain range control of DEAs.

An electrochromic alarm system for smart contact lenses

Wearable devices are becoming essential tools for mandatory daily health checks. The technology permits the sounding of alarms in response to critical conditions and as part of a continuous, real-time smart healthcare system. Among wearable devices, the smart contact lens is a pivotal technology, as it permits vital-sign monitoring through lachrymation and an augmented visual reality that can be used for the provision of information. Past research regarding smart contact lenses has relied on wireless communication for data transmission, which has necessitated the use of additional receivers. Furthermore, no research has thus far been published that deals with the provision of information through image visualization on the contact lens. Here, we describe an electrochromic alarm system that operates via electrochemical reactions with ions in tears and achieves data transmission and the provision of information. The system was shown to function in harsh conditions and with limited space and thickness. It was able to maintain contact with tears as a result of its curved shape. The voltage and duration of the potential applied to our electrochromic system were controlled in a way that achieved a broad range of color changes and frequencies. Furthermore, diverse patterns were demonstrated by controlling the duration of the applied voltage, and words were visualized via telecommunication with Morse code. We believe that the electrochromic alarm system reported here is able to be integrated into smart contact lens while extending the possibilities of data transmission and information provision for the users.

Ratiometric fluorescent nanosensor for dosage-sensitive visual discrimination of glucose based on electron transfer mechanism

Owing to the great role of glucose in biological systems and food industry, it is significant to maintain the dynamic balance of organisms. Various methods widely reported are focused on the glucose detection with high sensitivity and low detection limit. However, the sensor with ultra-low concentration sensitivity is not suitable for the direct detection of high concentration of glucose in human serum and food samples. Additionally, the application of ratiometric fluorescence probe is usually limited by the narrow range of color changes and insensitivity color change of the target. Here, a novel dual-emission ratiometric fluorescence probe with green to red fluorescence intensity of 6:1 was first constructed by fluorescein isothiocyanate (FITC) with green fluorescence as signal unit and silica coated quantum dot (QD@SiO2) with red fluorescence as the stable internal standard. The glucose was oxidized to generate H2O2 by the catalysis of glucose oxidase, which can oxidize Fe2+ to form Fe3+ ion. The formation of Fe3+ ion will cause the quenching of FITC fluorescence, which can realize the continuous fluorescence color change from green to yellow to orange to red for the qualitative and quantitative detection of blood glucose and fruit juice. The proposed method is cheap, simple, intuitive and has a wide detection range for glucose detection, which is of significance in designing the dual-emission ratiometric fluorescence sensor with wide range of color change.

Study on the Twisted and Coiled Polymer Actuator with Strain Self-Sensing Ability.

Twisted and coiled polymer actuators (TCAs) are a kind of efficient artificial muscles, which have good prospects for application in soft robots, bionic devices, and biological, medical, and other high-tech fields. However, the inability to dynamically sense and adjust the strain of the actuator will lead to uncertainty in the accuracy of deformation and strain, resulting in imprecise target action. Herein, TCAs with strain self-sensing ability (TCASA) are prepared by integrating the stretchable optomechanical film (SOMF) sensors into TCAs, which provides a simple strategy for dynamical strain sensing. These SOMFs have a wide range of color changes during deformation of TCAs, and the strain is perceived by observing the color change according to the corresponding relationship between color change and strain. Furthermore, the proposed TCASA maintain excellent cycling stability of strain self-sensing during cyclic tests (200 cycles) and excellent strain self-sensing performance to perform strain control compared to TCAs without SOMFs. The results indicate that the proposed structure is a promising soft actuator with excellent strain self-sensing ability, which is well suited for soft robots, bionic devices, biological and medical fields, smart wearable technologies, and so forth, especially when controlled, repetitive deformations are required.

Color Stability of Fermented Mare's Milk and a Fermented Beverage from Cow's Milk Adapted to Mare's Milk Composition.

Color is important for the consumer when making a purchase decision. Mare’s milk and, thus, fermented mare’s milk is little known to consumers. Thus, it is worth presenting research showing the extent of color change during the production and storage of mare’s milk. Herein, we examined the range of color changes in mare’s milk and cow’s milks adapted to mare’s milk composition. These samples were further fermented and stored for 3 weeks at 5 ± 1 °C. Starter cultures containing Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus were used for fermentation. Mare’s milk reached the required pH of 4.5 during fermentation faster (255 min) than cow’s milk (300 min). After fermentation, mare’s milk compared to cow’s milk and adapted cow’s milk had lower titratable acidity (0.75%) and firmness (145. 6 |(g∙s)|). The water holding capacity (95.6%) and number of Lactobacillus (7.71 log CFU/mL) and Streptocococcus (7.20 log CFU/mL) in mare’s and other’s milks were the same. Mare’s milk was furthest from the ideal white (WI) color, with its chrome (C*) being 1.5-times larger than cow’s milk. However, fermented mare’s milk was darker than the fermented adapted milk and cow’s milk by 36% and 58%, respectively. Storage caused a decrease in the WI, C*, and yellowness index (YI). The fermented mare’s milk color stability during production and storage was less than that of fermented cow’s milk. After 3 weeks storage, it was observed that the titratable acidity increased to 1.05%, and the pH decreased to 4.3 in fermented mare’s milk. The water holding capacity decreased but was still higher compared to fermented cow’s milk.