Chromatic Transitions Research Articles

An AIE-active Schiff base derivative with reversible thermochromism based on two-step isomerization in the solid state

Thermoresponsive aggregation-induced emission (AIE) luminogens, especially in the solid state, have attracted extensive attention due to their potential applications as smart materials. Herein, we report an AIE-active tetraphenylethene (TPE)-based Schiff base derivative (TPENOMe-I) that exhibits rapid and reversible thermochromism along with luminescence in the solid state. The excited-state intramolecular proton transfer-induced AIE and efficient thermochromism (rather than photochromism) are facilitated by the relatively compact crystal packing and polymorphism of TPENOMe-I, which effectively suppress cis-to-trans isomerization. Theoretical calculations demonstrated that the two-step isomerization process between the enol isomer and the cis- and twisted cis-keto isomers is responsible for the thermochromic behavior of solid-state TPENOMe-I. The chromic transitions may result from the reversible interconversion between various twisted cis-keto forms during the thermal isomerization process. Three composites containing TPENOMe-I that were simply prepared with low cost excited reversible thermochromism and were successfully demonstrated in thermochromic patterns. The findings suggest that these TPENOMe-I composites have promising applications for use in warning labels, thermochromic textiles, and thermal printing.

Dynamic multicolour tuning in π-conjugated polymers towards flexible electrochromic displays

Multicolour electrochromic materials have been considered as a promising alternative to achieve dynamic full-colour tuning towards next-generation electronic display technology. However, the development of electrochromics with wide colour gamut and subtle multicolour tunability still remains challenging due to inflexible energy level structures in intrinsic active materials. Herein, the electrochromic π-conjugated polymers with rich and subtle colour tunability were designed and developed based on a fine adjustment on the energy level structures. The chromatic transition covers almost full-colour gamut, and each colour scheme has a rich variety of categories stemming from versatile hues, chromas and lightnesses. Moreover, the multicolour π-conjugated polymers also demonstrate superior overall electrochromic performance, including fast switching (∼1.0 s), high colouration efficiency (160.4 cm2 C−1@550 nm) and good reversibility (over 90 % retention after 10,000 cycles). As a proof of concept, ultrathin and flexible prototype devices are developed by utilizing the multicolour π-conjugated polymers as electrochromic active layer, exhibiting a wide colour gamut and highly saturated multicolour tunability. The design principles proposed in this work may also be applicable to diverse optoelectronic applications.

Bidirectional Voltage Regulation for Integrated Photovoltachromic Device Based on P3HT-Electrochromic Unit and Perovskite/Organic Tandem Solar Cells.

Integrated electrochromic devices powered by photovoltaic cells have evoked a lot of interest due to their promising commercial prospects. However, their application has been restricted by the voltage adaption between the self-powered voltage and the color-changing threshold voltage (Vt). Herein, a strategy of bidirectional voltage regulating is proposed to develop a novel stand-alone integrated photovoltachromic device (I-PVCD), which integrates perovskite/organic tandem solar cells (P/O-TSCs) to drive color-changing process of conjugated poly(3-hexylthiophene) (P3HT) films. To lower the driving-voltage of electrochromic layer, C60 is introduced to decrease the onset oxidation potential of P3HT film, and thus leading to a reduced Vt of 0.70V benefiting from the enhanced highest occupied molecular orbital level and decreased charge transfer resistance from 67.46 to 49.89 Ω. Simultaneously, PBDB-T is utilized as the hole transport layer in the interconnecting layer of CsPbI2Br/PTB7-Th:IEICO-4F P/O-TSC to improve its open-circuit voltage (Voc) to 1.85V. Under their synergetic merits, a I-PVCD with a wider self-adaptive voltage range is achieved. This device can undergo fast and reversible chromic transition from beautiful magenta to transparent only under the solar radiation, and demonstrates a coloration efficiency of 351.90 cm2 C-1 and a switching time of 2 s besides its excellent operating reliability.

Mechanical Properties of Polydiacetylene Multilayers Studied by AFM Force Spectroscopy.

The blue-to-red chromatic phase transition of polydiacetylene (PDA) is accompanied by the twist and rearrangement of its side chains, which results in shortening of the conjugation length in the backbone. However, how these morphological changes affect its mechanical properties remains elusive. In this work, force spectroscopy mapping by atomic force microscopy was employed to quantify mechanical parameters of PDA thin films such as breakthrough force and Young's modulus at the monomer, blue, and red phases during the chromatic transition. We found that the breakthrough force increased by 113% and Young's modulus decreased by 21% during the blue-to-red transition, highlighting that the subtle change in the side-chain configuration has a dramatic impact on its mechanical properties.

Real-time and visual monitoring coating damage and metal corrosion based on the multiple chromatic transition of TMB triggered by highly active N-CDs/Fe3O4 peroxidase mimics and Fe3+

Self-reporting corrosion protection coatings offer effective means to detect potential failures in advance, allowing for timely maintenance and extending the lifespan of metal materials. However, there currently remains a challenge in developing techniques capable of concurrently monitoring coating damage and metal corrosion throughout a procedure. Herein, N-CDs/Fe3O4 hybrid nanoparticles with high peroxidase-like activity were fabricated through a two-step hydrothermal process which exhibit superior affinity (Km=1.2 mM) towards H2O2 than HRP and effectively turn-on the color of TMB. Combined with the excellent responsiveness towards 8-HQ and the strict linear dependent relationships towards Fe3+ (ranging from 0.75 to 15.15 μM), a novel colorimetric assay is established to not only turn on the signals to report the appearance of damage, but additionally switch the colors of TMB system to reveal the possible crack propagation and metal corrosion underneath. Moreover, the pre-existing corrosion, characterized by higher Fe3+ concentration, is successfully indicated according to the color intensity enhancement compared with pristine metal sheet. Notably, such a multifunctional colorimetric assay enables the real-time and visual monitoring coating damage and metal corrosion simply through a Python program integrated into smartphones, serving as a promising strategy for promptly alerting of potential structural failures.

Colorimetric probe for the determination of osmium through a novel optical sensor in environmental samples

A novel optical probe has been successfully developed for the selective detection of Os(VIII) ions. This osmium-sensing platform was intricately designed by incorporating 4-(thiazol-2-yldiazenyl)benzene-1,3-diol (TDBD) as the ionophore within a plasticized PVC membrane, and tributylphosphate (TBP) serving as the plasticizer. Upon exposure to Os(VIII) ions in a 0.5 M HClO4 acid milieu, the sensing membrane undergoes a distinctive chromatic transition, shifting from a yellow to a pink hue. The preparation of the sensor and the methodology for Os(VIII) determination were meticulously refined to achieve optimal performance. Under these carefully optimized experimental conditions, the proposed optode demonstrated an impressive linear detection range spanning from 2.5 × 10−9 to 2.5 × 10−5 M for Os(VIII), alongside remarkable detection and quantification limits of 7.24 × 10−10 and 2.4 × 10−9 M, respectively. The sensor consistently delivered highly reproducible results, as evidenced by relative standard deviation (RSD) values of 1.45% and 1.30% for Os(VIII) concentrations at 7.5 × 10−7 and 2.5 × 10−6 M, respectively, underscoring its precision and reliability. Furthermore, the sensor exhibited a swift response time of 3.0 min, further emphasizing its efficiency. The incorporation of PIMs into the sensor architecture led to a remarkable eight-fold enhancement in its response compared to counterparts lacking PIMs, signifying a significant performance improvement. In assessing potential interference, an investigation into the influence of other ions on Os(III) determination revealed that the prepared sensor displayed exceptional selectivity for Os(VIII) ions, with negligible responses observed in the presence of common ions. Collectively, these experimental findings underscore the sensor's efficacy as an invaluable tool for the precise analysis of osmium content in water samples, aligning it with the rigorous standards of international scientific research.

Single and Double Microencapsulation of Organic Thermochromic Material

With the increase in temperature, urban areas face issues like urban heat islands. The reduction of green vegetation across urban areas has led to a tremendous rise in temperature. Many studies suggest significant cities are currently experiencing this issue to a greater extent. Many researchers are working on building paints and dyes to reduce the heat intake of the building. Organic thermochromic materials are one such alternative for building dye and stain. The main issue with using organic thermochromic materials is that they quickly degrade under sunlight, which makes them less useful for building paint. To overcome this issue, many organic thermochromic black dye materials (OTCBDM) are encapsulated with inorganic materials such as metal oxide, which block sunlight and reduce the effect of degradation. Encapsulation is achieved via the emulsification method of metal oxide. This paper deals with the single and double microencapsulation methods with different surfactant concentrations, metal oxides, and combinations thereof. Various techniques were used such as Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) with energy‐dispersive X‐ray spectroscopy technique (EDS), and differential scanning calorimeter (DSC), UV‐Vis spectroscopy, thermogravimetric analysis (TGA), and CIE Lab space analysis to determine the materials’ encapsulation and chromatic nature. The FTIR spectra suggested the absorption peaks for the Ti─OH bond (at 814, 903, and 913 cm−1) and Si─OH group (at 1,084 and 1,178 cm−1) for the commercial dye encapsulated with TiO2 and SiO2. The Ti─O─Si bonds at 1,054 and 1,145 cm−1 showed for the double encapsulation of SiO2 and TiO2 either (i) doped or in (ii) layered structures. From the EDS analysis, we can clearly say that the presence of SiO2 and TiO2 indicates the encapsulation of the commercial thermochromic black dye material. The SEM micrographs of the TiO2 encapsulation of OTCBDM seem more promising and uniform core–shell structure formation with CTAB as a surfactant than the SDBS. Moreover, the SEM microstructure results of double encapsulation using both TiO2 and SiO2 suggested thicker coating of particles when compared with single encapsulated counterparts. The cold phase of layered double encapsulation of OTCBDM + SiO2/TiO2 shows a darker color than the doped combination as obtained from the CIE Lab results. This feature suggested that an efficient encapsulation and chromatic transition are achieved in a layered combination of double encapsulation than in a doped combination. The DSC spectra indicated the increase in enthalpy at the heat cycle from 94.147 J/g for the SiO2 microencapsulated OTCBDM sample compared to all other samples shows thermal energy storage behavior for outdoor building applications. The UV–Vis absorbance spectra show two distinct peaks at 470 and at 610 nm related to the OTCBDM. The single‐layer encapsulated organic thermochromic black dye material shows less absorbance compared to the plain organic thermochromic black dye material. The double encapsulated sample has the highest absorbance compared to all other samples suggesting the material having better retention of peaks at 470 and at 610 nm. The thermographic analysis (TGA) shows when compared to the plain and single encapsulated OTCBDM samples, the double encapsulated samples demonstrated higher thermal endurance characteristics due to thicker layer coatings of the shell over the core structure. The novelty of this work relies on the double encapsulation of OTCBDMs using SiO2 and TiO2 to improve the photodegradation behavior of the organic core dye particles, and we have demonstrated that the cationic surfactant CTAB outperforms than the SDBS in microencapsulation processes.

Thermochromic Behavior of Polydiacetylene Nanomaterials Driven by Charged Peptide Amphiphiles.

The tunability of chromatic phases adapted by chromogenic polymers such as polydiacetylene (PDA) is key to their utility for robust sensing applications. Here, we investigated the influence of charged peptide interactions on the structure-dependent thermochromicity of amphiphilic PDAs. Solid-state NMR and circular dichroism analyses show that our oppositely charged peptide-PDA samples have distinct degrees of structural order, with the coassembled sample being in between the β-sheet-like positive peptide-PDA and the relatively disordered negative peptide-PDA. All solutions exhibit thermochromicity between 20 and 80 °C, whereby the hysteresis of the blue, planar phase is much larger than that of the red, twisted phase. Resonance Raman spectroscopy of films demonstrates that only coassemblies with electrostatic complementarity stabilize coexisting blue and red PDA phases. This work reveals the nature of the structural changes responsible for the thermally responsive chromatic transitions of biomolecule-functionalized polymeric materials and how this process can be directed by sequence-dictated electrostatic interactions.

Evaluation of Physical-Chemical Properties of Contemporary CAD/CAM Materials with Chromatic Transition "Multicolor".

The use of materials for computer-aided design/computer-aided manufacturing (CAD/CAM) has been rapidly increasing in daily practice. However, one of the main issues regarding modern CAD/CAM materials is their aging in the oral environment, which may lead to significant changes in their overall properties. The aim of this study was to compare the flexural strength, water sorption, cross-link density (softening ratio%), surface roughness, and SEM analysis of three modern CAD/CAM "multicolor" composites. Grandio (Grandio disc multicolor-VOCO GmbH, Cuxhaven, Germany), Shofu (Shofu Block HC-Shofu Inc., Kyoto, Japan), and Vita (Vita Enamic multiColor-Vita Zahnfabrik, Bad Sackingen, Germany) were tested in this study. They were prepared in stick-shaped specimens and submitted to different tests after several aging protocols, such as thermocycling and mechanical cycle loading challenge. Further disc-shaped specimens were also created and tested for water sorption, cross-link density, surface roughness, and SEM ultramorphology, before and after storage in an ethanol-based solution. For flexural strength and ultimate tensile strength, Grandio showed the greatest values both at baseline and after aging (p < 0.05). Grandio and Vita Enamic presented the highest modulus of elasticity and the lowest water sorption (p < 0.05). A significant reduction (p < 0.05) in microhardness after ethanol storage (softening ratio%) was observed especially in Shofu. Grandio had the lowest roughness parameters compared to the other tested CAD/CAM materials, while ethanol storage significantly increased the Ra and RSm values in Shofu (p < 0.05). Despite the comparable modulus of elasticity of Vita and Grandio, this latter showed greater flexural strength and ultimate tensile strength both at baseline and after aging. Hence, Grandio and Vita Enamic may be employed for the anterior teeth and for those restorations requiring load-bearing capacity. Conversely, aging seems to affect several properties of Shofu, so its use for permanent restorations should be well-pondered based on the clinical situation.

The solvatochromism and selective discrimination of dopamine substituted polydiacetylene vesicle towards typical water-miscible organic solvents

Conjugated polydiacetylene (PDA) based functional materials are well known for the naked-eyes detectable colorimetric changes upon various environmental stimuli. And the solvatochromic property of PDA in response to organic solvents is appealing extensive research interests. In this work, at first dopamine substituted polydiacetylene was polymerized under UV irradiation in the form of vesicle in aqueous solution. Then some typical water-miscible organic solvents, including methyl alcohol, ethyl alcohol, acetone, acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide and tetrahydrofuran, were added into the vesicle contained aqueous solution, among which tetrahydrofuran could induce the obvious blue-to-red color change of PDA immediately, while the other solvents could only induce partial blue-to-purple color change of PDA after a long time. The differentiated chromatic transition behavior of PDA vesicle to these seven organic solvents was studied thoroughly in both qualitative and quantitative characterization methods depending on UV–visible absorption spectroscopy, fluorescence, Raman, theoretical calculation and so on. To the best of our knowledge, this is the first report focusing on the selective solvatochromism of PDA upon exposure to different organic solvents in water, which will contribute to a deeper investigation and application extension of functional PDA materials in the future.

Colorimetric and fluorometric ammonia sensor based on protonated bipyridyl-containing polydiacetylene

Chemical sensors based on stimulus-responsive chromogenic materials have found great importance due to their strong capability of manipulating optical properties and vivid color display. In this work, chromogenic polydiacetylene (PDA) is generated by the polymerization of protonated supramolecular assemblies of bipyridyl-containing diacetylene precursor (bpy-PCDA-H+). A blue-colored polymeric PDA of bpy-PCDA-H+ was obtained by UV irradiation of monomeric assembles. Since supramolecular architecture is preorganized through protonation-induced interactions of molecular blocks, bpy-PCPDA-H+ generated intriguing assembly-related sensory response via deprotonation mechanism, producing distinctive blue to red chromatic transition and fluorescence turn-on response against ammonia. The self-assembly behavior, topochemical polymerization, and ammonia sensing properties of bpy-PCPDA-H+ were investigated using spectroscopic methods.

OVERVIEW OF POLYPHONY AND NATIONALISM IN EUROPE, OTTOMAN AND OTTOMAN TÜRKİYE

Aim: This research investigates the relationships between the folk songs, which are the roots of choral music in Turkey, and the qualities in polyphony practices were questioned and the approaches with which they were polyphonic were investigated from a quantitative perspective. Method: Under the titles of melody and harmony of polyphonic works; The use of major-minor scales, pentatonic and maqam transitions, dynamic and expression terms, triad, multiplication, scoredorg, double-quadruple-quintet harmony were evaluated by quantitative analysis method, findings and results were obtained and interpreted. Polyphony practices in choral works, whose source is folk songs, have been researched with a comparative perspective. Findings: In order to eliminate the problems arising from modality while the works in which Turkish music maqam scales are used are polyphonic, different from the triple harmony system, which was defined by Kemal İlerici (1910-1986), it was formed by the overlapping of the quartets and based on the Hüseyni maqam. It was determined that the quartet harmony system was also used. Conclusion: Folk songs and polyphonic choral works that take them as a source show affinity in terms of musical characteristics. The words of the material have undergone few changes, some of them have been given a canonical structure, dynamic and expressive indicators have been added. Chromatic transitions, double, quadruple and quintuple intervals are used cyclically on SATB lines.

Tracking Mechanical Stress and Cell Migration with Inexpensive Polymer Thin-Film Sensors.

Polydiacetylene (PDA) Langmuir films are well known for their blue to red chromatic transitions in response to a variety of stimuli, including UV light, heat, bio-molecule bindings and mechanical stress. In this work, we detail the ability to tune PDA Langmuir films to exhibit discrete chromatic transitions in response to applied mechanical stress. Normal and shear-induced transitions were quantified using the Surface Forces Apparatus and established to be binary and tunable as a function of film formation conditions. Both monomer alkyl tail length and metal cations were used to manipulate the chromatic transition force threshold to enable discrete force sensing from ~50 to ~500 nN μm-2 for normal loading and ~2 to ~40 nN μm-2 for shear-induced transitions, which are appropriate for biological cells. The utility of PDA thin-film sensors was demonstrated with the slime mold Physarum polycephalum. The fluorescence readout of the films enabled: the area explored by Physarum to be visualized, the forces involved in locomotion to be quantified, and revealed novel puncta formation potentially associated with Physarum sampling its environment.

Dual-signal optical detection of Lead(II) ions (Pb2+) using galloyl group-functionalized polydiacetylene

In this study, we developed a novel galloyl group-functionalized polydiacetylene (Galloyl-PDA) sensor for colorimetric and fluorescent detection of Pb2+. Among three types of Galloyl-PDA vesicles prepared by changing the ratio of newly synthesized galloyl group-conjugated 10,12-pentacosadiynoic acid (Galloyl-PCDA) and matrix 10,12-tricosadinoic acid (TCDA), the blue Galloyl-PDA vesicles with 1:9 molar ratio of Galloyl-PCDA:TCDA showed the most dramatic color transitions to red with colorimetric response (CR) value of 46.66 ± 1.373% within 5 min upon addition of 50 μM Pb2+. However, they didn't exhibit any color change upon interaction with other heavy metals. Since the terminal galloyl moieties of the Galloyl-PDA vesicles could form coordination bonds with Pb2+, the Galloyl-PDA vesicles were stressed and showed obvious blue-to-red chromatic transitions. Besides, because the Galloyl-PDA vesicles exhibited nonfluorescent-to-fluorescent transitions, a linear response in colorimetric and fluorescent signals was observed in the range of 0–10 μM and 0.025–1 μM, respectively. From the colorimetric and fluorescent results, the limit of detection (LOD) was determined to be 1.329 μM and 0.068 μM, which is 8-fold and 12-fold better sensitivity than those of previously reported methods, respectively. Furthermore, the capability of our PDA sensor for detection of Pb2+ in tap water, river water, and human serum was validated with excellent precision and recovery rates of 97.14–100.0%, 99.05–103.3%, and 100.7–106.7%, respectively. As our PDA dual-signal sensor for Pb2+ is rapid, sensitive, specific, and detectable by the naked eye, this approach holds great promise for application in point-of-care testing (POCT).

Point-of-Care Immunoassay Based on a Multipixel Dual-Channel Pressure Sensor Array with Visual Sensing Capability of Full-Color Switching and Reliable Electrical Signals.

The point-of-care (POC) method with affordability and portability for the sensitive detection of biological substances is an emerging topic in rapid disease screening and personalized medicine. In this work, we demonstrated a diverse responsive platform based on a dual-channel pressure sensor (DCPS). The DCPS had a multilayer flexible architecture consisting of a photonic hydrogel with chromatic transitions and a piezoresistive pressure sensor as the electrical data transmission unit, both of which had the property of pressure-induced mechanical stimulus feedback. By incorporating a platinum nanoparticles-labeled detection antibody (PtNPs-dAb) into the sandwich-type immunoreaction for the target carcinoembryonic antigen (CEA, as a model analyte), gas decomposition could be triggered by the addition of hydrogen peroxide (H2O2) to induce a significant increase under pressure in a closed chamber. Meanwhile, the DCPS enabled an accurate electrical signal output, and the photonic hydrogel converted spatiotemporal stimuli into eye-readable colorations with string brilliance. In this way, the target concentration could be quantificationally related to the electrical response and intuitively perceived through visible color alterations. Under optimal conditions, a sensitive determination of CEA was performed in a detectable range of 0.3-60 ng/mL with a limit of detection (LOD) of 0.13 ng/mL. In addition, the proposed protocol had satisfactory selectivity, accuracy, and reproducibility. Furthermore, an array-based immunoassay device was fabricated to conceptually validate its application potential in high-throughput biomedical detection and inspire a dual-signal POC diagnostic platform in a friendly way for resource-limited settings.

Distinctive Colorimetric Response of Benzaldehyde Substituted Polydiacetylene Vesicle to Temperature, pH, and Organic Amines

AbstractHere, a benzaldehyde substituted diacetylene vesicle formed through a self‐assembly strategy in water is reported. Under UV irradiation, conjugated polydiacetylene (PDA) could be generated in the blue phase by 1,4‐addition topopolymerization. Furthermore, this newly developed PDA vesicle displays distinctive colorimetric response to triple stimuli, including temperature, pH, and organic amines. Specifically, a clear blue‐to‐purple‐to‐red chromatic transition is observed for the PDA vesicle upon a gradient heating procedure from 25 to 75 °C. Although no obvious colorimetric changes happen when the PDA vesicle is exposed to acidic environments, it gradually turns into red color in alkaline aqueous solution or atmosphere with increasing pH values. More interestingly, this PDA vesicle can serve as an excellent sensor to distinguish some typical aliphatic/aromatic amines based on its different colorimetric and morphologic transformation behaviors. It is suggested that the incorporated benzaldehyde head group in PDA plays an essential role for the resulting responsiveness to the various environmental stimuli. As the preparation method is simple and straightforward, the novel PDA vesicle introduced here holds great potential as a promising sensor with the naked eye.

The noninvasive monitoring of the redox status of photosynthetic electron transport chains in Hibiscus rosa-sinensis and Tradescantia leaves

We present an approach to the noninvasive determination of the electron capacity of the intersystem pool of electron carriers in chloroplasts in situ. As apt experimental models, we used the leaves of Hibiscus rosa-sinensis and Tradescantia species. Electron paramagnetic resonance and optical response of P700 (the primary electron donor in Photosystem I) were applied to measuring electron transport in chloroplasts. Electron capacities of the intersystem electron transport chain (ETC) were determined from redox transients of P700 upon chromatic transitions (white light → far-red light). During the induction period, we observed the nonmonotonic changes in the number of electron equivalents in the intersystem ETC per P700 (parameter Q). In Hibiscus rosa-sinensis, the light-induced rise of Q from ≈2.5 (in the dark) to Q ≈ 12 was followed by its decrease to Q ≈ 6. The data obtained are discussed in the context of pH-dependent regulation of electron transport in chloroplasts, which provides the well-balanced operation of the intersystem ETC. The decay of Q is explained by the attenuation of Photosystem II activity due to the lumen acidification and the acceleration of plastoquinol re-oxidation as a result of the Calvin-Benson cycle activation. Our computer model of electron and proton transport coupled to ATP synthesis in chloroplasts was used to analyze the up and down feedbacks responsible for pH-dependent regulation of electron transport in chloroplasts. The procedures introduced here may be important for subsequent works aimed at defining the plastoquinone participation in regulation of photosynthetic processes in chloroplasts in situ.

Colorimetric indicators of açaí anthocyanin extract in the biodegradable polymer matrix to indicate fresh shrimp

Colorimetric indicator or freshness indicators hold great potential to reduce food waste. Films off açaí anthocyanins extract (AE) with different concentrations molars of two plasticizers glycerol (GLY) or triethyl citrate (TEC), for application fresh shrimp, real time were evaluated. The AE undergoes a visible pink/violet to green/yellowish color change in response to different pH's, which is an indicator of microbial spoilage in shrimp. The CI were exposed to ammonia, and analyzed through infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), ultraviolet spectroscopy, and visual colorimetric. The immobilization of the plasticizers into the CA polymer matrices were confirmed through FT-IR spectra and SEM micrographs. In vitro chromatic transition of the indicators exposed to ammonia vapors, were visually more perceptible when they were produced with 7.2 mols of GLY or 1.8, 3.6, and 7.2 mols of TEC. For the real-time analysis of the application of colorimetric indicators in gray shrimp samples, the indicators that had plasticizers showed perfect color change at the exact time of food deterioration. The colorimetric indicators developed in this study using different molar concentrations of plasticizers are simple, effective and a great eco-friendly alternative to chemical sensors already developed so far.

Fabrication of a novel polydiacetylene-based gel system through self-assembly and the stimuli-induced colorimetric responsiveness

The gel provides a wonderful platform for the study of functional polymer properties in the soft matter state. Here in this work, a novel molecular gel was readily prepared through the self-assembly of isophthalic acid substituted diacetylene derivative in mixed DMF/H2O solvents. Upon UV irradiation, conjugated polydiacetylene (PDA) in blue phase was successfully generated in the molecular gel form by 1,4-addition topopolymerization. This PDA-based molecular gel illustrated a reversible blue-purple-red chromatic transition in response to heating, thus demonstrating a good thermal stability. The incorporation of carboxyl groups into PDA provided this molecular gel the ability to make a distinction between acidic and alkaline environments. In specific, when the PDA molecular gel was exposed to acidic environment, no obvious color change could be observed. However, when it was exposed to alkaline aqueous solution or atmosphere, a clear blue-to-red colorimetric responsive behavior took place within a short time. More interestingly, ten commonly used organic solvents were tested on this molecular gel, and the blue PDA turned into red phase only in the case of triethylamine, thus suggesting a great prospect for selective recognition by naked eyes.

Mechanochromic polymers with a multimodal chromic transition: mechanophore design and transduction mechanism

This review presents the recent progress in multi-chromic polymers embedded with mechanophores concentrating on transduction mechanisms and design concepts.