Noticeable Color Research Articles

Novel ultra-sensitive and highly selective cyanine sensors based on solvent-free microwave synthesis for the detection of trace hypochlorite ions in drinking water

The adoption of chlorine in drinking water disinfection with the determination of residual chlorine in the form of hypochlorite ion (ClO-) is in widespread demand. Several sensors including colorimetric, fluorometric, and electrochemical methods are currently in use, but detection limits and ease of application remain a challenge. In this work, two new cyanine derivatives-based ClO- sensors, that were prepared by solvent-free microwave synthesis, are reported. The two sensors are highly sensitive and selective to ClO-, exhibiting a noticeable color change visible to the naked eye. Additionally, the sensors can detect ClO- without interference from other potential water pollutants, with low detection limits of 7.43 ppb and 0.917 ppb based on absorption performance. When using fluorometric methods, the sensors' detection limits are pushed down to 0.025 ppb and 0.598 ppb for sensors I and II, respectively. The sensors can be loaded with paper strips for field and domestic detection of ClO- in tap water treatment installations. Using the quartz crystal microbalance (QCM) technique, these sensors showed strong detection sensitivity to ClO-, with detection limits of 0.256 ppm and 0.09 ppm for sensors I and II, respectively. Quantum chemical studies using density functional theory (DFT) calculations, natural bond orbital (NBO) analysis, molecular electrostatic potential (MESP), and time-dependent density functional theory (TD-DFT) supported the findings. The sensing mechanism is rationalized in terms of radical cation formation upon ClO- oxidation of cyanine sensors I and II.

Resazurin-impregnated gelatin-based indicator for intelligent packaging applications

Modified resazurin (Res) incorporating gelatin (Gel) based indicator films were prepared to monitor the quality of packed shrimp in real time. FE-SEM micrographs show uniform dispersion of Res with minimal irregularities in the indicator film. The integration of Res increased the film's load-bearing ability and tensile strength without affecting the film's transparency and water vapor permeability. FT-IR and XPS profiles showed high compatibility and intermolecular H-bonds between the Res and Gel polymer matrices. The release rate of Res from the Gel-Res indicator film depended on the food simulant showing higher release rates in aqueous solutions (water and 10% ethanol) than in alcohol solutions (50% and 95% ethanol solutions). The Gel-Res indicator film exhibited excellent color stability even after storage for 60 days at room temperature. It was sensitive to ammonia vapor and alkaline pH solutions with a color change from yellow to pink with a total color difference (ΔE) of 15.4. In shrimp packaging tests, Gel-Res films exhibited noticeable color changes, which corresponded well with TVB-N levels and pH changes. These results suggest that the Gel-Res indicator films have acquired ideal prerequisites for potential intelligent seafood packaging.

Electrochemical and In-situ exhibited spectroelectrochemical properties of novel 4,4′-(3,5-di-tert-butyl-1,2-phenylene)bis(oxy) substituted ball-type phthalocyanine compounds

In this study, binuclear ball-type metallophthalocyanine compounds Co2Pc2(2), Fe2(OAc)2Pc2(3), Mn2(OAc)2Pc2(4), Ni2Pc2(5), Zn2Pc2(6) were obtained by using 4,4′-((3,5-di-tert-butyl-1,2-phenylene)bis(oxy))diphthalonitrile, and metal salts (mol ratio of metal salts and ligand:5/1), and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as a catalyst in 0.25 mL dimethylethanolamine at reflux temperature for about 20 min. Phthalocyanines have shown high solubility in common organic solvents since they contain eight bulky butyl groups and showed minimal aggregation in common solvents. The chemical structure of the complexes and their precursor has been characterized by spectral methods and elemental analysis. Electron transfer properties of all ball-type metallophthalocyanines were studied by using electrochemical and in-situ spectroelectrochemical measurements in non-aqueous media. Two kinds of electron transfer processes, i.e., metal-based and phthalocyanine ring-based redox processes, were revealed by these complexes. The electrochemical experiments displayed the establishment of discrete mixed-valenced oxidized as well as reduced groups resulting from intramolecular interactions between the two phthalocyanines and two metal units in novel ball-type complexes. Advanced redox properties of these complexes developed noticeable spectral and color changes, detected by in-situ spectroelectrochemical measurements in a solution medium.

Fabrication of a re-usable benzoxazole-based colorimetric sensor for selective and sensitive recognition of sarin mimic, diethylchlorophosphate

This report introduces a colorimetric benzoxazole-scaffold molecule, BPDA, to recognize a toxic sarin gas mimic, diethylchlorophosphate (DCP), in both solution and gas phases, respectively. The yellow color of the BPDA solution is slowly transferred into a noticeable fuchsia-pink color for the gradual accumulation of DCP, which is visualized in the bare eye. The fuchsia-pink color of the BPDA-DCP solution is wholly reversed to the yellow color of free BPDA due to the steady addition of triethylamine (TEA). Our developed BPDA-based colorimetric sensor shows excellent selectivity towards DCP with a detection limit of 44.5 nM. Also, a paper strip and smartphone-based assay analysis have been demonstrated for the practical utility of our BPDA for immediate detection of DCP within the stockpiles of similar toxic analytes. Also, a dip-stick method has been employed to identify and quantify the DCP vapor selectively among the other analogous poisonous organophosphates.

Bifunctional manganese-doped silicon quantum dot-responsive smartphone-integrated paper sensor for visual multicolor/multifluorescence dual-mode detection of nitrite

Considering great threats of nitrite in food toward public health, it is significant to develop portable, dependable, and cost-effective methods to detect the target. In comparison with traditional colorimetric or fluorometric strategies relying on the intensity variation at a single wavelength, multimodal measurement with notable color changes is a more attractive paradigm because of its stronger resistance against external conditions, expanded application scenario, improved reliability, and naked-eye distinguishable readouts. However, it remains a challenge on how to attain this goal. Here we proposed a smartphone-integrated paper sensor based on manganese-doped silicon quantum dots (Mn-SiQDs) for the visual dual-mode multicolor/multifluorescence determination of nitrite. The Mn-SiQDs featured both photoluminescence and oxidase-mimetic catalytic activity, and could stimulate the colorless 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation to a blue species TMB+. When nitrite existed, the generated TMB+ selectively reacted with the analyte to produce yellow diazotized TMB+. Meanwhile, the photoluminescence of Mn-SiQDs could be suppressed by the diazotized TMB+ via inner filter effect. As a result, with a facile electrostatic assembly of Mn-SiQDs and [Ru(bpy)3]2+, the formed complex Mn-SiQDs/[Ru(bpy)3]2+ led to the variations of both color and photoluminescence upon different levels of nitrite. By combining the principle with paper strips and smartphone sensing, the fabricated sensor offered naked-eye visible multicolor/multifluorescence dual-mode response toward nitrite, exhibiting excellent specificity, performance stability, and practicability in food analysis. Our work provides an effective tool to achieve the multicolor/multifluorescence bimodal measurement of nitrite, and it will inspire future effort on designing versatile materials for advanced sensing applications.

Colour descriptors for plant-based milk alternatives discrimination.

Colour characteristics of plant-based milk alternatives (PBMAs: almond, coconut, cashew, oat, soy) were monitored during long-term storage to select suitable descriptors for PBMAs differentiation. All colour descriptors evaluated varied depending on the raw material used in the plant-based milk alternative production. Long-term storage of plant-based beverages resulted in slightly noticeable (0.5-1.5) and noticeable (1.5-3.0) colour changes. Based on all colour descriptors, an absolute differentiation of PBMAs according to the type of raw material and storage time was achieved using canonical discriminant analysis. The results also indicate the possibility of using colour descriptors to detect the addition of honey to these products. Statistical analysis identified yellowness, browning index and lightness as the most discriminating parameters.

Comparison of Composite Resin (Duo-Shade) Shade Guide with Vita Ceramic Shades Before and After Chemical and Autoclave Sterilization.

BACKGROUND This study aimed to compare a composite resin (Duo-Shade) shade guide with Vita ceramic shades before/after chemical and autoclave sterilization. MATERIAL AND METHODS Color values (L*a*b*) were recorded directly from shade tabs of prefabricated composite resin (Brilliant NG Universal Duo-Shade) and ceramic (Vita classic) shade guide with a calibrated spectrophotometer (Vita Easy Shade Advance 4.0). Seventy-two composite resin disk samples with 6 different shades (A1/B1, A2/B2, A3/D3, A3.5/B3, A4/C4, and C2/C3) (n=12 each) were divided into 2 groups (Gp) - Gp A (Autoclave) and Gp C (Chemical) (15 cycles) - to assess their influence on respective shades. Mean values calculated the color differences (ΔE) while differences in color values (L*a*b*) were graded on the National Bureau of Standards (NBS) 6-grade scale and assessed for Clinical Acceptance/Perceptible Threshold (CAT), (CPT). All differences were considered significant if the color difference ΔE was ≥3.3. RESULTS Only 2 out of 12 Shade tabs (C2C3, A4C4) of composite resin matched to Vita shade tab C2 and C4 (ΔE ≤3.3). Both groups showed notable color differences after respective sterilization protocols, with color differences in Gp A significantly higher than Gp C (DE ³3.3). Within groups, all shades in Gp A showed remarkably different color changes, with shade C2C3 and A1B1 being denoted as clinically unacceptable. CONCLUSIONS Manufacturer-provided shade guides do not match ceramic shades as claimed and chemical sterilization using 10% Deconex was associated with less color changes than with autoclave sterilization.

PH-sensitive smart indicators based on cellulose and different natural pigments for tracing kimchi ripening stages

Five natural pigments including water-soluble [butterfly pea (BP), red cabbage (RC), and aronia (AR)] and alcohol-soluble [shikonin (SK) and alizarin (ALZ)] were extracted, characterized, and loaded onto cellulose for preparing pH-sensitive indicators. The indicators were tested for their color response efficiency, gas sensitivity, response to lactic acid, color release, and antioxidant activity. Cellulose-water soluble indicators showed more obvious color changes than alcohol-soluble indicators in lactic acid solution and pH solutions (1−13). All cellulose-pigment indicators exhibited prominent sensitivity to ammonia compared to acidic vapor. Antioxidant activity and release behavior of the indicators were influenced by pigment type and simulants. Kimchi packaging test was carried out using original and alkalized indicators. The alkalized indicators were more effective in showing visible color changes during kimchi storage than the original indicators, and cellulose-ALZ displayed the most distinct color change from violet (fresh kimchi, pH 5.6, acidity 0.45 %) to gray (optimum fermented kimchi, pH 4.7, acidity 0.72 %), and to yellow (over fermented kimchi, pH 3.8, acidity 1.38 %) which followed by BP, AR, RC, SK respectively. The findings of the study suggest that the alkalization method could be used to show noticeable color changes in a narrow pH range for application with acidic foods.

An effective colorimetric and fluorescent chemosensor derived from modified curcumin for the detection of the Fe3+ ion

From curcumin and 1-aminonaphthalene, the chemosensor NIBMP (4,4'-(3,5-bis(naphthalene-1-ylimino)hepta-1,6-diene-1,7-diyl)bis(2-methoxyphenol)) has been prepared. For Fe3+ as opposed to other metal ions, NIBMP serves as both a colorimetric and a fluorescence turn-off sensor. Interactions between NIBMP and Fe3+ reveal a noticeable colour shift from yellow to brown. The absorption and fluorescence studies reveal new peaks at 326 nm and quenching at 530 nm, respectively. The limit of detection, 0.139 µM, is found to be significantly lower than the EPA's standard for drinking water (5.37 µM). There is evidence for a 1:1 stoichiometry between NIBMP and Fe3+ utilizing Job's plot analysis and ESI-HRMS. Additionally, a Stern-Volmer plot has been created, and its quenching constant has been computed. Moreover, EDTA's fluorescence analysis has been used to test whether the complexation of NIBMP with Fe3+ is reversible. Significantly, Fe3+ is successfully detected using NIBMP in actual water samples with excellent recoveries.

D-A Structural Oligomers Containing Benzothiadiazole or Benzophenone as Novel Multifunctional Materials for Electrochromic and Photodetector Devices.

In this study, six conjugated oligomers containing D-A structures were synthesized using the Stille coupling reaction and named PHZ1-PHZ6. All the oligomers utilized demonstrated excellent solubilities in common solvents and notable color variations in the domain of electrochromic characteristics. By designing and synthesizing two electron-donating groups modified with alkyl side chains and a common aromatic electron-donating group, as well as cross-binding them with two electron-withdrawing groups with lower molecular weights, the six oligomers presented good color-rendering efficiencies, among which PHZ4 presented the best color-rendering efficiency (283 cm2·C-1). The products also demonstrated excellent electrochemical switching-response times. PHZ5 presented the fastest coloring time (0.7 s), PHZ3 and PHZ6 presented the fastest bleaching times (2.1 s). Following 400 s of cycling activity, all the oligomers under study showed good working stabilities. Moreover, three kinds of photodetectors based on conducting oligomers were prepared, and the experimental results show that the three photodetectors have better specific detection performances and gains. These characteristics indicate that oligomers containing D-A structures are suitable for use as electrochromic and photodetector materials in the research.

A BODIPY-based fluorescent chemosensor with 2, 6-substitution for visual and highly selective detection of S2–

BODIPY derivatives have often been employed as fluorescent sensors to probe toxic ions in environment and living systems, such as sulfide ion (S2−). Whilst many structure modifications have been exploited on groups at the 3, 5, 8-positions, there are quite few examples on tailoring the 2,6-substituents for chemosensor investigations. Herein, we design and synthesize a 2,6-substituted BODIPY molecule, LM-BDP, to use as a fluorescent probe for detecting S2− in aqueous media. The electronic and crystal structures of the probe are studied by density functional theory (DFT) calculations and single-crystal X-ray diffraction analysis. Spectroscopy investigations are performed in a variety of conditions, showing that LM-BDP exhibits a noticeable color change from pink to dark red and a fluorescence shift from yellow to pink channel with decreased intensity upon addition of S2−. The selectivity and sensitivity measurements show that LM-BDP can only response to S2− with a detection limit of 0.29 μM in less than 100 s. The remarkable contrast in fluorescence images in test-stripe and RAW 264.7 cell experiments indicates that the probe is a proper candidate for the application in detecting exogenous S2−.

Rapid Detection of Ag(I) via Size-Induced Photoluminescence Quenching of Biocompatible Green-Emitting, l-Tryptophan-Scaffolded Copper Nanoclusters.

Atomically precise metal nanoclusters capped with small molecules like amino acids are highly favored due to their specific interactions and easy incorporation into biological systems. However, they are rarely explored due to the challenge of surface functionalization of nanoclusters with small molecules. Herein, we report the synthesis of a green-emitting (λex = 380 nm, λem = 500 nm), single-amino-acid (l-tryptophan)-scaffolded copper nanocluster (Trp-Cu NC) via a one-pot route under mild reaction conditions. The synthesized nanocluster can be used for the rapid detection of a heavy metal, silver (Ag(I)), in the nanomolar concentration range in real environmental and biological samples. The strong green photoluminescence intensity of the nanocluster quenched significantly upon the addition of Ag(I) due to the formation of bigger nanoparticles, thereby losing its energy quantization. A notable color change from light yellow to reddish-brown can also be observed in the presence of Ag(I), allowing its visual colorimetric detection. Portable paper strips fabricated with the Trp-Cu NC can be reliably used for on-site visual detection of Ag(I) in the micromolar concentration range. The Trp-Cu NC possesses excellent biocompatibility, making it a suitable nanoprobe for cell imaging; thus, it can act as an in vivo biomarker. The nanocluster showed a significant spectral overlap with anticancer drug doxorubicin and thus can be used as an effective fluorescence resonance energy transfer (FRET) pair. FRET results can reveal important information regarding the attachment of the drug to the nanocluster and hence its role as a potential drug carrier for targeted drug delivery within the human body.

One-year clinical observation of the effect of internal bleaching on pulpless discolored teeth.

This study aimed to observe the color rebound and rebound rates of non-pulp discolored teeth within 1 year after routine internal bleaching to guide clinical practice and prompt prognosis. In this work, the efficacy of bleaching was observed in 20 patients. The color of discolored teeth was measured by using a computerized colorimeter before bleaching; immediately after bleaching; and at the 1st, 3rd, 6th, 9th, and 12th months after bleaching. The L*, a*, and b* values of the color of cervical, mesial, and incisal parts of the teeth were obtained, and the color change amounts ΔE*, ΔL*, Δa*, and Δb* were calculated. The overall rebound rate (P*) and the color rebound velocity (V*) were also analyzed over time. In 20 patients following treatment, the average ΔE* of tooth color change was 14.99. After bleaching, the neck and middle of the teeth ΔE* and ΔL* decreased in the 1st, 3rd, 6th, 9th, and 12th months, and the differences were statistically significant. Meanwhile, from the 9th month after bleaching, the rebound speed was lower than that in the 1st month, and the difference was statistically significant. The incisal end of the tooth ΔE* and ΔL* decreased in the 6th, 9th, and 12th months after bleaching, and the differences were statistically significant. No significant difference was found in the rebound speed between time points. However, this rate settled after the 9th month, with an average color rebound rate of 30.11% in 20 patients. The results indicated that internal bleaching could cause a noticeable color change on pulpless teeth. The color rebound after bleaching was mainly caused by lightness (L*), which gradually decreased with time, and it was slightly related to a* and b*. The color of the teeth after internal bleaching rebounded to a certain extent with time, but the color rebound speed became stable from the 9th month. Clinically, secondary internal bleaching can be considered at this time according to whether the colors of the affected tooth and the adjacent tooth are coordinated and depending on the patient's needs.

Preparation of molecularly imprinted ratiometric fluorescence sensor for visual detection of tetrabromobisphenol A in water samples.

A sensitive molecularly imprinted ratiometric fluorescence sensor was constructed for the first time to visually detect tetrabromobisphenol A (TBBPA). The blue fluorescent carbon quantum dots (CQDs) were coated with SiO2 through the reverse microemulsion method to obtain a stable internal reference signal CQDs@SiO2. The ratiometric fluorescence sensor was finally prepared using red fluorescent CdTe QDs as the response signal in the presence of CQDs@SiO2. When the molecularly imprinted polymers were combined with TBBPA, the fluorescence of CdTe QDs (Ex = 365nm, Em = 665nm) was rapidly quenched, while that of CQDs (Ex = 365nm, Em = 441nm) remained stable, resulting in a noticeable fluorescence color change. Moreover, the fluorescence intensity ratio (I665/I441)0/(I665/I441) of the sensor showed a linear response to TBBPA in the concentration range 0.1 to 10μM with a low detection limit of 3.8nM. The prepared sensor was successfully applied to detect TBBPA in water samples. The recoveries were in the range 98.2-103%, with relative standard deviations lower than 2.5%. Furthermore, a fluorescent test strip for visual monitoring of TBBPA was constructed to streamline the procedure. The excellent results demonstrate that the prepared test strip has a broad prospect for the offline detection of pollutants.

Color Stability of Nanoparticles-Modified Dental Resin-Based Composites

To evaluate the effect of beverages (coffee, tea, Cola-Cola, and mineral water) on the color stability of resin-based composite (RBC) materials modified with different nanoparticles (NPs). The specimens (70/beverage) were fabricated from light-cured RBCs and divided according to NPs into four groups: one control, unmodified (N0); and three experimental—ZrO2 (Zr), TiO2 (Ti), and SiO2 (Si) groups. Each experimental group was further subdivided into two subgroups according to NP concentrations: 3 wt.% and 7 wt.% (n = 10). A spectrophotometer was used to assess the color change (∆E) before and after six months of immersion. Data were analyzed and compared using one-way-ANOVA followed by Bonferroni’s post-hoc test (α = 0.05) and subsequently ∆E value conversion to National Bureau of Standards (NBS) units. The modified light-cured RBCs with ZrO2, TiO2, and SiO2 demonstrated smaller color changes after immersion in the beverages than the unmodified group (p < 0.001). Zr groups showed the lowest ΔE, followed by Ti and Si groups; a 3% concentration resulted in a lower mean ΔE than the 7% concentration. NBS findings showed that coffee and tea produced marked unacceptable color changes (NBS units were >3), and Coca-Cola resulted in noticeable color changes (NBS units between 1.5 and 3), while water produced slight color changes (NBS ≤ 1). Modification of RBCs with both concentrations of ZrO2, as well as 3% of TiO2 and SiO2, may improve its color stability. Based on NBS results, RBCs immersed in mineral water and Coca-Cola showed clinically acceptable color changes, while those immersed in coffee and tea were clinically unacceptable.

A thieno[2,3-a]carbazole-based multifunctional probe: Colorimetric detecting of Fe3+/Cu2+/Hg2+ and fluorescent sensing of Cu2+

A novel thieno[2,3-a]carbazole-based multifunctional probe 2-amino-3-(((5-(14-(2-hexyldecyl)-14H-benzo[c]benzo[4,5]thieno[2,3-a]carbazol-3-yl)thiophen-2-yl)methylene)amino)maleonitrile (C4) with a diaminomaleonitrile unit was synthesized. The ability of the probe to sense various ions was studied by visual inspection, absorption spectroscopy, and fluorescence spectroscopy. The probe exhibits high selectivity and sensitivity towards Fe3+/Cu2+/Hg2+ in acetonitrile/H2O (8:2, v/v). When interacting with Fe3+/Cu2+/Hg2+, the probe shows a noticeable color response from yellow to light yellow/colorless/pink and selective Cu2+-sensing ability with fluorescence enhancement. It can work in the pH range of 4–10 with Fe3+/Cu2+/Hg2+ without interfering with other competing ions. The detection (LOD) limits for Fe3+, Cu2+, and Hg2+ are 5.4 μM, 0.374 μM, and 0.296 μM, respectively. Therefore, C4 demonstrates a promising potential to detect Fe3+/Cu2+/Hg2+ in acetonitrile/H2O.

Does the smartphone's eye protection mode work?

People spend about 5-8 hours per day on phones, causing circadian disruption and eye fatigue, thus raising a great need for comfort and health. Most phones have eye protection modes, claiming a potential eye protection effect. To examine the effectiveness, we investigated the color quality, namely gamut area and just noticeable color difference (JNCD), and circadian effect, namely equivalent melanopic lux (EML) and melanopic daylight efficacy ratio (MDER), characteristics of two smartphones: iPhone 13 and HUAWEI P30, in normal and eye protection mode. The results show that the circadian effect is inversely proportional to color quality when the iPhone 13 and HUAWEI P30 changed from normal to eye protection mode. The gamut area changed from 102.51% to 82.5% sRGB and 100.36% to 84.55% sRGB, respectively. The EML and MDER decreased by 13 and 15, and, 0.50 and 0.38, respectively, affected by the eye protection mode and screen luminance. The EML and JNCD results in different modes show that the eye protection mode benefits the nighttime circadian effect at the cost of the image quality. This study provides a way to precisely assess the image quality and circadian effect of displays and elucidates the tradeoff relationship between them.

Disinfection of Mould-contaminated Archival Material by X-ray Irradiation – New Research Results on the Effect on Moulds and Cellulose

Abstract This research project examines the effects of X-rays on cellulose and some moulds frequently found on paper. The aim was to identify applications for X-ray irradiation that can be used as a disinfection method for archival material. The question was if X-rays are suitable as an alternative to gamma radiation and if they are less harmful. For this purpose, the minimum X-ray dose required to reduce the microbial count to a harmless level was determined. The material-altering effect was examined on samples treated with X-rays and gamma radiation. Spectrophotometric measurements showed that there is no noticeable colour change with either type of radiation. The determination of the molecular weight distribution, in turn, showed that the molar mass of the cellulose is considerably reduced with both treatment methods. Using mechanical tests, however, it could be demonstrated that this has no significant influence on the tensile strength. The examination of the oxidation behaviour also showed no significant difference between the differently treated samples. The studies demonstrated that both methods have an almost identical effect on cellulose. Thus, X-ray treatment is primarily a supplement to the known disinfection methods and is particularly suitable for objects that would not withstand treatment with alcohol.

Investigating the effect of gravity on the optical performance of large-sized liquid crystal displays

This paper proposes a method to investigate the effect of gravity on optical performance of large-sized liquid crystal displays (LCDs). Combined with the finite element analysis and the LCD optical simulation, the change in optical performance of large-sized LCDs under the influence of gravity is analyzed. Compared with the condition without tilt angle, the Δu'v' is 0.025 in the bottom area of the 100-in LCD with the substrate thickness of 0.3 mm at a tilt angle of 1.5°, leading to a noticeable color shift. With the decrease of tilt angle or the increase of substrate thickness, the change in optical performance becomes unnoticeable and thus avoids the occurrence of visible display defect. Utilizing the proposed method, the assembly precision of large-sized LC panels can be calculated and the display defect caused by gravity can be effectively prevented.

Synthesis and Characterization of Novel Triphenylamine-Containing Electrochromic Polyimides with Benzimidazole Substituents.

Two novel electrochromic aromatic polyimides (named as TPA-BIA-PI and TPA-BIB-PI, respectively) with pendent benzimidazole group were synthesized from 1,2-Diphenyl-N,N'-di-4-aminophenyl-5-amino-benzimidazole and 4-Amino-4'-aminophenyl-4″-1-phenyl-benzimidazolyl-phenyl-aniline with 4,4'-(hexafluoroisopropane) phthalic anhydride (6FDA) via two-step polymerization process, respectively. Then, polyimide films were prepared on ITO-conductive glass by electrostatic spraying, and their electrochromic properties were studied. The results showed that due to the π-π* transitions, the maximum UV-Vis absorption bands of TPA-BIA-PI and TPA-BIB-PI films were located at about 314 nm and 346 nm, respectively. A pair of reversible redox peaks of TPA-BIA-PI and TPA-BIB-PI films that were associated with noticeable color changed from original yellow to dark blue and green were observed in the cyclic voltammetry (CV) test. With increasing voltage, new absorption peaks of TPA-BIA-PI and TPA-BIB-PI films emerged at 755 nm and 762 nm, respectively. The switching/bleaching times of TPA-BIA-PI and TPA-BIB-PI films were 13 s/16 s and 13.9 s/9.5 s, respectively, showing that these polyimides can be used as novel electrochromic materials.