Clear Color Change Research Articles

TCF-ALP: a fluorescent probe for the selective detection of Staphylococcus bacteria and application in "smart" wound dressings.

Alkaline phosphatase (ALP) is an important enzyme-based biomarker present in several bacterial species; however, it is currently undervalued as a strategy to detect pathogenic bacteria. Here, we explore our ALP-responsive colorimetric and fluorescent probe (TCF-ALP) for such applications. TCF-ALP displayed a colorimetric and fluorescence response towards Staphylococcus aureus (S. aureus), with a limit of detection of 3.7 × 106 CFU mL−1 after 24 h incubation. To our surprise, TCF-ALP proved selective towards Staphylococcus bacteria when compared with Enterococcus faecalis (E. faecalis), and Gram-negative P. aeruginosa and E. coli. Selectivity was also seen in clinically relevant S. aureus biofilms. Owing to the high prevalence and surface location of S. aureus in chronic wounds, TCF-ALP was subsequently encapsulated in polyvinyl alcohol (PVA)-based hydrogels as a proof-of-concept “smart” wound dressing. TCF-ALP hydrogels were capable of detecting S. aureus in planktonic and biofilm assays, and displayed a clear colour change from yellow to purple after 24 h incubation using ex vivo porcine skin models. Overall, TCF-ALP is a simple tool that requires no prior knowledge, training, or specialist equipment, and has the potential to overcome issues related to invasive swabbing and tissue biopsy methods. Thus, TCF-ALP could be used as a tool to monitor the early development of infection in a wound and allow for the rapid provision of appropriate treatment for Staphylococcal bacterial infections.

96-Well Microtiter Plate Made of Paper: A Printed Chemosensor Array for Quantitative Detection of Saccharides.

Simple, rapid, and accurate detection methods for saccharides are potentially applicable to various fields such as clinical and food chemistry. However, the practical applications of on-site analytical methods are still limited. To this end, herein, we propose a 96-well microtiter plate made of paper as a paper-based chemosensor array device (PCSAD) for the simultaneous classification of 12 saccharides and the quantification of fructose and glucose among 12 saccharides. The mechanism of the saccharide detection relied on an indicator displacement assay (IDA) on the PCSAD using four types of catechol dyes, 3-nitrophenylboronic acid, and the saccharides. The design of the PCSAD and the experimental conditions for the IDA were optimized using a central composite design. The chemosensors exhibited clear color changes upon the addition of saccharides on the paper because of the competitive boronate esterification. The color changes were employed for the subsequent qualitative, semiquantitative, and quantitative analyses using an automated algorithm combined with pattern recognition for digital images. A qualitative linear discrimination analysis offered discrimination of 12 saccharides with a 100% classification rate. The semiquantitative analysis of fructose in the presence of glucose was carried out from the viewpoint of food analysis utilizing a support vector machine, resulting in clear discrimination of the various concentrations of fructose. Most importantly, the quantitative detection of fructose in two types of commercial soft drinks was also successfully carried out without sample pretreatments. Thus, the proposed PCSAD can be a powerful method for on-site food analyses that can meet the increasing demand from consumers for sensors of saccharides.

Electrochromic Alarm System with Computer Vision in Smart Contact Lens

Recent advances in smart healthcare system using IoT are becoming mandatory with continuous and real time healthcare monitoring system. This system can give signal to the user by sound or stimulation when health condition become severe. As one of them, smart contact lens can be used to monitor vital signals from glucose level of the tear related to diabetes1 and intraocular pressure related to glaucoma2. However, previous researches about smart contact lens used wireless communication for signal transfer which need external receiver and antenna inside. Moreover, research that deals with data transmission to the user by image visualization on the contact lens has not been yet published. Herein, we have demonstrated electrochromic alarm system which uses color change to give direct signal transfer to the user by electrochemical reaction with ions in tear. This system showed clear color change with curved shape in limited spaces. Also, diverse intensities and frequencies of color change were controlled by the various voltages and duration of voltage application to this system. In addition, various color changing patterns can be shown to the user by controlling the duration of voltage application and Morse code was used to transfer words to the user in specific purpose. With the help of computer vision, color changing patterns were detected and interpreted. We believe that our electrochromic alarm system with diverse patterns suggest new method for direct data transmission to the user with the help of computer vision. Also, it can be integrated into smart contact lens with battery and various sensors.References D. H. Keum, S.-K. Kim, J. Koo, G.-H. Lee, C. Jeon, J. W. Mok, B. H. Mun, K. J. Lee, E. Kamrani, C.-K. Joo, S. Shin, J.-Y. Sim, D. Myung, S. H. Yun, Z. Bao, S. K. Hahn, Wireless smart contact lens for diabetic diagnosis and therapy. Sci. Adv. 6, eaba3252 (2020).J. Kim, M. Kim, M.-S. Lee, K. Kim, S. Ji, Y.-T. Kim, J. Park, K. Na, K.-H. Bae, H. K. Kim, F. Bien, C. Y. Lee, J.-U. Park, Wearable smart sensor systems integrated on soft contact lenses for wireless ocular diagnostics. Nat. Commun. 8, 14997 (2017). Figure 1

Fabrication and optical characterization of silver-coated gradient-grown anodic aluminum oxide

Here, we introduce gradient-grown anodic aluminum oxides (G-AAO) produced using a gear-train with a ratio of 1:16 and controlling the drawing velocity during a 2nd anodization period (t2A). After silver (Ag) deposition on G-AAOs, their optical behaviors are investigated as an interference-plasmonic coupling effect. First, we examine the geometrical and optical characteristics of statically grown AAO (S-AAO) on which 20 nm thick Ag is deposited. An obvious color change is found from blue (t2A = 30 s) to red (t2A = 90 s) due to an interference-plasmonic coupling. Second, we fabricate G-AAOs using a dynamic 2nd anodization with two different drawing velocities of 1.1 mm s−1 and 2.2 mm s−1. As a result, a linear increase in thickness (about 1.23 nm s−1) is found in G-AAOs. After Ag deposition, a clear color change is not found but an optical red shift in absorption is observed on Ag-coated G-AAOs. Thus, our results provide the first constraints on optical behavior of a metal-coated G-AAO, with a variety of nano-optical applications.

A green synthesis of gold–palladium core–shell nanoparticles using orange peel extract through two-step reduction method and its formaldehyde colorimetric sensing performance

Gold–palladium core–shell nanoparticles (Au@PdNPs) have been successfully synthesized through a two-step facile and green method. HAuCl4 and H2PdCl4 were used as the precursors, while orange peel extract (OPE) was used as both reducing and stabilizing agent. Initially, OPE was used to synthesize the gold core nanoparticles (AuNPs), followed by the reduction of PdCl42− solution to produce the Pd shell. The synthesized nanoparticles showed a strong visible absorbance at 534 nm indicated the formation of AuNPs at an optimum water/OPE ratio of 16.67, while the formation of Au@PdNPs was indicated by the disappearance of the peak at 534 nm. Further characterization by using IR spectroscopy indicated that –OH groups of OPE plays the main role in the nanoparticles formation, while TEM images observed a core–shell structure of the Au@PdNPs with an average core diameter of 40 nm and an average shell thickness of 7 nm. In the presence of different formaldehyde concentrations, the core–shell nanoparticles showed a clear color change from light to dark brown. Linearity of the absorbance responses from the formaldehyde concentration range of 36.3 mM to 3.63 M (R2 = 0.991) was achieved with an estimated LOD of 304.9 mM, suggested that the developed nanoparticles are promising to be applied for formaldehyde sensing.

Ratiometric visual detection of tetracycline residues in milk by framework-enhanced fluorescence of gold and copper nanoclusters.

We reported a novel dual-emission fluorescence probe fabricated by encapsulating both gold (AuNCs) and copper nanoclusters (CuNCs) into zeolitic imidazolate framework-8 (ZIF-8). Obtained composite (AuCuNCs@MOF) was utilized for ratiometric determination of Tetracycline (Tcy) antibiotic. Under excitation at 400nm, the AuCuNCs@MOF composite displayed two emission peaks at 520 and 650nm which were originated from AuNCs and CuNCs, respectively. Upon the addition of Tcy, the red emission intensity of the nanoparticles at 615nm was significantly decreased, while the green emission at 520nm stayed almost constant which resulted in a clear fluorescence color change from red to green under a UV lamp. The logarithm of the fluorescence ratio against the concentration of Tcy exhibited a satisfactory linear relationship from 20 to 650nM with a detection limit (LOD) of 4.8nM. Current probe was applied for Tcy quantification in milk samples with superior results.

Synthesis and application of a new chemosensor based on the thiazolylazo-quinazolinone hybrid for detection of F- and S2- in aqueous solutions.

A new chemosensor based on the thiazolylazo-quinazolinone hybrid (TAQH) was designed and synthesized for naked-eye sensitive detection of F- and S2-in aqueous acetonitrile solution. Spectral characterization of TAQH using FT-IR, 1H NMR, and 13C NMR analysis revealed that the probe TAQH was successfully synthesized using a two steps reaction, including the diazotization-coupling and condensation reactions, respectively. The ion sensing ability of TAQH toward a wide range of anions and metal ions was evaluated by naked-eye detection method and UV-Vis absorption spectroscopy. The chemosensor TAQH displayed a fast and clear color change from yellow to red in the presence of F- and S2- ions, enabling easily detect with the naked eye. This clear color change is due to the effective interaction of the basic F- and S2- anions with hydroxyl group of chemosensor as a binding site. The experimental data also revealed that the F- and S2- ions were sensed by the probe TAQH over a wide pH range from 3 to 8. The results also confirmed that the TAQH has a wide linear detection range for F- and S2- ions. From UV-vis titration experiment, the limit of detection (LOD) for F- and S2- ions was found to be 3.1μM and 5.7μM, respectively. For quantitative measurements, the paper test strips containing TAQH were successfully fabricated and applied to detect F- and S2- ions in aqueous solutions. Furthermore, Job's plot based on spectroscopic data showed one-to-one stoichiometry for the interaction of anions with probe TAQH. Therefore, the proposed chemosensor with excellent features like the cost-effective, high sensitively and selectively and short response times can be utilized in any physical and biological conditions.

A chelated-type colorimetric chemosensor for sensing Co2+ and Cu2+

A chelated-type colorimetric chemosensor TAMS (6,6′-((1E,1′E)-((thiobis(2,1-phenylene))bis(azanylylidene))bis(methanylylidene))bis(2-methoxyphenol)) was designed for sensing Co2+ and Cu2+ in aqueous solution. TAMS can detect Co2+ and Cu2+ by a clear color change of colorless to yellow with the low detection limits (0.66 μM for Co2+ and 0.88 μM for Cu2+). TAMS could quantify both Co2+ and Cu2+ in water samples. TAMS-Cu2+ could be distinguished from TAMS-Co2+ by using GSH. Based on the UV–vis experiments, ESI-mass, FT-IR, and theoretical calculations, the sensing mechanisms of TAMS to Co2+ and Cu2+ were demonstrated.

Reversible Nontoxic Thermochromic Microcapsules

Thermochromic materials exhibit a color change in response to a change in temperature. Creating nontoxic microcapsules containing thermochromic materials for applications in ink and film materials is historically challenging. In this study, we develop a nontoxic chlorophenol red (CPR)-water thermochromic system and its microcapsules with silicone shells via a reaction between water and octadecyltrichlorosilane (OTS) at the interface of a w/o emulsion. The obtained microcapsules exhibit a clear color change with full reversibility and are successfully used as inks by screen printing and as additives in films. Nontoxicity of both microcapsules and films is demonstrated through cell cytotoxicity assays. These features make these novel materials applicable to the next generation of intelligent sensors, coating, and food packaging materials.

Fabrication and characterization of GaAs nanoparticles achieved using femtosecond laser ablation

GaAs Nanoparticles (NPs) were produced using femtosecond pulsed laser (∼50 fs, 1 kHz repetition rate, 800 nm) ablation of bulk GaAs in distilled water. Effect of different laser energies such as 100 μJ, 200 μJ, and 500 μJ on the produced NPs was investigated. The produced NPs possessed size distribution in the range of 10–200 nm, most of the particles having an average particle size around 57 nm. In addition, nanoflake like structures having amorphous nature were also observed. With an increase in laser energy it was observed that there was a slight increase in the NPs size. For ablation performed at an energy of 500 μJ, a clear colour change (yellowish) of solution was observed due the increase in the efficiency of ablation, which could be due to a higher concentration of the NPs. Optical properties of these nanoparticles depict the absorption in the range of 264–274 nm and emission in the range of 410–440 nm. The longitudinal optical phonon-plasmon coupled (LOPC) and longitudinal optic (LO) modes observed near 266 cm−1 and 288 cm−1 in the Raman spectrum confirmed the presence of GaAs. The small shift observed in the Raman modes of GaAs NPs may be due the stress formed during the ablation. The X-ray diffraction studies revealed that the produced nanoparticles possessed cubic zinc blende structure of the GaAs.

Size-controllable Fe-N/C single-atom nanozyme with exceptional oxidase-like activity for sensitive detection of alkaline phosphatase

Nanozymes become currently a frontier of chemical research. However, exploiting a novel nanozyme with high activity, good stability and reproducibility is challenging. Here, size-controllable Fe-N/C nanozymes containing exclusive single Fe atoms coordinated Fe-Nx sites were succesfully prepared through a facile pyrolysis of size controllable Fe-Zn ZIFs precursors. The Fe-N/C nanozymes exhibit exceptional high oxidase-mimicking activity able to catalyze oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) by dissolved oxygen to generate blue product. Their catalytic activities can be regulated by modulating the molar ratios of methanol to metal salts (e.g., Fe and Zn) through which the size controllable Fe-Zn ZIFs precursors are obtained. Upon introduction of ascorbic acid (AA) into Fe-N/C/TMB system, complete inhibition of TMB oxidation was observed, resulting in significant decline in absorbance with a clear color change. In the presence of alkaline phosphatase (ALP), ascorbic acid 2-phosphate (AAP) is hydrolyzed to produce AA. When coupled with AAP, a novel colorimetric biosensor platform was fabricated for ALP activity screening in the range of 0.05 U/L-100 U/L (four orders of magnitude) with an ultra-low limit of detection of 0.02 U/L. The work provides a promising strategy to rationally design the transition metal-N/C single-atom nanozyme with high oxidase-like activity.

Ultrasensitive Detection of MicroRNA via a Au@Ag Nanosnowman.

MicroRNAs (miRNAs) play key roles in many serious diseases, such as cancer. As a consequence, miRNAs are of great interest as biomarkers in clinical diagnostics. Simple, fast, selective, and sensitive detection of miRNAs, however, is challenged by their short length, homogeneous sequence, susceptibility to degradation, and low abundance in human serum. Here, we present a new strategy for highly sensitive and selective detection of miRNA based on the formation of a plasmonic Au@Ag nanosnowman. When triggered by miRNA-21, bimetallic nanoparticles with an asymmetric Au@Ag head-body structure were formed with significant red shift of the localized surface plasmon resonance (LSPR) scattering wavelength and clear color change from green to red. When combined with exonuclease III (Exo III)-assisted target recycling and hybridization chain reaction (HCR) amplification strategy, the proposed bioassay showed excellent selectivity toward miRNA-21 with a proportional band from 1 fM to 100 pM and ultrahigh sensitivity with a limit of detection of 0.60 fM under dark-field microscopy. The proposed strategy is universal, which shows good application prospects in clinical analysis.

A simple pyrimidine based colorimetric and fluorescent chemosensor for sequential detection of copper (II) and cyanide ions and its application in real samples.

In this study, a new pyrimidine-based chemosensor (PyrCS) has been developed for sequential detection of copper (II) and cyanide ions. The PyrCS has revealed high sensitivity and selectivity toward copper ion over other metal ions in aqueous media. The PyrCS as an optical probe exhibited a distinct color change and a bathochromic shift in UV spectra in the presence of copper ion in a few seconds due to the formation of stable complex (PyrCS-Cu2+). The results confirmed that the PyrCS has a widely linear detection range of 0.3-30 μM toward Cu2+. The calculated limit of detection for Cu2+ ions was low as 0.116 μM. Moreover, the fluorescent intensity of PyrCS at 507 nm was significantly quenched in the presence of Cu2⁺ and Fe2⁺ ions. Additionally, complex PyrCS-Cu2+ was successfully used to detect cyanide ions via Cu2+ displacement approach. The free PyrCS was recovered after adding the CN‾ ions in a few seconds due to the formation of the stable copper cyanide complex Cu(CN)x. The calculated LOD for CN‾ ions was low as 0.320 μM. The data also clarified that the other competing anions did not create a clear color change in solutions. Since the proposed method could provide a vivid colorimetric response in the presence of detected analytes within the pH range of 3-9, we can claim that the developed chemosensor can be utilized in any physical and biological conditions.

A selective sulphur‐containing colorimetric chemosensor for Cu2+

AbstractA highly selective sulphur‐containing colorimetric chemosensor APTS ((E)‐2‐(tert‐butyl)‐6‐(((2‐(phenylthio)phenyl)imino)methyl)phenol) was synthesised for detecting Cu2+. APTS showed a clear colour change from colourless to yellow with Cu2+. The detection limit of APTS for Cu2+ was 0.52 μmol/L. APTS could also be used as a test strip for detecting Cu2+. To understand the binding mode of APTS with Cu2+, ultraviolet‐visible spectroscopy and electrospray ionisation‐mass spectrometry analyses were conducted. The sensing mechanism of sensor APTS towards Cu2+ was proposed to be the combination of intramolecular charge transfer and ligand‐to‐metal charge‐transfer through theoretical calculations.

Development of MRSA and MRAB detection kit employing loop–mediated isothermal amplification and colorimetric indicator dye

Methicillin-resistant Staphylococcus aureus (MRSA) and Multidrug-resistant Acinetobacter baumannii (MRAB) are serious life-threating pathogens. The rapid detection of those pathogens is a challenge for the most clinical microbiology laboratories. A nucleic acid amplification technique, loop-mediated isothermal amplification (LAMP) that enables to amplify target DNA sequences in a short time period, is an excellent technique to detect the pathogens with high efficiency. We developed LAMP detecting kits against both MRSA and MRAB that utilizing a newly developed colorimetric Mg2+ ion indicator dye D-649 and novel sets of primers. An aqueous soluble dye D-649 is stable over physiological pH range and displays clear color change upon binding to Mg2+ ion. The addition of 0.12 mM of D-649 to LAMP solution did not disturb the amplification process, and the positive reaction would be easily confirmed by the color change of reaction mixture from ruby to purple in naked eye under ambient light. Each primer set was designed to recognize mecA/femB gene of MRSA and blaOXA-23/blaOXA51–like gene of MRAB, and the detection limits for both DNAs were shown as 1 pg. These LAMP detection kits will be beneficial for the detection of MRSA and MRAB in clinical laboratories.

IDENTIFIKASI DAN ANALISIS KADAR FLAVONOID EKSTRAK GETAH ANGSANA (Pterocarpus indicus Willd) DI DUSUN WANATH KECAMATAN LEIHITU KABUPATEN MALUKU TENGAH

Background: Medicinal plants have many benefits that make it a traditional medicine for society. One of the medicinal plants used by the community, especially the Wanath Hamlet community, is the angsana gum (Pterocarpus indicus Willd.) In treating diseases.
 Method: This study aims to identify and analyze flavonoid levels in angsana sap (Pterocarpus indicus Willd.) In Wanath Hamlet qualitatively (flavonoid color test) and quantitative (flavonoid content analysis).
 Results: The results show a change in color to yellow which indicates that the sap is positive for flavonoids, while in aquades it shows clear color changes which indicate negative.
 Conclusion: Qualitative test (color test) of angsana gum extract positively contains flavonoids when identified with several flavonoid reagents which produce yellow

Natural Plant Extracts as Acid-Base Indicator and Determination of Their pKa Value

Commonly used indicators for acid-base titrations are synthetic, and this work was focused to identify the eco-friendly natural indicators and to determine their pKa values. The analytical potential of the flower extracts is very promising as seen in its application in acid-base titrimetry. These selected flower extracts were found to perform well in titrating strong acid-strong base than in weak acid-strong base. We have obtained a sharp and clear colour change from red to brownish yellow for the Bougainvillea glabra extract, from red to yellow for the Bauhinia purpurea extract, and from red to brownish yellow for the Impatiens balsamina extract. All the three flower extracts gave clear colour change with acids and bases, and the colour change was maintained with different acids and bases. The sharp contrast between their colours in acid and base made the pigment suitable for use as acid-base indicators. As these flower extracts have very simple,cost-effective, environment friendly extraction procedure and excellent performance with sharp colour change in end points of the titrations, it would be possible to replace the standard indicators being used in conventional laboratories with natural flower indicators.

Smart bandage dyed with sensor probe encapsulated in alginate for wound healing monitoring ضمادة ذکية مصبوغة بصبغة استشعار مغلفة بألجينات الکالسيوم لرصد التئام الجروح

الملخص العربي تم تطوير ضمادة ذکية لمتابعة التئام الجروح ، وذلک اعتمادا علي تغير اللون عند التئام الجروح. يمکن أن يؤدي تطوير اداة استشعار لدرجة الحموضة بالتقنية اللونية النسيجية إلى استخدام تطبيقات فعالة ، حيث أنه يمثل إمکانية متابعة الاس الهيدروجيني بطريقة سريعة باستخدام خامة رخيصة ومرنة. تم تحضير صبغة التراي سيانوهيدرازون واستخدامها کمادة استشعار لدرجة الحموضة والقاعدية. حيث تم تغليف صبغة التراي سيانوهيدرازون المتجاوبة لدرجة الاس الهيدروجيني کمادة داخلية والجينات الکالسيوم کجدار خارجي للکبسولة ، والتي تم تحميلها على شاش قطني بطريقة الغمر. هذه التغيرات في اللون القابل لاعادة الاستخدام والتي تتجاوب مع تغيرات الأس الهيدروجيني کانت نتيجة لتخليق الشحنة الاليکترونية العالية لمرکب التراي سيانوهيدرازون أنيون المنتج الذي يؤدي إلى انتاج جزيء من نوع الکوينويد حيث تم استخدام هذا الملون في المواد النسيجية التقنية لاکسابها القدرة على استشعار الرقم الهيدروجيني. اعتمد النهج المعتمد في هذه الدراسة على صباغة القطن الشاش باستخدام صبغة التراي سيانوهيدرازون محملة داخل کابسولات الکالسيوم الجينات لمتابعة التئام الجروح. أظهر الشاش المصبوغة تغيرا واضحا في اللون عند التعرض لمحاليل قاعدية وحمضية کما هو موضح بإحداثيات اللون. تشير نتائجنا إلى تغير واضح في اللون يظهر بالعين المجردة ، من اللون البرتقالي إلى اللون الأرجواني ، والتي يمکن التعرف عليها على سطح الأقمشة المستخدمة. تم دراسة التشکل السطحي وتکوين الشاش القطني المعالج تحت المجهر الإلکتروني الماسح الضوئي ، الأشعة السينية المشتتة للطاقة ، ورسم الخرائط العنصري. تمت دراسة الشاش القطني المعالج من خلال استکشاف نفاذية الهواء ، والصلابة ، وثبات اللون Abstract Novel in-situ dressing bandage-based disposable probe that changes color upon wound healing was developed. Developing colorimetric technical textile pH-sensor can lead to attractive end-use applications as it represents the potential for inexpensive, fast, flexible pH-sensors. Herein we describe the preparation of tricyanofuran-hydrazone based disperse colorant to act as a color changeable pH-sensor. The pH responsive tricyanofuran-hydrazone was encapsulated as a core material in Ca-alginate microcapsule as a wall-former, which was loaded onto a cotton gauze by padding. This reversible color change depending on pH variations was due to charge delocalization of tricyanofuran-hydrazone anion form generated that led to a quinoid-type molecular switching. This tricyanofuran-hydrazone colorant was employed for use in technical textile materials with a pH sensing capability. The approach adopted in the present study was based on dyeing of cotton gauze using tricyanofuran-hydrazone that can afford numerical results for the pH of the wound fluid. The dyed gauze matrix showed a clear reversible color change upon exposure to acid-base solutions as indicated by color coordinates. Our results indicate an obvious color change shown to the naked eye, from orange to purple, which can be recognized at the surface of the employed fabrics when exposed to basic conditions. The surface morphology of the treated cotton gauze was investigated under scanning electron microscopy, energy-dispersive X-ray, and mapping.The treated cotton gauze was studied by exploring of the air-permeability, stiffness, and colorfastness.

Chromo-Fluorogenic Detection of Soman and Its Simulant by Thiourea-Based Rhodamine Probe.

Here, we introduced a novel thiourea-based rhodamine compound as a chromo-fluorogenic indicator of nerve agent Soman and its simulant diethyl chlorophosphate (DCP). The synthesized probe N-(rhodamine B)-lactam-2-(4-cyanophenyl) thiourea (RB-CT), which has a rhodamine core linked by a cyanophenyl thiosemicarbazide group, enabled a rapidly and highly sensitive response to DCP with clear fluorescence and color changes. The detection limit was as low as 2 × 10−6 M. The sensing mechanism showed that opening of the spirolactam ring following the phosphorylation of thiosemicarbazides group formed a seven-membered heterocycle adduct, according to MS analysis and TD-DFT calculations. RB-CT exhibited high detecting selectivity for DCP, among other organophosphorus compounds. Moreover, two test kits were employed and successfully used to detect real nerve agent Soman in liquid and gas phase.

A novel bis(dihydroxypropyl) viologen-based all-in-one electrochromic device with high cycling stability and coloration efficiency

Electrochromism and related devices have been studied for a few decades from both fundamental and technological point of view. At the present stage, screening electrochromic materials with excellent properties is still an interesting job. In our previous work, we have demonstrated that hydroxyalkyl viologens could exhibit satisfying electrochromic behavior. Further, in this paper, the bis(dihydroxyalkyl) viologen, (1,1‘-bis(2,3-dihydroxypropyl) 4,4‘-bipyridine derivative dichloride, DHPV2+2Cl-, was synthesized and incorporated as an electrochromic chromophore in the all-in-one electrochromic devices (ECDs) on the basis of poly (vinyl butyal) (PVB)-carbonate and poły (vinyl alcohol) (PVA)-borax gel electrolytes, respectively. It was found that DHPV2+ 2Cl- in PVB-based gel ECDs underwent reversible switching between transparent and deep blue hue, whereas the clear color changes from colorlessness to amaranth in PVA-borax-based ones upon the potential ranges from 0 V to −1.0 V. For PVB-based gel ECD, spectroelectrochemical studies demonstrated that it only needs a low coloration voltage down to −0.6 V, and exhibites high coloration efficiency (η) up to 301 cm2/C. The optical contrast of it only reduces by 1% after consecutive operation for 10000 cycles between −1.0 V and 0 V, demonstrating an excellent cycling stability of this kind of device. The ECD based on PVA-borax gel modified with glycerol shows burgundy, and good electrochromic performance. It is interesting to note that a relatively large-area PVB-based gel electrochromic devices up to 168 cm2 was realized, the driving voltage and response time being −1.5 V and 12 s, respectively, for blue-violet coloration state. The advantages of electrochromic properties exhibited by 1,1‘-bis(2,3-dihydroxypropyl) viologen dichloride over those reported can be regarded as a pronounced improvement for organic electrochromic materials, and are expected to set the stage for novel electrochromic devices such as smart window and display applications and so forth.