Colorimetric Changes Research Articles

Fluorescent sensing film decorated with ratiometric probe for visual and recyclable monitoring of Cu2+

Specifically, visually, and quantitatively monitor copper ion (Cu2+) is critical in the area of biological and environmental detection. Herein, a ratiometric fluorescent probe with benzoxazole appended xanthenes skeleton was constructed and further employed to monitor Cu2+ in Hela cells, real water samples, and test strips. An easily distinguishable colorimetric (colorless to red) and fluorescence (green to red) change could be observed by naked eye under the portable UV lamp (365 nm) and the changes could be recovered by adding S2−. Furthermore, electrospinning technique was employed to fabricate a probe composited fluorescent sensing film (PMMA) for realizing the visual and recyclable monitoring of Cu2+, indicating that the probe-composited fluorescent sensing film has great potential for on-site and naked-eye detection of Cu2+ in practical.

Acidity-Driven Bidirectional Room-Temperature Spin-State Switch and Fluorescence Modulation of a Mononuclear Fe(II) Complex

Room-temperature switchable materials showing multiple responses toward external stimuli are highly desired. Herein, we report bidirectional spin-state switch and fluorescence modulation of an Fe(I...

Antibody assisted graphene oxide coated gold nanoparticles for rapid bacterial detection and near infrared light enhanced antibacterial activity

Nowadays, foodborne disease emerging as major health concern, can add extra burden to our existing health system. Mostly, conventional method used to monitor the food bacterial contamination, but these methods are cumbersome, thus can’t fulfil the needs of modern time. Currently, nanotechnology have emerged as a wonderful tool for bacterial detection. The unique optical and plasmonic properties of metallic nanoparticles make them exceptional and novel for their integration into biosensor for bacterial detection. In this work, graphene oxide (GO) coated gold nanoparticles (AuNPs) based hybrid antibody biosensor has been developed for fast, specific and higher sensitivity foodborne bacterial detection. Polyethylene glycol (PEG) grafted GO coated AuNPs were covalently conjugated with two different types of antibodies using well known EDC-NHS chemistry. Various spectrophotometric and microscopic techniques have been used to probe the sensitivity of prepared biosensor. A colorimetric and spectrophotometric change upto 103 and 102 CFU, respectively was observed by incubating probe for 5 min. with Escherichia coli and Salmonella typhimurium. Immobilized antibodies on hybrid nanoparticle biosensor are specific for bacteria, however prepared biosensor also exhibited specific photoablation of bacteria after infra-red (NIR) exposure. Rapid optical detection and extermination of foodborne bacteria were achieved by antibody functionalized hybrid nanoparticles based biosensor.

Synthesis and photophysical investigation of novel imidazole derivative an efficient multimodal chemosensor for Cu(II) and fluoride ions

Aminophenylbenzimidazole derivative of theonyl trifluoro acetone has been designed, synthesized and characterized to sense Cu(II) and fluoride ions. The probe showed very selective colorimetric and ratiometric fluorescence changes with copper(II), turn-on fluorescence behavior with fluoride ions. ESI-MS analysis and jobs plots analysis provided the information about the interaction mode between Cu(II) and the probe. Density functional theory calculations carried out on the probe with/without Cu(II) and fluoride ions to support the observed photophysical changes. The Probe can be utilized to detect Cu(II) ions via electrochemical detection and hence it can be used to detect copper ions by multiple modes. The fluorescence and absorbance change with fluoride ions showing that the probe is very sensitive towards fluoride ions among other anions. The detection limits for the detection of Cu(II) and fluoride ions were found to be 23 nM and 0.54 nM respectively.

Multifunctional behavior of bis-acylhydrazone: Real-time detection of moisture in organic solvents, halochromism and aggregation induced emission

A versatile novel indenopyrazine/indenoquinoxaline appended acylhydrazones (1 and 2) have been designed and synthesized successfully. Compounds 1 and 2 are designed such that, it comprises of acylhydrazone, which is responsible for moisture detection via deprotonation of the original molecule, pyrazine, pyridine and hydrazone unit which is responsible for halochromism via protonation and deprotonation, further the integrated twisted molecular structure results in the aggregation-induced emission features. Successive treatment of Fˉ and moisture to compound 1 and 2 produce reversible colorimetric responses that are easily visualized by the naked eye. Further, the corresponding mechanism was effectively confirmed by 1H NMR spectral analysis. The inherent halochromic features of appended unique pyrazine and pyridine core in compounds 1 and 2 were studied by the sequential addition of trifluoroacetic acid (TFA) and triethylamine (TEA) which is authenticated by reversible colorimetric changes as well as absorption spectral studies. Compound 1 adopts a twisted scissor-like structure and due to multiple weak interactions results in an interesting supramolecular network. Furthermore, both compound 1 and 2 exhibits the aggregation-induced emission features in DMF/water mixture, which was expansively confirmed through DLS particle analysis and TEM images. The integration of three distinct features into a single molecule are scarce.

DOUBLE SUBSTITUTED CARBONATED HYDROXYAPATITE FOR STONE CONSOLIDATION

This paper aims with the preparation of Sr2+ and Zn2+ double substituted carbonated hydroxyapatite (Sr-Zn-CHAp) by the nanoemulsion method and to evaluate its consolidation capacity on artificial stone samples. The changes in CHAp lattice parameters were observed by a synergy between the shrinkage and dilatation induced by the two metallic ions, with different ionic radii by comparison with calcium. The changed morphology obtained by calcination was evidenced by SEM analysis. Also, the tendency to agglomerate of the double substituted CHAp as micron- and sub-micron-sized particles with spherical and irregular form was observed. The FTIR, XRD and EDS results confirmed that the CHAp was successfully substituted with Sr2+ and Zn2+ by replacing Ca2+ resulting a AB-type CHAp. The efficacity of Sr-Zn-CHAp as inorganic consolidant for the stone was tested by mechanical strength, resistance at freeze–thaw artificial aging test, thermal shock weathering, colorimetric changes of the artificial stone sample, all the results being correlated with the water absorption test, water repellency, and pore structure changes. By treating the stone with 0.5 g/L Sr-Zn-CHAp led to an improvement of the above-mentioned characteristics, without significant chromatic changes.

Polymer Electrochromism Driven by Metabolic Activity Facilitates Rapid and Facile Bacterial Detection and Susceptibility Evaluation.

The electrochromism of a water-soluble naturally oxidized electrochromic polymer, ox-PPE, is harnessed for rapid and facile bacterial detection, discrimination, and susceptibility testing. The ox-PPE solution shows distinct colorimetric and spectroscopic changes within 30 min when mixed with live bacteria. For the underlying mechanism, it is found that ox-PPE responds to the reducing species (e.g. cysteine and glutathione) released by metabolically active bacteria. This reduction reaction is ubiquitous among various bacterial strains, with a noticeable difference that enables discrimination of Gram-negative and Gram-positive bacterial strains. Combining ox-PPE with antibiotics, methicillin-susceptible and -resistant S. aureus can be differentiated within 2.5 h. Proof-of-concept demonstration of ox-PPE for antimicrobial susceptibility testing is carried out by incubating E. coli with various antibiotics. The obtained minimum inhibition concentrations are consistent with the conventional culture-based methods, but with the procedure time significantly shortened to 3 h.

Design and synthesis of new salicylhydrazone tagged indole derivative for fluorometric sensing of Zn2+ ion and colorimetric sensing of F− ion: Applications in live cell imaging

A novel, bifunctional, colorimetric, highly selective and sensitive “turn-on” fluorescent probe, 2-((E)-(((E)-(5-bromo-1H-indol-3-yl) methylene) hydrazono) methyl) phenol (IHP) has been designed and synthesized for the detection of Zn2+/F− ions in DMSO: H2O (9:1, v/v) medium. The probe IHP exposed an excellent fluorescence enhancement towards Zn2+ ion owing to the inhibition of ESIPT with concurrent enhancement of LMCT operated on IHP. Upon addition of F− ion, the probe IHP displayed an obvious colorimetric change and it can be simply observed by naked eye. Further, 1:1 binding stoichiometric ratio of probe with Zn2+/F− ions was confirmed via Job’s plot and highly supported by 1H NMR titration and 19F NMR analysis for F− ion. The plausible mechanistic pathway and the fluorescence enhancement of IHP with Zn2+ ions were highly gauged by density functional theoretical (DFT) calculations. Moreover, the probe IHP has been successfully employed for monitoring Zn2+ ion in HeLa cells and live cell imaging analysis in Zebrafish embryos.

Accelerated Ageing Procedures to Assess the Stability of an Unconventional Acrylic-Wax Polymeric Emulsion for Contemporary Art.

This research evaluates the stability of an aqueous emulsion of acrylic copolymers and waxes. Edelwachs, generally applied on wood, has been recently used as an unconventional medium in contemporary painting. Through Pyrolysis–Gas Chromatography–Mass Spectrometry (Py-GC-MS) and Fourier Transformed Infrared Attenuated Total Reflectance (FT-IR-ATR) analyses, the composition of Edelwachs was defined as a mixture of acrylic polymers (MA, MMA, nBA, nBMA), Carnauba and microcrystalline waxes and additives. Mock-ups-obtained mixing Edelwachs with titanium white, zinc white and ultramarine blue were subjected to UV, high temperatures, and high relative humidity accelerated ageing. The effect of the ageing procedures was evaluated through optical microscopy, colourimetric measurements, FT-IR-ATR, Thermogravimetry and Differential Scanning Calorimetry (TG-DSC) and wettability measures. FT-IR-ATR spectra do not show significant variations in terms of chemical stability, indicating a fair stability of Edelwachs as a painting binder. UV and high temperature treatments show the most relevant effects in terms of colorimetric changes (increasing of b*) and thermal stability. The TG-DSC highlights the influence of the pigments (specifically zinc white) mainly on the thermal behaviour of the acrylates. The unexpected decrease of wettability of the paint films, registered after ageing, may indicate a possible phase separation among acrylates and waxes.

A novel and efficient chromophore reaction based on a lactam-fused aza-BODIPY for polyamine detection

Polyamines (such as spermine, spermidine) play important roles in biomedical and food field. The elevated polyamines have been proposed to serve as target analytes for monitoring meat spoilage. Because of structural similarity and low concentration of polyamines in real samples, it is exceedingly challenging to design and develop sensitive probes for visual detection of polyamines. To address this issue, a highly efficient probe was reported based on a newly developed chromophore reaction between lactam-fused aza-BODIPY (abbreviation: LAB) and polyamines by virtue of unique multiple amino groups character of polyamines. This chromophore reaction includes a kinetic-controllable reaction of a B–N bond cleavage by polyamines followed by a fast hydrolysis reaction to yield much smaller conjugated molecules. With 130 nm hypsochromic shift of the absorption peak and up to 99% fluorescence quenching within 1 min, LAB can be used as a highly sensitive fluorescent probe for detection of polyamines solution and monitoring fish spoilage with synchronous colorimetric and fluorescent changes.

Colorimetric based sensing of dopamine using ionic liquid functionalized drug mediated silver nanostructures

The present work reports the drug mediated synthesis of silver nanoparticles (AgNPs) for sensing of dopamine (biomarker Parkinson’s disease and others). Augmentin drug was chosen because of functionalities and aromaticity in its structure which will not only work in the synthesis of AgNPs but also enhance the electron density on nanoparticles (NPs) for better sensing properties. 1-H-3-methylimidazolium acetate ionic liquid (IL) having characteristic properties of aromaticity and conductivity were coated on to the surface of NPs to further enhance the mentioned properties. The FTIR, Raman spectroscopy and XRD analysis demonstrate the characteristic peaks assigned to AgNPs. SEM analysis shows round shaped morphology and EDX showed strong band for AgNPs. TGA analysis showed maximum degradation at 340 °C for the prepared AgNPs. The functionalized AgNPs/IL was used in sensing of dopamine. Different reaction conditions have been optimized to find the optimal performance of AgNPs/IL such as; (a) pH (b) amount of Ag/IL (c) time of incubation; (d) temperature. The response time of the proposed sensor for dopamine detection was only 4 min with a visible colorimetric change from light grey to brown color. The proposed sensor showed a wide linear range (1 × 10−8–3.6 × 10−6 M), low limit of detection 1.18 × 10−7 M, and limit of quantification 3.92 × 10−7 M with an R2 value of 0.9997. The IL capped Ag nano assembly exhibited no reactivity towards folic acid, urea, ascorbic acid, Ca+2, K+ and was successfully used to quantify dopamine in physiological sample.

Smart phone assisted quinoline-hemicyanine based fluorescent probe for the selective detection of glutathione and the application in living cells.

Quinoline appended hemicyanine 6MIM with strong ICT character was successfully synthesized through simple condensation reaction of 6-methoxy-2-chloro-3-formyl quinoline with 2-benzothiazolinium iodide. The photophysical characteristics of synthesized probe revealed that it would selectively detect glutathione (GSH) when it compared with different amino acids including biothiols and the detection limit is found to be 100nM. The turn off sensor is due to thiol-halogen SNAr nucleophilic substitution between 6MIM and thiol group in glutathione. More importantly, the biosensor 6MIM was effectively applied in the fluorescence bioimaging of GSH in living cells with low cell toxicity. The colorimetric detectable color change of 6MIM-GSH has been effectively integrated with smartphone assisted RGB color value application with lowest detection value of 120nM.

Hemicyanine-based colorimetric and near-infrared fluorescent off-on probe for Hg2+ detection and imaging in living cells and zebrafish

Herein, a novel near-infrared fluorescent probe (Cy-PT) for the detection of Hg2+ was designed and synthesized, which contained a hemicyanine skeleton as the near-infrared (NIR) fluorophore and carbonothioate moiety as the recognition unit. The very weak fluorescence of Cy-PT is greatly enhanced due to the destruction of thiocarbonate moiety by Hg2+, generating a hydroxyl group. The study shows that Cy-PT exhibits many advantages including NIR emission (708 nm), colorimetric change, off-on fluorescence, remarkably large Stokes shift (120 nm), rapid response, excellent sensitivity and high selectivity. In addition, Cy-PT can be used as a direct visualization detector for Hg2+ detection, allowing further application using test paper. Subsequent fluorescence imaging shows that Cy-PT probe has high ability to enter living cells and bodies, generating strong NIR fluorescence response in the presence of Hg2+. This study indicates that Cy-PT probe is a good candidate for Hg2+ detection in colorimetric and near-infrared fluorescence, which can be developed into an efficient method for Hg2+ detection in complex living samples.

An Integrated Smartphone-Based Genetic Analyzer for Qualitative and Quantitative Pathogen Detection.

The use of the smartphone is an ideal platform to realize the future point-of-care (POC) diagnostic system. Herein, we propose an integrated smartphone-based genetic analyzer. It consists of a smartphone and an integrated genetic analysis unit (i-Gene), in which the power of the smartphone was utilized for heating the gene amplification reaction, and the camera function was used for imaging the colorimetric change of the reaction for quantitative and multiplex foodborne pathogens. The housing of i-Gene was fabricated by using a 3D printer, which was equipped with a macro lens, white LEDs, a disposable microfluidic chip for loop-mediated isothermal amplification (LAMP), a thin-film heater, and a power booster. The i-Gene was installed on the iPhone in alignment with a camera. The LAMP mixture for Eriochrome Black T (EBT) colorimetric detection was injected into the LAMP chip to identify Escherichia coli O157:H7, Salmonella typhimurium, and Vibrio parahaemolyticus. The proportional–integral–derivative controller-embedded film heater was powered by a 5.0 V power bank to maintain 63 °C for the LAMP reaction. When the LAMP proceeded, the color was changed from violet to blue, which was real-time monitored by the smartphone complementary metal oxide semiconductor camera. The images were transported to the desktop computer via Wi-Fi. The quantitative LAMP profiles were obtained by plotting the ratio of green/red intensity versus the reaction time. We could identify E. coli O157:H7 with a limit of detection of 101 copies/μL within 60 min. Our proposed smartphone-based genetic analyzer offers a portable, simple, rapid, and cost-effective POC platform for future diagnostic markets.

C3-symmetric triaminoguanidine based colorimetric and fluorometric chemosensor: Sequential detection of Zn2+/PPi, its RGB performance for detection of Zn2+ ion and construction of IMPLICATION logic gate

In this work, new ethyl(E)-2-cyano-3-(1H-pyrrol-2-yl)acrylate appended C3-symmetric star-shape triaminoguanidine based Schiff base (LH3) was designed and synthesized from simple synthons. New probe, LH3 was completely analyzed by 1H NMR, 13C NMR and mass spectrum. In the present probe LH3, effective π-conjugated ethyl(E)-2-cyano-acrylate unit was introduced on the periphery of the pyrrole-triaminoquanidine conjugates by using carefully chosen building units. The probe LH3 shows high selectivity and sensitivity towards Zn2+ ion via colorimetric and fluorometric changes. The yellowish orange color of LH3 solution turned to wine red color upon addition of Zn2+ solution, along with red shifted absorption maxima from 450nm to 550nm, this indicates the formation of LH3-Zn2+ species. Job's plot and mass spectrum analysis confirms the formation of 1:3 stoichiometric complex between the LH3 and Zn2+ ions. Further this ensemble shows selective detection towards PPi anion over the other anions based on displacement metal ion approach. Hence, reversible colorimetric/emission response of LH3 towards Zn2+ and PPi ions via "on-off-on" manner could allow the construction of IMPLICATION logic gate functions. The practical efficacy of the probe LH3 was established by utilization of the probe for the detection of Zn2+ ions in real water sample analysis. Further, the significant noticeable colorimetric changes of the probe LH3 upon addition of Zn2+ ion have been successfully integrated with a smartphone app RGB color value to construct a real-time analysis of Zn2+ ions.

A rapid-response near-infrared fluorescent probe with a large Stokes shift for senescence-associated β-galactosidase activity detection and imaging of senescent cells

Detection of senescence-associated β-galactosidase (SA-β-gal) activity at an increased lysosomal pH is one of the most reliable approaches for probing senescent cells. Herein, we developed a novel near-infrared fluorescent probe (KSL0401) for sensing SA-β-gal activity and applying in visualization of aging. This probe was designed by connecting a cleavable d-galactose residue to the coumarin-dicyanoisophorone hybrid fluorophore KSL0401-OH via a β-glycosidic bond. The spectral properties of KSL0401 reaction with β-gal were measured in aqueous solution at pH 6.0, and a remarkable enhancement of fluorescence emission at 706 nm was observed, along with a visible colorimetric change. Probe KSL0401 was highly selective and sensitive to SA-β-gal, and displayed large Stokes shift (218 nm) and good biocompatibility. Moreover, it exhibited extremely rapid response to β-gal within 80 s, which surpassed most of the reported SA-β-gal probes. Additionally, KSL0401 also enabled to detect the endogenous SA-β-gal activity in living cells, and distinguish between senescent cells and non-senescent cells and qualify the degree of aging. These findings demonstrate that KSL0401 is a potential detection tool in the imaging research of aging.

A novel colorimetric and fluorometric probe for biothiols based on MnO2 NFs-Rhodamine B system

Herein, a novel bimodal ratiometric probe for sensitive and selective detection of biothiols (including glutathione (GSH), cysteine (Cys) and homocysteine (Hcys)) was constructed, which was based on the redox reaction between manganese dioxide nanoflakes (MnO2 NFs) and rhodamine (RhB) and biothiols. When MnO2 NFs was added into RhB solution, RhB was oxidized to a series of derivatives, accompanying with the colorimetric color changing from purple to light pink and fluorescence changing from red to green. In the presence of GSH, Cys or Hcys, they could reduce MnO2 NFs to Mn2+, thereby preventing the following oxidization of RhB and the corresponding color and fluorescence changes. The absorption intensity ratio and fluorescence intensity ratio showed good linear relationships with the concentrations of biothiols. The colorimetric detection limits for GSH, Cys and Hcys were 0.057 μM, 0.140 μM and 0.087 μM, respectively. And the fluorescence detection limits were 0.177 μM, 0.282 μM and 0.161 μM. More importantly, this probe was successfully applied to monitor the concentration of GSH/Cys/Hcys in human serum samples, with satisfactory recovery. Thus, this MnO2 NFs-RhB platform can potentially be a candidate for the detection of biothiols.

A SERS-colorimetric dual-mode aptasensor for the detection of cancer biomarker MUC1.

Human mucin-1 (MUC1) has attracted considerable attention owing to its overexpression in diverse malignancies. Here, for the rapid and efficient detection of MUC1, we present a SERS-colorimetric dual-mode aptasensor, by integrating SERS probes with magnetic separation, which has several distinctive advantages. Using such a dual-mode aptasensor, the colorimetric functionality is distinguishable by the naked eye, providing a fast and straightforward screening ability for the detection of MUC1. Moreover, SERS-based detection greatly improves the detection sensitivity, reaching a limit of detection of 0.1U/mL. In addition, the combination of SERS and colorimetric method holds the advantages of these two techniques and thereby increases the reliability and efficiency of MUC1 detection. On the one hand, the magnetic nanobeads functionalized with MUC1-specific aptamer were utilized as an efficient capturing substrate for separating MUC1 from biological complex medium. On the other hand, the gold-silver core-shell nanoparticles modified with Raman reporters and the complementary sequences of MUC1 were used as the signal indicator, which could simultaneously report the SERS signal and colorimetric change. This strategy can achieve a good detection range and realize MUC1 analysis in real patients' samples. Thus, we anticipate that this kind of aptasensor would provide promising potential applications in the diagnosis and prognosis of cancers. Graphical abstract.

A new mechanism for selective recognition of cyanide in organic and aqueous solution

A simple colorimetric and fluorimetric chemosensor 3,5‐dinitro‐(N‐phenyl)benzamide (DNBA), was synthesized for selective determination of cyanide anion in organic and aqueous solutions via novel chemodosimeter approach. The chemosensor DNBA showed a chromogenic and fluorogenic selective response to CN– against competing anions such as F–, AcO–, and H2PO4– in organic (DMSO and ACN) and in aqueous solutions (in DMSO/H2O: 8:2, v/v). The intensive colorimetric and fluorimetric color changes were observed in ambient light and UV‐light (λex. 365 nm) after cyanide interacted with DNBA. A method that can be used in the synthesis of new biologically active benzisoxazole compound was described by the reaction of DNBA with TBACN and KCN in DMSO or DMSO/H2O, respectively. All interaction mechanisms between DNBA and cyanide and fluoride anions were demonstrated by experimental studies using various spectroscopic methods such as UV/Vis, fluorescence, 1H/13C NMR, and mass spectrometry as well as X‐ray diffraction method. In addition, the experimental results were also explained with theoretical data. The spectroscopic results showed that cyanide interacts with three different mechanisms; deprotonation, nucleophilic aromatic substitution, and formation of benzisoxazole ring.

Early visualization of skin burn severity using a topically applied dye-loaded liquid bandage

Skin burns are a significant source of injury in both military and civilian sectors. They are especially problematic in low resource environments where non-fatal injuries can lead to high morbidity rates, prolonged hospitalization, and disability. These multifaceted wounds can be highly complex and must be quickly diagnosed and treated to achieve optimal outcomes. When the appropriate resources are available, the current gold standard for assessing skin burns is through tissue punch biopsies followed by histological analysis. Apart from being invasive, costly, and time-consuming, this method can suffer from heterogeneous sampling errors when interrogating large burn areas. Here we present a practical method for the early visualization of skin burn severity using a topically applied fluorescein-loaded liquid bandage and an unmodified commercial digital camera. Quantitative linear mixed effects models of color images from a four day porcine burn study demonstrate that colorimetric changes within the HSB colorspace can be used to estimate burn depth severity immediately after burning. The finding was verified using fluorescence imaging, tissue cross-sectioning, and histopathology. This low-cost, rapid, and non-invasive color analysis approach demonstrates the potential of dye-loaded liquid bandages as a method for skin burn assessment in settings such as emergency medicine triage and low resource environments.