Rapid Color Research Articles

12. Rapid colour change in the agile frog [Rana dalmatina] in north-west Italy

12. Rapid colour change in the agile frog [Rana dalmatina] in north-west Italy

Colorimetric microneedle patches for multiplexed transdermal detection of metabolites

Skin Interstitial Fluid (ISF) is an alternative source for biomarkers. Herein, a highly swellable microneedle patch (MNP) to rapidly extract ISF painlessly and bloodlessly is presented. The MNP is made of crosslinked methacrylated hyaluronic acid (MeHA) and dissolvable hyaluronic acid (HA) with the optimal balance of mechanical strength (0.6 N/MN) and absorption capability (16.22 μL in 20 min). Incorporated with wax-patterned and sensing-reagent-decorated test paper (TP) for multiplexed colorimetric detection of metabolites (glucose, lactate, cholesterol, and pH), this TP-MNP biosensor gives rapid color change in biomarker concentration-dependent manner based on specific enzymatic reactions, whereby allowing diagnosis by the naked eye or quantitative RGB analysis. Both the in vitro and in vivo experiments demonstrate the feasibility of TP-MNPs to detect multiple biomarkers in skin interstitial fluid within minutes. Such convenient and self-administrable profiling of metabolites shall be instrumental for home-based long-term monitoring and management of metabolic diseases.

The physiological cost of colour change: evidence, implications and mitigations.

Animals benefit from phenotypic plasticity in changing environments, but this can come at a cost. Colour change, used for camouflage, communication, thermoregulation and UV protection, represents one of the most common plastic traits in nature and is categorised as morphological or physiological depending on the mechanism and speed of the change. Colour change has been assumed to carry physiological costs, but current knowledge has not advanced beyond this basic assumption. The costs of changing colour will shape the evolution of colour change in animals, yet no coherent research has been conducted in this area, leaving a gap in our understanding. Therefore, in this Review, we examine the direct and indirect evidence of the physiological cost of colour change from the cellular to the population level, in animals that utilise chromatophores in colour change. Our Review concludes that the physiological costs result from either one or a combination of the processes of (i) production, (ii) translocation and (iii) maintenance of pigments within the colour-containing cells (chromatophores). In addition, both types of colour change (morphological and physiological) pose costs as they require energy for hormone production and neural signalling. Moreover, our Review upholds the hypothesis that, if repetitively used, rapid colour change (i.e. seconds-minutes) is more costly than slow colour change (days-weeks) given that rapidly colour-changing animals show mitigations, such as avoiding colour change when possible. We discuss the potential implications of this cost on colour change, behaviour and evolution of colour-changing animals, generating testable hypotheses and emphasising the need for future work to address this gap.

Fast responding and highly reversible gasochromic H2 sensor using Pd-decorated amorphous WO3 thin films

For the safe use of H2 gas, an eco-friendly energy source in the spotlight but highly explosive at the same time, the need for gas sensors for early H2 detection has been highly increasing. Although promising H2 sensors have been developed with different sensor principles, most of them accompany bulky and large measurement systems which limit their further application to everyday life. In this study, we propose gasochromic H2 sensors based on Pd nanoparticle-decorated amorphous WO3 film (Pd-aWO3) that can visualize H2 detection by the rapid color change of the film with high reversibility using dissociated H+ ions. In specific, extremely fast H+ diffusion coefficient through amorphous WO3 film prepared by electron beam evaporation enables rapid and highly reversible operation that could not be achieved by previously reported crystalline WO3 film. As a result, Pd-aWO3 could exhibit a transmittance change of 57% and super rapid recovery time (16 s), which is the fastest compared to previously reported gasochromic H2 sensors to the best of the authors’ knowledge. Moreover, in-situ surface analysis using ambient pressure X-ray photoelectron spectroscopy revealed detailed coloring and beaching mechanisms. This study can provide promising perspectives to future advances in gasochromic H2 sensors toward everyday life application.

Lab-on-a-Molecule Probe: Multitarget Detection of Five Aromatic Pesticides Using a Supramolecular Probe under Single Wavelength Excitation.

In order to prevent and control the effects of pesticide residues on human health and the ecological environment, the rapid, highly sensitive, and selective detection of multiple pesticide residues has become an urgent problem to be solved. Herein, a lab-on-a-molecule probe based on a host-guest complex (ThT@Q[8] probe) has been developed to simultaneously analyze multiple aromatic pesticides under single wavelength excitation, such as fuberidazole, thiabendazole, carbendazim, thidiazuron, and tricyclazole. The fluorescence titration spectra of the ThT@Q[8] probe with the five pesticides mentioned above showed that the fluorescence intensity exhibited a good linear correlation with the pesticide concentration and the limit of detection was as low as 10-7 M. Because the ThT@Q[8] probe exhibits diverse fluorescence color changes to the five pesticides studied under a 365 nm ultraviolet lamp, we fabricated a single probe used to detect multiple analytes in the RGB triple channel by extracting the RGB variations. Principal component analysis and linear discriminant analysis proved that the ThT@Q[8] probe can recognize and distinguish five pesticides and can be applied at different concentrations. In real samples, the ThT@Q[8] probe recognized and distinguished five pesticides in tap water and Huaxi River water. The 1H NMR spectra results proved that a charge-transfer complex of ThT and pesticides in the Q[8] cavity may be formed. Moreover, we selected a test strip as a carrier to detect pesticides. The results indicate it can be used to quickly and conveniently detect different pesticides due to the rapid color change. Besides, the ThT@Q[8] probe has good cell permeability and can be used to detect pesticide residues in living cells. This work has laid the foundation for the qualitative and quantitative multitarget detection of pesticide residues.

Ajwa-Dates (Phoenix dactylifera)-Mediated Synthesis of Silver Nanoparticles and Their Anti-Bacterial, Anti-Biofilm, and Cytotoxic Potential

Green nanotechnology is the evolution of cost-effective and environmentally friendly processes for the production of metal-based nanoparticles due to medicinal importance and economic value. The aim of the present study was to biosynthesize and characterize silver nanoparticles (AgNPs) using the seed extract of Ajwa dates (Aw). The anti-bacteriostatic activity of biosynthesized Aw–AgNPs against Gram-positive and Gram-negative bacterial strains was evaluated. The anti-biofilm activity was examined by the tissue culture plate method. Lastly, the anti-cancer potential of Aw–AgNPs was investigated against the human breast cancer cell line HCC712. UV–visible absorption spectra exhibited the plasmon resonance peak at 430 nm, with the solution undergoing rapid color changes that verified the existence of biosynthesized silver nanoparticles in the solution. TEM and SEM images illustrated that the Aw–AgNPs were spherical and between 15 and 80 nm in diameter. The reduction and stabilization of Aw–AgNPs was due to the functional groups present in the biomolecules of the Ajwa seeds, as identified by FTIR. The Aw–AgNPs exhibited significant anti-bacterial activity against all the tested bacterial strains. Moreover, the Aw–AgNPs efficiently hampered the biofilm formation of the bacterial strains and exhibited cytotoxicity at various concentrations. Overall, these findings suggest that biosynthesized Aw–AgNPs may be used as a potential therapeutic formulation against bacterial infections and breast cancer.

Study of the reaction between genipin and amino acids, dairy proteins, and milk to form a blue colorant ingredient

Currently, one of the biggest challenges of the colorant industry is to obtain natural blue colorants. Among the different options, a blue pigment can be formed by a crosslinking reaction between genipin and primary amine groups. However, at the industrial level, obtaining an ingredient from pure compounds, such as amino acids, is economically unfeasible. The present work aimed to study the reaction and kinetics of the blue color formation, starting the study with pure compounds (genipin and amino acids) to more complex and cheaper natural sources, such as Genipa americana L. fruits and milk. The reaction kinetics of the monomers/dimers for different amino acids reacting with genipin was evaluated, as well as the preferential amino acid, genipin:amino acid ratio and pH, to obtain the most rapid and intense blue color. Finally, the blue pigment formed using milk and its proteins was characterized by SDS-PAGE. The results suggest that the reaction kinetic is influenced by the type and concentration of the amino acid used and the pH of the medium, which could facilitate the further standardization of the industrial process. We also suggested milk as an excellent reaction medium to obtain the colorant from genipin as it presents an ideal pH and favorable amino acid composition to facilitate the reaction.

The effect of surface tension on the color Doppler ultrasound twinkling artifact

Imaging crystalline structures with Doppler ultrasound can produce a rapid color shift, termed the twinkling artifact, that can assist in diagnosing pathological mineralizations such as kidney stones, heterotopic ossification, gout, and breast microcalcifications. Twinkling is theorized to arise from scattering off surface crevice microbubbles, which are affected by the surface tension between the bubble and surrounding medium. In this study, we evaluated the effect of surface tension on twinkling in pure crystals. Cholesterol, calcium phosphate, and uric acid crystals were grown in vitro (n = 5 each) and imaged with a Philips/ATL L7-4 transducer and Vantage-128 research ultrasound system. Crystals were imaged in water while varying surfactant concentration (0%–4%) leading to surface tensions that ranged from 45–72 mN/m. Surface tension of the solution was determined by measuring the contact angle of 0.1-mL droplet on an acrylic sheet exposed to air. As the concentration of surfactant increased, twinkling was found to decrease by ∼20% for cholesterol and calcium phosphate and ∼10% for uric acid. These results continue to support the crevice bubble theory of twinkling and suggest the importance of surface tension when evaluating minerals with the twinkling artifact. [Work supported by NSF-CAREER-1943937 and NSF-GRFP-DGE1255832.]

Functionalized organic–inorganic hybrid composites used as colorimetric chemosensors for hydrogen sulfide detection

AbstractDetection of trace‐level hydrogen sulfide (H2S) gas is of great importance both in industrial production and disease diagnosis. In this article, two simple but smart colorimetric chemosensors for H2S detection were designed based upon the principle of colorimetric reaction. Ag NPs, as the main detection agent was loaded onto the primary carrier, silica sulfonic acid. Thus, a silver‐modified silica sulfonic acid (Ag‐SSA) was prepared successfully. Then the Ag‐SSA was integrated with two kinds of secondary substrate materials. One is the cotton‐woven textile and the other one is polyvinyl alcohol (PVA) nanofibrous membrane. Finally, two functionalized organic–inorganic hybrid composite systems for H2S detection were formed. Both of them were able to exhibit a rapid visual color change in response to H2S. Ag‐SSA/cotton textile was tested in the aqueous state and the limit of detection (LOD) of H2S solution was around 10−6 mol/L. For the Ag‐SSA/PVA nanofibers membrane detected in the atmospheric condition, the LOD of H2S gas reached 6.5 ppm. This research has been successfully demonstrated for the application in sensitive and selective detection of hydrogen sulfide in aqueous solution and gaseous state.

Pt/WO3 Nanoparticle-Dispersed Polydimethylsiloxane Membranes for Transparent and Flexible Hydrogen Gas Leakage Sensors.

Hydrogen gas is a promising, clean, and highly efficient energy source. However, to use combustible H2 gas safety, high-performance and safe gas leakage sensors are required. In this study, transparent and flexible platinum-catalyst-loaded tungsten trioxide (Pt/WO3) nanoparticle-dispersed membranes were prepared as H2 gas leakage sensors. The nanoparticle-dispersed membrane with a Pt:W compositional ratio of 1:13 was transparent and exhibited a sufficient color change in response to H2 gas. The membrane containing 0.75 wt.% of Pt/WO3 nanoparticles exhibited high transparency over a wide wavelength range and the largest transmittance change in response to H2 gas among the others. The heat treatment of the particles at 573 K provided sufficient crystallinity and an accessible area for a gasochromic reaction, resulting in a rapid and sensitive response to the presence of H2 gas. The lower limit of detection of the optimized Pt/WO3 nanoparticle-dispersed membrane by naked eye was 0.4%, which was one-tenth of the minimum explosive concentration. This novel membrane was transparent as well as flexible and exhibited a clear and rapid color response to H2. Therefore, it is an ideal candidate sensor for the safe and easy detection of H2 gas leakage.

All-in-One Process for Color Tuning and Patterning of Perovskite Quantum Dot Light-Emitting Diodes.

Although post‐synthetic anion exchange allows halide perovskite quantum dots to easily change the optical bandgap of materials, additional exchange of shorter ligands is required to use them as active materials in optoelectronic devices. In this study, a novel all‐in‐one process exchanging ligands and halide anions in film‐state for facile color tuning and patterning of cesium lead halide perovskite colloidal quantum dot (PeQD) light‐emitting diodes (LEDs) is proposed. The proposed all‐in‐one process significantly enhances the performances of PeQD LEDs by passivating the PeQD with shorter ligands. In addition, the all‐in‐one process is repeated more stably in the film state. Red, green, and blue LEDs with extremely narrow emission spectra using cesium lead bromide PeQDs and appropriate butylammonium halide solutions are fabricated. Furthermore, the proposed all‐in‐one process in film‐state facilitated rapid color change in localized areas, thereby aiding in realizing fine patterns of narrow widths (300 µm) using simple contact masks. Consequently, various paint‐over red/green/blue patterns in PeQD LEDs by applying halide solutions additively are fabricated.

Light-Emitting Redox Polymers for Sensing and Removal-Reduction of Cu(II): Roles of Hydrogen Bonding in Nonconventional Fluorescence

Here, intrinsically luminescent multifunctional n-butyl prop-2-enoate-co-butyl 3-(N-(hydroxymethyl)prop-2-enamido)propanoate-co-N-(hydroxymethyl)prop-2-enamide (NBP-co-BHMPP-co-HMP) luminogens with 1:2, 1:4, 1:8, and 1:20 mole ratios of NBP/HMP are synthesized via free radical polymerization, where the amidic BHMPP comonomer is anchored via N–C coupling of HMP and NBP. The optimum nonconventional fluorescent polymer (NCFP, NBP/HMP = 1:8) is suitable for sensitive detection, selective binding, and removal-reduction of Cu(II). The structures and light-emitting properties of NCFP, NCFP aggregates, Cu(II)-NCFP, and Cu(I)-NCFP; oxygen donor selective coordinations; and removal-reduction of paramagnetic Cu(II) are explored via spectroscopic, microscopic, density functional theory-reduced density gradient, rapid color change under visible light, chromaticity-1931 plots, and electrochemical measurements. The striking aggregation-enhanced green fluorescence is associated with extensive nonconventional and conventional hydrogen bondings in NCFP aggregates and through space electronic interactions involving NBP, HMP, and BHMPP moieties. Here, the Cu(II)/Cu(I) redox couple is confirmed via shifting of Epc from −1.08/+0.15 to +0.95/+0.16 V; Epc and Epa at +0.15 and −0.34/+0.41 V, respectively; green color of Cu(I)-NCFP under visible light; Fourier transform infrared and Cu 2p X-ray photoelectron spectroscopies; and computational studies. The limit of detection, Stern–Volmer constant, redox potentials, and adsorption capacity of NCFP are 3.61 nM/0.229 ppb, 4.27 × 103 [M]−1, and +0.15/+0.41/–0.34 V, and 49.41 mg g–1, respectively.

Reusable radiochromic semiconductive MOF for dual-mode X-ray detection using color change and electric signal

This work puts forward the idea of dual-mode X-ray detection using color change and electric signal, and provides a MOF (metal–organic framework)-based host–guest strategy to synthesize rewritable radiochromic semiconductive materials, which are promising to avoid the lack of digital processing ability and reusability of commercial radiographic/radiochromic films and the non-portability of commercial electric detectors. The obtained semiconductor with photochromism-active viologen exhibited rapid color change from colorless to blue and photocurrent response upon irradiation of X-ray and was easily bleached after thermal annealing for reuse. As an application example, the inner detail of a printed circuit board was successfully revealed through radiochromic imaging. Meanwhile, a single-crystal detector of the semiconductor achieved a sensitivity of 3216 µCGy–1cm−2, which is higher than those of all reported MOF-based detectors and commercial α-Se detectors.

An ionic liquid-based ratio fluorescent sensor for real-time visual monitoring of trace Hg2+

As a brand probe material, functional ionic liquids (ILs) have already been successfully employed in the detections of many targets, however, few of them focused on the real-time visual monitoring of trace Hg2+, one of the most representative heavy metal ions. Herein, we report a novel ratio fluorescent sensor using facile mixture of [RDB] [P66614] IL and 7-hydroxycoumarin (HDC) for the on-site monitoring of Hg2+ ignoring background interferences. To utilize and enhance the affinity characteristics of rhodamine B for Hg2+, it was first covalently linked onto the anion of IL and further mixed with HDC to construct a novel ratio fluorescent sensor for the achievement of self-calibration. Furthermore, this novel sensor showed a rapid and obvious color rendering performance from light white to opera pink even towards trace mercury(Ⅱ) in the range of 0.1–50 nM and could be further used even in common real samples such as waste water, urine, human plasma et. al. Most importantly, the sensor could be assembled into a paper sensor for the on-site visual monitoring of trace Hg2+ ranging from 10 to 400 nM only taking 2 s, which enable to meet requirements for mercury(Ⅱ) limitations of WHO (30 nM) and EPA (10 nM).

Dual pH-/Photo-Responsive Color Switching Systems for Dynamic Rewritable Paper.

Smart color switching materials that can change color with a fast response and a high reversibility have attracted increasing attention in color-on-demand applications. However, most of them can only respond to a single stimulus from their external environment, which dramatically limits their broad applications. To address this problem, we report a new strategy in developing a dual pH-/photo-responsive color switching system by coupling the pH-dependent and redox-driven color switchable neutral red (NR) with photoreductive TiO2-x nanoparticles. The biodegradable TiO2-x nanoparticles/NR/agarose gel film shows a rapid color switching between yellow and red upon stimulation with acidic/basic vapors in more than 20 cycles because of the protonation and deprotonation process of NR. Moreover, the film shows interesting photoreversible color switching properties under both acidic and basic conditions, including a fast response time and a high reversibility. Taking advantage of the excellent dual pH-/photo-responsive color switching properties, we demonstrated the potential applications of the TiO2-x nanoparticles/NR/agarose gel film in dynamic rewritable paper, in which the created patterns by photo-printing produce dynamic color changing upon applying an acidic or a basic vapor. We believe that the result will enable a new path for the development of dual- and even multi-responsive color switching systems, broadening their new applications.

A Charge-Switchable Zwitterionic Peptide for Rapid Detection of SARS-CoV-2 Main Protease.

The transmission of SARS-CoV-2 coronavirus has led to the COVID-19 pandemic. Nucleic acid testing while specific has limitations for mass surveillance. One alternative is the main protease (Mpro ) due to its functional importance in mediating the viral life cycle. Here, we describe a combination of modular substrate and gold colloids to detect Mpro via visual readout. The strategy involves zwitterionic peptide that carries opposite charges at the C-/N-terminus to exploit the specific recognition by Mpro . Autolytic cleavage releases a positively charged moiety that assembles the nanoparticles with rapid color changes (t<10 min). We determine a limit of detection for Mpro in breath condensate matrices <10 nM. We further assayed ten COVID-negative subjects and found no false-positive result. In the light of simplicity, our test for viral protease is not limited to an equipped laboratory, but also is amenable to integrating as portable point-of-care devices including those on face-coverings.

A Charge‐Switchable Zwitterionic Peptide for Rapid Detection of SARS‐CoV‐2 Main Protease

AbstractThe transmission of SARS‐CoV‐2 coronavirus has led to the COVID‐19 pandemic. Nucleic acid testing while specific has limitations for mass surveillance. One alternative is the main protease (Mpro) due to its functional importance in mediating the viral life cycle. Here, we describe a combination of modular substrate and gold colloids to detect Mpro via visual readout. The strategy involves zwitterionic peptide that carries opposite charges at the C‐/N‐terminus to exploit the specific recognition by Mpro. Autolytic cleavage releases a positively charged moiety that assembles the nanoparticles with rapid color changes (t&lt;10 min). We determine a limit of detection for Mpro in breath condensate matrices &lt;10 nM. We further assayed ten COVID‐negative subjects and found no false‐positive result. In the light of simplicity, our test for viral protease is not limited to an equipped laboratory, but also is amenable to integrating as portable point‐of‐care devices including those on face‐coverings.

Voltage-tunable elastomer composites that use shape instabilities for rapid structural color changes.

Structurally colored materials can switch colors in response to external stimuli, which makes them potentially useful as colorimetric sensors, dynamic displays, and camouflage. However, their applications are limited by the angular dependence, slow response, and absence of synchronous control in time and space. In addition, out-of-plane deformation from shape instability easily occurs in photonic films, leading to inhomogeneous colors in photonic-crystal materials. To address these challenges, we combine structurally colored photonic glasses and dielectric elastomer actuators. We use an external voltage signal to tune color changes quickly (much less than 0.1 s). The photonic glassses produce colors with low angular dependence, so that their colors are homogeneous even when they become curved due to voltage-triggered instabilities (buckling or wrinkling). As proof of concept, we present a pixelated display in which segments can be independently and rapidly turned on and off. This wide-angle, instability-tolerant, color-changing platform could be used in next-generation soft and curved color displays, camouflage with both shape and color changes, and multifunctional sensors.

A rapid assay of granulocytic esterase in the discharge of conjunctival sac as a tool for the recognition of bacterial ocular surface inflammation

AbstractPurposeOcular surface inflammation (OSI) is one of the most common diseases in ophthalmic practice. Bacteria can be one of many reasons of OSI. Topical antibiotics are prescribed in many cases of OSI. There is an important reason of the increase the antibiotic resistance. An enzyme granulocystic esterase (GE) is a marker of neutral granulocytes activated during bacterial inflammation. The goal of our study was to check the usage of rapid assay of GE in the discharge coming from conjunctival sac in patients with OSI.MethodsDischarge was collected from the conjunctival sac by sterile swab for microbiological cultures and the rapid assay of GE. There is a color reaction of indoxyl with diazonium salt in the assay. The positive result gives the purple color of the test area and its intensity is dependent on the amount of GE.ResultsThe intensity of the of the rapid assay color was the highest in patients with purulent discharge. In most cases, the presence of Staphylococcus aureus and Staphylococcus epidermidis was confirmed. Very low GE activity was found in most patients without purulent discharge. There were few patients without purulent discharge but with positive results of rapid assays and microbiological cultures. There was lack of correlation between intensity of subjective and objective symptoms (except purulent discharge) and positive result of rapid assay and microbiological cultures.ConclusionsA rapid assay of GE seems to be easy tool for the recognition of bacterial etiology of ocular surface inflammation. It can help to limit topical antibiotics usage in the treatment of ocular surface inflammations and reduce the antibiotic resistance.

Reversible colorimetric sensing of volatile analytes by wicking in close proximity to a photonic film.

Isolation of volatile analytes from environmental or biological fluids is a rate-determining step that can delay the response time for continuous sensing. In this paper, we demonstrate a colorimetric sensing system that enables the rapid detection of gas-phase analytes released from a flowing micro-volume fluid sample. The sensor platform is an analyte-responsive metal-insulator-metal (MIM) thin-film structure integrated with a large area quartz micropillar array. This allows precise planar alignment and microscale separation (310 μm) of the optical and fluidic structures. This configuration offers rapid and homogeneous color changes over large areas that permits detection by low-resolution optics or eye, which is well-suited to portable/wearable devices. For our proof-of-principle demonstration, we utilized a poly(methyl methacrylate) (PMMA) spacer and evaluated the sensor's response (color change) to ethanol vapor. We show that the RGB color value is quantitatively linked to the spacer swelling, which is reversible and repeatable. The optofluidic platform reduces the sensor response time from minutes to seconds compared with experiments using a conventional chamber. The sensor's concentration-dependent response was examined, confirming the potential of the reported sensing platform for continuous, compact, and quantitative colorimetric analysis of volatile analytes in low-volume samples, such as biofluids.