Color Change Of Solution Research Articles

Visual monitoring of polystyrene nanoplastics < 100 nm in drinking water based on functionalized gold nanoparticles

Nanoplastics (NPLs), of which polystyrene (PS) plastics are typical representatives, are of global concern as emerging contaminants, especially the leakage of NPLs into drinking water, which is directly related to human health. To onsite visually assess the extent of NPLs contamination in drinking water in a rapid and non-destructive manner, this work extends the application of the highly sensitive response to pH of mercaptoundecanoic acid (MUA)-functionalized gold nanoparticles (Au NPs). Further, a visual sensing method based on the binding of alkyl chains to PS NPLs with hydrophobic force to suppress pH-induced aggregation of functionalized nanoparticles was constructed. Particularly, the designed analytical strategy is a significant renewal of the first strategy for the visual detection of PS NPLs, featuring non-destructive, fast response (∼30 s), high selectivity, and detection limit (26 μg/L). Importantly, it can reliably distinguish the more hazardous PS NPLs of smaller particle size (<100 nm). Moreover, visualization-based detection observes the color change of the reaction solution from dark purple to wine red. The employment of a smartphone installed App to read the color three-channel value R further ensures the credibility of the analysis results. The proposed visual analysis strategy will provide a promising new avenue for efficient detection of surface hydrophobic NPLs and further evaluation of their particle size or shape.

Formation of stable naphthalenediimide radical anion: Substituent-directed synergistic effects of hydrogen bonding and charge transfer interactions on chromogenic response towards hydrazine

Naphthalimide-based chromogenic probes have been developed with different electron-withdrawing terminal functional groups. All the compounds showed a dose-dependent gradual change in solution color from pale yellow to dark yellow to light brown and finally dark brown upon the addition of hydrazine hydrate. Concomitantly, the appearance of intense green fluorescence is noticed. The mechanistic investigations, as supported by 1H NMR and ESR studies, indicate the hydrazine induces formation of radical anion species in the reaction medium. The presence of electron-withdrawing substituents not only improves the degree of chromogenic response but also the stability of the radical species. It is found that the substituents take an active role in the adsorption of hydrazine via hydrogen bonding interactions, which facilitates the subsequent charge transfer from hydrazine to probe molecules. In this context, a detailed density functional theory (DFT) based first-principle calculations are performed to theoretically study the cooperative effect of hydrogen bonding interaction in the sensing of hydrazine. It is observed that on changing substituents, significant changes in the numbers of possible chemisorption sites and binding energies at individual sites for hydrazine, as well as the magnitude of charge transfer from the hydrazine at individual binding sites. Finally, chemically modified biodegradable paper strips have been developed on on-location naked-eye sensing of hydrazine.

Emerging electrochemiluminescence biosensing and visual technique for potential applications in point-of-care testing of microRNAs

An increasing number of biosensor design strategies have emerged in recent years, capable of providing potential practical applications for point-of-care testing (POCT) in various human diseases. Compared to conventional biosensors, the latest POCT assays research aims at improving sensor precision, cost-effectiveness and time-consumption. Here，an electrochemiluminescence biosensor and colorimetric method is emerged for rapid, accurate and sensitive determination of biomarker microRNA-141. The target firstly opens the hairpins formed by Ag(I) that acting as a bridge between two cytosine, and the released Ag(I) is selectively recognized by CdTe quantum dots resulting in a decrease in electrochemiluminescence signal and a color change in solution as a visual signal. Then, the introduction of assistant DNA triggers a subsequent catalytic hairpin assembly reaction (CHA), allowing the target to be continuously cycled and further scaled up. The emerging sensor has the advantages of simple, fast (the whole detection process takes about 4 h，takes less time than other biosensors), high sensitivity, good selectivity, and wide linear range (100 aM to 100 pM, with a low LOD as 41.6 aM for electrochemiluminescence and 123.8 aM for colorimetric, respectively), eliminating probe labeling and analysis strategies, which greatly improves the practicality of the method and is expected to realize low-cost and high-sensitivity POCT of microRNAs.

Colorimetric and antioxidant films based on biodegradable polymers and black nightshade (Solanum nigrum L.) extract for visually monitoring Cyclina sinensis freshness.

In this study, colorimetric and antioxidant films were developed by using cassava starch (CS), κ-carrageenan (KC) and black nightshade fruit anthocyanins (BNA), and their physical and functional properties were investigated. We found BNA presented significant color changes in different pH solutions. And incorporation of BNA significantly increased the tensile strength, water vapor permeability, UV-vis light barrier property, pH-sensitivity and antioxidant activity of CS-KC film. Results of structural characterization indicated that H-bonds were formed between CS, KC and BNA in films and the film compactness was significantly improved by BNA incorporation. Results of the rheological property assay showed the films had high apparent viscosity with an obvious shear-thinning behavior. When applied to monitoring the quality change of Cyclina sinensis, CS-KC-BNA films exhibited significant color changes with the degradation process of C. sinensis qualities. Our results suggested CS-KC-BNA films could be utilized in smart packaging in food industry.

MINI REVIEW: PENGEMBANGAN BIOSENSOR KOLORIMETRI BERBASIS AGREGASI NANOPARTIKEL EMAS

&lt;p class="abstrak"&gt;Gold nanoparticle (AuNP) is a material commonly used in colorimetric detection for biological sensors due to its low production cost, simplicity, and ease use. AuNP is known to generate different colors depending on the particle aggregation level. In the last two decades, changes in AuNP aggregation status have become the basis for developing a sensor to detect analytes in the sample. The solution color changes could be observed without sophisticated equipment, allowing ,more straightforward interpretation of the detection result. This review focuses on developing AuNP aggregation-based colorimetric tests for detecting various biological analytes. It discusses multiple mechanisms, strategies, functionalization, the latest research, and perspectives of AuNP use in colorimetric detection, which could be considered for future biosensor development. The concept of colloidal gold nanoparticle aggregation and stabilization is emphasized in this review. &lt;/p&gt;

Color change kinetics of lac dye as influenced by some food spoilage metabolites: validation for spoilage monitoring of strawberries

Purpose The purpose of this paper was to study the color change kinetics of lac dye in response to aldehydes, carbon dioxide and other food spoilage metabolites for its potential application in intelligent food packaging. Design/methodology/approach UV–Vis spectroscopy was used to study the color change of dye solution. Ratio of absorbance of dye solution at 528 nm (peak of ionized form) to absorbance at 488 nm (peak of unionized form) was used to study the color change. Color change kinetics was studied in terms of change in absorbance ratio (A528/A488) with time using zero and first-order reaction kinetics. Lac dye-based indicator was prepared to validate the result of study for monitoring quality of strawberries. Findings Lac dye was orange-red in acidic medium and purple in alkaline medium. Color change of dye in response to benzaldehyde followed zero-order reaction kinetics, whereas for carbon dioxide first-order model was found best. No color change of dye solution was observed for alcohols, ketones and sulfur compounds. In the validation part, the color of the indicator label changed from purple to orange when the strawberries spoiled. Originality/value The study expands application area for lac dye as sensing reagent in intelligent food packaging for spoilage or ripeness detection of fruits and vegetables.

Heterocyclic boronates as colorimetric and chemical sensors for dialkyltin derivatives

The relevance of recognition for diorganotin (IV) species has been increased due to biological and environmental issues. The development of molecules able to carry out the recognition process of diorganotin (IV) compounds by simple analytical techniques is an interesting research topic. This paper describes the synthesis of three heterocyclic boronates obtained by the reaction of one equivalent of 5-formyl-2-furanboronic acid with two equivalents of 2-aminophenol (1), 4‑hydroxy-3-aminobenzoic acid (2) or 4-nitro-2-aminophenol (3). Reactions resulted in a π-conjugated systems by the formation of two new six membered fused heterocycles since the furan ring opening, as corroborated by single X-ray diffraction analysis for compound 1. Compounds 1–3 are green-colored solids with melting points higher than 300 °C. A solvatochromic effect was observed having the absorption band maxima values between 525 and 600 nm. The presence of donor atoms (N, O) in the boronates allow the use as chemical sensors for dialkyltin derivatives (Me2SnO, Bu2SnO, Me2SnCl2, Bu2SnCl2) by UV–Vis and fluorescence techniques. The recognition process for dialkyltin derivates was detected by color changes in solution and even because the presence of a new absorption band in UV–Vis spectra which is shifted to 600 and 621 nm for compounds 1 and 2, respectively. Boronate 2 showed lower Limit Of Detection values (LOD) of 237 nM for Me2SnCl2 and 234 nM for Bu2SnCl2. Less affinity was noticed for trialkyl derivates ((CH3)3SnCl and (CH3)3SnOH).

Potency of entomopathogen Beauveria bassiana fungus as biofertilizer and biostimulant to increase the plant growth of Cayenne pepper (Capsicum frutescens L.)

This research aimed to determine the Beauveria bassiana entomopathogen fungus as a biofertilizer and biostimulant. The research was conducted at the Biological Control laboratory and Wire House, Universitas Andalas. The potency of B. bassiana produced the IAA hormone was carried out by a This was qualitative research by observing a pink color change in the Salkowsky solution while the potency of B. bassiana to dissolve phosphate by using Pikovskaya medium. The test results on Pikovskaya media showed that all tested isolates had the potential to dissolve phosphate at 7, 10, and 14 days. The largest clear zone area was in the 14 days, found in Bb WS isolates (5.42 mm) followed by TD312 isolates (5.28mm). To test of plant growth in the laboratory was carried out by testing the germination of seeds by blotter test and test on paper. The design used was a non-factorial Completely Randomized. The results showed that the highest percentage of germination was found in TD312 and BbWS isolates. The potency of B. bassiana isolates as growth promoters can be seen from an increase in plant height and the number of chili leaves. All of the results indicated that entomopathogen fungus can be applied as biological fertilizers and biostimulants on cayenne pepper plants.

Metal ion responsive bifunctional bis(indolyl)methane derivative: Excitation-triggered alteration in the sensing behavior

Bisindolyl based chromogenic probe with a bispicolyl binding site has been designed, that can form nanoscopic aggregates in water medium. The compound showed selective chromogenic response towards Cu2+ and Hg2+, solution color changes from red to light brown immediately as a result. Interestingly, we can specifically excite either monomer or aggregate species by choosing a suitable excitation channel. The compound showed turn-off response selectively upon addition of Hg2+ when excite at monomer excitation channel (λex = 390 nm). On the contrary, fluorescence quenching was observed with both Cu2+ and Hg2+ ions when excited through the aggregate channel (λex = 470 nm). Not only selectivity, but the sensitivity of the compound towards target metal ions depends on the excitation wavelength. Further, the detection of metal ions, such as Cu2+ and Hg2+ is performed in the biological matrices, such as diluted blood serum and plasma samples, etc. Finally, bioimaging of Hg2+ is achieved both in bacterial (E. Coli) and mammalian (HEK293T) cells.

A new benzothiazole azo dye colorimetric chemosensor for detecting Pb2+ ion

In this work, a new benzothiazole azo dye sensor (BTS) was synthesized, and its cation binding affinity was studied using the colorimetric method, UV–vis, and 1H NMR spectral data. The results revealed that the sensor BTS exhibits a remarkable tendency for Pb2+ ion to perform spontaneous visual color change from blue (BTS) to pink (BTS + Pb2+), without any color change in the aqueous solutions of other cations such as Hg2+, Cu2+, Al3+, Ni2+, Cd2+, Ag+, Ba2+, K+, Co2+, Mg2+, Na+, Ca2+, Fe2+, and Fe3+ ions. The observed selectivity could be due to the formation of the complex (BTS + Pb2+), which led to a blue shift from 586 nm (BTS) to 514 nm (BTS + Pb2+) in the UV spectrum. The job’s plot provided the stoichiometry ratio of the complex (BTS + Pb2+) to be 1:1. The limit of detection (LOD) of BTS for Pb2+ ion sensing was obtained at 0.67 µM. Additionally, the binding constant for BTS toward Pb 2+ ion was studied using the Benesi-Hildebrand equation. As a result of the BTS test paper strips investigations, it was found that the synthesized sensor BTS could be used as a rapid colorimetric chemosensor for the detection of the Pb2+ ions in the distilled, tap, and sea waters.

Visual detection and highly sensitive quantification of antibiotic meropenem in pharmaceutical and human plasma samples using gold nanoparticles

ABSTRACT Meropenem is a broad-spectrum β-lactam antibiotic effective against a wide variety of gram-positive and gram-negative organisms, and has been extensively used in the intensive care unit (ICU) for severe infections caused by susceptible microorganisms that are resistant to other available drugs. A novel visual detection and highly sensitive method for meropenem quantification has been developed for the first time, based on the aggregation of citrate-capped gold nano particles (AuNPs) induced by the interaction with meropenem, leading to the change in surface plasmon resonance (SPR) properties of AuNPs. By naked eyes, one can detect meropenem trace by the visual change of gold solution color from red to blue, corresponding to the shift of absorbance maximum in the UV-Vis spectrum from 520 nm to 660 nm. Quantification of meropenem is possible through a linear relationship between the optical absorption ratio A660/A520 and the logarithm of meropenem concentrations. The present method has high recovery (97.6–101.5%), high precision (RSD<4.5%), and selectivity over other possible interferences such as glucose, sucrose, lactose, and sodium carbonate. This method has been successfully applied to determine meropenem in several pharmaceutical samples with a very low limit of detection (LOD) of 0.06 mg/L. Cross-checks with HPLC-DAD method show a good agreement between the two methods. For blood analysis, in combination with liquid-liquid extraction, the developed method presents high specificity, low LOD of 0.64 mg/L, and applicability to analysis of plasma samples taken from patients treated with meropenem under intensive care.

A chemodosimeter with high selectivity for ratiometric detection of mercury ions in buffer solution

A new isophorone-based chemodosimeter was designed and synthesized for a rapid, ratiometric and selective detection of Hg2+ ions in buffer solution. Hg2+ ions promoted the deprotection of the dithioacetal group of probe SWJT-11, leading to a red shift from 574 nm to 636 nm in its fluorescence spectrum, which also accompanied the change of solution color from yellow to pale yellow. The probe toward Hg2+ ions presented a good linear relationship in the 0–10.0 μM concentration range, with the LOD of 0.2 μM. In addition, the probe has been successfully used to detect Hg2+ ions in test strips and Chinese medicinal materials.

Green Synthesis of Silver Nanoparticles Using Nigella sativa Callus and Cellular Suspension Cultures with Different pH Values

The current study included an extensive protocol for the first time globally. This protocol was concerned with the green synthesis of silver nanoparticles (AgNPs) from Nigella sativa callus and cellular suspended cultures. The results confirmed the success of the process of green synthesis of AgNPs from Nigella sativa callus by the color change in the reaction solution from colorless to brown and reddish-brown as a result of the reduction of Ag ions in the extract after addition of AgNO3 solution (1:1 v/v). UV-Vis spectroscopy was used to initially prove the existence of AgNPs, which showed an absorption peak ranging between (420-440 nm) caused by the phenomenon of Surface Plasmon Resonance (SPR) of AgNPs. (SEM) showed nanoparticle objects ranging from (18.341 - 40.932) nm for standard extracts and (17.261 - 29.13) nm for suspended cultures extracts. (EDX) proved the success of producing AgNPs in different proportions depending on the type of tissue cultures used and the difference in the pH value of the extracts (6, 9, 12), as the highest % of AgNPs production reached 4.46% in suspended cultures extracts from pH 12, followed by callus extracts, which reached 4.12% at pH 12. biologically prepared AgNPs proved their effectiveness in inhibiting the growth of Gram+ and Gram- bacteria, as the inhibition zone ranged (19– 35 mm) depending on the type of extract and the degree of acidity (pH) applied to the extract.

A combinatorial effect of TICT and AIE on bisulfate detection using a pyrenylated charge-transfer luminogen

A donor-acceptor based fluorogenic probe, 4-(2-pyren-1-yl-vinyl) pyridine, 1 is synthesized that can form pH-sensitive nanoscopic aggregates in the aqueous medium. The fluorescence response of 1 in apolar solvents originates from LE state, while in polar solvents, it is dominated by TICT state. On the contrary, emissions from both TICT and AIE states is observed in water. A change in solution color from pale yellow to deep yellow is observed specifically upon the addition of HSO4¯ ions with a concomitant change in fluorescence color. The mechanistic investigations indicate the hydrogen bonding interaction of HSO4¯ ions with the pyridine nitrogen end, which can effectively alter the extent of charge transfer. Moreover, the interaction with HSO4¯, leading to larger aggregate formation. Further, the current system is involved in the analysis of water samples and screening care-kit products. Finally, the dye-coated paper strips are designed for cost-effective, on-location detection of HSO4¯.

Using the Colorimetric Oscillating Reaction for Simple Quantification of Ethanol in Commercial Liquors in an Undergraduate Chemistry Laboratory

Undergraduate-level laboratory experiments that integrate multidisciplinary chemistry concepts into a single activity are very appealing and thought-provoking for chemistry students. Here, we use the oscillating chemical reaction to introduce students to the analytical detection concept. The Belousov–Zhabotinsky reaction is employed as a simple but efficient system to determine the content of ethanol in liquor samples. This experiment is based on the periodic solution color change from red to blue under the perturbation of ethanol, which can be simply followed by using a smartphone in video mode. Students can establish the calibration curve by plotting the average times required for the change in the solution color oscillating pattern from blue to red to blue, defined as the oscillation period, against ethanol concentrations. Using this strategy, students can quantify the ethanol concentrations in alcoholic samples without the need for sophisticated instruments or skilled operators. Also, this designed experiment allows all students to conduct the activity within a traditional laboratory block of time.

N-Doped Carbon/CeO2 Composite as a Biomimetic Catalyst for Antibacterial Application.

Exploring new and high efficiency mimic enzymes is a vital and novel strategy for antibacterial application. Haloperoxidase-like enzymes have attracted wide attention thanks to their amazing catalytic property for hypohalous acid generation from hydrogen peroxide and halides. However, few materials have displayed halogenating catalytic performance until now. Herein, we synthesized N-doped C/CeO2 (N-C/CeO2) composite materials by a combination of the liquid and solid-state method. N-C/CeO2 can possess haloperoxidase-like catalytic activity by catalyzing the bromination of organic signaling compounds (phenol red) with H2O2 at a wide range of temperatures (20 °C to 55 °C), with a solution color changing from yellow to blue. Meanwhile, it exhibits high catalytic stability/recyclability in the catalytic reaction. The synthesized N-C/CeO2 composite can effectively catalyze the oxidation of Br- with H2O2 to produce HBrO without the presence of phenol red. The produced HBrO can resist typical marine bacteria like Pseudomonas aeruginosa. This study provides an efficient biomimetic haloperoxidase and a novel sustainable method for antibacterial application.

Red emitting nitrogen-doped carbon dots for fluorescence and colorimetric dual-mode detection of Cu2+ and biological sensing

Herein, red-emitting nitrogen-doped carbon dots (N-CDs) were prepared using p-phenylenediamine and polyethylene glycol 20,000 as precursors. The N-CDs are spherical and uniformly distributed with average particle sizes of 2.36 nm. The N-CDs display excitation-independent fluorescence behavior with the optimal excitation and the maximum emission wavelengths centered at 487 and 628 nm, respectively. Results indicated that as prepared CDs can provide a rapid and highly selective recognition of Cu2+ with the range of 45–70 µM and a detection (LOD) limit of 45.87 µM. A clear color change of the N-CDs solution (orange-red to black) can also be visualized by adding Cu2+. Moreover, a smartphone-based platform for the detection of Cu2+ was developed to detect Cu2+ in real time by analyzing RGB values, giving a linear range of 20–140 µM. and a LOD limit of 35.83 µM. In addition, it was applied for the detection of Cu2+ in tap water, the recoveries were 86.18 %-104.95 %, and the relative standard deviations were 1.64 %-2.43 %. The N-CDs can be used to detect Cu2+ in vitro and in vivo.

Monitoring freshness of chicken using intelligent pH indicator packaging film composed of polyvinyl alcohol/guar gum integrated with Ipomoea coccinea extract

With enormous amounts of food being wasted at every level of consumption, the future of food security is in jeopardy. The confusion aroused due to “best before” or “use by” can be eliminated by intelligent colorimetric indicators which communicate the quality of food. pH indicators have gained their attention because they are simple and visually informative. Using natural pigments to fabricate pH indicators can help reducing use of carcinogenic chemicals in packaging. In this work, anthocyanins extracted from a novel flower source named Ipomoea coccinea (ICE) were added to polyvinyl alcohol (PVA) and guar gum (GG) matrix in varying amounts and was applied as antioxidant and intelligent pH indicator film to monitor the freshness of chicken fillets and to visually communicate the quality of chicken. The pH indicator was characterized for halochromism, antioxidant activity, thermogravimetry, water solubility, water contact angle, surface morphology, colorimetry and X-ray diffractograms. The color change of the extract was observed from orange to red to yellow. Film with highest amount of anthocyanin extract has increased thickness of 150.5 ± 17.86a (μm), decreased water vapor transmission rate of 4.95 ± 0.29a (mg day−1 cm−2) and has a crystallinity of 52.35%. Anthocyanins started to degrade at 65 °C according to thermogravimetric analysis. The film with 20% ICE showed an excellent color change in pH solutions and the highest antioxidant activity of ∼91%. The food study results suggested that the developed film has the potential to be employed as an active and intelligent visual indicator in poultry packaging.

Rationally Constructed De Novo Fluorescent Nanosensor for Nitric Oxide Detection and Imaging in Living Cells and Inflammatory Mice Models.

For the early diagnosis and effective evaluation of treatment effects of inflammation, a de novo bioanalytical method is urgently needed to monitor the metabolite nitric oxide (NO) associated with inflammatory diseases. However, developing a reliable detection method with excellent water solubility, biocompatibility, long retention time, and blood circulation is still challenging. In this work, we reported for the first time a de novo host-guest self-assembled nanosensor CTA for the quantitative detection and visualization of NO levels in inflammatory models. CTA mainly consists of two parts: (i) an adamantyl-labeled guest small-molecule RN-adH containing a classical response moiety o-phenylenediamine for a chemical-specific response toward NO and fluorophore rhodamine B with excellent optical properties as an internal reference for self-calibration and (ii) a remarkable water-soluble and biocompatible supramolecular β-cyclodextrin polymer (Poly-β-CD) host. In the presence of NO, the o-phenylenediamine unit was reacted with NO at a low pH value of ∼7.0, accompanied by changes in the intensity of the two emission peaks corrected for each other and the change in fluorescence color of the CTA solution from fuchsia to pink. Furthermore, CTA was an effective tool for NO detection with a fast response time (∼60 s), high selectivity, and sensitivity (LOD: 22.3 nM). Impressively, the CTA nanosensor has successfully achieved the targeted imaging of NO in living inflammatory RAW 264.7 cells and mice models with satisfactory results, which can provide a powerful molecular tool for the visualization and assessment of the occurrence and development of NO-related inflammatory diseases in complex biosystems.

Characterization of Firmiana colorata (Roxb.) leaf extract and its silver nanoparticles reveal their antioxidative, anti-microbial, and anti-inflammatory properties.

Nanotechnology is the integrative science in the field of physics, chemistry and biology. For the synthesis of silver nanoparticles, a simple approach was applied using Firmiana colorata(Roxb.) aqueous leaf extract. During the synthesis of this silver nanoparticle, the solution color changes from green to deep brown due to the reduction of silver. The phytocompounds present in the Firmiana colorata(Roxb.) leaf extract acts as a reducing as well as a capping agent. Identifying the presence of bioactive compounds responsible for the reduction of silver was extensively characterized by UV-Vis spectrophotometer, FTIR, SEM, and EDX. Moreover, to know the efficacy of the silver nanoparticles (AgNps) antioxidant and antimicrobial studies were evaluated against the human pathogenic bacteria. Furthermore, GC-MS analysis of the leaf extract of Firmiana colorata has been done followed by the in-silico molecular docking against the Anti-inflammatory and oxidative protein. Here within this study, a comparative evaluation was done among the Firmiana colorata(Roxb.) leaf extract and the synthesized silver nanoparticles. Results indicate that ethnomedicinally lesser known Firmiana colorata(Roxb.) and AgNps have the potency to act as anti-inflammatory, antioxidative, and antimicrobial agents.