Blue Research Articles

Cu–N–C single-atom nanozyme as an ultrasensitive sensing platform for α-glucosidase detection

Alpha-glucosidase (α-Glu) is a hydrolase that promotes the rise of glucose in the blood during the digestion process, and it plays a crucial role in regulating glucose levels within a normal range. Herein, we developed an ultrasensitive colorimetric platform by preparing a Cu–N–C single-atom nanozyme (Cu–N–C SAzyme) with a potent oxidase-like effect on accurately detection of α-Glu and efficient screening of its potential inhibitors. This artificial nanoenzyme was able to catalyze the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to blue oxide (oxTMB) without the assistance of H2O2. In addition, with the participation of α-Glu, l-ascorbic acid-2-O-α-d-glucopyranose (AAG) can be catalyzed to produce ascorbic acid (AA), which significantly reduces the oxidation, resulting in a noticeable fading of the blue color. Therefore, we designed a straightforward colorimetric test for α-Glu activity, achieving detection limits as low as 0.09 U/L and a linear response from 0.25 to 8 U/L. Most importantly, this platform has been effectively applied to measure α-Glu in real samples.

Development of point-of-need colourimetric, isothermal diagnostic assays for specific detection of Bacillus subtilis using shikimate dehydrogenase gene.

The largest obstacle in the promotion of biopesticides is the existence of counterfeit products available in the market. Identification and quantification of antagonistic organisms in biopesticide products are the key to the reduction of spurious microbial pesticides. In this study, we have developed a simple, sensitive, isothermal-based colourimetric assay for specific detection of Bacillus subtilis from the biopesticide formulations and soil samples. A region specific to B. subtilis which codes for shikimate dehydrogenase was identified through in silico analysis. We employed conventional PCR, loop-mediated isothermal amplification (LAMP), recombinase polymerase amplification (RPA), and qPCR for specific detection of B. subtilis in soil samples and biopesticide formulations. Specificity tests showed that the PCR primers amplified an amplicon of 521bp in four strains of B. subtilis only, and no amplification was found in negative control samples. Similarly, the LAMP assay showed sky blue colour in all four strains of B. subtilis and violet colour in negative control samples. Whereas in the RPA assay, upon the addition of SYBR Green dye, a bright green colour was seen in B. subtilis strains, while a brick-red colour was observed in negative control samples by visualizing under a UV transilluminator. The qPCR assay showed specific amplifications with a Ct value of 12 for B. subtilis strains and no amplification in negative control samples. In the sensitivity test, PCR could amplify DNA of B. subtilis up to 500pg/µL. DNA concentration as low as 10pg/µL was enough to show the colour change in the LAMP as well as the RPA assays, whereas the qPCR assay showed sensitivity till 100pg/µL. All four diagnostic assays developed in the study have been validated in soil samples and B. subtilis-based biopesticides. Compared to conventional PCR, the qPCR assay has the advantage of quantification and visualizing the result in real-time, whereas LAMP and RPA assays have the benefits of being colourimetric and less time-consuming. The other advantages are that the results can be visualized with the naked eye, and these assays do not require a costly thermal cycler and gel documentation system. Hence, LAMP and RPA assays are highly suitable for developing point-of-need diagnostic kits and, in turn, help regulators assess the quality of biopesticides in the market.

Paper-based colorimetric sensor using a single-atom nanozyme for the ultrasensitive detection of Cr(VI) in short-necked clams.

Single-atom nanozymes (SAzymes) as a class of highly active nanozymes with the advantages of high atom utilization, high catalytic activity and stability have attracted great attention. In this work, Fe-N-C SAzymes with exceptional oxidase (OXD)-like activity were achieved utilizing polyvinylpyrrolidone (PVP) as a template. The Fe-N-C SAzymes with remarkable OXD-like activity could oxidize TMB to blue oxTMB, but 8-hydroxyquinoline (8-HQ) as a metal chelator is capable of discoloring oxTMB. Thus, the addition of 8-HQ decolorized the solution. However, upon the introduction of Cr(VI) ions, 8-HQ preferentially chelated with the Cr(VI) ions, reversing the inhibition of the color reaction and restoring the blue color. Based on this phenomenon, we constructed a novel paper-based analytical device (PAD) that exhibited a linear range of 5-1000 μM and an LOD of 1.2 μM. Importantly, the PAD used in this study shows the merits of simplicity, low preparation costs, and rapid reaction times. When combined with smartphone RGB analysis, it enables the simultaneous analysis of eight different Cr(VI) concentrations without the need for large-scale instrumentation. Moreover, the proposed PAD displays high selectivity, accuracy and utility in testing actual short-necked clam samples. This work not only provides a simple and cost-effective method to detect Cr(VI) but also makes a contribution to rapid food testing.

A Machine Learning Approach for Efficiently Predicting Polymer Aging from UV-Vis Spectra.

This research has introduced an innovative approach that proficiently forecasts the alterations in ultraviolet-visible spectroscopy (UV-Vis) of polymer solutions during the aging effect. This method combines readily accessible feature descriptors with classical machine learning (ML) algorithms. Traditional spectral measurements, while precise in analyzing physical properties, are limited by their cost and efficiency. Therefore, this paper introduces a method that utilizes wavelength and the blue (B), green (G), and red (R) color values of the solutions as input features. We employed seven different ML models to train on these features with 10-fold cross-validation to ensure the reliability and generalizability of our results. After comparative analysis, all of the models performed excellently. Among them, the ExtraTree model demonstrated particularly high precision and excellent predictive ability on the testing set, with a Pearson correlation coefficient (r) of 0.9859 and a mean absolute error (MAE) of 0.0457. This study offers a practical solution for the rapid and cost-effective evaluation of polymer solutions' aging effect.

Coordination of movements: identification of age-related dynamics of its development in karate boys 7-11 years old

The purpose of the study is to identify the age-related dynamics of the manifestation of coordination among junior and pre-pubescent karate boys (7-11 years old) training in the karate section at the initial stage of preparation. Materials and methods. The study involved 65 children of younger and prepubertal age. They underwent testing of coordination abilities in order to determine the level of development and identify the features of their manifestation in accordance with age and skill level. The selected sample was divided into five ages 7, 8, 9, 10 11 years old, with 13 children in each group. The children and their parents were aware of all the features of the study and gave their consent to participate in the experiment. The technical level of the children corresponded to the students of the 10th, 9th, 8th grades of Kyu (orange, orange with a blue stripe and blue belt color). To solve the tasks, the following research methods were used: study and analysis of scientific and methodological literature, pedagogical observation, timing of educational tasks, testing of coordination abilities, pedagogical ascertaining experiment, methods of mathematical statistics. Results. One-way analysis of variance (ANOVA) showed a significant effect of the age factor on the level of indicators of coordination abilities for: differentiation of spatial-dynamic parameters of movements (F = 95.712; p = 0.000); reorganization of motor actions (F = 111.410; p = 0.000); differentiation of spatial-temporal parameters (F = 50.863; p = 0.000); coordination of hand movements (F = 96.764; p = 0.000); maintaining postural stability (F = 38.274; p = 0.000); maintaining vestibular stability (F = 61.291; p = 0.000). Conclusions. Based on the results of studies indicators of various manifestations of coordination, statistically significant age differences are observed between groups of boys aged 7 to 10 years (p < 0.05). At 10-11 years old, there are no significant statistically significant differences in all indicators (p > 0.05), except for dynamic balance (p < 0.05).

Rapid fabrication of polyoxometalate-enhanced photo responsive films from ethyl cellulose (EC) and polyvinylpyrrolidone (PVP)

Ethyl cellulose (EC), polyvinylpyrrolidone (PVP), and phosphomolybdic acid (PMoA) were the components of a new photochromic hybrid film composed of heteropoly acids (abbreviated EC-PVP/PMoA), created by solvent evaporation. The EC-PVP/PMoA mechanism, visible light photochromic behaviors, and microstructure were closely studied by transmission electron microscopy (TEM), atomic force microscopy (AFM), ultraviolet-visible (UV–visible) spectroscopy, X-ray photo electronics (XPS), and Fourier transmission infrared spectroscopy (FTIR). FTIR spectra show that neither the core structures of EC, PVP, nor the Keggin structure of PMoA in the EC-PVP/PMoA composite hybrid film were damaged during fabrication. In the presence of oxygen, the yellowish transparent hybrid film exhibited reversible photochromism and significant photochromic reactivity, becoming blue in the presence of visible light. Upon heating the film at 90 °C for 1 h its photoresponsive properties were enhanced, making the blue color more vibrant and stable due to polyethylene glycol (PEG). The XPS spectra demonstrated a proton transfer procedure during the photochromic process, and the presence of Mo+5 species indicated a photoreduction interaction between the PMoA particles and the EC-PVP matrix. To the best of our knowledge, this is the first EC-PVP combined hybrid film with POMs with promising prospects for solar UV detection and smart glass windows applications.

A vacuolar protein MaSCPL1 mediates anthocyanin acylation modifications in blue-flowered grape hyacinth

The grape hyacinth is renowned for its profuse blue flowers, which confer substantial scientific and ornamental significance as well as considerable potential for industrial applications. The serine carboxypeptidase-like acyltransferases (SCPL-ATs) family is crucial for the blue flower coloration. To elucidate SCPL-ATs involved in anthocyanin modification in grape hyacinth, we performed a transcriptomic analysis of grape hyacinth SCPL-ATs. Through gene expression profiling, we identified a promising candidate gene, MaSCPL1, whose expression patterns corresponded with variations in anthocyanin content throughout petal coloration. Subsequently, the functional role of the MaSCPL1 gene was validated using the native petal regeneration system, and the silencing of MaSCPL1 led to a decreased total anthocyanin content and Dp3MG content in grape hyacinth petals. Furthermore, we employed yeast one-hybrid (Y1H), electrophoretic mobility shift assay (EMSA), and dual-luciferase assays to explore the regulatory interactions between the anthocyanin biosynthesis transcription factor MaMybA and the MaSCPL1 promoter. Our findings indicate that MaMybA can bind to the MaSCPL1 promoter and significantly activate its expression. Furthermore, the MaMybA-RNAi resulted in a substantial multifold reduction in the expression of MaSCPL1, implying that the regulation of MaSCPL1 expression is mediated by MaMybA. This study revealed the MaSCPL1 gene has been associated with anthocyanin acylated modification in grape hyacinth and elucidated the important role of the MaMybA-MaSCPL1 module in colouration grape hyacinth.

Influence of Different Cow Manure Application Rates on the Growth, Yield and Indigo Blue Color of Indigofera suffruticosa Mill

Background: Indigo is a key ingredient in the natural dyeing of fabrics. However, the conventional use of chemical fertilizers in indigo cultivation has led to an increase in production costs and soil degradation. Low-fertility soils further compromise the growth and yield of indigo plants. To address these challenges, employing manure is recognized as a sustainable approach for indigo cultivation. The use of manure enhances soil nutrient levels, improves soil structure and mitigates production costs. In this study, our objectives were to compare different rates of cow manure in relation to indigo growth, yield and the effect of cow manure rate on the value of indigo blue color. Methods: The experiments were carried out at the Plant Science Field from June to October 2022. Employing a randomized complete block design (RCBD), the study featured four treatments with four replications each. The treatments included: Treatment 1: no fertilizer (control); Treatment 2: cow manure at a rate of 3,125 kg/ha; Treatment 3: cow manure at a rate of 6,250 kg/ha; and Treatment 4: cow manure at a rate of 9,375 kg/ha. Data collection included plant height, canopy width, number of branches, plant weight, indigo blue weight and indigo blue color value. The CIE color system (Commission International de l’Éclairage) determined the color value. Result: The application of cow manure at a rate of 9,375 kg/ha resulted in the highest plant height and canopy width, with the corresponding number of branches of 150.73 cm, 46.45 cm and 31.73 cm, respectively. As compared to the other treatments, these values were statistically different. The color that was associated with the indigo finished product was dark blue and the yield; plant weight and indigo blue weight were recorded as 15,663.44 kg/ha and 2,540.44 kg/ha, respectively. The color value of indigo blue showed that the L* values of 24.94, a* -9.32, b* -2.44 and C* 9.63 were not significant but h* 194.66 was statistically significant.

A Dy(III) Coordination Polymer Material as a Dual-Functional Fluorescent Sensor for the Selective Detection of Inorganic Pollutants.

A Dy(III) coordination polymer (CP), [Dy(spasds)(H2O)2]n (1) (Na2Hspasds = 5-(4-sulfophenylazo)salicylic disodium salt), has been synthesized using a hydrothermal method and characterized. 1 features a 2D layered structure, where the spasda3- anions act as pentadentate ligands, adopting carboxylate, sulfonate and phenolate groups to bridge with four Dy centers in η3-μ1: μ2, η2-μ1: μ1, and monodentate coordination modes, respectively. It possesses a unique (4,4)-connected net with a Schläfli symbol of {44·62}{4}2. The luminescence study revealed that 1 exhibited a broad fluorescent emission band at 392 nm. Moreover, the visual blue color has been confirmed by the CIE plot. 1 can serve as a dual-functional luminescent sensor toward Fe3+ and MnO4- through the luminescence quenching effect, with limits of detection (LODs) of 9.30 × 10-7 and 1.19 × 10-6 M, respectively. The LODs are relatively low in comparison with those of the reported CP-based sensors for Fe3+ and MnO4-. In addition, 1 also has high selectivity and remarkable anti-interference ability, as well as good recyclability for at least five cycles. Furthermore, the potential application of the sensor for the detection of Fe3+ and MnO4- was studied through simulated wastewater samples with different concentrations. The possible sensing mechanisms were investigated using Ultraviolet-Visible (UV-Vis) absorption spectroscopy and density functional theory (DFT) calculations. The results revealed that the luminescence turn-off effects toward Fe3+ and MnO4- were caused by competitive absorption and photoinduced electron transfer (PET), and competitive absorption and inner filter effect (IFE), respectively.

Blue in Food and Beverages—A Review of Socio-Cultural, Economic, and Environmental Implications

The presented review concerns the cross-disciplinary approaches to the subject of blue food and blue colourants, the socio-cultural aspects of blue food and beverage consumption, human health effects, environmental impact, and economic aspects. Blue colour in relation to food is not only about improving visual appeal, to which the addition of food colouring is usually limited when the food is coloured in some way that does not encourage eating. It is also the rich and complex sociological side related to food, that is, not only the food itself but also the background, dishware, and light, depending on whether we want to encourage—to increase consumption—or discourage—to, for example, reduce the amount of food eaten for dietary purposes. The negative side of consuming and disposing of synthetic dyes and the health-promoting aspects of natural dyes are also mentioned, with the economic and environmental aspects of sourcing natural dyes being discussed. The food industry uses blue dyes not only for consumption, but also for food quality control, taking advantage of the pH-dependent colour change properties of the compound.

Towards adjustable tri-response thermochromic fluorescent materials for information encryption via SO2CF3 terminal bis-tolane luminescent liquid crystals

A series of novel bis-tolane luminescence liquid crystals (LLCs) with SO2CF3 as terminal were first time achieved. These SO2CF3-based LLCs act as thermally responsive emission sources combined with a series of thermosensitive long-chain carboxylic acids with self-crystallization properties to obtain adjustable tri-response thermochromic fluorescent materials (TFMs). Notably, TFMs of (CH3)2N-2F-SO2CF3 exhibit excellent temperature sensitivity and tri-response thermochromic fluorescent character, which display outstanding thermochromic properties from 45 °C to 165 °C. These TFMs displayed an intuitively evident orange under ultraviolet (UV) irradiation then changed to orange-yellow color after adding long-chain carboxylic acids. Notably, it changed to yellow-green when heated to the long-chain carboxylic acids melting point of these phase change materials, further emitting a blue color at the mesophases transition when increasing temperature at 165 °C of (CH3)2N-2F-SO2CF3. Interestingly, the various thermochromic abilities and stimuli-responsive fluorescence of these TFMs could be regulated by substituents of LLCs and long-chain carboxylic acids. Therefore, such tri-response and high-contrasted thermochromic fluorescent character of TFMs are different from previous reports which promise candidates for information encryption.

Green synthesis and antimicrobial activity of copper nanoparticles (Cu-NPS) by Piper longum fruit extract

Many applications of green synthesis in the field of environment and biomedicine aiming at decreasing the use of toxic chemicals through utilizing of plants which are safe. In this study, at 0.1 M concentration of copper sulfate (CuSO4.5H2O), CuNPs were prepared and identified by changing the blue color into green color (ethanolic extract) and from blue color to black color (water extract) and the spectrophotometric detection of ultraviolet and infrared spectra. X-Ray diffraction (XRD) pattern was utilized to confirm the crystal structure of CuNPs. The morphology and size of the CuNPs was measured by a high-resolution transmission electron microscope (HR-TEM). Energy dispersive X-ray (EDX) was used for identification of the elemental composition of CuNPs involving copper and oxygen. Field emission scanning electron microscopy (FESEM) was utilized to confirm the shape of prepared copper nanoparticles. In vitro antibacterial activity was tested using two methods including desk diffusion assay considering zones of inhibition and minimum inhibitory concentration (MIC) against six types of certain bacterial types (Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Staphylococcus aureus, Streptococcus pneumoniae and Enterococcus faecalis). The results showed potent inhibitory activity of copper nanoparticles (CuNPs) and water extract (Ext. 2) against all bacterial strains. KEY WORDS: Copper nanoparticles, Piper Longum, Extract, Synthesis, Antibacterial Bull. Chem. Soc. Ethiop. 2024, 38(6), 1653-1666. DOI: https://dx.doi.org/10.4314/bcse.v38i6.12

Pharmacognostical evaluation and description of the leaf and root bark of Citropsis articulata Swingle & Kellerman

BackgroundCitropsis articulata Swingle & Kellerman (Family Rutaceae) is a renowned African traditional medicinal plant for the management of erectile dysfunction. The root bark is more commonly used than the leaves. Little has been done to evaluate the pharmacognostical parameters of both parts. PurposeThe aim of this study was to determine the pharmacognostical parameters of C. articulata leaves and root bark. MethodsThe plant parts were collected, washed, dried, and extracted by decoction and soxhlation. The World Health Organisation quality control methods for herbal materials were generally followed for the pharmacognostical evaluation of the root bark and leaf. This involved macroscopic and microscopic analysis, physicochemical analysis, hemolytic activity, and phytochemical analysis. ResultsMacroscopically, the distillate of the root bark showed a fluorescent blue colour under ultra violet light of wavelength 254 nm. Microscopic examination revealed the presence of cellulose, lignified, suberized and cuticular cell walls. Numerous aleurone grains were noted in the root bark. Phytochemical analysis showed the presence of reducing sugars, free amino acids, L-arginine, coumarin, glycosides, phenols, phytosterols, saponins, steroids, tannins, terpenoids, alkaloids and flavonoids. Thin layer and high performance liquid fingerprints were also developed. The C. articulata root bark decoction and Soxhlet extracts contained 12.35 ± 0.05, and 110.00 ± 0.03 while the leaf decoction and Soxhlet extracts contained 4.97 ± 0.03 and 39.65 ± 0.00 mg/g diosgenin equivalent saponins respectively. The L-arginine content for the dried root bark decoction and Soxhlet was 2681 ± 7.29, 1660 ± 2.99 µg/g, while that for the leaf decoction and Soxhlet extracts was 135.60 ± 8.28, and 130.20 ± 2.83 µg/g respectively. ConclusionThis study distinguished the root bark and leaf of Citropsis articulata and offered vital information for the quality control and standardization of the plant materials.

Synthesis and characterization of fluorescent carbon dots obtained from citrus x sinensis by an eco-friendly method

The synthesis and characterization of fluorescent carbon dots (CDs) obtained by an environmentally friendly method through carbonization, fragmentation and centrifugation of orange peel (citrus x sinensis) are reported. By thermogravimetry, 4 degradation regions associated with hemicellulose, lignin and organic matter were found. The SEM micrograph shows a rough surface morphology with flakes and granulation due to the carbonization process. X-ray diffraction (XRD) shows a hexagonal crystalline structure associated with graphitic carbon, which was confirmed by Raman scatterings, Raman spectroscopy that presented two main vibrational bands, D and G, associated with active defects in the graphitic carbon crystalline structure. The Transmission electron microscopy (TEM) micrograph showed CDs of size 33.65 ± 0.68n, and with High-Resolution TEM (HRTEM) an interplanar distance of 0.213 nm in the direction of the crystal planes (100) of graphitic carbon was obtained, which were confirmed by XRD and Raman spectroscopy. X-ray photoelectron spectroscopy revealed the relative atomic composition and identified the strongest photoelectron transitions of carbon, sp2 (286 eV) and sp3 (285 eV), in graphitic carbon. Ultraviolet–visible (UV–Vis) spectroscopy of the CDs obtained from fragmentation graphitic carbon showed a band at 205 nm associated with CC bonds π-π* of CC and n-π*, as well as two bands at 276 and 328 nm associated with bond transitions. The Fourier Transform Infrared (FTIR) spectrum showed bands associated with CHs bonds as well as CC, CN bonds of the CDs. Fluorescence spectroscopy showed three emission bands at 2.43, 2.54 and 2.87 eV. The CDs showed the emission of the characteristic blue colour.

Sr2BiF7: A New Bismuth-Based Host Material for Lanthanide Ions Doping: Synthesis, Downshifting, and Upconversion Luminescence Properties for Multimode Anticounterfeiting.

A new bismuth-based host material, i.e., Sr2BiF7, is explored in this work. Undoped and lanthanide ion-doped Sr2BiF7 nanomaterials are prepared using a simple coprecipitation technique at 120 °C. The undoped nanomaterials exhibit a blue color under 365 nm excitation. The downshifting and upconversion photoluminescent properties of Er and Yb codoped Sr2BiF7 nanomaterials are investigated. The optimum up-conversion luminescence is produced by nanomaterials doped with 5% Yb3+ and 0.2% Er3+. These nanomaterials show blue and magenta colors upon excitation at 365 and 395 nm wavelengths, respectively. Sr2BiF7 material doped with Er3+ shows green emission, while the codoped Er3+, Yb3+ nanomaterials exhibit an orange-red color under 980 nm light. A specific amount of polyvinyl chloride (PVC) is used for producing luminescent ink with these nanoparticles for multimode anticounterfeiting applications. The letters and patterns written with luminescent ink based on Er3+, Yb3+ doped nanomaterials show blue, magenta, and orange-red colors under 365, 395, and 980 nm light, respectively. These results establish that this material can be effectively used as a multimode photoluminescent covert tag to combat counterfeiting.

Spectrum of blue nevus-like lesions, including blue nevus, pigmented epithelioid melanocytoma & animal-type melanoma

Blue nevus-like lesions constitute a category of melanocytic lesions clinically identified by their blue coloration. Histologically, they exhibit two primary features: a dermal location and intense pigmentation. The latest World Health Organization (WHO) classification categorizes blue melanocytic lesions into benign entities (dermal melanocytoses, blue nevus, and deep penetrating nevus), melanocytic tumors with low to intermediate malignant potential (pigmented epithelioid melanocytoma, PEM), and malignant lesions (blue nevus-like melanoma and melanoma arising in blue nevus).Clinically, blue nevi are enduring and stable lesions, displaying a structureless blue pigmentation both clinically and dermatoscopically, with a straightforward histologic diagnosis. Conversely, lesions with recent onset and/or rapid growth are more commonly associated with diagnoses falling within the intermediate part of the spectrum or with melanoma. These lesions often present with a blue color along with additional features such as black blotches, irregular vessels, and irregular pigmented globules. They typically emerge de novo without recognizable precursors, they pose significant challenges for patient management.Melanoma on a blue nevus is an exceedingly rare entity with only a few cases described to date. Histologically, differentiating between lesions with intermediate malignant potential and melanoma is always challenging, necessitating a comprehensive evaluation of all morphologic findings of the lesion.

Colour tunability of Dy3+ & Sm3+ activated yttrium aluminium gallium nanocrystals for display applications

A set of powder samples of Y3AlGa4O12 doped with Dy3+ and Sm3+ with different concentration of Sm3+ ion were prepared via sol-gel synthesis. X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive (EDS), Fourier transform infrared (FTIR) and photoluminescence spectral studies were carried out. All the diffraction peaks matched the cubic lattice Y3AlGa4O12, as given by the XRD. The SEM images revealed aggregated spherical particles ranging from 50 to 130 nm. The EDS analysis confirmed the presence of the initial chemicals in the synthesized samples. FTIR spectrum was used to examine the vibrational modes in the sample. Under a 366 nm excitation wavelength, the emission spectrum showed the peaks at 492 nm (blue), 580 nm (yellow), 673 nm (red), and 760 nm (near-infrared) corresponding to the characteristic transitions 4F9/2 → 6H15/2,13/2,11/2,9/2 of the Dy3+ ion, respectively. In comparison, the peaks at 568 nm, 614 nm, 664 nm, and 711 nm corresponded to the characteristic transitions 4G5/2 → 6H5/2,7/2,9/2,11/2 of the Sm3+ ion. Under near ultraviolet light excitation, the superposition of these blue, yellow and red colours produced excellent white light emission. The intensities of these transitions varied with the concentration of Sm3+ ion and the excitation wavelength. The emission spectrum of Dy3+ overlapped with the excitation spectrum of Sm3+, indicated possible energy transfer from Dy3+ to Sm3+. According to Inokuti-Hirayama's theory of energy transfer, the mechanism of energy transfer was understood to be quadrupole-quadrupole interaction. The CIE chromaticity co-ordinates and correlated colour temperature values showed that these samples were suitable for light-emitting diode applications.

A colorimetric sensor array consisted of CaxMn1-xWO4 with high oxidase-like activity to detect antioxidants

Antioxidant detection is highly significant in practical applications. This study establishes an optical sensor array capable of simultaneous and convenient detection of multiple antioxidants in real samples. CaxMn1-xWO4 (CMW) synthesized via hydrothermal method with abundant surface oxygen vacancies and high internal electron transfer efficiency exhibits strong oxidase-like activity, which can oxidize TMB to blue product oxTMB using oxygen as reaction substrate. The presence of antioxidants weakens TMB oxidation, leading to a lighter blue color in the system. Therefore, CMW can be employed for colorimetric detection of antioxidants. Then CMW samples with varying Ca to Mn ratios were prepared, followed by the establishment of an optical sensor array. The detection systems were photographed, and PCA analysis of the RGB parameters was performed, enabling simultaneous qualitative and quantitative detection of nine kinds of antioxidants.

Dissolution‐Recrystallization: A Novel Mechanism for Fluorochromic Detection of Th4+ Using Color‐Tunable Luminescent Metal–Organic Frameworks

AbstractThorium, a predominant actinide in the Earth's crust, presents significant environmental and health risks due to its radioactive nature. These risks are particularly pronounced during the mining and processing of monazite for rare earth elements (REEs), which contain substantial thorium concentrations. Current instrumental analysis methods for thorium, offer high accuracy but require laborious sample preparations and expensive instruments, making them unsuitable for on‐site analysis. Herein, we present a class of color‐tunable luminescent lanthanide‐based metal–organic frameworks (Ln‐MOFs) as fluorochromic sensors for Th4+ cations. Utilizing a heterobimetallic Eu3+/Tb3+ doping strategy, the luminescence colors of EuxTb1‐x‐BDC‐OH can be finely tuned from red, to orange, and to green. More intriguingly, the higher Lewis acidity of Th4+ facilitates the transformation of EuxTb1‐x‐BDC‐OH into a UiO‐type Th‐MOF via a dissolution‐recrystallization mechanism. This process results in a gradual reduction of characteristic Ln3+ emissions and the emergence of blue color ligand‐based fluorescence, thereby leading to selective fluorochromic responses with increasing Th4+ concentrations and enabling visible detection of Th4+ cations. Additionally, a custom‐built portable optoelectronic device is fabricated, which directly converts luminescence colors into red‐green‐blue (RGB) values. This device enables easy quantification of Th4+ concentrations without the need for complex instrumentation.

Dissolution-Recrystallization: A Novel Mechanism for Fluorochromic Detection of Th4+ Using Color-Tunable Luminescent Metal-Organic Frameworks.

Thorium, a predominant actinide in the Earth's crust, presents significant environmental and health risks due to its radioactive nature. These risks are particularly pronounced during the mining and processing of monazite for rare earth elements (REEs), which contain substantial thorium concentrations. Current instrumental analysis methods for thorium, offer high accuracy but require laborious sample preparation and expensive instruments, making them unsuitable for on-site analysis. Herein, we present a class of color-tunable luminescent lanthanide-based metal-organic frameworks (Ln-MOFs) as fluorochromic sensors for Th4+ cations. Utilizing a heterobimetallic Eu3+/Tb3+ doping strategy, the luminescence colors of EuxTb1-x-BDC-OH can be finely tuned from red, to orange, and to green. More intriguingly, the higher Lewis acidity of Th4+ facilitates the transformation of EuxTb1-x-BDC-OH into a UiO-type Th-MOF via a dissolution-recrystallization mechanism. This process results in a gradual reduction of characteristic Ln3+ emissions and the emergence of blue color ligand-based fluorescence, thereby leading to selective fluorochromic responses with increasing Th4+ concentrations and enabling visible detection of Th4+ cations. Additionally, a custom-built portable optoelectronic device was fabricated, which directly converts luminescence colors into red-green-blue (RGB) values. This device enables easy quantification of Th4+ concentrations without the need for complex instrumentation.