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Indigo Carmine is a hazardous dye and produces an allergic action for humans despite the excessive use of the dye in several industrial fields. A sensitive and simple fluorescent assay for determining Indigo Carmine relying on quenching of the fluorescent europium-doped carbon dots by the action of inner filter effect was developed. This sensing platform involved the preparation of europium-doped carbon dots from the hydrothermal carbonization of tannic acid and europium chloride, which was used as fluorescent reagent with a distinctive excitation/emission wavelength at 307/340 nm. Both excitation and emission fluorescence of prepared carbon dots can be successfully quenched by adding Indigo Carmine dye. The developed spectrofluorimetric method exhibits good linearity with the concentration of Indigo Carmine dye in the range of 1.5 to 10.0 μg/ml and provided a limit of detection (LOD) value of 0.40 μg/ml. Furthermore, the prepared carbon nanoparticles were identified and characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR), and ultraviolet (UV)-spectrophotometer techniques. In addition, the developed detecting approach was applied to determine Indigo Carmine in juice samples with acceptable recovery., (© 2022 John Wiley & Sons Ltd.)

The design of a cheap, simple, and handy sensing system for rapid quantitation of pharmaceuticals becomes mandatory to ease drug development procedures, quality control, health care, etc. This work describes a simple, innovative, and easily manufactured paper-based device using a correction pen as a plotter for hydrophobic/lipophobic barriers and graphene quantum dots for recognition and quantification of the hemostatic drug carbazochrome, via fluorescence turn-off mechanism mediated by the inner filter effect. A smartphone-based all-in-one device fitted with an inexpensive 365 nm flashlight as a UV light source and a free image processing software was developed for rapid and reliable interpretation of the fluorescence change from the paper-based device upon introduction of the drug. The simple and convenient steps permit the analysis of many samples in a very short time. The smartphone-based all-in-one device featured excellent sensitivity for carbazochrome with a limit of detection equals to 12 ng/detection zone and good %recovery (100.0 ± 0.4). The reliability of the device was ascertained by favorable statistical comparison with the analogous optimized conventional fluorimetry method and a reference HPLC method. The device has been successfully applied for versatile quantitation of carbazochrome in tablets and on manufacturing equipment surfaces with excellent recoveries. The device offers many green aspects that definitely assist the implementation of the sustainability concept to analytical laboratories. The cost-efficiency, reliability, and ease of fabrication as well as the greenness and user friendship qualify the device for wide application in low-income communities., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Synthesis of photoluminescence carbon dots from red beetroot and utilizing its extract for spectrofluorimetric determination of tenoxicam. [Display omitted] • Photoluminescence carbon dots were synthesized for the first time from red beetroot. • The fluorescence intensity of the carbon dots was quenched by adding tenoxicam. • The acetonitrile extract of red beetroot exhibits fluorescence activity. • The fluorescence intensity of the extract was enhanced by adding tenoxicam. • The developed methods were applied to determine tenoxicam in different dosage forms. Tenoxicam (TNX) belongs to non-steroidal drugs that effectively treat many inflammatory disorders. In this study, luminescent carbon dots were synthesized from red beetroot as a green fluorescence probe. The synthesized carbon dots' morphology, size, and spectroscopic features were investigated and characterized by spectrophotometric, FTIR, SEM, spectrofluorimetric, and TEM techniques. The synthesized carbon dots possessed an emission at 430 nm and an excitation at 366.5 nm. Meanwhile, TNX is a yellow-colored compound with a spectrophotometric absorbance peak at 370 nm. Based on the inner filter effect mechanism, the emission fluorescence intensity of the synthesized carbon dots has been markedly quenched upon the addition of TNX. In addition, the quenching in the fluorescence intensity was quantitively related to the concentration of TNX at the linear range of 0.25 - 2.5 µg/mL (r2 = 0.9989) with a LOD of 0.08 µg/mL and LOQ of 0.24 µg/mL. The second side of this study is based on enhancing the fluorescence intensity of the acetonitrile extract of red beetroot upon the addition of TNX solution. This enhancement was recorded at a fluorescence emission of 357 nm with a fluorescence excitation of 305.5 nm. In addition, the enhancement in the fluorescence intensity was quantitively related to the concentration of TNX at the linear range of 0.5 - 8.0 µg/mL (r2 = 0.9995) with a LOD of 0.16 µg/mL and LOQ of 0.49 µg/mL. The analytical conditions were well-optimized, and the developed method was validated according to ICH guidelines. Finally, the proposed spectrofluorimetric approaches were applied to determine TNX in vials, tablets, and capsules with good recovery and accepted statistical results. [ABSTRACT FROM AUTHOR]

Determination of Metanil yellow dye using fluorescent Europium doped Carbon dots. [Display omitted] • Photoluminescent Eu doped Carbon dots were synthetized from Tannic acid and Eu(III). • The synthetized Eu-C-dots were characterized by UV, SEM, TEM, and FTIR techniques. • Eu-C-dots were utilized as fluorometric reagent for determining metanil yellow. • The method has been applied for determining metanil yellow in curcumin powder. Turmeric, a spice known for its therapeutic benefits, is a major source of curcumin which is a polyphenol with anti-inflammatory properties. It aids in treating arthritis, anxiety, metabolic syndrome, liver disease, hyperlipidemia, and inflammatory diseases. In this study, a novel fluorescence probe was designed to detect the adulteration of curcumin by metanil yellow (a harmful artificial dye). The probe was synthesized from the carbonization and conversion of the Tannic acid-Eu3+ complex to bright fluorescence Eu-carbon dots in the presence of orthophosphoric acid. The size, morphological, and optical features of the formed Eu-carbon dots were characterized by UV, SEM, TEM, and FTIR techniques. Furthermore, the formed Eu-carbon dots possess unique fluorescence excitation and emission features at 307.5 nm and 340.6 nm, respectively. These fluorescence features can be successfully quenched upon the addition of metanil yellow dye. The value of quenching in the fluorescence intensity of the Eu-C-dots was directly proportional to the dye's concentration. The LOD value for the proposed method was 0.390 µg/mL with a linear range of 1.0–15.0 µg/mL. Furthermore, the methodology exhibited good recovery values for determining the studied dye without any interference from the presence of curcumin. [ABSTRACT FROM AUTHOR]