Search

A sensitive dual immunochromatographic test strip (dual-ICTS) was developed to detect malachite green (MG) and its metabolite, leucomalachite green (LMG), using two types of gold nanoparticles: round-shaped (red) and star-shaped (blue). The detection limits were determined to be 0.221 μg L -1 for MG and 0.214 μg L -1 for LMG, respectively. The dual-ICTS provided a cut-off value of 1.8 μg L -1 for MG and LMG detection. The dual-ICTS successfully detected MG and LMG in food samples, with recovery rates ranging from 86 % to 116 %. The dual-ICTS was evaluated by correlation analysis between the proposed assay and the well-established enzyme-linked immunosorbent assay in the MG and LMG detection. This is the first report on the development of the ICTS that can detect both MG and LMG at the same time within only 5 min, making it a sensitive and rapid tool for on-site detection., 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 © 2024. Published by Elsevier Ltd.)

Fluorescent sensor-based carbon dots (CDs) have significantly developed for sensing metal ions because of their great physical and optical properties, including tunable fluorescence emission, high fluorescence quantum yield, high sensitivity, non-toxicity, and biocompatibility. In this research, a green synthetic approach via simple gamma irradiation for the carbon dot synthesis from water hyacinth was developed since water hyacinth has been classified as an invasive aquatic plant containing cellulose, hemicellulose, and lignin. The thiol moiety (SH) was further functionalized on the surface functional groups of CDs as the "turn-off" fluorescent sensor for metal ion detection. Fluorescence emission displayed a red shift from 451 to 548 nm when excited between 240 and 500 nm. The quantum yield of CDs-SH was elucidated to be 13%, with strong blue fluorescence emission under ultraviolet irridiation (365 nm), high photostability and no photobleaching. The limit of detection was determined at micromolar levels for Hg 2+ , Cu 2+ , and Fe 3+ . CDs-SH could be a real-time monitoring sensor for Hg 2+ and Cu 2+ as fluorescence quenching was observed within 2 min. Furthermore, paper test-strip based CDs-SH could be applied to detect these metal ions., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

A colorimetric and fluorescent sensor, selective for Cu 2+ ions, was synthesized in two steps using a rhodamine-based compound attached to the semicarbazide-picolylamine moiety (RBP). Spectroscopic measurements, including UV-Vis absorption and fluorescence emission, were conducted in the semi-aqueous medium containing acetonitrile/4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid, denoted as MeCN/HEPES buffer (2:8, v/v, pH 7.0). The sensor exhibited high selectivity towards Cu 2+ ions compared to other cations and demonstrated remarkable sensitivity towards Cu 2+ ions, with a limit of detection at the nanomolar level. The calculated transitions indicated a 1:1 stoichiometric binding of RBP to Cu 2+ ions based on a 4-coordination mode involving additional chelation in the semi-aqueous medium. The sensing mechanism for the detection of Cu 2+ ions was investigated using high-resolution mass spectroscopy. The sensor could be employed as a real-time chemosensor for monitoring Cu 2+ ions. Furthermore, the sensor has the potential for utilization in the detection of Cu 2+ ions in actual water samples with the high precision and accuracy, as indicated by the small relative standard derivation values. The 50 th percentile cytotoxicity concentration of RBP was found to be 22.92 μM. Additionally, the fluorescence bioimaging capability of RBP was demonstrated for the detection of Cu 2+ ions in human hepatocellular carcinoma (HepG2) cells., 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 © 2023 Elsevier B.V. All rights reserved.)

Blue photoluminescent carbon dots were synthesized from Lentinus polychrous Lèv. via a simple hydrothermal process without additional chemical reagents or functionalization. The carbon dots (hereafter referred to as LCDs) were quasi-spherical with an average diameter of 6.0 nm. The strong fluorescence emissions of LCDs were utilized as the basis of efficient turn-off probes for Fe 3+ . The quenching phenomenon could be used to rapidly determine Fe 3+ concentrations in the range of 0.0-2.0 mM in aqueous solution, with a limit of detection (LOD) of 16 μM. In the presence of interference, LCDs demonstrated good sensitivity and selectivity towards Fe 3+ in both solution-based and paper-based systems. The LCDs also exhibited excellent photostability and an eco-friendly nature, making them an ideal choice for environmental monitoring with significant potential for diagnostic applications., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A rhodamine-triazole fluorescent probe bearing a coumarin moiety RTC was synthesized using the Cu(I)-catalyzed click reaction. The rhodamine-triazole conjugate was highly selective to Cu 2+ among other metal ions, including Ca 2+ , Co 2+ , Cu 2+ , Cd 2+ , Mg 2+ , Fe 2+ , Fe 3+ , Hg 2+ , Zn 2+ , Ni 2+ , Pd 2+ and Pb 2+ in physiological conditions. Upon the addition of Cu 2+ , the colorless RTC solution turned pink and exhibited a significant fluorescence emission centered at 578 nm. The binding of Cu 2+ induced a hydrolysis reaction, leading to a release of the coumarin unit from the rhodamine probe, as confirmed by mass spectrometric data. From the fluorescence titration, the detection limit of RTC for Cu 2+ was determined to be 21 nM (1.3 ppb). The sensor was responsive to Cu 2+ in a wide pH range and successfully applied to monitor Cu 2+ in HEK293T cells by confocal fluorescence imaging., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

A new rhodamine B derivative (RDB) was synthesized and utilized for the colorimetric detection of copper ions (Cu 2+ ). This chemosensor utilized a paper strip as a support and a smartphone as a detector for on-site quantitative detection of Cu 2+ in water samples. Silica nanoparticles (SiNPs) were investigated as the modifier nanoparticles to achieve uniform color on the paper strip and showed a color response 1.9-fold higher than the one without SiNPs. The RDB chemosensor-based paper strip provided high selectivity toward Cu 2+ with a detection limit of 0.7 mg/L, and the working concentrations for Cu 2+ ranged from 1 to 17 mg/L. Parallel analyses of eight drinking water samples were conducted by inductively coupled plasma optical emission spectroscopy. The results were in good agreement, indicating the practical reliability of the established method with a short assay time and high selectivity. These indicate its great potential for on-site detection of Cu 2+ ., (© 2023. Springer-Verlag GmbH Germany, part of Springer Nature.)

A novel FRET-based sensor has been designed and developed through the conjugation of naphthyl and rhodamine via propylamine spacer, Naph-Rh. The naphthyl moiety serves as a FRET donor due to its emission spectrum overlapping with the rhodamine B absorption band. Naph-Rh exhibited a selectivity for sensing Fe 3+ over other metal ions with a visual color change and fluorescent enhancement. The ratio of the Naph-Rh and Fe 3+ was determined to be 1:1 based on Job's plot analysis with a detection limit of 83 nM. The probe exhibited a linear response to Fe 3+ in the range of 0-120 μM. Furthermore, the density functional theory (DFT) calculations of Naph-Rh were carried out to rationalize the design and portray the plausible Fe 3+ sensing mechanism., 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 © 2022 Elsevier B.V. All rights reserved.)

Background: The aroma intensity of rice is mixed of more than 100 volatile compounds. Fragrant rice is famous in Thailand due to specific aroma. One important volatile compound that contributes to aromatic intensity and represents a characteristic compound for fragrant rice is 2-acetyl-1-pyrroline (2AP). The production of volatile compounds and 2AP in rice is affected by various environmental factors, such as cultivation area, water content and temperature., Results: Our research employed 29 samples of fragrant colored rice (Luempua black glutinous rice cultivar) from Phetchabun province, Thailand from three harvested rice seasons (2015-2017). The cultivation areas of rice samples exhibited differences in rainfall (976.6-1260.5 mm y r -1 ) and altitude (26.26-1033.41 m). All volatile compounds and 2AP were identified by gas chromatography-mass spectrometry (GC-MS). In 29 rice samples, 2AP levels decreased with increasing of rainfall. The increase in altitude seems to increase 2AP levels, but some high-altitude cultivation areas resulted in low 2AP content. A variety of volatile compounds was observed in 29 rice samples from different cultivation areas. The results showed that differences in altitude and rainfall affected the production of volatile compounds in fragrant colored rice. Moreover, our results indicated that different environmental conditions in cultivation areas potentially affect volatile compound production during rice growth., Conclusion: The increase in 2AP levels under low rainfall conditions and the assortment of volatile compound varieties produced in colored rice grown in different cultivation areas may be useful information for rice cultivation management striving to produce rice with high aromatic intensities. © 2021 Society of Chemical Industry., (© 2021 Society of Chemical Industry.)

A highly selective rhodamine hydrazide-based fluorescent chemosensor for Au 3+ detection was developed. The aqueous solution of rhodamine N-hydroxysemicarbazide (RHS), in the presence of Au 3+ , exhibited a significant 55-fold turn-on fluorescence response at 591 nm and a colorimetric change from colorless to pink. Other interested ions including Li + , Na + , K + , Cs + , Mg 2+ , Ca 2+ , Ba 2+ , Pb 2+ , Mn 2+ , Co 2+ , Ni 2+ , Ag + , Cd 2+ , Cu 2+ , Hg 2+ , Zn 2+ , Sn 2+ , Fe 2+ , Fe 3+ , Cr 3+ , Ce 3+ did not induce any distinct color/spectral changes. The irreversible detection mechanism occurred via Au 3+ -promoted 5-exo-trig ring closure to yield 1,3,4-oxadiazole-2-one product. The RHS probe is non-responsive to other biologically relevant metal ions and the limit of detection for Au 3+ was calculated to be 0.5 µM with a linear range of 0 to 90 µM. Fluorescence bioimaging of Au 3+ in HepG2 cells was also successfully demonstrated.

A rhodol-based fluorescent probe has been developed as a selective hydrazine chemosensor using levulinate as a recognition site. The rhodol levulinate probe (RL) demonstrated high selectivity and sensitivity toward hydrazine among other molecules. The chromogenic response of RL solution to hydrazine from colorless to pink could be readily observed by the naked eye, while strong fluorescence emission could be monitored upon excitation at 525 nm. The detection process occurred via a ring-opening process of the spirolactone initiated by hydrazinolysis, triggering the fluorescence emission with a 53-fold enhancement. The probe rapidly reacted with hydrazine in aqueous medium with the detection limit of 26 nM (0.83 ppb), lower than the threshold limit value (TLV) of 10 ppb suggested by the U.S. Environmental Protection Agency. Furthermore, RL-impregnated paper strips could detect hydrazine vapor. For biological applicability of RL, its membrane-permeable property led to bioimaging of hydrazine in live HepG2 cells by confocal fluorescence microscopy., (Copyright © 2018 Elsevier B.V. All rights reserved.)

A rhodamine-based fluorescent chemodosimeter rhodamine hydrazide-triazole (RHT) tethered with a triazole moiety was developed for Cu 2+ detection. In aqueous medium, the RHT probe exhibited high selectivity and sensitivity toward Cu 2+ among other metal ions. The addition of Cu 2+ triggered a fluorescence emission of RHT by 384-fold (Φ = 0.33) based on a ring-opening process and a subsequent hydrolysis reaction. Moreover, RHT also showed a selective colorimetric response toward Cu 2+ from colorless solution to pink, readily observed with the naked eye. The limit of detection of RHT for Cu 2+ was calculated to be 1 nM (0.06 ppb). RHT was successfully demonstrated to detect Cu 2+ in Chang liver cells by confocal fluorescence microscopy., (Copyright © 2017 John Wiley & Sons, Ltd.)

A rhodol cinnamate fluorescent chemosensor (RC) has been developed for selective detection of hydrazine (N 2 H 4 ). In aqueous medium, the rhodol-based probe exhibited high selectivity for hydrazine among other molecules. The addition of hydrazine triggered a fluorescence emission with 48-fold enhancement based on hydrazinolysis and a subsequent ring-opening process. The chemical probe also displayed a selective colorimetric response toward N 2 H 4 from colorless solution to pink, readily observed by the naked eye. The detection limit of RC for hydrazine was calculated to be 300nM (9.6ppb). RC is membrane permeable and was successfully demonstrated to detect hydrazine in live HepG2 cells by confocal fluorescence microscopy., (Copyright © 2017 Elsevier B.V. All rights reserved.)