Yellow-green Fluorescence Research Articles

Quantitative determination of Penicillamine in pharmaceutical samples by Copper-Modified Drug-Based carbon dots utilizing a turn ON-OFF-ON strategy

In the present work, a sensitive and simple method is developed for sensing and quantifying Penicillamine (PA) in pharmaceutical samples utilizing a copper-conjugated carbon dots probe. The proposed method employed a turn ON-OFF-ON strategy with carbon dots fluorescence quenching by addition of copper and fluorescence recovery of up to 91 % by addition of PA. Expired moxifloxacin tablet powder was used as a novel carbon precursor during the synthesis of the carbon dots (MOX–CDs) which involved a single-step solvothermal procedure. The prepared MOX–CDs demonstrated excitation independent yellowish green fluorescence emission (Quantum yield ≈ 51 %) with the maximum excitation and emission wavelengths being observed at 410 nm and 510 nm respectively. The suggested strategy for assaying PA offered a detection limit of 0.14 µM (S/N = 3) and a linear response from 2.5 µM to 50 µM (R2 = 0.9987). In addition to offering merits like accuracy and sensitivity, the proposed probe also provides a method for solid waste treatment by reprocessing expired moxifloxacin powder.

A Portable Zn2+ Fluorescence Sensor for Information Storage and Bio-Imaging in Living Cells.

A fluorescence probe (Probe-ITR) was designed and synthesized for the rapid detection of Zn2+ based on the excited state intramolecular proton transfer (ESIPT) mechanism. The specific recognition ability of Probe-ITR to Zn2+ was tested using UV-VIS and fluorescence emission spectroscopy. The results demonstrated a rapid response within 40s upon addition of an appropriate amount of Zn2+ into the mixed solution of the target probe molecules (DMSO/PBS = 5/5). Under 365nm ultraviolet light irradiation, the colorless solution changed to yellow-green fluorescence with a 150-folds increase in intensity. Furthermore, the detection limit for specific recognition of Zn2+ by the probe molecule is only 17.3 nmol/L, indicating high sensitivity. The practical application potential of the probe molecules was enhanced by employing on information storage and conducting cell imaging experiments.

Preparation, Structure, Reactivity, Lewis Acidic and Fluorescence Properties of Arylpyridine Based Boron C,N-Chelates Featuring Weakly Coordinating Anions.

Herein, we present the preparation of a series of electronically and/or sterically distinct borenium-type species based on a simple 2-arylpyridine scaffold. Corresponding arylpyridine was firstly subjected to electrophilic borylation (BBr3/i-Pr2NEt) and formed BBr2 chelate was reduced with LiAlH4 to yield arylpyridine boron dihydride. Elimination of one hydride led to Lewis acidic borenium-like products. Four methods of hydride elimination were evaluated and influence of counterions on reactivity, Lewis acidic and luminescent properties was assessed both experimentally and computationally. Arylpyridine chelates featuring weakly coordinating counterions exhibit fluorescent properties upon UV irradiation. Several general trends were inferred to modulate emission wavelength and fluorescence quantum yield. Based on our observations, we have devised and prepared borenium-type fluorophores with yellow-green fluorescence and quantum yields up to 93 %.

Luz de Wood en dermatosis inflamatorias, autoinmunes, infecciones y cáncer cutáneo

Wood's light (WL) is a useful, economical and easy-to-learn diagnostic tool. Despite its advantages, the use of LW among dermatologists is limited. In porokeratosis, the “diamond necklace” sign has been described, corresponding to the white fluorescence of the hyperkeratotic scale. Subclinical morphea lesions are seen as well-defined dark macules. Among the pigmentary disorders, the bluish fluorescence of vitiligo, the increased contrast of epidermal melasma, and the follicular-centered red fluorescence of progressive macular hypomelanosis stand out. Regarding skin infections, erythrasma presents a coral red fluorescence; tinea versicolor, yellow-green fluorescence; Pseudomonas aeuriginosa, green fluorescence; and scabies, blue-white fluorescence in the acarine grooves. In skin cancer, LW has been used to delimit the surgical margins of both lentigo maligna and non-melanoma skin cancer, with variable results.

A specific ‘Turn-on’ fluorogenic probe for the detection of phosphate ions

Phosphate (PO43-) ions are an essential trace element in the human body and play a vital role in biological and ecological systems. However, excess consumption of PO43- ions causes various serious health issues and becomes hazardous to public safety. Thus, selective tracking and quantification of PO43- ions is a significant concern to the scientific communities. In the present article, we have introduced a chromo-fluorogenic probe APES, which instantly shows a characteristic color-fluorimetric change towards PO43- ions. APES shows an instant greenish-yellow fluorescence at 530 nm and a yellow to orange naked-eye visible colorimetric change in the presence of PO43- ions. The detection and quantification limit of PO43- ions employing APES is estimated as 1.5 µM and 5.0 µM respectively. The interaction affinity of APES towards PO43- ions is found by the Benesi-Hildebrand equation as 0.42 × 105 M-2 in a 20 % water-DMSO medium. Also, our modeled probe is biologically significant as it can detect and quantify PO43- ions within the range of 50 % water medium. A super handy paper-strips-based detection tool has also been fabricated utilizing APES which could be employed to track trace amounts of PO43- ions. The mechanism involved in the detection of PO43- ions is elucidated through 1H NMR and density functional theoretical analysis. Also to deeply entrust the selectivity with quantification capability and practical usability of our probe APES, a real sample analysis is performed to explore the fruitful real-time analysis by experimenting with different sources of water.

Biogenic silver nanomaterials synthesized from Ocimum sanctum leaf extract exhibiting robust antimicrobial and anticancer activities: Exploring the therapeutic potential

There is a surge in antibiotic consumption because of the emergence of resistance among microbial pathogens. In the escalating challenge of antibiotic resistance in microbial pathogens, silver nanoparticles (AgNPs)-mediated therapy has proven to be the most effective and alternative therapeutic strategy for bacterial infections and cancer treatment. This study aims to explore the potential of OsAgNPs derived from Ocimum sanctum's aqueous leaf extract as antimicrobial agents and anticancer drug delivery modalities. This study utilized a plant extract derived from Ocimum sanctum (Tulsi) leaves to synthesize silver nanoparticles (OsAgNPs), that were characterized by FTIR, TEM, SEM, and EDX. OsAgNPs were assessed for their antibacterial and anticancer potential. TEM analysis unveiled predominantly spherical or oval-shaped OsAgNPs, ranging in size from 4 to 98 nm. The (MICs) of OsAgNPs demonstrated a range from 0.350 to 19.53 μg/ml against clinical, multidrug-resistant (MDR), and standard bacterial isolates. Dual labelling with ethidium bromide and acridine orange demonstrated that OsAgNPs induced apoptosis in HeLa cells. The OsAgNPs-treated cells showed yellow-green fluorescence in early-stage apoptotic cells and orange fluorescence in late-stage cells. Furthermore, OsAgNPs exhibited a concentration-dependent decrease in HeLa cancer cell viability, with an IC50 value of 90 μg/ml noted. The study highlights the remarkable antibacterial efficacy of OsAgNPs against clinically significant bacterial isolates, including antibiotic-resistant strains. These results position the OsAgNPs as prospective therapeutic agents with the potential to address the growing challenges posed by antibiotic resistance and cervical cancer.

Fluorescent covalent organic framework as an ultrasensitive fluorescent probe for tyrosinase activity monitoring and inhibitor screening

BackgroundAs a significant biomarker of melanocytic lesions, tyrosinase (TYR) plays an essential role in the clinical diagnosis and treatment of melanin-related diseases. Thus, it is important to develop robust methods for assessing TYR activity. Covalent organic frameworks (COFs) have garnered considerable attention owing to their unique properties, including high chemical stability, good biocompatibility, and large surface area compared with organic dyes, noble metal nanoclusters, and semiconductor quantum dots. However, most COFs are insoluble in water and exhibit weak or no fluorescence emission. Therefore, the development of a water-soluble fluorescent COF for detecting TYR activity in biological samples remains highly desired. ResultsIn this work, a sensitive and facile fluorometric method based on fluorescent COF was constructed for the detection of TYR activity in human serum samples. The water-soluble COF was fabricated through the condensation polymerization of 4′,4‴,4′′′′′,4′′′′′′′-(1,2-ethene-diylidene) tetrakis [1,1′-biphenyl]-4-carboxaldehyde and 2,4,6-tris-(4-aminophenyl)-triazine. The resulting COF displayed yellow-green fluorescence with a maximum emission peak at 560 nm. Tyrosine was catalyzed by TYR to produce melanin-like polymers which formed a coating on the surface of COF and effectively quenched its fluorescence due to fluorescence resonance energy transfer. The proposed approach demonstrated a strong linear correlation in the range of 0.5–80 U/L with a low detection limit of 0.09 U/L. Additionally, the limit of detection for kojic acid, serving as a representative TYR inhibitor, was determined to be 0.0004 μg/mL. SignificanceOur proposed fluorometric sensing platform exhibited exceptional selectivity, sensitivity, and satisfactory recoveries in human serum samples, which is of paramount importance for the clinical diagnostics of melanin-related diseases. Furthermore, the proposed approach was further employed for the screening of TYR inhibitors, suggesting the potential applications in clinical treatment and pharmaceutical research.

A Ratiometric Fluorescence Detection Method for Berberine Using Triplex-Containing DNA-Templated Silver Nanoclusters.

Berberine (BBR), as a natural isoquinoline alkaloid, has demonstrated various pharmacological activities, and is widely applied in the treatment of diseases. The quantitative analysis of BBR is important for pharmacological studies and clinical applications. In this work, utilizing the specific interaction between BBR and triplex DNA, a sensitive and selective fluorescent detecting method was established with DNA-templated silver nanoclusters (DNA-AgNCs). After binding with the triplex structure in the template of DNA-AgNCs, BBR quenched the fluorescence of DNA-AgNCs and formed BBR-triplex complex with yellow-green fluorescence. The ratiometric fluorescence signal showed a linear relationship with BBR concentration in a range from 10 nM to 1000 nM, with a detection limit of 10 nM. Our method exhibited excellent sensitivity and selectivity, and was further applied in BBR detection in real samples.

Triflic acid-promoted Friedel–Crafts-type carbocyclization of alkenylated biphenyl derivatives: Synthesis and photophysical studies of novel 9,10-dihydrophenanthrenes

An efficient metal-free, triflic acid-promoted intramolecular Friedel–Crafts-type carbocyclization of alkenylated biphenyl derivatives is discussed. This method provides an elegant route for the construction of 9,10-dihydrophenanthrenes of biological significance in good to excellent yields. The carbocyclization reaction is likely to proceeds via activation of terminal CC bond of alkenylated biphenyl derivatives followed by subsequent aromatic electrophilic substitution to give desired carbocyclic products. Single crystal X-ray diffraction analysis of compound 10d revealed that the crystals are packed in AB-AB layer packing, where the molecules are aligned in anti-parallel fashion. Notably, all of the synthesized 9,10-dihydrophenanthrenes exhibited blue to greenish yellow fluorescence with λmax = 418–481 nm range. The stokes shift, quantum yield and optical band gap of tricyclic products were computed using their absorption and emission spectra. A significant positive solvatochromic effect was observed for 9,10-dihydrophenanthrene derivative 10l, which is a characteristic of ICT interactions.

A novel MNPs@GO biosensor- integrated upconversion fluorescence cuvette for simultaneous detection of Salmonella typhimurium and Staphylococcus aureus

An upconversion fluorescence biosensor was developed and employed in a self-designed cuvette engineered for the detection of Salmonella typhimurium and Staphylococcus aureus in chicken samples. The cuvette consisted of a hollow cylinder filled with alendronic acid-modified upconversion nanoparticles (ADA@UCNPs) and solid quartz cube blocks and could provide a stable and reusable fluorescent donor. In addition, the fluorescence inner filter mechanism (IEF) between two fluorescence quenchers (3,3′,5,5′-tetramethylbenzidine oxide (oxTMB) and 5-bromo-4-chloro-3-indolyl phosphate/nitroblue tetrazole (oxBCIP/NBT)) and ADA@UCNPs in the cuvette could be triggered. After sample injection, bacteria-targeting aptamers labeled with horseradish peroxidase (HRP) or alkaline phosphatase (AP) fell off the magnetic graphene oxide (MNPs@GO), resulting in the blockage of the enzymatic reaction. This led to an increase in the yellow-green upconversion fluorescence peaks at 547 nm and 658 nm. The whole detection process could be accomplished within 40 min and required the minimum amounts of ADA@UCNPs and MNPs@GO. The limit of detection was as low as 14 CFU/mL for Salmonella typhimurium and 33 CFU/mL for Staphylococcus aureus. To sum up, the upconversion fluorescence biosensor holds a potential in rapid analysis and detection of foodborne pathogenic bacteria.

Synthesis, Crystal Structure, Fluorescence and Theoretical Calculations of Three Zn(II)/Cd(II) Complexes with Bis-dentate N,N-Quinoline Schiff Base.

Three d10 metal complexes, ZnL(OAc)2 (1), CdL(OAc)2 (2) and [CdL2(NO3)2]·CH3CN (3) were synthesized using the ligand (E)-N-(3-methoxy-4-methylphenyl)-1-(quinolin-2-yl)methanimine (L) and characterized by FT-IR spectra, NMR spectra, and CHN elemental analysis. Single-crystal X-ray diffraction analysis revealed that complexes 1 and 2 are isostructural, with the central metal adopting a hexacoordinate octahedral geometry, while complex 3 adopts a triangular dodecahedron geometry. Thermal gravimetric analysis showed that these complexes exhibit good thermal stability. Solid-state fluorescence spectroscopy measurements demonstrated that complexes 1-3 exhibit bright yellow-green fluorescence (λem = 564nm for 1; 524nm for 2; 542nm for 3), suggesting their potential as photoluminescent materials. Furthermore, DFT calculations, including frontier molecular orbitals, energy levels, and surface electrostatic potential, provided insights into the structural and electronic spectral properties of complexes 1-3.

Pd(II)-Catalyzed Site-Selective Cross Coupling Reaction: Synthesis of Highly Fluorescent Aryl-Formyl-Chromenes and its Iminoantipyrine Analogues as Selective AChE Inhibitors.

A versatile and efficient chemo selective synthesis of 4-aryl-3-formyl-2H-chromenes (AFC) was undertaken using Pd-catalyzed cross-coupling conditions. The key oxidative transmetalation was successfully applied to a significant range of substitutions on the chromene moiety and aryl ring in Ar(BOH)3, accommodating both electron-rich and electron-deficient groups. These π-extended scaffolds exhibited green-yellow fluorescence with a large Stokes shift and high quantum yield. Measurement of photophysical properties revealed that the compound with methoxy substitution in the chromene ring, 3t, caused a significant bathochromic shift. The AFCs obtained from this method can be transformed into biologically active 4-aryl-3-iminoantipyrine-2H-chromenes (AAC) through functionalization of the formyl chromenes. The AFCs and AACs with methoxy substitutions (3t and 4e) were docked against AChE inhibition, and compound 4e had the lowest binding energy of -11.20 kcal/mol. DFT calculations performed on representative compounds revealed that compound 4e is more reactive than 3t, which is in accordance with the docking studies.

SYNTHESIS AND STUDY OF THE OPTICAL PROPERTIES OF THE COLLOIDAL FORM OF IRON WITH RIBOFLAVIN AND L-LYSINE

This paper presents the results of the development and study of a colloidal complex of the essential microelement iron with vitamin B2 riboflavin and the essential amino acid L-lysine. As a result, a method for obtaining a colloidal vitamin-microelement-amino acid complex has been developed, which is carried out in 2 stages. As a result of computer quantum chemical modeling, the most optimal configuration for the interaction of the components of the colloidal complex was determined. Namely, it was found that the connection of riboflavin with the iron ion occurs through oxygen at C4 and nitrogen N3, and lysine binds to the iron ion through the carboxo and amino group in α- position. The optical characteristics of the resulting compound were studied. From an analysis of the absorption spectrum of a 0.001% aqueous solution of an iron complex with riboflavin and L-lysine, the presence of 4 maxima in the spectrum with positions at 222, 265, 374 and 436 nm was established. In the spectrum, the absorption maximum at a wavelength of 436 nm corresponds to the auxochromic amino group; its hypsochromic shift by 20 nm relative to the absorption spectrum of pure riboflavin confirms the formed bond of the amino group with the iron ion in the complex molecule. The fluorescence maximum is located at a wavelength of 522 nm, which corresponds to intense green-yellow fluorescence in both a solution of pure riboflavin and a colloidal iron complex with riboflavin and L-lysine. Analysis of the histogram of the size distribution of micelles of the complex showed the presence of one phase with a size of about 96 nm, which allows us to define the resulting iron complex with riboflavin and the amino acid L-lysine as a colloidal system. For citation: Blinov A.V., Golik A.B., Rekhman Z.A., Gvozdenko A.A., Kolodkin M.A., Bakholdina T.N. Synthesis and study of the optical properties of the colloidal form of iron with riboflavin and L-lysine. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 7. P. 96-102. DOI: 10.6060/ivkkt.20246707.6999.

Unusually Sensitive Solid State Emissive 1,8-naphthalimide for Detection of Acid Vapors in Turn-off Mode and Base Vapors in Turn-on Mode.

A 4-amino-1,8-naphthalimide containing tetramethylpiperidine in N-position was synthesized. The prepared 1,8-naphthalimide was found to possess bright yellow-green fluorescence in a solid state, which could be switched-off in the presence of acid vapors and then switched-on after exposure on base vapors. The observed fluorescence quenching or enhancement, respectively, was more than 10-fold. This behavior was quite opposite to that of the similar 4-oxy-1,8-naphthalimide, in which a well-pronounced PET process operates. In addition, the observed fluorescence quenching was accompanied with color change from yellow to red. Based on these results, the reported 4-amino-1,8-naphthalimide was successfully applied as a reversible solid-state emissive chemosensing material for rapid detection of acid-base vapors for multiple usage.

Nitrogen and Chlorine Co-Doped Carbon Dots with Yellow-Green Emission as a Ratiometric Fluorescent and Colorimetric Dual-Signal Probe for Quercetin Detection and Cell Imaging

Despite the emergence of numerous carbon dots (CDs)-based sensors, most of them are fluorescent probes. To improve the reliability of the results, using ratiometric fluorescence/UV-vis absorption dual-signal probes is an effective method. Herein, nitrogen and chlorine co-doped carbon dots (N, Cl-CDs) with yellow-green fluorescence were prepared and used as a dual-function probe for ratiometric fluorescence/UV-vis. The detection range of the fluorescence method was 0.05–78[Formula: see text][Formula: see text]M, and the limit of detection (LOD) was 1.2[Formula: see text]nM (3[Formula: see text]/s). For the colorimetric method, the linear range was 0.05–186[Formula: see text][Formula: see text]M with LOD of 10.7[Formula: see text]nM. Importantly, the N, Cl-CDs were successfully used to detect Quercetin (QT) in actual water samples. Besides, due to their good biocompatibility, the N, Cl-CDs were applied to in vivo biological imaging of oocysts and shown the potential for environmental survey and biological assay.

Fluorescent responsive membrane based on terbium coordination polymer and carbon dots with AIE effect for rapid and visual detection of fluoroquinolone

In this study, based on aggregation-induced emission (AIE) effect and antenna effect, a novel portable fluorescent responsive membrane was constructed with red carbon dots (R-CDs) as reference signal and terbium coordination polymer (Tb-AMP CPs) as response signal for visual, instrument-free, and sensitive detection of fluoroquinolones (FQs). Specifically, the fluorescent responsive membrane (R-T membrane) was prepared by physically depositing R-CDs with AIE property and Tb-AMP CPs on the surface of polyvinylidene fluoride filter membranes at ambient temperature. In the presence of FQs, Tb3+ in the Tb-AMP CPs of the prepared membrane coordinated with the β-diketone structure of FQs, which turned on the yellow-green fluorescence through the “antenna effect”. As the concentration of FQs increased, the R-T membrane achieved a fluorescent color transition from bright pink to yellow-green. Its visual detection sensitivity for three FQs, including ciprofloxacin, difloxacin, and enrofloxacin, was 0.01 μM, and the detection limits were 7.4 nM, 7.8 nM, and 9.2 nM, respectively, by analyzing the color parameter green. In the residue analysis of FQs in real samples, the constructed membrane also exhibited remarkable anti-interference and reliability, which is of great significance for ensuring the safety of animal-derived food.

β-Glucuronidase-triggered reaction for fluorometric and colorimetric dual-mode assay based on the in situ formation of silicon nanoparticles

Backgroundβ-Glucuronidase (GUS) is considered as a promising biomarker for primary cancer. Thus, the reliable detection of GUS has great practical significance in the discovery and diagnosis of cancer. Compared with traditional organic probes, silicon nanoparticles (Si NPs) have emerged as robust optical nanomaterials due to their facile preparation, superior photobleaching resistance and excellent biocompatibility. However, most nanomaterials-based methods only output a single signal which is easily influenced by external factors in complex systems. Hence, developing nanomaterial-based multi-signal optical assays for highly sensitive GUS determination is still urgently desired. ResultsIn this study, we developed a simple and efficient one-step method for the in situ preparation of yellow color and yellow-green fluorescent Si NPs. This was achieved by combining 3-[2-(2-aminoethylamino) ethylamino] propyl-trimethoxysilane with p-aminophenol (AP) in an aqueous solution. The obtained Si NPs showed yellow-green fluorescence at 535 nm when excited at 380 nm, while also exhibiting an absorption peak at a wavelength of 490 nm. Taking inspiration from the easy synthesis step regulated by AP, which is generated through the hydrolysis of 4-aminophenyl β-D-glucuronide catalyzed by GUS, we constructed a direct fluorometric and colorimetric dual-mode method to measure GUS activity. The developed fluorometric and colorimetric sensing platform showed high sensitivity and accuracy with detection limits for GUS determination as low as 0.0093 and 0.081 U/L, respectively. SignificanceThis study provides a facile dual-mode fluorometric and colorimetric approach for determination of GUS activity based on novel Si NPs for the first time. This designed sensing approach was successfully employed for the quantification of GUS in human serum samples and screening of GUS inhibitors, indicating the feasibility and potential applications in clinical cancer diagnosis and anti-cancer drug discovery.

Fluorometric “AND” logic gate for detection of tyramine and tyrosinase based on in-situ formation of silicon-containing nanoparticles

BackgroundTyramine is an important index of food freshness degree, and tyrosinase that can specifically oxidized monophenolamine to catecholamine plays a crucial part in the occurrence and development of melanin-related skin diseases. Therefore, it is crucial to develop sensitive and efficient methods for the detection of tyramine and tyrosinase. ResultsIn this work, encouraged by tyrosinase-triggered specific oxidation of tyramine to dopamine and the unique fluorescent reaction between dopamine and amino silane, we have developed a one-step synthetic strategy of silicon containing nanoparticles (Si CNPs) for “turn-on” detection of tyramine and tyrosinase. The Si CNPs formed with thoroughly studied mechanism exhibit uniform structure and robust yellow-green fluorescence. The low detection limits for tyramine (1.87 μM) and tyrosinase (0.0029 U/mL) demonstrate admirable sensitivity outstripping most methods. The proposed assay achieves satisfactory results in the determination of tyramine and tyrosinase activity in real samples. Furthermore, we leverage this new fluorescent assay to enable the fabrication of an “AND” Boolean logic gate. SignificanceThe entire process can be completed at easily available temperature and pressure with rapid response, convenient operation and visual observation. This fluorescent assay featured with excellent sensitivity, selectivity and stability has considerable prospects in the application of biosensors and disease diagnosis.

Down-conversion luminescence nanocomposites based on nitrogen-doped carbon quantum dots@bioplastic for applications in optical displays, LEDs and UVC tubes

Carbon quantum dots (CQDs)-based composites as luminous down-conversion materials are becoming more popular due to several advantages such as steady fluorescence, ease of functionalization, tailoring of emission in the visible range, and so on. We report an inexpensive and environmentally sustainable synthesis of fluorescent nitrogen doped-CQDs produced from Cissus quadrangularis, a low-cost plant precursor with therapeutic value. The morphological, structural, and physicochemical features of the material were carefully investigated. Under UV stimulation (365 nm), almost spherical shaped N-CQDs with an average diameter of 5.1 nm were discovered to generate yellow-green fluorescence, have excellent photostability, and strong water solubility, with a quantum yield of up to 5 %. Furthermore, as a solid-phase dispersion matrix for CQDs, ecologically friendly and biodegradable bioplastic is appealing. The down-conversion of solid-state fluorescence of LEDs and UVC tubes was demonstrated by creating a nanocomposite by inserting N-CQDs into the solid matrix of a wheat starch-based bioplastic. Furthermore, employing constructed quantum dot-based optical displays, down-converted LEDs, and UVC tubes, the impacts of varied CQD concentrations and pH sensitivity were examined.

A Naphthoquinoline-Dione-Based Cu2+ Sensing Probe with Visible Color Change and Fluorescence Quenching in an Aqueous Organic Solution.

Copper metal ions (Cu2+) are widely used in various industries, and their salts are used as supplementary components in agriculture and medicine. As this metal ion is associated with various health issues, it is necessary to detect and monitor it in environmental and biological samples. In the present report, we synthesized a naphthoquinoline-dione-based probe 1 containing three ester groups to investigate its ability to detect metal ions in an aqueous solution. Among various metal ions, probe 1 showed a vivid color change from yellow to colorless in the presence of Cu2+, as observed by the naked eye. The ratiometric method using the absorbance ratio (A413/A476) resulted in a limit of detection (LOD) of 1 µM for Cu2+. In addition, the intense yellow-green fluorescence was quenched upon the addition of Cu2+, resulting in a calculated LOD of 5 nM. Thus, probe 1 has the potential for dual response toward Cu2+ detection through color change and fluorescence quenching. 1H-NMR investigation and density functional theory (DFT) calculations indicate 1:1 binding of the metal ion to the small cavity of the probe comprising four functional groups: the carbonyl group of the amide (O), the amino group (N), and two t-butyl ester groups (O). When adsorbed onto various solid surfaces, such as cotton, silica, and filter paper, the probe showed effective detection of Cu2+ via fluorescence quenching. Probe 1 was also useful for Cu2+ sensing in environmental samples (sea and drain water) and biological samples (live HeLa cells).