Significant Fluorescence Enhancement Research Articles

Tuning Zn(Ⅱ) selectivity by conjugating vitamin B6 cofactors over bovine serum albumin stabilized red-emitting silver nanoclusters

The red-emitting bovine serum albumin stabilized silver nanoclusters (BSA-AgNCs) were conjugated with the vitamin B6 cofactors pyridoxal 5′-phosphate (PLP) and pyridoxal (PL). The deconvoluted bands in XPS revealed that the conjugation occurred due to the formation of imine-linkage between the vitamin B6 cofactors and the BSA functionalized over BSA-AgNCs. The TEM images supported the formation of pseudo-spherical shaped nano-aggregates upon conjugating vitamin B6 cofactor PLP over BSA-AgNCs. An emission band appeared at 532 nm after the conjugation of PLP or PL over the surface of BSA-AgNCs. The in situ formed nano-assembly PLP_BSA-AgNCs and PL_BSA-AgNCs showed a significant fluorescent enhancement, respectively, at 490 nm and 481 nm in the presence of Zn2+. The complexation-induced fluorescence enhancement from PLP_BSA-AgNCs and PL_BSA-AgNCs was reversed by adding a strong chelating agent EDTA. In addition, the fluorescence of PL_BSA-AgNCs was irreversibly quenched with the appearance of an emission band at 423 nm in the presence of Hg2+. The analytical performance and sensing mechanism of the developed nanoprobes PLP_BSA-AgNCs and PL_BSA-AgNCs were discussed, and the highly selective and sensitive nanoprobe PLP_BSA-AgNCs was applied for the quantification of Zn2+ in real samples.

Inverse opal microneedles arrays for fluorescence enhanced screening skin interstitial fluid biomarkers

Infectious diseases caused by bacteria have become serious health concerns. Efficient and sensitive early detections are of pivotal significance in the diagnosis and treatment of bacterial infection. Here, we develop novel inverse opal microneedles (MNs) arrays for in situ extraction and fluorescence-enhanced detection of target biomarkers in skin interstitial fluid (ISF). As the MNs array is fabricated by applying a resin to replicate the colloidal crystal-filled negative mold, it possesses the exceptional arranged porous structure and unique photonic band gap (PBG) properties. Benefitting from these features, the inverse opal MNs array enables non-invasive skin ISF sampling and provides enhanced fluorescence signal intensity towards specific bio-probes, facilitating improved detection sensitivity. On the basis of the inverse opal MNs array, we have further verified its value of in situ extraction and fluorescence-enhanced detection of lipopolysaccharide (LPS) with high efficiency and sensitivity in skin ISF from infected rats. These results indicate the great potential value of the inverse opal MNs array in non-invasive clinical diagnosis and other related biomedical applications.

Development of a tandem signal amplification strategy for label-free sensing polynucleotide kinase activity in cancer cells

Polynucleotide kinase (PNK) involves in various cellular events by regulating phosphorylation processes, and abnormal expression of PNK may induce many human diseases. Herein, we develop a tandem signal amplification strategy for label-free sensing PNK activity in cancer cells. In the presence of PNK, the hairpin probe is phosphorylated to initiate the ligation reaction with the assistance of T4 DNA ligase. Subsequently, a tandem signal amplification can be activated to generate abundant triggers with the ligated sequence as the template and the corresponding 3′-OH end of the 5′- phosphorylated hairpin probe as the primer. Eventually, the addition of SYBR Green II lights up the triggers to produce an enhanced fluorescence signal. Notably, only target PNK can effectively phosphorylate the hairpin probe to initiate the ligation-dependent reaction, endowing this assay with improved specificity. Moreover, the high amplification efficiency of tandem signal amplification endows this assay with enhanced sensitivity. Furthermore, this assay can accurately measure endogenous PNK activity at single-cell level, screen inhibitors, and analyze enzyme kinetic parameters, facilitating PNK-related clinical diagnosis and drug discovery.

In situ imaging miRNAs using multifunctional linear DNA nanostructure

The microRNAs (miRNAs) play a critical role in many biological processes and are essential biomarkers for diagnosing disease. However, the sensitive and specific quantification of microRNAs (miRNAs) expression in living cells still faces a huge challenge. Our study designed a multifunctional linear DNA nanostructure (MLN) as a carrier of molecular beacons (MB-21) for detecting and intracellular imaging miRNA-21. The MLN-MB consists of three parts: aptamer, MLN, and MB-21. The aptamer (AS1411) could media MLN-MB enter live cells without additional transfection reagents. Once inside the cells, the intracellular miRNA-21 could hybridize the MB-21s, resulting in significantly enhanced fluorescence signals. The whole process was enzyme-free, autonomous, and continuous, which avoided the necessity of adding external fuel strands or enzymes. We demonstrated that the MLN-MB could be used to screen the miRNA-21 with a detection limit of 320 pM in a short time (10 min) and show high specificity toward miRNA-21 against other miRNAs. Moreover, the proposed MLN-MB could detect the miRNA-21 in complex matrixes stably. With its outstanding stability, dual recognition, and biocompatibility, MLN-MB is capable of delivering into living cells to identify specific cancer cells. Therefore, our sensing approach, with high sensitivity, specificity, and simplicity advantages, holds great potential for early cancer diagnosis.

Construction of ratiometric fluorescence sensor and test strip with smartphone based on dual-emission carbon dots for the specific detection of chlortetracycline.

Concerns about environmental and food contamination caused by chlortetracycline (CTC) residues have prompted people to explore efficient and convenient CTC monitoring platforms. However, the reported fluorescent probes generally fail to selectively detect CTC due to the structural similarity of tetracycline antibiotics. Herein, an intrinsic dual-emission carbon dots (D-CDs) ratiometric fluorescence sensor was prepared for highly sensitive and selective determination of CTC over other tetracyclines by one-step synthesis. The sensor exhibited a significant fluorescence enhancement at 425 nm after introducing CTC. The fluorescence "turn on" of the sensing system is due to aggregation-induced emission (AIE) phenomenon formed by hydrogen bonds and π conjugation promoting the specific recognition of CTC by D-CDs. The linear detection varied from 0.98 to 143.67 ng mL-1 with a low limit of detection (LOD) of 1.29 ng mL-1 (R2 = 0.998), which was lower than most reported in the literature. The D-CDs sensor was applied to detect CTC in spiked milk, blocked normal human serum, and fish samples with recoveries of 95.5-104.2% and relative standard deviations (RSDs) of 2.6%. Particularly, D-CDs based test papers with a smartphone were prepared for portable and visual detection of CTC by analyzing the various color changes of RGB of fluorescence color, with an LOD of 7.18 ng mL-1 (R2 = 0.9909). The fluorescence sensor designed in this work could be used as a rapid tool with high performance and selectivity for monitoring control in foods.

Target-templated molecular nano-machine for auto-catalytic recycling amplification detection of low-abundant antibody in human serum

The development of convenient and sensitive sensing method capable of monitoring low-abundant antibody is appealing for pathogens diagnosis and vaccine immunotherapy evaluation. With regards to this, we herein constructed a simple molecular nano-machine for ultrasensitive monitoring of Anti-Digoxigenin (Anti-Dig) antibody via a target-initiated auto-cycling proximity recording (APR) amplification. One target bivalent Anti-Dig antibody can simultaneously recognize two Dig-labeled catalytic hairpin DNAs (Dig-HP1) and bring them into close distance to form the proximity catalytic probe pairs. Subsequently, the 3′-overhang of the FAM/Dabycl labeled hairpin signal probes hybridize on the exposure primer binding domain at Dig-HP1 template and initiate the APR reaction to cross open and extend Dig-HP1 to generate many elongated DNA duplexes with the help of Bst DNA polymerase. These DNA duplexes make the fluorophore and quencher away from each other and thereby produce dramatically enhanced fluorescence signal for sensitive detection of target Anti-Dig antibody down to 0.18 nM. Moreover, this method can selectively monitor Anti-Dig antibody against other interference proteins, and also be extended to detect Anti-Dig antibody in serum samples, confirming its potential for ultrasensitive detection of low-abundant antibodies for early disease therapy and vaccine evaluation.

Water-stable nickel-based coordination polymer for selective and sensitive enhancing and quenching fluorescence sensing of ascorbic acid and acetylacetone

The novel Ni-based coordination polymer [Ni(H2edda) (bpe)] (CP 1) was successfully synthesized by employing 5,5′ (ethane-1,2-diylbis(oxy)) diisophthalic acid (H4edda) and 1,2-bis (4-pyridyl) ethylene (bpe) under hydrothermal conditions. Structural analysis indicates that CP 1 presents a 2-fold-interpenetrated two-dimensional (2 D) framework with a uninodal sql topology. Further investigation reveals that the newly obtained CP can be stable in water or even exposed in a certain acid/base aqueous solution (pH = 3–11) for a long period of time. Remarkably, CP 1 can further serve as a bifunctional sensor for ascorbic acid (AA) and acetylacetone (acac) in aqueous media according to fluorescence enhancing and quenching effects, respectively. Notably, both sensing processes are labeled with exceptional anti-interference property, high sensitivity and selectivity, wide linear range (0–50 μM for AA and 0.2–1.8 mM for acac) and low detection limit (1.37 nM for AA and 1.58 μM for acac). Theoretical simulations and experimental findings point out that in the process of AA detection by CP 1, the significant fluorescence enhancement could be caused by the photo-induced electron transfer (PET) process, while the inner filter effect (IFE) mechanism combined with PET should be responsible for the fluorescence quenching of CP 1 by acac.

Fluorescent turn-on sensing of albumin proteins (BSA and ovalbumin) using vitamin B6 cofactor derived Schiff base.

The detection of albumin proteins with high accuracy by facile analytical approaches is important for the diagnosis of various diseases. This manuscript introduced an easy-to-prepare Schiff base L by condensing vitamin B6 cofactor pyridoxal 5'-phosphate (PLP) with 2-aminothiophenol for the fluorescence turn-on sensing of bovine serum albumin (BSA) and ovalbumin (OVA). The weakly emissive L showed a significant fluorescence enhancement at 485 and 490 nm in the presence of OVA and BSA with an estimated sensitivity limit of 1.7 µM and 0.3 µM, respectively. The formation of protein-ligand complex restricted the free intramolecular rotation of L is expected to show the selective fluorescence enhancement. The molecular docking and molecular dynamics simulations were performed to examine the binding affinity and modes between BSA/OVA and L. The practical utility of L as a fluorescent turn-on sensor was validated by quantifying BSA and OVA in various real biological samples of milk, serum, egg white and urine with good recovery percentages.

Construction of an Entropy-Driven Dumbbell-Type DNAzyme Assembly Circuit for Lighting Up Uracil-DNA Glycosylase in Living Cells.

Sensitive monitoring of intracellular uracil-DNA glycosylase (UDG) in living cells is essential to understanding the DNA repair pathways and discovery of anticancer drugs. Herein, we demonstrate the construction of an entropy-driven dumbbell-type DNAzyme assembly circuit for lighting up UDG in living cells via the integration of entropy-driven DNA catalysis (EDC) with the DNAzyme biocatalyst. Target UDG excises the damaged uracil base, causing the breakage of detection probe and the release of trigger. The released trigger can initiate the downstream EDC reaction to form two catalytically active DNAzyme units. The resultant dual Mg2+-DNAzyme units serve as the signal transducers to cyclically cleave the fluorophore/quenched-modified reporters, generating an enhanced fluorescence signal. In contrast to the single-layered EDC method with a linear amplification, the proposed doublet EDC-DNAzyme strategy exhibits high signal gain and achieves a detection limit of 8.71 × 10-6 U/mL. Notably, this assay can be performed in one-step manner at room temperature without the requirement of strict temperature control and complicated reaction procedures, and it can further screen the UDG inhibitors, measure kinetic parameters, and discriminate cancer cells from normal cells. Moreover, this strategy can monitor intracellular UDG activity with improved signal gain, and it may be exploited for sensing and imaging of other types of DNA modifying enzymes with the integration of the corresponding detection substrate, providing a facile and robust approach for biological research studies and clinical diagnosis.

Anisotropic assembly and fluorescence enhancement of conjugated polymer nanostructures

AbstractThe electronic properties of conjugated polymers depend sensitively on their conformation and morphology. However, control over the morphology of conjugated polymers is highly challenging. Here, we demonstrate a facile approach for assembling conjugated polymers into anisotropic nanostructures. In a water–tetrahydrofuran (H2O–THF) binary solvent, we prepared ellipsoidal nanoparticles, which can subsequently self‐assemble into triangle‐ring and rod‐like nanostructures in a stepwise manner. The transitions among these morphologies can be rationally regulated by tuning the volume ratio of H2O to THF and the polymer concentration. The nanostructures show shape‐dependent absorption from 383 to 403 nm and significant fluorescence enhancement with a quantum yield up to 70%. The oxetane groups in the polymer side chains and the presence of surfactant in the solvent are decisive for the anisotropic assembly. We further demonstrate multicolor fluorescent nanowires with good structural integrity over doping of dye molecules or other fluorescent polymers. Single nanowires were characterized by high‐order super‐resolution optical fluctuation imaging, which revealed spatial distribution of the photooxidation sites along single nanowire for easily generating hole polarons.

Can Direct-Immersion Aqueous–Aqueous Microextraction Be Achieved When Using a Single-Drop System?

For the analysis of biological analytes in complex matrices, it is difficult to achieve extraction of analytes and enrichment in an aqueous-aqueous single-drop microextraction system. In this study, we proposed a pH-dependent polydopamine (PDA)-coated vesicle/Fe3O4 magnetic aqueous-aqueous in a single-drop microreactor (SDMR) for the direct fluorescence detection of glutathione S-transferase (GST), a metabolic enzyme involved with crucial biological processes, in biological samples. After extracting and enriching the GST target from an aqueous-aqueous single-drop interface, the extraction process was conducted rapidly in 6 s in the SDMR system. The GST was first extracted from the sample solution via the GST-Aptamer on the polydopamine-coated vesicle/Fe3O4 nanospheres (Fe3O4@PDA@GST-Aptamer). Then, as the pH changed from weakly acidic to weakly alkaline in the SDMR system, the GST and GST-Aptamer were released from Fe3O4@PDA@GST-Aptamer nanospheres and captured by polydiacetylene vesicles via the capture probe. These changes altered the effective conjugation length and angle of the vesicle trunk, generating a highly enhanced fluorescence signal. This not only achieved the purpose of target enrichment but also reduced interferences posed by matrix effects. The approach can be used for the direct detection of GST in genuine urine and blood without any sample pretreatment. The linear range was 0.005 to 0.5 μg/mL, and the limit of detection was 0.834 ng/mL. The recoveries of GST in genuine blood samples ranged from 90.8 to 108.0% and in urine from 91.6 to 102.8%. The method has the capability of handling complex samples directly by enabling microextraction in an aqueous-aqueous single-drop system.

A dual-functional fluorescent probe for simultaneous visualization and quantification of Au and Pd species in environmental and biological systems

Gold (Au) and palladium (Pd) species have been widely used in synthetic chemistry, biology, and environmental sciences, raising hard-to-ignore health and environment risks due to their potential toxicity. Herein, a novel dual-functional fluorescent probe was rationally designed and developed for simultaneous quantification and visualization of Au3+ and Pd species in the environmental and biological systems. Significant fluorescence enhancement at 484 and 606 nm and color changes were observed upon addition of Au3+ and Pd0 with high sensitivity. The detection limit for Au3+ and Pd0 was as low as 68 nM and 7 nM, respectively. Combined with smartphone chromaticity and dual-channel fluorescence imaging analysis, this probe was successfully applied to the quantification and visualization of Au3+ and Pd species in real water samples. Thus, simultaneous naked-eye visualization and quantification of Au3+ and Pd0 in real water samples was achieved using this probe. The probe was also successfully applied to fluorescence imaging of Au3+ and Pd0 in HeLa cells and zebrafish, promoting the monitor and understanding about gold and palladium species in environmental and biological systems.

Indole-Based Long-Wavelength Fluorescent Probes for Bioimaging of S-Nitrosylation in Mitochondria.

S-Nitrosylation has been found to play an important role in regulating mitochondrial function. However, probes for detection of protein S-nitrosylation in mitochondria remain unexplored. Herein, a novel 4-(pyridin-4-yl)vinyl-substituted indole was designed, exhibiting a long-wavelength emission and a high fluorescent quantum yield. Functionalization of the 7-position of the indole ring with an arylphosphine ester resulted with probes with efficient mitochondria-targeting ability. Furthermore, the indole-arylphosphine displayed a significant fluorescence enhancement upon exposure to S-nitrosoglutathione (GSNO) at low micromolar concentrations in A431 cells. Taken together, this study provides a new indole-based fluorescent probe with a unique long-wavelength emission for direct detection of S-nitrosylation in mitochondria, which may represent a powerful tool for understanding the critical roles of S-nitrosylation within mitochondria of living organisms.

Isoxazole Derivatives against Carbonic Anhydrase: Synthesis, Molecular Docking, MD Simulations, and Free Energy Calculations Coupled with In Vitro Studies.

Heterocyclic compounds with a five-membered ring as a core, particularly those containing more than one heteroatom, have a wide spectrum of biological functions, especially in enzyme inhibition. In this study, we present the synthesis of five-membered heterocyclic isoxazole derivatives via sonication of ethyl butyrylacetate with aromatic aldehyde in the presence of a SnII-Mont K10 catalyst. The synthesized compounds were characterized using sophisticated spectroscopic methods. In vitro testing of the compounds reveals three derivatives with significant inhibitory action against carbonic anhydrase (CA) enzyme. The compound AC2 revealed the most promising inhibitory activity against CA among the entire series, with an IC50 = 112.3 ± 1.6 μM (%inh = 79.5) followed by AC3 with an IC50 = 228.4 ± 2.3 μM (%inh = 68.7) compared to the standard with 18.6 ± 0.5 μM (%inh = 87.0). Molecular docking (MD) study coupled with extensive MD simulations (400 ns) and MMPBSA study fully supported the in vitro enzyme inhibition results, evident from the computed ΔGbind (AC2 = −13.53 and AC3 = −12.49 kcal/mol). The in vitro and in silico studies are also augmented by a fluorescence-based enzymatic assay in which compounds AC2 and AC3 showed significant fluorescence enhancement. Therefore, on the basis of the present study, it is inferred that AC2 and AC3 may serve as a new framework for designing effective CA inhibitors.

A highly sensitive NIR fluorescence probe for hypoxia imaging in cells and ulcerative colitis

Ulcerative colitis, a kind of inflammatory bowel disease (IBD), is caused by dysregulated immune response of intestinal bacteria. This chronic disorder can lead to a deficiency of O2 (hypoxia) in the colon microenvironment. Nitroreductase (NTR) is a highly expressed endogenous enzyme under hypoxia, so the detection of NTR can provide diagnostic information about ulcerative colitis. Herein, an ultrasensitive NTR-triggered fluorescence probe (WS-1-NO2) is developed for hypoxia imaging in ulcerative colitis. The probe shows a significant fluorescence enhancement (45-fold) after reacting with NTR, with an extremely low detection limit of 0.096 ng/mL. Furthermore, we apply it for fluorescence imaging of hypoxia in living cells, tumors and dextran sulphate sodium (DSS)-induced ulcerative colitis mouse models. We believe that the probe may be investigated as an effective potential tool for gaining insight into the hypoxia-relevant diseases, such as cancer and ulcerative colitis.

An activatable fluorescent probe enables in vivo evaluation of peroxynitrite levels in rheumatoid arthritis

An activatable probe able to detect RONS level underlying the development of rheumatoid arthritis (RA) would be far-reaching for the diagnosis and drug efficacy assessment of RA. Despite more and more evidence suggests that ONOO− is an important signaling molecule participating in the RA disease, only rare fluorescent probes can detect ONOO− in this disease with satisfying performance. To this end, we designed and synthesized a novel activatable AIE fluorescent probe (DPPO-PN) for the detection of ONOO− levels in RA. The probe linearly responds to 0–10 μM ONOO− with a significant far-red fluorescence enhancement at 632 nm in 30 s (F/F0 = 161-fold, LOD = 10 nM) upon the excitation of 490 nm, elucidating excellent sensing abilities for ONOO− in cuvettes. Moreover, the fluctuations of intracellular ONOO− levels caused by adscititious adding or stimulant provoking could be real-time captured and visualized with this probe by confocal imaging. Further, the intravital imaging of ONOO− in LPS-induced and CFA-induced RA mouse models also can be achieved with the aid of the probe, substantiating the burst of ONOO− in the RA process. Therefore, this work not only offers an auxiliary tool for the diagnosis of RA but also would benefit our understanding of the ONOO−‘s roles in RA.

Tailoring the photoluminescence of capmatinib towards a novel ultrasensitive spectrofluorimetric and HPLC-DAD monitoring in human serum; investigation of the greenness characteristics

This work reports for the first spectrofluorimetric investigation of the INC280, Capmatinib (CAPM). The photophysical characteristics of CAPM especially fluorescence was extensively studied. CAPM has a native green fluorescence at λem = 500 nm with λex = 250 nm, that could be influenced and optimized under various experimental conditions of solvents, pH, temperature and inclusion matrices. Generally, protic polar alcoholic solvents are the best solvents in sensitizing CAPM emission. Furthermore, addition of disodium hydrogen phosphate aqueous solution of pH 6 at 25 °C reveals the highest fluorescence intensity of CAPM. Sodium dodecyl sulfate (SDS) when added to CAPM in optimized concentration results in 81.4 % enhancement in the CAPM fluorescence signal which impacted an improved sensitivity in the fluorimetric assaying of CAPM. HPLC-DAD method was also applied for determination of cited drug. Native spectrofluorimetry and HPLC-DAD of CAPM exhibits wide linear dynamic range from 0.015 to 2.0 µg/ mL and 0.02–100 µg/ mL within limits of detection of 0.0038 and 0.0039 µg/ mL, respectively. Moreover, the two methods are of high accuracy and precision that reveal estimates of 93.16–100.91 % and 96.67–100.42 % for recovery % while the corresponding estimates of RSD% ranges from 0.926 to 2.668 % and 0.505–1.571 %. The two methods were validated with successful applicability in the assaying of spiked CAPM in human serum samples. Greenness characteristics for both spectroflourimetric and HPLC-DAD methods were assessed using AGREE and GAPI approaches.

Self-Customized Multichannel Exponential Amplifications Regulate Powered Monitoring of Terminal Deoxynucleotidyl Transferase Activity.

The discovery and function analysis of terminal deoxynucleotidyl transferase (TdT) add a new dimension to the understanding of leukemia mechanisms and stimulate the development of new analytical tools for leukemia diagnosis. Herein, taking advantage of the inherent property of TdT for performing DNA synthesis using only single-stranded DNA as the nucleic acid substrate, we developed a self-customized multichannel exponential amplification (SMEA) system for the fluorescent sensing of TdT activity. The SMEA design employs an intermolecular DNA interaction made of a nicking site-incorporated elongation primer (EP) and a nicking site-incorporated poly-thymine tailed molecular beacon (Poly-T-MB). The absence of TdT is unable to bridge the relationship between EP and Poly-T-MB, ensuring the SMEA has an ultralow background. The presence of TdT, however, leads to the elongation of EP to poly-adenine tailed EP (Poly-A-EP) under a dATP pool responsible for further hybridization with numerous Poly-T-MB. With the aid of polymerase and nickase to react with the hybridization product of Poly-A-EP/(Poly-T-MB)n, it can cause bidirectional strand nicking, polymerization, and displacement in many cycles and channels. In this case, the SMEA is found to be associated with the configuration transformation and splitting of all Poly-T-MBs for a significant fluorescence enhancement. Depending on this high target signal amplification and strong background inhibition abilities, the SMEA sensing system is powerful for the qualitative and quantitative determination of TdT activity, showing that it has great promise for biomedical study and disease diagnosis.

Multicolor Nitrogen-Doped Carbon Quantum Dots for Environment-Dependent Emission Tuning.

Carbon quantum dots (CQDs) have potential applications in many fields such as light-emitting devices, photocatalysis, and bioimaging due to their unique photoluminescence (PL) properties and environmental benignness. Here, we report the synthesis of nitrogen-doped carbon quantum dots (NCQDs) from citric acid and m-phenylenediamine using a one-pot hydrothermal approach. The environment-dependent emission changes of NCQDs were extensively investigated in various solvents, in the solid state, and in physically assembled PMMA–PnBA–PMMA copolymer gels in 2-ethyl-hexanol. NCQDs display bright emissions in various solvents as well as in the solid state. These NCQDs exhibit multicolor PL emission across the visible region upon changing the environment (solutions and polymer matrices). NCQDs also exhibit excitation-dependent PL and solvatochromism, which have not been frequently investigated in CQDs. Most CQDs are nonemissive in the aggregated or solid state due to the aggregation-caused quenching (ACQ) effect, limiting their solid-state applications. However, NCQDs synthesized here display a strong solid-state emission centered at 568 nm attributed to the presence of surface functional groups that restrict the π–π interaction between the NCQDs and assist in overcoming the ACQ effect in the solid state. NCQD-containing gels display significant fluorescence enhancement in comparison to the NCQDs in 2-ethyl hexanol, likely because of the interaction between the polar PMMA blocks and NCQDs. The application of NCQDs-Gel as a solid/gel state fluorescent display has been presented. This research facilitates the development of large-scale, low-cost multicolor phosphor for the fabrication of optoelectronic devices, sensing, and bioimaging applications.

A coumarin coupled electron donor-acceptor dyad for cascade detection of aluminium ions and explosive nitroaromatic compounds

A coumarin coupled electron donor–acceptor dyad (HL) has been synthesized and characterized by different conventional techniques. Details spectroscopic investigation has been carried out to understand the photophysical behavior of as-prepared HL. The UV–visible spectral behavior of HL is found to be intramolecular charge transfer in nature and shows broadband, having maxima at 432 nm with a shoulder peak around 348 nm in DMF. The emission spectrum of HL also gives broadband, having maxima located at 480 nm in DMF. Further, HL is employed for the cascade detection of Al3+ ions (ON) and picric acid (PA, OFF) in DMF-H2O (7:3, v/v) media. A colorimetric change from yellow to colorless is observed in the presence of Al3+ ions. A significant fluorescence enhancement is observed due to the well coordination of Al3+ ions with HL. A visual bluish-green color could be seen under 365 nm UV light irradiation, which is also well supported by the color chromaticity diagram. The fluorescence of the HL-Al3+ complex is quenched in the presence of PA among all the tested nitroaromatic compounds. The sensitivity of HL and HL-Al3+ complex towards detection of Al3+ ions and PA can be possible down to 0.638 μM and 0.623 µM, respectively. The developed chemosensor is employed for the practical application for mapping Al3+ ions in the living cell. The performance of HL toward Al3+ ions proved that it could be exploited as a signal tool for environmental and biological samples.