Strong Blue Fluorescence Emission Research Articles

A blue fluorescent waterborne polyurethane-based Zn(ii) complex with antibacterial activity

Abstract Polymer-based transition metal complexes have attracted much attention in many fields of application. In this article, a fluorescent polymer-based transition metal complex was prepared by bonding the transition metal complex with the polymer. First, Schiff base salicylaldehyde ethanolamine (HL) as a ligand was prepared by the reaction of salicylaldehyde with ethanolamine. Then, salicylaldehyde glycolamine Zn(ii) transition metal complexes (ZnL2) were synthesized with HL and Zn2+ as the central ion. Finally, a blue fluorescent waterborne-based polyurethane Zn(ii) complex (ZnL2-WPU) with an antibacterial function was prepared with ZnL2 as a chain extender by modified acetone method. The characteristics of fluorescence, heat stability, and bacteriostasis were characterized. Compared with ZnL2, the UV–vis absorption peak of ZnL2-WPU shows a blue shift of about 20 nm. ZnL2-WPU has a strong blue fluorescence emission at 450 nm, and the intensity increases significantly with ZnL2 content. Surprisingly, the fluorescence lifetime of ZnL2-WPU is obviously increased, reaching more than one time that of ZnL2. Interestingly, the antibacterial efficiency of ZnL2-WPU against E. coli reached an incredible 99%. More importantly, ZnL2-WPU uses water as the dispersing medium, which is more environmentally friendly.

Chiral benzo[ghi]perylene substituted [n]helicenes with strong blue fluorescent emission and circularly polarized luminescence

Chiral organic fluorescent molecules with circularly polarized luminescence (CPL) properties have attracted much attention for their potential applications in chiral optical and electronic devices. Benzo [ghi]perylene is one of the classical polycyclic aromatic hydrocarbons (PAHs) with good fluorescent properties and has many applications in the fields including optoelectronic devices and fluorescence probes. In this work, chiral benzo [ghi]perylene substituted [n]helicenes were directly obtained from chiral BINOL. The introduction of benzo [ghi]perylene structure greatly improved the fluorescent efficiency of the pristine helicene molecules. These benzo [ghi]perylene substituted [n]helicenes show strong blue fluorescent emission in organic solutions with good fluorescent quantum yields. These molecules could also exhibit moderate fluorescent emission in the solid-states. Based on the DFT calculations results, the HOMOs and LUMOs of these molecules are mainly contributed by benzo [ghi]perylene, which forms an orthogonal geometry with helicene moieties. The enantiomers of these molecules show opposite signals in CD and CPL spectra. The gabs and glum values could be increased with elongation of helicene structure. Compounds with [7]helicene moiety show relatively large gabs and glum values, which could reach up to 3.6 × 10−3 and 1.0 × 10−3, respectively. This work has provided a new strategy to develop chiral organic emitters through integration of benzo [ghi]perylene and helicene structures, which exhibit efficient fluorescent emission and intense CPL properties.

Facile Green Gamma Irradiation of Water Hyacinth Derived-Fluorescent Carbon Dots Functionalized Thiol Moiety for Metal Ion Detection.

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 548nm when excited between 240 and 500nm. The quantum yield of CDs-SH was elucidated to be 13%, with strong blue fluorescence emission under ultraviolet irridiation (365nm), high photostability and no photobleaching. The limit of detection was determined at micromolar levels for Hg2+, Cu2+, and Fe3+. CDs-SH could be a real-time monitoring sensor for Hg2+ and Cu2+ as fluorescence quenching was observed within 2min. Furthermore, paper test-strip based CDs-SH could be applied to detect these metal ions.

Preparation of One-Emission Nitrogen-Fluorine-Doped Carbon Quantum Dots and Their Applications in Environmental Water Samples and Living Cells for ClO- Detection and Imaging.

Hypochlorite (ClO-) has received extensive attention owing to its significant roles in the immune defense and pathogenesis of numerous diseases. However, excessive or misplaced production of ClO- may pose certain diseases. Thus, to determine its biological functions in depth, ClO- should be tested in biosystems. In this study, a facile, one-pot synthesis of nitrogen-fluorine-doped carbon quantum dots (N, F-CDs) was developed using ammonium citrate tribasic, L-alanine, and ammonium fluoride as raw materials under hydrothermal conditions. The prepared N, F-CDs demonstrate not only strong blue fluorescence emission with a high fluorescence quantum yield (26.3%) but also a small particle size of approximately 2.9 nm, as well as excellent water solubility and biocompatibility. Meanwhile, the as-prepared N, F-CDs exhibit good performance in the highly selective and sensitive detection of ClO-. Thus, a wide concentration response range of 0-600 μM with a low limit of detection (0.75 μM) was favorably obtained for the N, F-CDs. Based on the excellent fluorescence stability, excellent water solubility, and low cell toxicity, the practicality and viability of the fluorescent composites were also successfully verified via detecting ClO- in water samples and living RAW 264.7 cells. The proposed probe is expected to provide a new approach for detecting ClO- in other organelles.

Crayfish shells-derived carbon dots as a fluorescence sensor for the selective detection of 4-nitrophenol

ABSTRACT As a type of environmentally deleterious compound, 4-nitrophenol (4-NP) has become a global concern due to its extreme toxicity to aquatic organisms and humans. Herein, we used naturally available crayfish shells as precursors to prepare a new type of carbon dots (CDs) by the hydrothermal method. The as-synthesized CDs exhibited strong blue fluorescence emission which can be sensitively quenched by 4-NP through the static quenching effect because of the formation of a ground state complex between CDs and 4-NP. Accordingly, a facile and rapid fluorescence sensor was developed to detect 4-NP from 0 μM to 50 μM with a limit of detection (LOD) of 0.16 μM. Furthermore, the proposed sensor was successfully applied for the detection of 4-NP in fresh crayfish meat and aquatic water samples.

Novel "Turn-On" Luminescent Chemosensor for Arginine by Using a Lanthanide Metal-Organic Framework Photosensitizer.

Arginine is considered as a biomarker of cystinuria and other diseases, and thus, it is of urgency to develop a simple and rapid method with high sensitivity and selectivity for arginine detection to meet the demand of on-site analysis and bedside diagnosis. In this work, a lanthanide metal-organic framework, La(TATB), was prepared using a triazine-based planar ligand, 4,4',4″-s-triazine-2,4,6-triyltribenzoate (H3TATB), and lanthanide ion (La3+). La(TATB) can be used as a highly photosensitive agent to activate molecular oxygen to 1O2 to achieve efficient photosensitive oxidation of arginine accompanied by strong blue fluorescence emission under 302 nm UV irradiation. Due to the porous structure and high specific surface area of La(TATB), short-life 1O2 can effectively approach and react with amino acid substrate molecules, thus leading to higher sensitivity than other systems. Therefore, the "turn-on" fluorescence sensing of trace arginine can be realized, with a measured linear response range of 10-20,000 nM and a limit of detection as low as 7 nM. This method can be used for the detection of trace arginine in urine, which is conducive to the bedside diagnosis and rapid screening of cystinuria and other diseases. The proposed method not only expands the application scope of Ln-MOFs but also provides a new construction strategy for "turn-on" luminescence sensors.

Detection of Fe3+ ions in aqueous environment using fluorescent carbon quantum dots synthesized from endosperm of Borassus flabellifer

Natural products derived carbon quantum dots (CQDs) catch huge attention owing to their distinctive properties of smaller size, water dispersibility, high photostability, lower cost, tunable emission, biocompatibility, least toxicity, electrical conductivity, optical and catalytic properties, and easy modification. Herein high fluorescent CQDs were prepared using Borassus flabellifer (ice apple) as a carbon source utilizing the simplistic one-step hydrothermal method. The prepared CQDs possessed excellent photoluminescence, high photostability, and stability in an aqueous solution and harbored large of quantum yield and strong stability in high pH conditions with the characteristic strong blue fluorescence emission. With these superior properties, the CQDs have been used as sensing probes for the detection of Fe3+ ions having excellent selectivity and sensitivity with a 2.01 μM limit of detection. The CQDs decorated probe was found effective in detecting Fe3+ ions in the tap and drinking mineral water, suggesting the applicability of the prepared sensor. The developed sensor exhibited advantages, including simple, low-cost, label-free, rapid, and good sensitivity and selectivity towards Fe3+ ions, with a great application for detection of such ions in real water.

An Innovative Microwave-Assisted One-Step Green Synthetic Approach of Biowaste Derived Fluorescent Carbon-Dot Invisible Ink for Currency Anti-Counterfeiting Applications

The quest for the design and synthesis of carbon dots with anti-counterfeit properties that are derived via green, environmentally friendly and economical procedures is a continuous process. Carbon dots (C-dots) derived from biowaste are cheap to synthesize, possess good photo-stability and high synthetic yield, making them applicable in the anti-counterfeiting of currency. Herein, we report a novel eco-friendly, cheaper, and faster method for the synthesis of carbon dots with strong photoluminescence properties from monkey orange fruit (Strychnos spinosa) biowaste. The presence of the hydroxyl and carbonyl functional groups of the carbon dots were determined by the Fourier transform infrared spectroscopy (FTIR). The carbon dots showed strong blue emission fluorescence (emission wavelength of 452[Formula: see text]nm) when excited at 330[Formula: see text]nm. The morphology and size were determined by the atomic force microscopy (AFM) which indicated amorphous and spherical nanoparticles with an average size of less than 2[Formula: see text]nm. The no-crystallinity of the as-prepared carbon dots was confirmed using X-ray diffraction which showed the graphite-like structure. The carbon dots were produced and demonstrated good photo and chemical stability as well as high covert properties. The anti-counterfeiting of currency application by the synthesized carbon dots was demonstrated when the subsequent gel ink printed on the currency showed excellent chemical stability when exposed to washing with water, ethanol, and acetone. It also showed superior photostability when exposed to UV light at 365[Formula: see text]nm and daylight for an extended period of up to 6[Formula: see text]h. This work provides a facile, economical, and green approach for large scale production of carbon dots from the abundant biowaste.

Glutathione-stabilized copper nanoclusters mediated-inner filter effect for sensitive and selective determination of p-nitrophenol and alkaline phosphatase activity

A simple and highly selective fluorescence biosensor has been exploited for p-nitrophenol (p-NP) and alkaline phosphatase (ALP) activity detection based on the glutathione-stabilized copper nanoclusters (GSH-CuNCs) mediated-inner filter effect (IFE). The GSH-CuNCs were prepared by employing GSH as stabilizer and ascorbic acid (AA) as reductant. The obtained GSH-CuNCs exhibited a strong blue fluorescence emission at 420 nm with an excitation wavelength of 365 nm, which overlapped largely with the absorption spectra of p-nitrophenol (p-NP). Therefore, the luminescence of GSH-CuNCs could be quenched by p-NP through inner filter effect. In addition, ALP catalyzed the substrate p-nitrophenyl phosphate (p-NPP) to form p-nitrophenol (p-NP), which also leading to the fluorescence quenching of GSH-CuNCs. The fluorescent strategy was realized for the sensitive determination of p-NP and ALP activity with the promising limit of detection of 20 nM (for p-NP) and 0.003 mU⋅mL−1 (for ALP). Furthermore, the method could be applied to detect the p-NP content in river water samples and ALP activity in human serum samples.

Highly selective and sensitive fluorescence determination of m-Phenylenediamine

This work presented a new fluorescence method for the determination of m-phenylenediamine (MPD) based on the reaction between MPD and acetylacetone. The formed compound Hacac-MPD exhibited strong blue fluorescence emission under 365 nm excitation. Its fluorescence intensity had an excellent correlation with the MPD concentration Under the optimal conditions, the developed method gave a linear range of 10–600 μg L−1 with a low detection limit of 4 μg L−1. Furthermore, the coexistence of common inorganic ions and other aromatic amines had hardly influence on the determination of MPD, demonstrating high selectivity. Additionally, the MPD in spiked water samples and hair dye samples was successfully detected by the developed method, and the recoveries were 97.5%-101.6% and 98.3%-98.9%, respectively. The established method exhibited a good application prospect for the determination of MPD in environment and daily necessities.

Room temperature driven highly crystalline fluorine-doped carbon quantum dots for sensitive tetracycline sensing

Carbon quantum dots (CQDs) with semiconductor-like properties have received considerable attention because of their unique photoelectric properties and electron transfer ability. However, the preparation of highly crystalline CQDs with strong fluorescence (FL) emission by the room temperature (RT) synthesis is a challenging task. Herein, we develop a highly-efficient RT synthesis strategy based on the Schiff base condensation reaction for preparing the fluorine-doped CQDs (F-CQDs) with good crystallinity. The as-prepared F-CQDs show strong blue FL emission with a high quantum yield of 39%, which is the highest values yet recorded for carbon dots prepared by RT synthesis. Moreover, the F-CQDs can be used for sensitive tetracycline sensing based on inner filter effect. The FL intensity ratio (F0/F) of the F-CQDs is proportional to the concentration of tetracycline in the range of 0.1–25 μM with the limit of detection of 85 nM. This sensitive assay has a good application prospect for tetracycline detection in the complex matrixes because of its simplicity and sensitivity.

Characterization and luminescence sensing behaviour of a newly constructed hydrolytic stable Pb(II) coordination polymer

Sensing and detecting toxic pollutants like Fe3+, chromate anions and trinitrophenol (TNP) in water are especially important due to their hazardous effects on environmental and ecological systems. In this work, the hydrolytic stable Pb(II) CP {[Pb(asba)(obix)]•2H2O}n (1) [H2asba = 2-amino-4-sulfobenzoic acid, obix = 1, 2-(methylenebenzene)bisimidazole] was constructed and well characterized. 1 exhibits reversible de-/re-hydration behavior. The wide indirect band gap was obtained through the analysis of the solid-state diffuse reflectance UV–Vis spectrum of 1, which is consistent with the calculated value using the CASTEP program in Materials Studio. 1 keeps its crystallinity and structural integrity in various solvents. Interestingly, 1 shows solvent-dependent fluorescence emissions. A strong blue fluorescence emission occurs in water. 1 can sense the Fe3+ and chromate anions selectively and sensitively in the presence of the co-existent different metal cations and inorganic anions, respectively. Moreover, 1 also shows efficient sensing of Fe3+ in the simulative biological system. Furthermore, 1 demonstrates sensitive sensing of TNP. 1 displays excellent recyclability in sensing of these analytes. 1 can determine the related trace analytes in ppm level.

Facile hydrothermal synthesis of nitrogen, phosphorus-doped fluorescent carbon dots for live/dead bacterial differentiation, cell imaging and two nitrophenols detection

The blue fluorescent nitrogen, phosphorus doped carbon dots (Tg N,P-CDs) deriving from Thelephora ganbajun Zang were successfully obtained by hydrothermal method. Tg N,P-CDs possessed excellent fluorescence features and displayed strong blue fluorescence emission at 444 nm under 356 excitation with good water solubility. Tg N,P-CDs exhibited low biotoxicity and excellent biocompatibility by live/dead bacterial differentiation, cell imaging and onion epidermal staining. Furthermore, the nanoprobes showed high selectivity and sensitivity in detecting 2,4-dinitrophenol (2,4-DNP) and 4-nitrophenol (4-NP), and excellent linear range of 0–50 μM (R2 = 0.9923) and 0–50 μM (R2 = 0.9926) with low detection limits of 35.09 nM and 78.62 nM for 2,4-DNP and 4-NP, respectively. The Tg N,P-CDs was successfully applied to determine 4-NP and 2,4-DNP in real water and soil samples. It revealed that the inner filter effect quenching mechanism dominated in quenching of Tg N,P-CDs fluorescent by 2,4-DNP and 4-NP. It provides a new insight on the bioimaging application and environmental pollutant detection.

Architecture of New Rare Earth Metal Complexes as Precursors for the Fabrication of a New Class of OLEDs with Blue Shift Fluorescence

Due to the high demand for blue organic light‐emitting diodes (blue‐OLED), in this work, a new class of them with lanthanide complexes is engineered based on a chemical design. Four new rare‐earth metals complexes, Nd2(C11H9NO)4(NO3)4(CH3COO)2·2(CH3OH) (1), Pr2(C11H9NO)4(NO3)4(CH3COO)2·2(CH3OH) (2), Sm2(C11H9NO)4(NO3)4(CH3COO)2·2(CH3OH) (3), and Tm2(C11H9NO)4(NO3)4(CH3COO)2·2(CH3OH) (4) as new precursors for fabrication of blue‐OLED were synthesized using 8‐hydroxy‐2‐methylquinoline as the primary ligand. The synthesized complexes were characterized by UV/Vis and infrared spectroscopy, elemental analysis, and X‐ray powder diffraction. The molecular structure of 1 and 2 as representative complexes were accomplished by single‐crystal X‐ray diffraction. The single‐crystal structures showed complexes 1 and 2 are iso‐structural. The similar X‐ray powder diffraction patterns of prepared complexes revealed the same structure for all of them. The results showed that the photoluminescence spectra of the complexes could scrutinize by the impact of rare‐earth metals. The strong blue fluorescence emission spectra of the prepared complexes showed they are suitable for the fabrication blue light‐emitting diodes using a simple processing method, and this may overcome the high demand of blue‐OLED.

Photophysical properties and bisulfite recognition of a coumarin cyanopyridine derivative

A coumarin cyanopyridine derivative 1 (3-(7-diethylamino-2-oxo-2H-chromen-3-yl)-2-pyridin-4-yl-acrylonitrile) was developed as bisulfite fluorescence chemosensor. Two different crystals 1a (blue block, triclinic system, P-1 space group) and 1b (red plate, monoclinic, P 21/n space group) were obtained from acetonitrile (1a) and dichloromethane (1b), respectively, by slow solvent evaporation. The probe emits strong blue fluorescence emission (468 nm, 482 nm) and high fluorescence quantum yield (0.22) in hexane. Fluorescent peak of the probe exhibits linear relationship to solvent polarity with high linear correlation coefficient and then can track environmental polarity. The probe can recognize bisulfite (HSO3−) in HEPES solution with blue fluorescence (485 nm) enhancement response and low detection limit being 1.02 nM, which has high sensitivity compared with other chemosensors for HSO3− reported in references. The mechanism analysis by in situ 1H NMR and mass spectrum indicates that HSO3− is added to the CC bond and the broken charge transfer from diethylcoumarin to pyridine group leads the strong blue fluorescence appearance from coumarin. The probe also has the potential application in monitoring HSO3− in living cells.

Syntheses, crystal structures, and characterizations of a series of divalent metal carboxylate-phosphonates

The hydrothermal reactions of divalent metal salts with 4-HOOC–C6H4–CH2–NH2CH2PO3H2 (H3L) led to four Metal-organic phosphonates (MOPs), namely, Ni(HL)(H2O)2 (1), Cd(HL) (2), CdCl(H2L) (3), and Pb1.5Cl2(H2L) (4). All these compounds exhibited 2D layer substructures with various features based on metal centers and –PO3 groups of the ligands. Differently, the layers cross-linked each other in compounds 1 and 4via hydrogen bonds generating 3D supramolecular frameworks. While in compounds 2 and 3, they were connected by carboxylate group of the ligands to form 3D pillared-layer frameworks. Such differences were related to the coordination mode of the metal centers, and the pH of the reaction system also played a important role on the coordination ability of the ligands. The magnetic properties reveal the presence of ferromagnetic interactions in compound 1 through a Ni–O–P–O–Ni five-member chain. Luminescent measurements indicate that compounds 2–4 each displays strong blue fluorescent emissions.

Nitrogen-doped carbon dots used as an “on–off–on” fluorescent sensor for Fe3+ and glutathione detection

A novel kind of nitrogen-doped carbon dots (N-CDs) with strong blue fluorescence emission was synthesized via microwave pyrolysis method using humic acid, urea, and citric acid as the precursor. We found that the fluorescence emission of N-CDs can be firstly quenched by Fe3+ (turn-off) and then recovered by glutathione (turn-on). Moreover, N-CDs applied as an “on-off-on” fluorescent sensor for the detection of Fe3+ and glutathione (GSH) was further studied in this work. N-CDs showed good selectivity and sensitivity towards Fe3+ than other metal ions, and the limit of detection (LoD) is lower to 0.102 μM. Furthermore, the stable N-CDs/Fe3+exhibited a high sensitivity detection for GSH with a LoD of 0.226 μM. In addition, density functional theory calculations were further performed to reveal the mechanism of the “turn-off” and “turn-on” process. According to geometries and frontier molecular orbital (FMO) results, N-CDs exhibited strong interaction with Fe3+ rather than other metal ions, and the N-CDs/Fe3+ complex exhibited the highest stability among other complexes. Furthermore, this “on–off–on” fluorescent sensor was successfully applied as a stain-screening detector for Streptococcus thermophilus with high production of GSH.

Ethanol-Precipitation-Assisted Highly Efficient Synthesis of Nitrogen-Doped Carbon Quantum Dots from Chitosan.

Nitrogen-doped carbon quantum dots (NCQDs) were prepared from chitosan through a hydrothermal reaction. When ethanol precipitation was used as the purification method, a high product yield of 85.3% was obtained. A strong blue fluorescence emission with a high quantum yield (QY) of 6.6% was observed from the NCQD aqueous solution. Physical and chemical characteristics of the NCQDs were carefully investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), Raman spectra, X-ray photoelectron spectroscopy (XPS), and transient fluorescence spectra. Experimental results showed that diameters of the NCQDs were in the range of 2–10 nm. The carbon quantum dots possess good water dispersibility and precipitation by ethanol. When used for metal ion detection, the detection limit of the NCQDs for Fe3+ was as low as 1.57 μM. This work proposed a facile method to synthesize NCQDs from chitosan with high yield and demonstrated that carbon quantum dots derived from chitosan were promising for ion detection.

The role of the chemical composition on the photoluminescence properties of N-doped carbon nanoparticles

Carbon nanoparticles (CNPs) have aroused a great interest due to its strong blue fluorescence emission. However, the blue fluorescence limits its applications in several cases; therefore, the synthesis of CNPs with multicolor emissions becomes mandatory. A widely used strategy of modulation of CNP photoluminescence is doping the carbon network with nitrogen atoms. Despite the great number of works carried out with N-doped CNPs, some contradictory experimental observations have been reported. These contradictions seem to be due to structural differences resulting of the different synthesis routes. Therefore, it is difficult to correlate the Photoluminescence properties with the nanoparticle structure. To address this issue, we study the Photoluminescence properties of CNPs with different chemical composition and sizes. Nanoparticles were synthesized by an acidic treatment for cutting carbonaceous materials previously reported and five different precursors. Using this methodology, we obtained five different materials which allow correlating the Photoluminescence spectrum with chemical composition and nanoparticle sizes.

Thermally Activated Delayed Fluorescence Polymer Emitters with Tunable Emission from Yellow to Warm White Regulated by Triphenylamine Derivatives

By virtue of electron-rich structure, relatively low electronic band gap, and strong blue fluorescence emission, triphenylamine derivatives (TPAs) can serve as effective host units for the π-conjug...