Absolute Fluorescence Quantum Yield Research Articles

Investigation of column purified dye derived carbon nanomaterials for security printing and supercapacitor applications

Literature evidence reveals versatile applications of carbon dots (CDs), but generally mixtures of various types of carbon nanomaterials, molecular intermediates as well as side products are obtained upon hydrothermal treatment of the precursor material. This demands isolation of pure components and their complete characterization before these nano carbonaceous materials are chosen for suitable applications. In the present study, perylenetetracarboxylic dianhydride (PTCDA) is subjected to hydrothermal treatment and the mother liquor obtained is separated using column chromatography technique using dichloromethane-methanol solvent system to isolate fractions of various fluorescent carbonaceous nanostructures. The TEM imaging of nano carbonaceous particles of all five fractions indicated that the first and third fractions were composed of nanoribbons, while the latter two fractions largely contained quasi-spherical nanoparticles of both lesser (carbon quantum dots) and greater (carbon nanodots) than 10 nm dimensions. The XPS results of all the fractions suggested separation based on polarity difference. The ID/IG ratios obtained from Raman spectra implied the presence of several defects on the CDs. The time resolved fluorescence spectra of third, fourth and fifth fractions revealed mono-exponential decay of fluorophores with excitation independent average lifetime values. The fifth fraction exhibited good biocompatibility and the highest absolute fluorescence quantum yield of 58.47 % among all the isolated samples. As these CDs displayed a remarkable rise in the quantum yield to 88.60 % when dispersed in water, a water-based flexo-ink was formulated. The photostable pale yellow flexo print proofs obtained on UV dull paper exhibited a green fluorescence under 365 nm illumination, whereas a yellow glow when shined with blue light, which can serve as an authentication feature for security documents and currency notes. Moreover, as the third fraction constitutes mainly of carbon nanoribbons (CNRs), an optimized polymer electrolyte was prepared along with sodium alginate (SA), and MgCl2 to understand their potential use in energy storage application. A supercapacitor was fabricated and tested for its electrochemical performance such as cyclic voltammtery (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge (GCD). An enhanced current window was observed in the CV of SA/CNRs compared to pure SA and SA/CNRs/Mg films, which indicated a structural interaction of CNRs with SA. The conductivity of SA/CNRs/Mg was lesser than SA/CNR in EIS studies due to the presence of Mg ions, while pure SA showed lesser conductivity. The dual ionic interaction of Na and Mg along with enhanced structural stability due to doped CNRs favors its convenient supercapacitor application. The fabricated eco-friendly supercapacitor showed a specific capacitance of 84 F/g. The GCD of the device displayed pseudocapacitance behaviour and was quite stable for 2000 cycles with coulombic efficiency of 96 %

Stable, porous, light-emitting post-modification covalent organic frameworks conjugated molecularly imprinted polymers for selective detection of pyrraline in salami products

Molecular imprinting is one of the most frequently occurring post-modification in the preparation of covalent organic frameworks (COFs) to enhance selectivity and specificity. In this study, we prepared a 2D layer structure of methoxy-conjugated COFs with the modification of azide (4-azido-L-phenylalanine), named [4-ALP]0.17-COFs, which exhibited a large specific surface area of 827.6 m2/g, good stability of water, polar solvents, chemistry, and thermodynamics. Fluorescent COF nanosheets ([4-ALP]0.17-CONs) obtained by liquid-assisted ultrasonic stripping have excellent blue luminescence properties and ultra-high absolute fluorescence quantum yield of 33.34 %. The modifiable functional groups in the surface of [4-ALP]0.17-CONs interacted with the targets and functional monomers of molecularly imprinted polymers (MIPs) through hydrogen bonding interactions, to form the 3D holes with recognition sites. The quantitative detection of pyrraline (PRL) could be achieved in the concentration range of 0.05–4 μg/L with the LOD was 34.81 ng/L. The spiked recovery of PRL in meat products was 88.01–106.00 %. The [4-ALP]0.17-CONs@MIPs sensing system showed excellent stability, reliability, reusability, and practicability, promising its potential for targeted monitoring of trace molecules in real matrices.

Novel Metal-Free Synthesis of 3-Substituted Isocoumarins and Evaluation of Their Fluorescence Properties for Potential Applications.

A novel metal-free synthesis of 3-substituted isocoumarins through a sequential O-acylation/Wittig reaction has been established. The readily accessible (2-carboxybenzyl)-triphenylphosphonium bromide and diverse chlorides produced various 1H-isochromen-1-one in the presence of triethylamine, employing sequential O-acylation and an intramolecular Wittig reaction of acid anhydride. Reactions using these facile conditions have exhibited high functional group tolerance and excellent yields (up to 90%). Moreover, the fluorescence properties of isocoumarin derivatives were evaluated at the theoretical and experimental levels to determine their potential application in fluorescent materials. These derivatives have good photoluminescence in THF with a large Stokes shift and an absolute fluorescence quantum yield of up to 14%.

Organotin(IV)-tetraphenylethylene acylhydrazone compounds with aggregation-induced emission property and application in anticancer therapy

Organotin (IV)-tetraphenylethylene (TPE) acylhydrazone compounds with aggregation-induced emission (AIE) property were prepared and characterized. The organotin (IV) compounds showed a conspicuous fluorescence improvement with a high absolute fluorescence quantum yield of 25.2 % (ClSnTPE) in the aggregation state, and restriction of intramolecular rotation (RIR) contributed to this AIE property. Using suitable fluorescence, confocal tests verified that these compounds could accumulate in the mitochondria of A549 cancer cells and decrease the mitochondrial membrane potential. Meanwhile, compounds could improve the intracellular reactive oxygen species (ROS) levels and inhibit the cell cycle (G1/G0 phase), then contributing to apoptosis. In addition to favorable in-vitro anti-proliferative activity (the similar to cisplatin), these compounds could also suppress A549 cancer cell migration. Above all, organotin (IV)-TPE acylhydrazone compounds show the promise as the mitochondrial targeting anticancer drugs for further study.

Novel diphenylacrylonitrile-decorated cyclotriveratrylene columnar liquid crystals with high fluorescence

ABSTRACT Although some cyclotriveratrylene (CTV) liquid crystals had been reported, the CTV liquid crystal with high fluorescence in mesophase was not presented up to now. By introducing diphenylacrylonitrile units on CTV skeleton, two CTV derivatives with AIE units (7a and 7b) were prepared for the first time. Their structures and crown conformations were characterised by 1H NMR, 13C NMR, MALDI-MS spectra and elemental analysis. Samples 7a and 7b exhibited the reversible liquid crystalline behaviours with hexagonal columnar mesophase supported by the DSC, POM and XRD analysis. The studies on photophysical properties of samples 7a and 7b suggested the high fluorescence in solid state and mesophase. The absolute fluorescence quantum yield of 7b in mesophase was as high as 0.45. This work not only reported the first CTV liquid crystals with high fluorescence in aggregated state but also provided a good strategy for constructing the novel CTV liquid crystals with excellent fluorescence.

Configuration of super-fast Cu2+-responsive chemosensor by attaching diaminomaleonitrile to BODIPY scaffold for high-contrast fluorescence imaging of living cells

A highly fluorescent Cu2+-responsive sensor, 2-amino-3-(BODIPYmethyleneamino)maleonitrile (BD) was constructed by attaching diaminomaleonitrile to a BODIPY scaffold. Cu2+ can be selectively recognized on a 2-s time-scale by way of fluorescence emission. When Cu2+ and BD coexist in solution, typical BODIPY emission was observed and the emission intensity could be increased to 334 times that of the blank dye solution. The mechanism of fluorescence increase is based on the generation of highly fluorescent species by Cu2+-triggered oxidative cyclization of the attached diaminomaleonitrile. The absolute fluorescence quantum yield (AFQY) of the cyclization product is 98% determined by integrating sphere. The highly emissive character can be attributed to the imidazole ring and dicarbonitrile on the BODIPY scaffold. It surpasses the meso-phenyl substituted analogue in AFQY and detection limits (DL). The specific Cu2+ recognition behavior was also validated in Hela cells with high-contrast fluorescence images.

Highly sensitive detection of microRNA-21 by nitrogen-doped carbon dots-based ratio fluorescent probe via nuclease-assisted rolling circle amplification strategy

Highly sensitive and selective detection of microRNA-21 (miRNA-21) in biological samples is critical for the disease diagnosis and cancer treatment. In this study, a nitrogen-doped carbon dots (N-CDs)-based ratio fluorescence sensing strategy was constructed for miRNA-21 detection with high sensitivity and excellent specificity. Bright-blue N-CDs (λex/λem = 378 nm/460 nm) were synthesized by facile one-step microwave-assisted pyrolysis method by using uric acid as the single precursor, and the absolute fluorescence quantum yield and fluorescence lifetime of N-CDs were 35.8% and 5.54 ns separately. The padlock probe hybridized with miRNA-21 firstly and then was cyclized by T4 RNA ligase 2 to form a circular template. At the present of dNTPs and phi29 DNA polymerase, the oligonucleotide sequence in miRNA-21 was prolonged to hybridize with the surplus oligonucleotide sequences in circular template, generating long and reduplicated oligonucleotide sequences containing abundant guanine nucleotides. Separate G-quadruplex sequences were generated after the addition of Nt.BbvCI nicking endonuclease, and then hemin bound with G-quadruplex sequence to construct the G-quadruplex DNAzyme. Such G-quadruplex DNAzyme catalyzed the redox reaction of o-phenylenediamine (OPD) with H2O2, finally producing the yellowish-brown 2,3-diaminophenazine (DAP) (λem = 562 nm). Due to the inner filter effect between N-CDs and DAP, the ratio fluorescence signal of DAP with N-CDs was utilized for sensitive detection of miRNA-21 with detection limit of 0.87 pM. Such approach has practical feasibility and excellent specificity for miRNA-21 analysis during highly homological miRNA family in HeLa cell lysates and human serum samples.

A ratiometric fluorescent probe for simultaneous detection of L-ascorbic acid and alkaline phosphatase activity based on red carbon dots/polydopamine nanocomposite

Herein, efficient red carbon dots (R-CDs) were synthesized by one-step hydrothermal treatment of N-(4-amino phenyl) acetamide and (2,3-difluoro phenyl) boronic acid. The optimal emission peak of R-CDs was at 602 nm (under 520 nm excitation) and the absolute fluorescence quantum yield of R-CDs was 12.9%. Polydopamine, which was formed by the self-polymerization and cyclization of dopamine in alkaline condition, emitted characteristic fluorescence with peak position of 517 nm (under 420 nm excitation) and affected the fluorescence intensity of R-CDs through inner filter effect. L-Ascorbic acid (AA), which was the hydrolysis product of L-ascorbic acid-2-phosphate trisodium salt under the catalytic reaction of alkaline phosphatase (ALP), effectively prevented the polymerization of dopamine. Combined with the ALP-mediated AA production and the AA-mediated polydopamine generation, the ratiometric fluorescence signal of polydopamine with R-CDs was correlated closely with the concentration of both AA and ALP. Under optimal conditions, the detection limits of AA and ALP were 0.28 μM during linear range of 0.5–30 μM and 0.044 U/L with linear range of 0.05–8 U/L, respectively. This ratiometric fluorescence detection platform can efficiently shield the background interference of sophisticated samples by introducing a self-calibration as reference signal in a multi-excitation mode, which can detect AA and ALP in human serum samples with satisfactory results. Such R-CDs/polydopamine nanocomposite provides a steadfast quantitative information and makes R-CDs be excellent candidate for biosensors via combining target recognition strategy.

Room-temperature synthesis of a covalent organic framework with hydrazine linkages for sensitive fluorescent detecting and renewable removing of copper ions

A hydrazone bonded covalent organic framework (TFPB-DHzDs) was successfully synthesized with acetic acid as the catalyst and acetonitrile as the solvent at room temperature. It was proved that TFPB-DHzDs has good crystallinity and stability, as well as excellent luminescence properties. The solid-state absolute fluorescence quantum yield of TFPB-DHzDs was 6.19%. It is found that copper ions have a specific strong fluorescent quenching effect and can be absorbed by TFPB-DHzDs, which makes it possible for the selective sensing of copper ions. The TFPB-DHzDs COF exhibited excellent ability to determine Cu2+ in aqueous solution ranging from 0.1 to 5 μM with the detection limit of 47.8 nM. Furthermore, TFPB-DHzDs was also proved to be an excellent porous adsorbent for Cu2+ in water matrix and the maximum adsorption capacity is 203 mg g−1. The recycling use of TFPB-DHzDs for detecting and removing of Cu2+ can be easily realized by adding a chelating agent. And it can be recovered and recycled at least six times. This work explores the attractive potential of COF TFPB-DHzDs simultaneously as a sensitive fluorescent sensor and an efficient sorbent material, which broadens the application of COFs in fluorescence sensing, metal removal, and environmental analysis.

Tunable Aggregation-induced Emission and Emission Colors of Imidazolium and Pyridinium Based Hydrazones.

Aggregation-induced emission (AIE) materials have drawn great attention for their wide applications as optical materials. The applications of AIE materials, however, are restricted by the complicated syntheses, hydrophobic properties and short emission wavelengths. Herein, an imidazolium based hydrazone (E)-1-(4-methoxyphenyl)-2-((1-methyl-1H-imidazol-2-yl)methylene)hydrazine hydrochloride (1) and a pyridinium based hydrazone (E)-1-(4-methoxyphenyl)-2-(pyridin-4-ylmethylene)hydrazine hydrochloride (2) have been synthesized. Notably, 1 and 2 in crystals show distinct green and near-infrared (NIR) fluorescence, with emission peaks at 530 and 688nm, and Stokes shifts of 176 and 308nm, respectively. After grinding the crystals to powder, the absolute fluorescence quantum yield (ΦF) of 1 is increased from 4.2% to 10.6%, and the ΦF of 2 is increased from 0.2% to 0.7%. X-ray crystallography studies together with theoretical calculations indicate that the enhanced emission of 1 arises from hydrogen bonding induced rigid network, and the fluorescence in the NIR region and large Stokes shift of 2 are attributed to its twisted molecular structure and strong push-pull effect.

In Vitro and In Vivo Antitumor Assay of Mitochondrially Targeted Fluorescent Half-Sandwich Iridium(III) Pyridine Complexes

Half-sandwich iridium(III) complexes show potential value in the anticancer field. However, complexes with favorable luminescence performance are rare, which limits further investigation of the anticancer mechanism. In this paper, 10 triphenylamine-modified fluorescent half-sandwich iridium(III) pyridine complexes {[(η5-Cpx)Ir(L)Cl2]} (Ir1-Ir10) were prepared and showed potential antiproliferative activity, effectively inhibiting the migration of A549 cells. Ir6, showing the best activity among these complexes, exhibited excellent fluorescence performance (absolute fluorescence quantum yield of 15.17%) in solution. Laser confocal detection showed that Ir6 followed an energy-dependent cellular uptake mechanism, specifically accumulating in mitochondria (Pearson co-localization coefficient of 0.95). A Western blot assay further confirmed the existence of a mitochondrial apoptotic channel. Additionally, Ir6 could arrest the cell cycle at the G2/M phase, catalyze NADH oxidation, reduce the mitochondrial membrane potential, induce an increase in the level of intracellular reactive oxygen species, and exhibit a mechanism of oxidation. An in vivo antitumor assay confirmed that Ir6 can effectively inhibit tumor growth and is safer than cisplatin.

High-Performance Polyimides Derived from Biomass: Design, Synthesis, and Properties

The development of sustainable polyimides (PIs) from abundant renewable biogenic feedstocks has been limited by the bio-based content and the lack of mechanical and thermal properties. This study synthesized a series of daidzein-based PIs with a high bio-based content of up to 53%, which was significantly higher than the reported bio-based content (approximately 40%). The mechanical and thermal stability of the obtained polymer is comparable with that of commercial PIs, with the tensile strength of 148.6 MPa and the glass transition temperature (Tg) of 318.2 °C. Additionally, the daidzein-based PIs showed excellent fluorescence characteristics with a maximum fluorescence efficiency of 45.18 ns and an absolute fluorescence quantum yield of 14.1%. Such a performance combination has not been reported in bio-based PIs, even petrochemical PIs. Interestingly, the integration of experiments and density functional theoretical calculations revealed an effective intermolecular and intramolecular conjugation and the inhibition effect of intramolecular charge transfer by “enone and ether bonds” in daidzein-derived PIs. This work provides a possible route for the design and synthesis of multifunctional PIs with high bio-based content.

N- and S-codoped carbon quantum dots for enhancing fluorescence sensing of trace Hg2.

Carbon-quantum-dot-based fluorescence sensing of Hg2+ is a well-known cost-effective tactic with fast response and high sensitivity, while rationally constructing heteroatom-doped carbon quantum dots with improved fluorescence sensing performances through tuning the electronic and chemical structures of the reactive site still remains a challenging project for monitoring trace Hg2+ in aquatic ecosystems to avoid harm resulting from its high toxicity, nonbiodegradabilty and accumulative effects on human health. Herein, intriguing N,S-codoped carbon quantum dots were synthesized via a facile one-step hydrothermal procedure. As an admirable fluorescent probe with plentiful heteroatom-related functional groups, these N,S-codoped carbon quantum dots can exhibit an absolute fluorescence quantum yield as high as 11.6%, excellent solubility and stability over three months, remarkable sensitivity for Hg2+ detection with an attractive detection limit of 0.27 μg L-1 and admirable selectivity for Hg2+ against thirteen other metal ions. Density functional theory calculations reveal that electron-enriched meta-S of the unique graphitic N with homocyclic meta-thiophene sulfur structure can regulate this N site to have more electrons and preferable affinity towards Hg, hence achieving enhanced fluorescence quenching due to greater charge transfer from N to Hg after the coordination interaction. This strategy provides a promising avenue for precisely designing purpose-made quantum dots with the dedicated fluorescence sensing applications.

Photoinduced chlorophyll charge transfer state identified in the light-harvesting complex II from a marine green alga Bryopsis corticulans

The light-harvesting complex II of Bryopsis corticulans (B-LHCII), a green alga, differs from that of spinach (S-LHCII) in chlorophyll (Chl) and carotenoid (Car) compositions. We investigated ultrafast excitation dynamics of B-LHCII with visible-to-near infrared time-resolved absorption spectroscopy. Absolute fluorescence quantum yield (Φ FL) of LHCII and spectroelectrochemical (SEC) spectra of Chl a and b were measured to assist the spectral analysis. Red-light excitation at Chl Qy-band, but not Car-band, induced transient features resembling the characteristic SEC spectra of Chl a ⋅+ and Chl b ⋅-, indicating ultrafast photogeneration of Chl-Chl charge transfer (CT) species; Φ FL and 3Car∗ declined whereas CT species increased upon prolonging excitation wavelength, showing positive correlation of 1Chl∗ deactivation with Chl-Chl CT formation. Moreover, ultrafast Chl b-to-Chl a and Car-to-Chl singlet excitation transfer were illustrated. The red-light induction of Chl-Chl CT species, as also observed for S-LHCII, is considered a general occurrence for LHCIIs in light-harvesting form.

Facile fabrication of helical hybrid silica ribbons with high-efficiency circularly polarized luminescence

• A bis(triethoxysilane) with aggregation-induced emission properties was synthesized. • Self-assemblies of a natural triterpenoid-based amphiphile were used as templates. • Hybrid silica ribbons were fabricated by supramolecular templating polymerization. • Hybrid silicas exhibited circularly polarized luminescence with efficient emission. We present a facile strategy for the construction of single-handed helical organic–inorganic hybrid silica micro/nanomaterials with circularly polarized luminescence (CPL) properties and high fluorescence efficiency. Two right-handed helical hybrid silica ribbons were fabricated through a supramolecular templating polymerization of tetraethoxysilane (TEOS) and organosiloxanes with aggregation-induced emission (AIE) characteristics, using the self-assemblies of a natural triterpenoid-based amphiphile as the templates. It was found that the chirality has been transferred from the supramolecular templates to the hybrid silica ribbons. The resultant hybrid silicas exhibited high thermal stabilities and intense CPL with the luminescence dissymmetry factor up to –8.8 × 10 -3 and the absolute fluorescence quantum yield up to 55.2%.

Highly Emissive Luminogens in Both Solution and Aggregate States

Highly Emissive Luminogens in Both Solution and Aggregate States

A New Deep‐Red to Near‐infrared Emission and Polarity Sensitive Fluorescent Probe Based on β‐Diketone‐boron Difluoride and Coumarin Derivative

AbstractA new polarity sensitive fluorescent probe CO‐DBD with deep‐red to near‐infrared emission was designed and synthesized. CO‐DBD consists of β‐diketone‐boron difluoride and coumarin moieties, showing higher fluorescence intensity and shorter emission wavelength in low‐polarity solvent. Notably, CO‐DBD gives high absolute fluorescence quantum yield of 0.631 in toluene. Theoretical calculation results verify that the polarity response is attributed to intramolecular charge transfer and twisted intramolecular charge transfer process. Further experimental data demonstrate that CO‐DBD displays high selectivity, sensitivity and excellent stability. The precise polarity of binary mixture can be quantified by ratio fluorescence intensity of CO‐DBD. Moreover, this probe is successfully applied for live cell imaging with high contrast.

Naked-eye chemosensor with high absolute fluorescence quantum yield for selective detection of Cu(II) and cell imaging

The regulation of copper in the human body is important for the prevention of several diseases. Therefore, a rhodamine B-based chemosensor 1 that demonstrates substantial affinity and selectivity was synthesized for the fluorescence imaging of copper(II). In the presence of Cu2+, the chemosensor underwent a color change from colorless to amaranth that was visible to the naked eye, and the fluorescence intensity did not change when excess EDTA was added to the solution. Furthermore, strong fluorescence was observed at 575 nm. The limit of detection was determined as 12.1 nM. The absolute fluorescence quantum yield was as high as 77 % and the stoichiometry between 1 and Cu2+ was determined to be 1:1 using a job plot. An analytical method was developed and successfully used to evaluate the sensor’s ability for the fluorescence imaging of Cu2+ in HeLa tumor cells.

Tunable Multicolor Circularly Polarized Luminescence via Co-assembly of One Chiral Electron Acceptor with Various Donors

Tunable Multicolor Circularly Polarized Luminescence via Co-assembly of One Chiral Electron Acceptor with Various Donors

Highly stable aqueous phase black phosphorus quantum dots with enhanced fluorescence property

Black phosphorus quantum dots (BPQDs) are a kind of outstanding optical material due to the tunable band structure. However, their fluorescence property and stability are obviously weakened in the aqueous phase, which extremely restricts the development of BPQDs. Here, we propose a new method to prepare stable BPQDs in an aqueous solution directly with high absolute fluorescence quantum yield. Aqueous phase BPQDs are synthesized by liquid exfoliation and hydrothermal with NH2-polyethylene glycol (PEG)-NH2 as the modification agent to protect the BPQDs, which have high stability more than six months. In addition, NH2-PEG-NH2 is also a surface passivation agent to enhance the emission of BPQDs by forming P–N bonds, which is confirmed by an absolute fluorescent quantum yield of 11.5%. Moreover, BPQDs show excellent resistance to a strong acid environment and high ionic strengths except for Fe3+. Therefore, the BPQDs are a kind of highly selective and linear response fluorescence probe for Fe3+. Considering the good biocompatibility of BPQDs, they are employed as cell fluorescent label probes and show excellent fluorescence imaging contrast. Based on the unique structural stability and fluorescence performance in the aqueous phase, BPQDs are potential candidates for Fe3+ detection and optical bio-imaging.