High Fluorescence Efficiency Research Articles

A phthalocyanine-porphyrin triad for ratiometric fluorescent detection of Lead(II) ions

A phthalocyanine-porphyrin hetero-triad H2Pc-β-(ZnPor)2 (1) was designed for the ratiometric fluorescent detection of lead(II) ions. The triad 1 features a high efficient intramolecular fluorescence resonance energy transfer (FRET) process from the two zinc-porphyrin (ZnPor) units to the metal-free phthalocyanine (H2Pc) unit. The selective binding of Pb2+ to H2Pc can effectively quench the emission of phthalocyanine unit, also recover the emission of ZnPor units by suppressing the intramolecular FRET process, thus leading to remarkable ratiometric fluorescent responses. The emission intensity ratio of ZnPor and H2Pc (F605/F700) experiences an 82-fold enhancement upon the addition of Pb2+ (0–3 equiv) to a solution of 1 (2.0 μM in THF/CH3OH, 4:1 in v/v), and displays a good linear relationship to Pb2+ concentration in the range of 0–2.0 μM, resulting in a limit of detection (LOD) value down to 4.1 nM (0.86 ppb).

Quantitative and rapid detection of explosives using an efficient luminogen with aggregation-induced emission characteristics

The development of fluorescent sensors for explosive detection with high sensitivity is of great importance for antiterrorism and environmental protection. A new efficient AIE luminogen, abbreviated as TPE-SFX, is designed and synthesized. It enjoys typical AIE features and high solid-state fluorescence quantum yield. It can be fabricated into fluorescent dots for explosive detection with good selectivity and rapid response. The fluorescence quenching process and mechanism are investigated. Taking advantage of its high solid-state fluorescence efficiency, TPE-SFX is further utilized on filter paper as solid-state sensor. Through analysis of grayscale variation of fluorescence images, a simple and reliable method is developed for quantitative analysis of picric acid (PA) with a low detection limit to 0.12 nmol/cm2. It is the first report of efficient luminogen utilized on filter paper for quantitative analysis of explosives with high sensitivity. Moreover, the fluorescent filter paper can be regenerated through an environmentally benign method simply by washing with water. In addition, the fluorescent filter paper enjoys good thermal stability, which can endure a high temperature up to 100 °C. These good results will shed some light on the development of quantitative, sensitive, and portable devices for in situ explosive detection in the environment.

Red-Near-Infrared Fluorescent Probe for Time-Resolved in Vivo Alkaline Phosphatase Detection with the Assistance of a Photoresponsive Nanocontainer.

The monitoring of alkaline phosphatase (ALP) activity in different tissues is significant for disease diagnosis and therapy. However, the time-resolved in vivo sensing of ALP activity remained unresolved. Herein, a novel red-near-infrared fluorescent ALP probe (Cl2-BDCM-ALP) based on a dichloro-substituted dicyanomethylene-4H-chromene derivative was designed and synthesized with high fluorescence efficiency and stability under biological pH range. By using Cl2-BDCM-ALP, ALP activity under an acidic microenvironment such as a tumor site can be sensitively imaged, which cannot be achieved by some previously reported ALP probes. By further loading the Cl2-BDCM-ALP into a near-infrared (NIR) light-responsive nanocontainer, time-resolved long-term imaging of ALP activity was facilely achieved with noninvasive NIR light remote control. Time-resolved variation of ALP activity of the drug-induced acute liver injury mice was successfully monitored in vivo for the first time. This strategy holds great promise in the in situ ALP detection under a broad pH range with temporal resolution.

Synthesis, aggregation-induced emission (AIE) and electroluminescence of carbazole-benzoyl substituted tetraphenylethylene derivatives

Aggregation-induced emission (AIE) materials offer a solution to obtain high fluorescence efficiencies in solid state which is desirable for optoelectronic devices and display. Here in this work, three new types of D-π-A-π-D AIE luminogens based on carbazole-benzoyl substituted tetraphenylethylene (TPE) derivatives were designed and successfully synthesized. Meanwhile, their photophysical properties as well as electroluminescence (EL) characteristics were studied. These luminogens show good AIE property with high solid-state fluorescence quantum yields. Furthermore, the emission wavelengths for these three luminogens, both in solutions and in solid state, exhibit negligible variation by increasing the number of donor group. All three luminogens show solvatochromism and negative solvatokinetic effect in different solvents. More interesting is that on increasing number of donor groups, their thermal and morphological stability present regular change by increasing the number of carbazole-benzoyl group. The performance of non-doped OLED device based on TPE-3BZ-Cz is superior than the other two luminogens, which has been proved by further electroluminescence evaluation.

Design and synthesis of novel indole derivatives with aggregation-induced emission and antimicrobial activity

New heterocyclic compounds containing indolylthienopyrimidine have been synthesized and their structures were confirmed using elemental and spectral analyses. The photophysical measurements demonstrated that some selected compounds display “aggregation-induced emission” (AIE) activity with high fluorescence efficiency in the solid state (ex. 21.4%). From the density functional theory (DFT) calculations, emission lifetime, and decay constants, it was found that some functional groups that can form effective intermolecular interactions between the aggregated molecules can open new channels for the radiative relaxations and improve the emission efficiency. Moreover, these materials can emit strongly at temperatures higher than 200 °C. Also, the antimicrobial activity and thermal behavior have been investigated and the compounds showed strong biological activities and high thermal stabilities (ex. 295 °C as the 5% weight loss). Since these materials have both the AIE and antimicrobial activity, they can be considered as expected candidates for biosensors, biomedical imaging, and to image bacteria.

Novel Bromide Quaternary Ammonium Ligand for Synthesizing High Fluorescence Efficiency CsPbBn Perovskite Quantum Dots and Their Fabrication of White Light-Emitting Diodes with Wide Color Gamut

We proposed a novel bromine quaternary ammonium ligand to synthesize high quantum yield (QY) CsPbBr3 quantum dots (QDs). The QY of CsPbBr3 QDs synthesized by this ligand reached 95% and the full width at half maximum (FWHM) was as narrow as 17nm. The peak wavelength of the prepared CsPbBr3 QDs was 530nm. And these QDs emitted high purity green light under ultraviolet light. The color coordinate of white LED (WLED) prepared with the CsPbBr3 QDs was (0.29, 0.31), which was very close to pure white light. The color gamut of the WLED covered 130% of the national television system committee (NTSC) color standard and 96% of the ITU-R Recommendation BT.2020 (Rec.2020) color standard.

Ratiometric Detection of γ-Glutamyltransferase in Human Colon Cancer Tissues Using a Two-Photon Probe.

γ-Glutamyltransferase (GGT) plays a role in cleaving the γ-glutamyl bond of glutathione. The GGT is known to be overexpressed in some tumors and has been recognized as a potential biomarker for malignant tumors. Colon cancer is one of the most common cancers worldwide; however, there is no quantitative method for detecting cancer cells in human colon tissues. In this study, we report a ratiometric two-photon probe for GGT that can be applied in human colon tissues. The probe (Probe 2) showed high fluorescence efficiency, marked fluorescence changes, excellent kinetics, and selectivity for the GGT in live colon cells. Additionally, we obtained ratiometric two-photon microscopy images of GGT activity in human colon tissue. We used this method to compare normal and cancer tissues based on their ratio values; the ratio value was higher in cancer tissue than in normal tissue. This study provides a method for quantitative analysis of GGT, particularly in human colon cancer, which will be useful for studying GGT-related diseases and diagnosing colon cancer.

Tetraphenylethene-containing cruciform luminophores with aggregation-induced emission and mechanoresponsive behavior

Two D-A type cruciform luminophores MODCS-TPE and FMDCS-TPE were successfully prepared via a two-step route involving Suzuki cross-coupling and Knoevenagel condensation reactions, and their intramolecular charge-transfer (ICT) and solid-state fluorescence were studied in detail. The results show that MODCS-TPE and FMDCS-TPE exhibit AIE behavior with high solid state fluorescence efficiency of 0.321 and 0.312. Interestingly, MODCS-TPE and FMDCS-TPE exhibit both typical AIE behavior with the AIE factors of 138 and 51and high contrast MFC effects. Once grinding had been performed, the emission of the two cruciform luminophores was red shifted by 34 nm and 44 nm from the blue regions (λmax = 471 nm and 478 nm) to the green and yellowish green regions (λmax = 505 nm and 522 nm), respectively. Moreover, the mechanochromic switching behavior was reversible and repeated many times without any fatigue in the grinding-heating (for MODCS-TPE) or grinding-fuming (for MODCS-TPE and FMDCS-TPE) fluorochromic process. The mechanism of MFC behavior that the transformation between crystalline and amorphous states upon external stimuli is revealed by PXRD and DSC analysis, and the large red-shifts induced by grinding originate from extended conjugation and subsequent planar intramolecular charge transfer (PICT) after grinding.

γ-Radiation Enhanced Luminescence of Thiol-Capped Quantum Dots in Aqueous Solution.

Quantum dots (QDs) have attracted great attention due to their unique optical properties. High fluorescence efficiency is very important for their practical application. In this study, we report a simple and efficient strategy to enhance the photoluminescence of water-dispersed thiol-capped QDs using γ-radiation. Three kinds of QDs with different surface ligands and cores (MPA-CdTe, MPA-CdSe and Cys-CdTe) were fabricated and irradiated by high-energy γ-ray in an aqueous solution. Their photoluminescence intensities were significantly enhanced after irradiation, which were closely related to the radiation dose and the structure of QDs. The positions of the fluorescence emission peaks did not shift obviously after irradiation. The mechanism of photoluminescence enhancement was discussed based on the results of photoluminescence (PL) spectra, UV-visible light absorption (UV-vis) spectra, transmission electron microscope (TEM), X-ray diffraction (XRD) patterns, Fourier transform infrared (FT-IR) spectra and X-ray photoelectron spectroscopy (XPS). This method can be employed to uniformly treat large batches of QDs at room temperature and without other chemicals.

Fluorene vs carbazole substituent at quinoline core toward organic electronics

Two novel 2,4-difluorenylquinoline derivatives with different length of alkyl chain at fluorene unit (Q-F1 with methyl and Q-F2 with octyl chain) of donor-acceptor (D-A) type were synthesized and comprehensively characterized. The compounds exhibited bright emission in the blue spectral region at 400 nm and high fluorescence efficiency of 63–97% in solution. The EL measurements of OLEDs with Q-F1, and for comparison 2,4-dicarbazolylquinoline (Q-C1) were performed to determine any correlations between the device performance and the different D units at quinoline core. These fluorenyl and carbazolyl substituted quinolines (Q-F1 and Q-C1) were found to display good thermal stability with a decomposition temperature of 301 and 416 °C, respectively. A molecule with carbazole units (Q-C1) dispersed in a host matrix exhibited higher PL quantum yield (15%) compared to Q-F1 (11%). The devices with structure ITO/PDOT:PSS/PVK:PBD:compound/Al with 15 (Q-F1) and 2 (Q-C1) wt. % of compound content in a blend were constructed. The diode based on Q-C1 emitted green light with EL maximum at 550 nm under an applied external voltage. Furthermore, by incorporation of a layer of plasmonically active silver nanowires into the device based on Q-C1 (ITO/PEDOT:PSS + AgNWs/PVK:PBD:Q-C1 (2 wt%)/Al) the noticeably more intense EL signal was detected. These results show that these compounds are promising candidates and may be used in organic light emitting devices.

The synthesis, characterization and fluorescence properties of new benzimidazole derivatives

Abstract New ligands obtained in the reaction of o-phenylenediamine and series of aldehydes (L1-L5) were synthesized. Molecular architecture of the synthesized ligands L1-L5 has been determined by the X-ray crystal structure analysis. 1H NMR NOE diff. spectra (differential Nuclear Overhauser Effect) of ligands indicate that they have different conformation in the solution in comparison to the solid state (crystal structure). The substrates molar ratio and the reaction time allowed the controlled synthesis of mono substituted o-phenylenediamine or benzimidazole derivatives with no catalyst used. For all compounds the relatively high fluorescence efficiency was observed in the range 0.41–0.83 in MeCN and 0.48–0.96 in CH2Cl2 solution. Based on DFT calculations the fluorescence mechanism was associated with HOMO→LUMO transition between aromatic rings and benzimidazole moieties.

Deep-Blue Thermally Activated Delayed Fluorescence Polymers for Nondoped Solution-Processed Organic Light-Emitting Diodes

The exploitation of deep-blue polymeric emitters is of great importance for the application of solution-processed organic light-emitting diodes (OLEDs) in full color display. The highly efficient deep-blue thermally activated delayed fluorescence (TADF) polymers are rarely reported up to now. Herein, we developed a series of deep-blue TADF polymers to fabricate highly efficient nondoped solution-processed OLEDs. By incorporating appropriate host with high triplet energy and deep-blue emitter with high fluorescent efficiency, the polymers are endowed with distinct TADF features. Using these deep-blue polymeric emitters, the nondoped single polymer based OLEDs achieve a maximum external quantum efficiency of 5.3% with the Commission Internationale de L’Eclairage (CIE) coordinates of (0.15, 0.09), which represents the state-of-the-art device performance for the TADF-based deep-blue polymer light-emitting diodes (PLEDs).

Synthesis of Linear and V-Shaped Carbazolyl-Substituted Pyridine-3,5-dicarbonitriles Exhibiting Efficient Bipolar Charge Transport and E-Type Fluorescence.

With the aim of developing all-organic bipolar semiconductors with high charge mobility and efficient E-type fluorescence (so-called TADF) as environmentally friendly light-emitting materials for optoelectronic applications, four noble metals-free dyes with linear and V-shapes were designed using accepting pyridine-3,5-dicarbonitrile and donating carbazole units. By exploiting a donor-acceptor design strategy and using moieties with different donating and accepting abilities, TADF emitters with a wide variety of molecular weights were synthesized to achieve the optimum combination of charge-transporting and fluorescent properties in one TADF molecule. Depending on molecule structures, different TADF emitters capable of emitting in the range from 453 to 550 nm with photoluminescence quantum yields up to 98 % for the solutions in oxygen-free toluene were obtained. All compounds showed bipolar charge-transport. Hole mobility of 2.8×10-3 cm2 /Vs at 7×105 V cm-1 was observed for the compound containing two di-tert-butyl-substituted carbazole moieties. The compounds were tested in both non-doped and doped organic light-emitting diodes using different hosts. It was shown that the developed TADF emitters are suitable for different color devices with electroluminescence ranging from blue to yellow and with brightness, maximum current and external quantum efficiencies exceeding 10 000 cd m-2 , 15 cd/A, and 7 %, respectively.

A quantitative description of photoluminescence efficiency of a carbazole-based thermally activated delayed fluorescence emitter

The present results reveal that the dominant charge transfer characteristics in the S1 and T1 states produce a small energy difference between the two states, and consequently an efficient reverse intersystem crossing process and a high fluorescence efficiency.

Methyl-restricted rotor rotation on the stator produces high-efficiency fluorescence emission: a new strategy to achieve aggregation-induced emission.

At present, we have realized that the aggregation-induced emission (AIE) achieves the purpose of fluorescence enhancement by restricting rotations to reduce intermolecular or intramolecular energy loss. Based on this idea, we synthesized a novel fluorene-based fluorescent compound with a restricted rotor rotation on the stator through the Suzuki coupling reaction. The luminescence effect was evaluated by comparing its fluorescence intensity with that of the control compound. Finally, theoretical calculations showed that the presence of methyl groups hindered the thermal rotation of the fluorenyl groups. Thus, the results indicated that the fluorescence of this compound was better than that of the control compound. A new synthetic pathway for high-efficiency AIE-based fluorescent luminogens has been developed.

Analyte-triggered cyclic autocatalytic oxidation amplification combined with anupconversion nanoparticle probe for fluorometricdetection of copper(II).

The authors describe an upconversion nanoparticle-based (UCNP-based) fluorometric method for ultrasensitive and selective detection of Cu2+. The UCNPs show a strong emission band at 550nm under near-infrared excitation at 980nm. The principle of the strategy is that gold nanoparticles (AuNP) can quench the fluorescence of UCNP. In contrast, the addition of L-cysteine (Cys) can induce the aggregation of AuNP, resulting in a fluorescence recovery of theUCNPs. On addition of Cu2+, it oxidizes Cys to cystine and is reduced to Cu+. The Cu+ thusformedcan be oxidized cyclically to Cu2+ by dissolved O2, which catalyzes and recycles the whole reaction. Thus, the aggregation of AuNP is inhibited and the fluorescence recovered by Cys is quenched. Under the optimal condition, the quenching efficiency shows a good linear response to theconcentrations of Cu2+ in the 0.4-40nM range. The limit of detection is 0.16nM, which is 5 orders of magnitude lower than the U.S. Environmental Protection Agency limit for Cu2+ in drinking water (20μM). The method has been further applied to monitor Cu2+ levels in real samples. The results of detection are wellconsistent with those obtained by atomic absorption spectroscopy. Graphical abstract Gold nanoparticles (AuNP) as a high efficient fluorescence quenching reagent of upconversion nanoparticles (UCNP) were used in a fluorometric method for detection of Cu2+ based on acyclic catalytic oxidation amplification strategy.

Efficient donor-acceptor-donor borylated compounds with extremely small ΔEST for thermally activated delayed fluorescence OLEDs

Borane-based complexes have attracted considerable attention as thermally activated delayed fluorescence (TADF) emitters because of their thermal stability, high fluorescence efficiency, and favourable carrier mobility. In this work, we provide a facile way for borylated compounds to enable the spatially adjacent electron donor and acceptor groups to form a near-orthogonal configuration, generating an extremely small energy gap between triplet and singlet excited states (ΔEST, ∼30 meV). We demonstrate here a new series of donor-acceptor-donor borylated compounds using functional acridan derivatives as the electron donors and dimesitylborane as the acceptor moieties, which easily generates an intramolecular charge transfer upon excitation. All compounds achieved strong TADF emission and were used as dopants to fabricate TADF OLEDs. Yellow-emitting devices A and B yielded maximum efficiencies of 7.6% (22.2 cd/A) and 10.1% (32.2 cd/A), respectively. Moreover, the green-emitting device C achieved a maximum efficiency of 19.3% (56.8 cd/A) and subsequently dropped to 18.2% (53.6 cd/A) at luminance levels of 102 cd/m2. Overall, the high electroluminescent (EL) efficiencies, together with mitigated efficiency roll-off, illustrate that these compounds have a high potential for EL applications.

Synthesis and Characterization of a Novel Green Cationic Polyfluorene and Its Potential Use as a Fluorescent Membrane Probe.

In the present work, we have synthesized a novel green-emitter conjugated polyelectrolyte Copoly-{[9,9-bis(6′-N,N,N-trimethylammonium)hexyl]-2,7-(fluorene)-alt-4,7-(2-(phenyl) benzo[d] [1,2,3] triazole)} bromide (HTMA-PFBT) by microwave-assisted Suzuki coupling reaction. Its fluorescent properties have been studied in aqueous media and in presence of model membranes of different composition, in order to explore its ability to be used as a green fluorescent membrane probe. The polyelectrolyte was bound with high affinity to the membrane surface, where it exhibited high fluorescence efficiency and stability. HTMA-PFBT showed lower affinity to zwitterionic membranes as compared to anionic ones, as well as a more external location, near the membrane-aqueous interface. Fluorescence microscopy studies confirmed the interaction of HTMA-PFBT with the model membranes, labelling the lipid bilayer without perturbing its morphology and showing a clear preference towards anionic systems. In addition, the polyelectrolyte was able to label the membrane of bacteria and living mammalian cells, separately. Finally, we explored if the polyelectrolyte can function also as a sensitive probe able of detecting lipid-phase transitions. All these results suggest the potential use of HTMA-PFBT as a green membrane marker for bioimaging and selective recognition of bacteria cell over mammalian ones and as a tool to monitor changes in physical state of lipid membranes.

Synthesis of multifunctional fluorescent magnetic nanoparticles for the detection of Alicyclobacillus spp. in apple juice

An approach based on multifunctional fluorescent magnetic nanoparticles was proposed for the enrichment and identification of Alicyclobacillus spp. in apple juice simultaneously. The prepared Fe3O4 magnetic particles (MNPs) were modified by the sol-gel process and a silica shell was formed to improve the reactivity, and then the obtained MNPs@SiO2-SH nanoparticles were conjugated with Thioglycolic acid functionalized CdTe/CdS QDs via thiols chemistry. The characteristic evaluation results indicated that the MNPs-QD nanocomposites exhibited good magnetic properties and optical characterization. The polyclonal anti-Alicyclobacillus IgG antibody was immobilized onto the surface of MNPs-QD materials via esterification reactions. The maximum antibody immobilization capacity was 119.62 μg/mg and the adsorption reaction could be accomplished in 60 min. The adsorption process could be represented by Langmuir model and pseudo-second order kinetics equation, respectively. Based on the high immunocapture efficiency and sensitive fluorescence characteristics, the obtained MNPs-QDs-antibody conjugates could be applied to recognize the contamination of Alicyclobacillus spp. and a quantitative analysis method was established for target cells detection. The minimum quantitative limit was 104 CFU (colony forming unit)/mL and the testing process could be completed in 90 min. The results indicated that the MNPs-QDs-antibody conjugates can be successfully applied for immunocapture and detection of Alicyclobacillus spp. in apple juice. That is to say, the developed MNPs-QDs-antibody conjugates have exhibit more attractive and great potential for the immunocapture and recognition of target bacteria, fully demonstrated a new method for enrichment and rapid detection of Alicyclobacillus spp. in fruit juices.

Synthesis, aggregation-induced emission and electroluminescence of new luminogens based on thieno[3,2-b]thiophene S,S-dioxide

Organic luminescent materials with high fluorescence efficiencies in the solid state are highly desired in OLED devices. In this work, we report the synthesis and characterization of a series of novel dipolar luminogens based on thieno [3,2-b]thiophene S,S-dioxide (TTDO). The crystal structures, photophysical property, thermal stability, electronic structures and electrochemical behaviors of these TTDO-based luminogens are investigated. These luminogens have good aggregation-induced emission (AIE) property with high solid-state fluorescence quantum yields, and their emission wavelengths are tuned from green to red by different electron-donating substituents. They enjoy high thermal and morphological stabilities and have low LUMO energy levels. Nondoped OLEDs are fabricated with these new luminogens, providing orange to red electroluminescence (568–610 nm) with maximum external quantum efficiencies of up to 2.79%. These results demonstrate that these new AIE-active luminogens could be promising candidates for OLEDs.