Fluorescence Character Research Articles

Effect of the Al(PO3)3 content on the optical properties of Tm3+-doped fluorophosphate glass

A series of glasses composed of xAl(PO3)3-(30-x)AlF3-55ReF2 (Re = Ca, Sr, Ba) −15YF3-1TmF3 (x = 11, 12, 13, 14, and 15 mol%) were implement employing the traditional melt-quenching method. The effect of Al(PO3)3 content on the physical and fluorescence character of fluorophosphate glass was studied. The thermal and spectral properties of the glass were analyzed by differential scanning calorimetry, absorption spectra and fluorescence spectra. The structure of the glass was analyzed by Raman and nuclear magnetic resonance (NMR) spectra. The Judd-Ofelt theory was used to analyze the local environmental changes of rare earth ions. The thermal stability and gain of glass samples doped with 12 mol% Al(PO3)3 are 127 °C and 2.46 × 10−21 cm2 ms, and the emission cross section is 4.79 × 10−21 cm2. The results show that the fluorophosphate glass is an ideal candidate material for 2 μm laser gain medium.

High-Throughput Screening of Antioxidant Drug Candidates from Natural Antioxidants with a "Zero" Intrinsic Fluorescence Peroxynitrite Sensing Precursor.

The fluorescence high-throughput screening method is of importance for new antioxidant drug candidate discovery for the treatment of serious hepatorenal syndrome, which displayed an obvious upregulated peroxynitrite level. However, most of the current ONOO- probes possessed incomplete fluorescence quenching efficiency, which can result in non-negligible probe inherent fluorescence. Hence, we utilized the probe conjugated structure disruption strategy to construct hydrogenation phosphorus-substituted rhodamine (H-PRh) with "zero" probe inherent fluorescence character. Based on the precursor, a series of natural products were screened for identifying antioxidant drug candidates. Luteolin was screened out by activating the Sirt1-Nrf2-HO-1 signaling pathway to regulate the accumulation of ONOO- in the hepatorenal syndrome. Overall, the "zero" probe inherent fluorescence ONOO- sensor constructed here applies for a promising and versatile toolbox for illuminating the ONOO--related pathological process in the hepatorenal syndrome. Besides, this strategy of constructing highly sensitive sensors could serve as a valuable reference for further fluorescent probes.

Climate Impact on Dissolved Organic Carbon Composition in a North‐Temperate Peatland and Recipient Surface Water

AbstractClimate may regulate dissolved organic carbon (DOC) composition across the peat‐water interface, but experimental evidence is scarce. We manipulated the climate in peatland and recipient surface water mesocosms to reflect four different climate warming scenarios. In half of the mesocosms, the water level was managed to avoid drought, after which responses were recorded during two annual cycles. It was hypothesized that warming and drought increase the aromaticity and humic‐like fluorescence character of DOC, and that this change propagate to recipient waters. Pore water DOC concentrations increased with temperature and peaked in hydrologically unmanaged mesocosms. Aromaticity increased as expected after drought in the warmest scenario (+3.2°C), but the overall evidence for hypothesized changes in DOC aromaticity and fluorescence composition (%) was limited. In managed warming scenarios, one aromatic humic component expectedly increased together with microbially derived humic fluorescence, whereas two other humic‐like components decreased. In the unmanaged mesocosms which were exposed to drought, water level exerted an overriding control of humic DOC; for example, as the microbially derived humic fluorescence diminished after drought in all climate scenarios. In the surface water recipients, warming had nearly no impact on humic‐like fluorescence, but there were decreases in protein‐like fluorescence. Overall, this experiment revealed no conclusive support for the hypothesized aromatization and humification of peatland‐derived DOC in response to drought or warming. Nonetheless, both factors increase the quantity of DOC in peatland pore waters and affect composition in complex ways, calling for further investigation of chemical and functional traits of peatland DOC in a changing environment.

Diradicaloid Strategy for High‐Efficiency Photothermal Conversion and High‐Sensitivity Detection of Near Infrared Light

AbstractOrganic molecules are promising near infrared (NIR) photothermal materials because of their structural flexibility and fine‐tuned properties. However, weak NIR absorption and strong fluorescence character lead to low photothermal conversion efficiency (PCE). Herein, NIR quinoidal diradicaloids are designed and synthesized by a heteroaromatic‐bridged Blatter radical strategy. Benefiting from the relatively planar framework and diradical character, these singlet diradicaloids exhibit strong and broad absorption in the NIR region (750–1100 nm) in both solution and aggregate states, which do not show any fluorescence. High PCE up to 71.4% is evaluated under 808 nm laser. On this basis, a NIR detector employing a blend of the diradicaloids and conductive ionic liquid is fabricated, yielding a remarkably high thermal response of 1100% at 0.5 W cm−2. This work reveals that π‐conjugated diradicaloids are promising candidates for NIR detection.

Exciplex-Forming Cohost Systems with 2,3-Dicyanopyrazinophenanthrene-based Acceptors to Achieve Efficient Near Infrared OLEDs.

Two new 2,3-dicyanopyrazinophenanthrene-based acceptors (A) p-QCN and m-QCN were synthesized to blend with a donor (D) CPTBF for the exciplex formation. The energy levels of p-QCN and m-QCN are modulated by the peripheral substituents 4- and 3-benzonitrile, respectively. Exciplex-forming blends were identified by the observation of the red-shifted emissions from various D : A blends with higher ratios of donor for suppressing the aggregation of acceptor. The two-component relaxation processes observed by time-resolved photoluminescence support the thermally activated delayed fluorescence (TADF) character of the exciplex-forming blends. The device employing CPTBF : p-QCN and (2 : 1) and CPTBF : m-QCN (2 : 1) blend as the emitting layer (EML) gave EQEmax of 1.76 % and 5.12 %, and electroluminescence (EL) λmax of 629 nm and 618 nm, respectively. The device efficiency can be further improved to 4.32 % and 5.57 % with CPTBF : p-QCN and (4 : 1) and CPTBF : m-QCN (4 : 1) as the EML, which is consistent with their improved photoluminescence quantum yields (PLQYs). A new fluorescent emitter BPBBT with photoluminescence (PL) λmax of 726 nm and a high PLQY of 67 % was synthesized and utilized as the dopant of CPTBF : m-QCN (4 : 1) cohost system. The device employing CPTBF : m-QCN (4 : 1): 5 wt.% BPBBT as the EML gave an EQEmax of 5.02 % and EL λmax centered at 735 nm, however, the weak residual exciplex emission remains. By reducing the donor ratio, the exciplex emission can be completely transferred to BPBBT and the corresponding device with CPTBF : m-QCN (2 : 1): 5 wt.% BPBBT as the EML can achieve EL λmax of 743 nm and EQEmax of 4.79 %. This work manifests the high efficiency near infrared (NIR) OLED can be realized by triplet excitons harvesting of exciplex-forming cohost system, followed by the effective energy transfer to an NIR fluorescent dopant.

Construction and Application of a New Polarity‐Sensitive Fluorescent Probe Based on the Excited‐State Intramolecular Proton Transfer Mechanism

AbstractA new excited‐state intramolecular proton transfer based near‐infrared emission and polarity‐sensitive fluorescent probe (E)‐3‐((E)‐2‐chloro‐3‐((E)‐2‐(3‐ethyl‐1,1‐dimethyl‐1H‐benzo[e]indol‐2(3H)‐ylidene)ethylidene)cyclohex‐1‐en‐1‐yl)‐1‐(2‐hydroxyphenyl)prop‐2‐en‐1‐one (M‐NA) was developed. This probe consisted of benzomerocyanine unit and o‐hydroxyacetophenone unit. In high‐polar solvent, M‐NA displayed higher fluorescence and longer emission wavelength. Theoretical calculations data showed that M‐NA had larger emission oscillator strength and lower non‐radiative decay in high polarity media, corresponding with the fluorescence character. Further experiments verified that M‐NA possessed excellent selectivity and stability, and could further quantify the accurate polarity as well as the water content of binary mixed solvent.

Nearly 100% energy transfer at the interface of metal-organic frameworks for X-ray imaging scintillators

<h2>Summary</h2> In this work, we describe a highly efficient and reabsorption-free X-ray-harvesting system using luminescent metal-organic framework (MOF)-fluorescence chromophore composite films. The ultrafast time-resolved experiments and density functional theory calculations demonstrate that a nearly 100% energy transfer from a luminescent MOF with a high atomic number to an organic chromophore with thermally activated delayed fluorescence (TADF) character can be achieved. Such an unprecedented efficiency of interfacial energy transfer and the direct harnessing of singlet and triplet excitons of the TADF chromophore led to remarkable enhancement of radioluminescence upon X-ray radiation. A low detection limit of 256 nGy/s of the fabricated X-ray imaging scintillator was achieved, about 60 times lower than the MOF and 7 times lower than the organic chromophore counterparts. More importantly, this detection limit is about 22 times lower than the standard dosage for a medical examination, making it an excellent candidate for X-ray radiography.

Perovskite-Nanosheet Sensitizer for Highly Efficient Organic X-ray Imaging Scintillator

The weak X-ray capture capability of organic scintillators always leads to poor imaging resolution and detection sensitivity. Here, we realize an efficient and reabsorption-free organic scintillator at the interface of perovskite nanosheets using a very efficient energy transfer strategy. Our steady-state and ultrafast time-resolved experiments supported by density functional theory calculations demonstrate that an efficient interfacial energy transfer from the perovskite nanosheet to the organic chromophore with thermally activated delayed fluorescence (TADF) character can be achieved. Interestingly, we found that the direct harnessing of both singlet and triplet excitons of the TADF chromophores also contributed greatly to its remarkably enhanced radioluminescence intensity and X-ray sensitivity. A high X-ray imaging resolution of 135 μm and a low detection limit of 38.7 nGy/s were achieved in the fabricated X-ray imaging scintillator.

A bis indole analog molecule fluorescent probe for living cell staining

In this study, the fluorescent probe property of a bis indole compound (5,14-dimethyl-5,6,7,8,9,14-hexahydroindolo [2 ', 3′: 3,4] cycloocta [1,2-b] indole), a Caulerpin derivative, which is a member of the indole family, was investigated. For this purpose, firstly, the fluorescence character of the molecule was investigated by absorption and fluorescence spectroscopy techniques in both solvent and surfactant environments. Afterwards, the cytotoxicity of the molecule was tested on the human colon cancer HT-29 cells and breast cancer MCF-7 cells as well as mouse fibroblast 3T3-L1 cells. After determining that the molecule has no cytotoxic effect against all the tested cell lines by 100 µM, the cell staining feature of the probe was examined. The obtained data showed us that the molecule, whose confocal microscopy images were taken at 360 nm excitation wavelength, stained the cell cytoplasm. In addition, optical absorption spectra, oscillator strength (f), transition configuration and transition characteristics of the Ars-In in different solvents were investigated at the theoretical level using Time Dependent-Density Functional Theory (TD-DFT). In conclusion, these results confirm that this indole derivative molecule could be evaluated as an effective fluorescence probe for biological systems.

A highly sensitive and dual-readout immunoassay for norfloxacin in milk based on QDs-FM@ALP-SA and click chemistry

A dual-readout immunoassay based on QDs-FM@ALP-SA and click chemistry was developed for quick and sensitive detection of norfloxacin (NOR), which is an important fluoroquinolone antibiotic. In the system, the NOR-biotin conjugate (NOR-Biotin) was synthesized by click chemistry for signal transformation, and alkaline phosphatase–labeled streptavidin (ALP-SA) was attached to quantum dot fluorescence microspheres (QDs-FM) by an activated ester method to form QDs-FM@ALP-SA for signal amplification. Here, QDs-FM was a dual-functional carrier: it was used not only as a chemiluminescence signal amplification carrier but also as a fluorescent signal due to its fluorescence character. The NOR antibody was coated on a 96-well chemiluminescence microtiter plate, and NOR-Biotin was bound to the antibody specifically. Then, QDs-FM@ALP-SA was combined with NOR-Biotin to develop a direct competition chemiluminescence/fluorescence immunoassay (dc-CLIA/FIA). The IC50 values were 0.345 and 1.206 ng/mL for dc-CLIA/FIA, respectively. The linear range was 0.013–12.48 ng/mL and 0.042–39.86 ng/mL, respectively. The recovery from the standard fortified blank milk samples was in the range of 86.44%–101.3%. Therefore, this method could be a useful tool for routine screening of NOR residues in milk.

Novel tetracoordinated organoboron emitters for thermally activated delayed fluorescence organic light-emitting diodes

A novel three-dimensional tetracoordinated organoboron acceptor bearing C^N^C chelate was developed by the direct borylation of pyridine derivatives. Donor-acceptor type emitter based on this novel organoboron acceptor exhibited good stability, high photoluminescence quantum yield (PLQY) and thermally activated delayed fluorescence (TADF) character. By selecting different donors with different electron donating abilities, two distinct electroluminescence devices with white and green emission achieved maximum external quantum efficiency of over 10%.

Highly efficient blue TADF emitters incorporating bulky acridine moieties and their application in solution-processed OLEDs

Two bulky acridine moieties, 9,9-diphenyl-9,10-dihydroacridine (DPAc) and 10H-spiro [acridine-9,9′-fluorene] (SpiroAc), were selected as electron donors. Compared with commonly used 9,9-dimethyl-9,10-dihydroacridine (DMAc), phenyl modified acridines exhibited low-lying highest occupied molecular orbital (HOMO) levels and relatively weak electron-donating abilities, which make them potential units to create blue TADF emitter. DPAc and SpiroAc were connected with a triarylboron group and constructed centrosymmetric 3D-A architectures, namely 3DPAc-TB and 3SpiroAc-TB, respectively. Density functional theory calculations showed that both molecules exhibited large dihedral angles between the triarylboron unit and acridine planes. The well-separated frontier molecular orbitals contributed to small energy gaps between S1 and T1 states of the designed molecules (0.12 and 0.07 eV, respectively). Both molecules exhibited distinct thermally activated delayed fluorescence (TADF) character. The bulky acridine donors endowed both molecules with rigid structures and realized high photoluminescent quantum yields (71.6% and 84.3%, respectively). Solution-processed organic light-emitting diodes (OLEDs) utilizing 3DPAc-TB and 3SpiroAc-TB as emitters exhibited blue emissions with emission peaks of 472 nm and 490 nm, respectively. The maximum external quantum efficiencies of 3DPAc-TB and 3SpiroAc-TB based devices were 12.8% and 17.3%, respectively.

Quick simultaneous analysis of bambuterol and montelukast based on synchronous spectrofluorimetric technique.

Sensitive, simple and green analytical methodology for simultaneous estimation of bambuterol and montelukast as a combined medication based on their native fluorescence character was developed. The method relies on synchronous spectrofluorimetry to solve the problem of the overlapping emission spectra of the studied drugs. Using second derivative synchronous spectra enabled the simultaneous quantitation of bambuterol and montelukast without interference. The peak amplitudes of the aqueous solutions at Δλ = 20 nm were estimated at 284 and 304 nm for bambuterol and at 374 and 384 nm for montelukast. A linear relationship was achieved over the concentration range of 0.2–1.00 µg ml–1 for bambuterol and 0.4–2.00 µg ml−1 for montelukast. All factors and parameters were carefully studied to obtain the highest sensitivity and good precision of the proposed method. Additionally, the validation criteria were assessed in accordance with International Council of Harmonization (ICH) guidelines. The method was used for the estimation of both drugs in their raw materials, synthetic mixtures as well their combined tablets with good agreement between its results and those from the comparison method.

Malononitrile based ternary AIE-ML materials: Experimental proof for emission switch from non-TADF to TADF

Abstract Three malononitrile based D-A-D compounds with TPA, PhCz and DMAC donor (DPMM-2TPA, DPMM-2PhCz and DPMM-2DMAC) at the para-position of phenyl group on the DPMM unit are synthesized and their photophysical properties are systematically investigated. All compounds display positive solvatochromic behaviour, good thermal and electrochemical stability. Moreover, pronounced aggregation-induced emission and mechanochromic luminescence are observed in their solid states. DPMM-2TPA and DPMM-2DMAC realized red fluorescence, extremely small ΔEST of 0.06 and 0.01 eV and significant thermally activated delayed fluorescence character, due to the operative RISC process via spin orbit coupling from 3LE to 1CT and hyperfine coupling between 3CT and 1CT, respectively. Nevertheless, TADF cannot be detected for DPMM-2PhCz because of its large 1CT and 3CT gap (0.34 eV) and inaccessible endothermic energy transfer. These results suggest that the energy level of 1CT, 3LE and 3CT is adjustable by carefully designing the molecular configuration and thus enable the emission switch from non-TADF to TADF. Multilayer OLEDs based on DPMM-2TPA and DPMM-2DMAC exhibit a maximum EQE of 16.5% and 12.7%, respectively, which is 3–4 times higher than DPMM-2PhCz based non-TADF OLEDs (EQE = 4.4%).

Tumor-specific fluorescence activation of rhodamine isothiocyanate derivatives

Fluorescence is routinely used for in vivo tracking and imaging of molecules and nanostructures with assuming that the fluorescence intensity is proportional to the dye concentration. Herein, we report the unique tumor-specific fluorescence character of rhodamine B isothiocyanate derivatives (RBITCs), which emits fluorescence selectively in cancerous tissues, including small metastatic tumors, but is quenched in blood and healthy tissues. A preliminary mechanism study shows that binding of the thiourea group in the RBITCs on hemoglobin quenches their fluorescence, but the oxidation of the thiourea by the elevated reactive oxygen species in tumor activates the fluorescence. Thus, the fluorescent intensity of RBITCs is associated with the microenvironment of tissues and positively correlates with the cancer stages. These findings suggest that the RBITCs are not suitable for tracking of cargos in the presence of red blood cells but may be useful for cancer imaging and early diagnosis, and probing the tumor microenvironment.

Two‐Dimensional Conjugated Polymer Synthesized by Interfacial Suzuki Reaction: Towards Electronic Device Applications

AbstractPreparing two‐dimensional conjugated polymers (2DCPs) with desirable structures and semiconducting properties is promising but remains a great challenge. Presented here is a new 2DCP, named 2D polytriethyltriindole (2DPTTI), which is efficiently synthesized by a modified interfacial Suzuki reaction from 2,7,12‐tribromo‐5,10,15‐triethyltriindole (2‐BrTTI) and 1,4‐benzenediboronic acid dipinacol ester (BADE) precursors at room temperature. Wafer‐scale free‐standing 2DPTTI films with controllable thicknesses between 2.5 and 46.0 nm were obtained by adjusting the experimental conditions. The resulting 2DPTTI films, used as an active layer in organic field effect transistors (OFETs), exhibited typical p‐type semiconducting properties and superior UV optoelectronic performance with a photosensitivity of 3.7×103 and responsivity of 1.4×103 A W−1, as well as a light‐blue fluorescence character. This report provides a general approach for constructing various semiconducting 2DCPs, by an interfacial Suzuki reaction, towards multifunctional organic electronics.

Efficient Aggregation-Induced Delayed Fluorescence Luminogens for Solution-Processed OLEDs With Small Efficiency Roll-Off.

Purely organic small molecules with thermally-activated delayed fluorescence have a high potential for application in organic light-emitting diodes (OLEDs), but overcoming severe efficiency roll-off at high voltages still remains challenging. In this work, we design and synthesize two new emitters consisting of electron-withdrawing benzoyl and electron-donating phenoxazine and 9,9-dihexylfluorene. Their electronic structures, thermal stability, electrochemical behaviors, photoluminescence property, and electroluminescence performance are thoroughly investigated. These new emitters show weak fluorescence in dilute solution, but they can emit strongly with prominent delayed fluorescence in the aggregated state, indicating the aggregation-induced delayed fluorescence (AIDF) character. The solution-processed OLEDs based on the two emitters show high external quantum efficiency of 14.69%, and the vacuum-deposited OLEDs can also provide comparable external quantum efficiency of 14.86%. Significantly, roll-offs of the external quantum efficiencies are very small (down to 0.2% at 1,000 cd m−2) for these devices, demonstrating the evidently advanced efficiency stability. These results prove that the purely organic emitters with AIDF properties can be promising to fabricate high-performance solution-processed OLEDs.

Two-Dimensional Conjugated Polymer Synthesized by Interfacial Suzuki Reaction: Towards Electronic Device Applications.

Preparing two-dimensional conjugated polymers (2DCPs) with desirable structures and semiconducting properties is promising but remains a great challenge. Presented here is a new 2DCP, named 2D polytriethyltriindole (2DPTTI), which is efficiently synthesized by a modified interfacial Suzuki reaction from 2,7,12-tribromo-5,10,15-triethyltriindole (2-BrTTI) and 1,4-benzenediboronic acid dipinacol ester (BADE) precursors at room temperature. Wafer-scale free-standing 2DPTTI films with controllable thicknesses between 2.5 and 46.0 nm were obtained by adjusting the experimental conditions. The resulting 2DPTTI films, used as an active layer in organic field effect transistors (OFETs), exhibited typical p-type semiconducting properties and superior UV optoelectronic performance with a photosensitivity of 3.7×103 and responsivity of 1.4×103 A W-1 , as well as a light-blue fluorescence character. This report provides a general approach for constructing various semiconducting 2DCPs, by an interfacial Suzuki reaction, towards multifunctional organic electronics.

Strong Solid-State Fluorescence Induced by Restriction of the Coordinate Bond Bending in Two-Coordinate Copper(I)-Carbene Complexes.

The photophysical properties of two-coordinate copper(I) complexes have become a new research hotspot due to their nearly perfect luminescent properties and low price and promising applications in organic light-emitting diodes (OLEDs). In this work, we employ the hybrid quantum mechanics and molecular mechanics (QM/MM) approach, coupled with our early developed thermal vibration correlation function (TVCF) rate formalism, to study the aggregation effect on the luminescent properties of the cyclic (alkyl)(amino)carbene-copper(I)-Cl complex. Our calculations reveal that the transition properties changes from metal-ligand-charge-transfer (MLCT) in solution to hybrid halogen ligand charge-transfer (XLCT) and MLCT in solid state, which induces the blue-shifted emission spectra from solution to solid phase. Upon aggregation, the restriction of the bending vibrations of the C-Cu-Cl and Cu-C-N bonds largely slow down the nonradiative decay, which induces strong fluorescence. This study provides a clear rationalization for the highly efficient fluorescence character of two-coordinate Cu(I) complexes.

Halloysite nanotube-based H2O2-responsive drug delivery system with a turn on effect on fluorescence for real-time monitoring

In this paper, a novel halloysite-based hydrogel with a “turn-on” fluorescence character upon H2O2 was facilely prepared and used to construct the H2O2-responsive drug delivery system, in which a coprecipitation method was proposed to afford the drug-loaded halloysite nanotubes (DHNTs). DHNTs were carefully characterized by FTIR, TGA, XPS, XRD and TEM to demonstrate that the drugs were mainly loaded into the cavity rather than attached on the external surface of halloysite nanotubes (HNTs). The B-C linkage in the as-prepared hydrogel was broken in the presence of H2O2, resulting in the degradation and thereby a responsive release. The drug release was almost not occurred under the physiological concentration ([H2O2] = 0.02 μM), while a complete release (>90%) can be achieved under pathological concentration ([H2O2] = 200 μM). Moreover, the broken of B-C linkage triggered a transformation from arylboronates to phenols, in which the formed fluorescein gave rise to the change from non-fluorescent to fluorescent of the hydrogels. The fluorescence intensity enhanced with the increase of release rate, in which a good linear relationship can be achieved. The attractive properties make the halloysite-based hydrogels a promising application in the field of biomedicine.