Triplet Exciton Transition Induced Highly Efficient Fluorescent Channel in Organic Electroluminescence

The in.jection of charge carriers from the electron/hole injection or transport layers in polymer light-emitting diodes potentially increases the device efficiency not by changing of charge intensity but by lattice distortion variation and quasi-particle interactions. From the low-dimensional condensed matter physics perspective, a valid mechanism is proposed to bring a type of novel channels that, under a proper external electric field, transition- forbidden triplet excitons are transformed and partially charged by charge carriers （polarons/bipolarons）, thus are able to emit light and to enhance fluorescence greatly.

Highly Red Emissive Conjugated Homopolymers Based on Double B←N Bridged Bipyridine Unit

Conjugated homopolymers based on six-member rings,e.g.,polyfluorene,always exhibit blue emission and conjugated homopolymers based on five-member rings,e.g.,polythiophene,can give red emission with low efficiency.In this work,we report a series of new conjugated homopolymers based on six-member rings with high-efficiency deep-red emission.The repeating units of the red light emitting homopolymers are double B←N bridged bipyridine(BNBP)with the boron atoms functionalized with diphenyl,borafluorene,and 2,7-di-tert-butyl-borafluorene groups,respectively.The relationship between the chemical structures and the opto-electronic properties of the monomers and the homopolymers has been systematically studied.The three polymers emit pure red light(λ_(max)=656 nm)or deep red light(λ_(max)=693 nm)with fluorescence quantum efficiency in solution higher than 60%.The polymers can be used as the emitters in solution-processed organic light-emitting diodes with red emission and decent device performance.This work indicates a new strategy to design highly efficient light emitting conjugated polymers.

Thermally activated delayed fluorescence carbazole-triazine dendrimer with bulky substituents

Carbazole-triazine dendrimers with a bulky terminal substituent were synthesized,and the thermally activated delayed fluorescence(TADF)property was investigated.Compared to unsubstituted carbazole dendrimers,dendrimers with bulky terminal substituents showed comparable to better photoluminescence quantum yields(PLQY)in neat films.Phenylfluorene(PF)-substituted dendrimers showed the highest PLQY of 81%,a smallΔEst of 0.06 eV,and the fastest reverse intersystem crossing(RISC)rate of∼1×10^(5 )s^(−1) compared to other dendrimers.Phosphorescence measurements of dendrimers and dendrons(fragments)indicate that the close proximity of the triplet energy of phenylfluorene-substituted carbazole dendrons(^(3)LE)to that of phenylfluorene-substituted dendrimers(^(1)CT,^(3)CT)contributes to RISC promotion and improves TADF efficiency.Terminal modification fine-tunes the energy level and suppresses intermolecular interactions,and this study provides a guideline for designing efficient solution-processable and non-doped TADF materials.

Enhancement of electroluminescent properties of organic optoelectronic integrated device by doping phosphorescent dye

Organic optoelectronic integrated devices（OIDs） with ultraviolet（UV） photodetectivity and different color emitting were constructed by using a thermally activated delayed fluorescence（TADF） material 4, 5-bis（carbazol-9-yl）-1, 2-dicyanobenzene（2 CzPN） as host. The OIDs doping with typical red phosphorescent dye [tris（1-phenylisoquinoline）iridium（Ⅲ）, Ir（piq）3], orange phosphorescent dye {bis[2-（4-tertbutylphenyl）benzothiazolato-N,C-（2＇）]iridium（acetylacetonate）,（tbt）2 Ir（acac）}, and blue phosphorescent dye [bis（2, 4-di-fluorophenylpyridinato）-tetrakis（1-pyrazolyl）borate iridium（Ⅲ）, FIr6] were investigated and compared. The（tbt）2 Ir（acac）-doped orange device showed better performance than those of red and blue devices, which was ascribed to more effective energy transfer. Meanwhile, at a low dopant concentration of 3 wt.%, the（tbt）2 Ir（acac）-doped OIDs showed the maximum luminance, current efficiency, power efficiency of 70786 cd/m^2, 39.55 cd/A, and 23.92 lm/W, respectively, and a decent detectivity of 1.07 × 10^11 Jones at a bias of -2 V under the UV-350 nm illumination. This work may arouse widespread interest in constructing high efficiency and luminance OIDs based on doping phosphorescent dye.

A highly specific ratiometric two-photon fluorescent probe to detect dipeptidyl peptidase Ⅳ in plasma and living systems

Subject Code:H30With the support by the National Natural Science Foundation of China and National Basic Research Program of China,the group led by Prof.Ge Guangbo(葛广波)and Prof.Yang Ling(杨凌)from the Laboratory of Pharmaceutical Resource Discovery,Dalian Institute of Chemical Physics,Chinese Academy of Sciences,reported a highly specific ratiometric two-photon fluorescent probe to detect

Novel seven-membered ring-fused naphthalimide derivatives with potentials for cancer theranostics

Naphthalimide derivatives have good planarity and large conjugated structure and therefore possess photophysical properties and biological activities. Previously, our group discovered seven-membered heterocyclic derivatives via modifying 4-and 5-positions of naphthalimide skeleton and found the derivatives had good water solubility and showed large stokes shift and strong fluorescence in water. In this article, we designed and synthesized more seven-membered ring-fused naphthalimide derivatives(Y1-Y16)by introducing different substitutions on the imide group. Among them, Y1, Y5, Y9 were found to show similar cytotoxic activities with Amonafide against A549 and HL60 cells, with IC50values at 10^(-6)mol/L.What is more, the asymmetry derivatives(Y1 and Y5) showed high fluorescent quantum yields in the aqueous phase(Ф = 0.47). Considering the great fluorescence quantum yields in water and the potent anti-tumor activities of the representative seven-membered ring-fused naphthalimides, they have potentials to be used as agents for cancer theranostics.

Dynam,c Changes of IsiA-Containing Complexes during Long-Term Iron Deficiency in Synechocystis sp, PCC 6803

Iron stress-induced protein A （IsiA）, a major chlorophyll-binding protein in the thylakoid membrane, is significantly induced under iron deficiency conditions. Using immunoblot analysis and 77 K fluorescence spectroscopy combined with sucrose gradient fractionation, we monitored dynamic changes of IsiA- containing complexes in Synechocystis sp. PCC 6803 during exposure to long-term iron deficiency. Within 3 days of exposure to iron deficiency conditions, the initially induced free IsiA proteins preferentially con- jugated to PSI trimer to form IsiA18-PS I trimers, which serve as light energy collectors for efficiently trans- mitting energy to PS h With prolonged iron deficiency, IsiA proteins assembled either into IsiA aggregates or into two other types of IsiA-PS I supercomplexes, namely IsiA-PS I high fluorescence supercomplex （IHFS） and IsiA-PS I low fluorescence supercomplex （ILFS）. Further analysis revealed a role for IsiA as an energy dissipater in the IHFS and as an energy collector in the ILFS. The trimeric structure of PS I mediated by PsaL was found to be indispensable for the formation of IHFS/ILFS. Dynamic changes in IsiA-containing complexes in cyanobacteria during long-term iron deficiency may represent an adaptation to iron limitation stress for flexible light energy distribution, which balances electron transfer between PS I and PS II, thus minimizing photooxidative damage.

A strategy to achieve efficient green-emission dual-mode luminescence of Yb^(3+),Er^(3+) doped NaBiF_(4)

A series of hexagonal phase NaBiF_(4):x Yb^(3+),y Er^(3+) were successfully synthesized by solvothermal method.The morphology,phase structure,up-conversion luminescence and down-conversion luminescence properties of Yb^(3+) and Er^(3+) doping concentration and the energy transfer mechanism were studied.It shows that the doping of Yb^(3+) and Er^(3+) does not cause the phase transition of NaBiF_(4),but influences its morphology.In the NaBiF_(4):Yb^(3+),Er^(3+),Yb^(3+) can transfer energy with Er^(3+),enhancing up-conversion green emission.With Yb^(3+) doping concentration increasing,the up-conversion red-green ratio will increase while the down-conversion intensity of the green emission decreases and that of the red emission increases.Considering the potential application of Na BiF4:x Yb^(3+),y Er^(3+) phosphors in optical illumination,the thermal stability was carried out.