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1.
Chemistry ; 30(1): e202302624, 2024 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-37806959

RESUMO

A pair of isomers, IDT-BOF containing S⋅⋅⋅O/F⋅⋅⋅H noncovalently configurational locks and IDT-BFO containing F⋅⋅⋅H/O⋅⋅⋅H noncovalently configurational locks, with an acceptor-π-donor-π-acceptor (A-π-D-π-A) structure have been designed and synthesized by choosing 4,9-dihydro-s-indaceno[1,2-b : 5,6-b']dithiophene (IDT) as the D unit, an F/n-hexyloxy substituted phenyl ring as π bridge, and 3-(dicyanomethylidene)indan-1-one as the A unit. Owing to the S⋅⋅⋅O/F⋅⋅⋅H or F⋅⋅⋅H/O⋅⋅⋅H noncovalently configurational locks, both IDT-BOF and IDT-BFO have a completely planar structure. IDT-BOF exhibits a similar LUMO to IDT-BFO, but higher HOMO energy levels, leading to a smaller optical bandgap and red-shifted absorption. However, IDT-BOF-based bulk-heterojunction organic solar cells (BHJ-OSCs) coupled with PBDB-T, and PCE-10 as donor materials both exhibited a lower PCE than that of IDT-BFO (PBDB-T: 5.2 vs. 6.1 %; PCE-10: 1.7 vs. 3.2 %). Comprehensively comparing and investigating IDT-BOF : PBDB-T and IDT-BFO : PBDB-T OSCs suggested that the large phase separation and serious charge recombination of IDT-BOF-based OSCs contributed to its lower power conversion efficiency. Importantly, ternary solar cells based on PBDB-T : Y5 as control devices with an additional 10 % IDT-BFO exhibited a 5 % enhancement in the PCE compared to the control device (14.3 vs. 13.46 %).

2.
Environ Sci Technol ; 58(13): 6007-6018, 2024 Apr 02.
Artigo em Inglês | MEDLINE | ID: mdl-38513264

RESUMO

Knowledge gaps in mercury (Hg) biomagnification in forest birds, especially in the most species-rich tropical and subtropical forests, limit our understanding of the ecological risks of Hg deposition to forest birds. This study aimed to quantify Hg bioaccumulation and transfer in the food chains of forest birds in a subtropical montane forest using a bird diet recorded by video and stable Hg isotope signals of biological and environmental samples. Results show that inorganic mercury (IHg) does not biomagnify along food chains, whereas methylmercury (MeHg) has trophic magnification factors of 7.4-8.1 for the basal resource-invertebrate-bird food chain. The video observations and MeHg mass balance model suggest that Niltava (Niltava sundara) nestlings ingest 78% of their MeHg from forest floor invertebrates, while Flycatcher (Eumyias thalassinus) nestlings ingest 59% from emergent aquatic invertebrates (which fly onto the canopy) and 40% from canopy invertebrates. The diet of Niltava nestlings contains 40% more MeHg than that of Flycatcher nestlings, resulting in a 60% higher MeHg concentration in their feather. Hg isotopic model shows that atmospheric Hg0 is the main Hg source in the forest bird food chains and contributes >68% in most organisms. However, three categories of canopy invertebrates receive ∼50% Hg from atmospheric Hg2+. Overall, we highlight the ecological risk of MeHg exposure for understory insectivorous birds caused by atmospheric Hg0 deposition and methylation on the forest floor.


Assuntos
Mercúrio , Compostos de Metilmercúrio , Poluentes Químicos da Água , Animais , Mercúrio/análise , Cadeia Alimentar , Monitoramento Ambiental/métodos , Poluentes Químicos da Água/análise , Florestas , Invertebrados , Aves , Isótopos , Isótopos de Mercúrio/análise
3.
Angew Chem Int Ed Engl ; 63(4): e202312534, 2024 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-37968890

RESUMO

Currently, purely organic compounds showing ambient phosphorescence with high efficiency (ΦP ) and ultra-long lifetime (τP ) are quite rare and often need to be achieved in hydrophilic poly(vinyl alcohol)-based hosts. This severely limits their applications. Here, we provide a solution to this issue by constructing an ortho-linked donor-acceptor (D-A) dyad whose D moiety has not only a long-lived T1 state to achieve a long τP , but also a Tn state that is close to the S1 state of the dyad to trigger effective spin-orbit charge transfer intersystem crossing (SOCT-ISC). The rationality of this strategy was validated by a new phosphor OF-BCz that is able to show a τP of 1.92 s and a ΦP of 30 % even in a less rigid matrix of poly(methyl methacrylate) (PMMA). Excitingly, OF-BCz exhibited its potential as both a photocuring initiator and an in situ quality indicator, allowing for the visual detection of defects in photolithographic patterning.

4.
Angew Chem Int Ed Engl ; 63(1): e202314447, 2024 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-37968894

RESUMO

Although long-lived triplet charge-transfer (3 CT) state with high energy level has gained significant attention, the development of organic small molecules capable of achieving such states remains a major challenge. Herein, by using the through-space electronic coupling effect, we have developed a compound, namely NIC-DMAC, which has a long-lived 3 CT state at the single-molecule level with a lifetime of 210 ms and a high energy level of up to 2.50 eV. Through a combination of experimental and computational approaches, we have elucidated the photophysical processes of NIC-DMAC, which involve sequential transitions from the first singlet excited state (S1 ) that shows a 1 CT character to the first triplet excited state (T1 ) that exhibits a local excited state feature (3 LE), and then to the second triplet excited state (T2 ) that shows a 3 CT character (i.e., S1 (1 CT)→T1 (3 LE)→T2 (3 CT)). The long lifetime and high energy level of its 3 CT state have enabled NIC-DMAC as an initiator for photocuring in double patterning applications.

5.
Anal Chem ; 95(21): 8150-8155, 2023 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-37155725

RESUMO

Accurate quantification on the quantum yields (φ) of both the prompt fluorescence (PF) and the delayed fluorescence (DF) species is quite essential for the clarification of molecular design rationales for thermally activated delayed fluorescence (TADF) luminogens. Currently, most φPF and φDF data of TADF fluorophores were acquired through time-correlated single-photon counting (TCSPC) lifetime measurement systems. However, because of their equal-time-channel working manner, so far all the commercially available TCSPC systems cannot render accurate measurement on φPF of TADF materials due to the lack of enough valid data points in the faster decay region of the corresponding photoluminescence (PL) decay curves. Although an intensified charge coupled device (ICCD) system equipped with a streak camera or an optical parametric oscillation laser has been proven to be a powerful tool for accurate determination of φPF and φDF of TADF fluorophores, the ultrahigh cost of these ICCD systems makes them inaccessible to most users. Herein, by replacing the timing module of a commercial TCSPC system with a low-cost and versatile time-to-digital converter (TDC) module, we developed a modified TCSPC system that can work in an unequal-time-channel manner. The resultant TDC-TCSPC system can not only concurrently determine the accurate lifetime of PF and DF species whose lifetime span even exceeds 5 orders of magnitude in just one time window but also render accurate measurements on φPF and φDF of TADF fluorophores. The reliability of the TDC-TCSPC method was verified through TCSPC- and ICCD-based comparative experiments on ACMPS, a known TADF fluorophore. Our results not only can provide a low-cost and convenient test method for accurate determination of key experimental data of TADF materials but also will facilitate deeper understanding of the molecular design principles for high-performance TADF materials.

6.
Environ Sci Technol ; 56(19): 14154-14165, 2022 10 04.
Artigo em Inglês | MEDLINE | ID: mdl-36150175

RESUMO

Plant roots are responsible for transporting large quantities of nutrients in forest ecosystems and yet are frequently overlooked in global assessments of Hg cycling budgets. In this study, we systematically determined the distribution of total Hg mass and its stable isotopic signatures in a subtropical evergreen forest to elucidate sources of Hg in plant root tissues and the associated translocation mechanisms. Hg stored in roots and its isotopic signatures show significant correlations to those found in surrounding soil at various soil depths. The odd mass-independent fractionation (MIF) of root Hg at a shallow soil depth displays a -0.10‰ to -0.50‰ negative transition compared to the values in aboveground woody biomass. The evidence suggests that root Hg is predominantly derived from surrounding soil, rather than translocation of atmospheric uptake via aboveground tissues. The cortex has a more negative mass-dependent fractionation (MDF) of -0.10‰ to -1.20‰ compared to the soil samples, indicating a preferential uptake of lighter isotopes by roots. The similar MDF and odd-MIF signals found in root components imply limited Hg transport in roots. This work highlights that Hg stored in plant roots is not a significant sink of atmospheric Hg. The heterogeneous distribution of Hg mass in roots of various sizes represents a significant uncertainty of current estimates of Hg pool size in forest ecosystems.


Assuntos
Mercúrio , Ecossistema , Monitoramento Ambiental , Florestas , Isótopos , Mercúrio/análise , Isótopos de Mercúrio/análise , Solo
7.
Environ Sci Technol ; 56(9): 5950-5959, 2022 05 03.
Artigo em Inglês | MEDLINE | ID: mdl-35420795

RESUMO

Vegetation uptake represents the dominant route of Hg input to terrestrial ecosystems. However, this plant-directed sink is poorly constrained due to the challenges in measuring the net Hg0 exchange on the ecosystem scale over a long period. Particularly important is the contribution in the subtropics/tropics, where the bulk (∼70%) of the Hg0 deposition is considered to occur. Using the relaxed eddy accumulation technique, this study presents for the first time a whole ecosystem Hg0 flux record over an evergreen hardwood forest. This tower-based micrometeorological method gauged a cumulated net Hg0 flux of -41.1 µg m-2 over 16 months, suggesting that the subtropical montane forest acts as a large and continuous sink of atmospheric Hg0. The monthly net fluxes were consistently negative (-7.3 to -1.0 µg m-2 month-1) throughout the year, with the smallest absolute values occurring during the mild and dry subseason in spring, which was also the annual lowest in vegetation activity. Colocated measurements of multilevel gradients of Hg0 concentration and its stable isotopic composition support the finding of year-round Hg0 deposition. The stable Hg isotope measurements also show that in-canopy bi-directional Hg0 exchange is prevalent.


Assuntos
Ecossistema , Mercúrio , Monitoramento Ambiental/métodos , Florestas , Isótopos , Mercúrio/análise
8.
J Cell Mol Med ; 25(9): 4444-4454, 2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33837652

RESUMO

Increasing evidences have showed that autophagy played a significant role in oral squamous cell carcinoma (OSCC). Purpose of our study was to explore the prognostic value of autophagy-related genes (ATGs) and screen autophagy-related biomarkers for OSCC. RNA-seq and clinical data were downloaded from The Cancer Genome Atlas (TCGA) database following extracting ATG expression profiles. Then, differentially expressed analysis was performed in R software and a risk score model according to ATGs was established. Moreover, comprehensive bioinformatics analyses were used to screen autophagy-related biomarkers which were later verified in OSCC tissues and cell lines. A total of 232 ATGs were extracted, and 37 genes were differentially expressed in OSCC. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis demonstrated that these genes were mainly located in autophagosome membrane and associated with autophagy. Furthermore, the risk score on basis of ATGs was identified as potential independent prognostic biomarker. Moreover, ATG12 and BID were identified as potential autophagy-related biomarkers of OSCC. This study successfully constructed a risk model, and the risk score could predict the prognosis of OSCC patients accurately. Moreover, ATG12 and BID were identified as two potential independent prognostic autophagy-related biomarkers and might provide new OSCC therapeutic targets.


Assuntos
Proteínas Relacionadas à Autofagia/genética , Autofagia , Biomarcadores Tumorais/genética , Carcinoma de Células Escamosas/patologia , Biologia Computacional/métodos , Regulação Neoplásica da Expressão Gênica , Neoplasias Bucais/patologia , Apoptose , Proteínas Relacionadas à Autofagia/metabolismo , Biomarcadores Tumorais/metabolismo , Carcinoma de Células Escamosas/genética , Carcinoma de Células Escamosas/metabolismo , Proliferação de Células , Feminino , Perfilação da Expressão Gênica , Ontologia Genética , Redes Reguladoras de Genes , Humanos , Pessoa de Meia-Idade , Neoplasias Bucais/genética , Neoplasias Bucais/metabolismo , Prognóstico , Taxa de Sobrevida , Células Tumorais Cultivadas
9.
Environ Sci Technol ; 55(18): 12352-12361, 2021 09 21.
Artigo em Inglês | MEDLINE | ID: mdl-34449213

RESUMO

Air-soil exchange of elemental mercury vapor (Hg0) is an important component in the budget of the global mercury cycle. However, its mechanistic detail is poorly understood. In this study, stable Hg isotopes in air, soil, and pore gases are characterized in a subtropical evergreen forest to understand the mechanical features of the air-soil Hg0 exchange. Strong HgII reduction in soil releases Hg0 to pore gas during spring-autumn but diminishes in winter, limiting the evasion in cold seasons. Δ199Hg in air modified by the Hg0 efflux during flux chamber measurement exhibit seasonality, from -0.33 ± 0.05‰ in summer to -0.08 ± 0.05‰ in winter. The observed seasonal variation is caused by a strong pore-gas driven soil efflux caused by photoreduction in summer, which weakens significantly in winter. The annual Hg0 gross deposition is 42 ± 33 µg m-2 yr-1, and the corresponding Hg0 evasion from the forest floor is 50 ± 41 µg m-2 yr-1. The results of this study, although still with uncertainty, offer new insights into the complexity of the air-surface exchange of Hg0 over the forest land for model implementation in future global assessments.


Assuntos
Mercúrio , Poluentes do Solo , Monitoramento Ambiental , Florestas , Mercúrio/análise , Isótopos de Mercúrio/análise , Solo , Poluentes do Solo/análise
10.
Chemistry ; 26(53): 12140-12144, 2020 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-32573863

RESUMO

Although (E)-4-(2-(4-(dicyanomethylene)-4H-chromen-2-yl)vinyl)phenolate anion (DCPO- ) has recently emerged as a potential near infrared (NIR) biosensor signaling unit, the pKa value of its conjugate acid is relatively high (∼9); this will lead to relatively low concentrations of DCPO- under physiological conditions and, hence, unsatisfactory sensitivity of DCPO- -based bio-probes. By difluoro-substitution on DCPO- , we have exploited a new fluorophore of o-FDCPO- whose conjugate acid has a much lower pKa value of 7.42. Meanwhile, o-FDCPO- is NIR emissive with λem =693 nm and has a 0.76-fold higher fluorescence efficiency than DCPO- . The significant superiority of o-FDCPO- over DCPO- in sensitivity for NIR biosensor applications was confirmed by comparative studies on two HNO probes, namely o-FDCPO-P and DCPO-P, which bear signaling units of o-FDCPO- and DCPO- , respectively. Moreover, o-FDCPO-P has been demonstrated to be a high-performance HNO probe with high selectivity, high sensitivity (detection limit: 50 nm), and a rapid response, together with a two-photon NIR-excitation imaging capability.


Assuntos
Técnicas Biossensoriais , Corantes Fluorescentes , Ionóforos/química , Fenóis/química , Fótons
11.
Inorg Chem ; 59(1): 332-342, 2020 Jan 06.
Artigo em Inglês | MEDLINE | ID: mdl-31854988

RESUMO

In this paper, we systemically investigated the photoelectric properties of three new deep-red quinoxaline-based iridium(III) complexes: Ir-0, Ir-1, and Ir-2. (MPQ)2Ir(dpm) (Ir-0) bore a 2-methyl-3-phenylquinoxaline cyclometalated ligand, while (c-PyMPQ)2Ir(dpm) (Ir-1) and (t-PyMPQ)2Ir(dpm) (Ir-2) possessed a 1-pyrene substituent that connected at the 6/7 position of the corresponding ligands. The configurations of the latter two complexes were well-confirmed by single-crystal X-ray diffraction, and both of them had large dihedral angles between the quinoxaline and pyrene units, preventing the emission peaks of the three complexes from being altered too much. Based on the density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations, we concluded that the emission of all complexes originated predominantly from the triplet metal-to-ligand/intraligand charge transfer (3MLCT/3ILCT) state of the non-pyrene-substituted counterpart Ir-0 core. Interestingly, we also obtained another type of pyrene-stacking characteristic crystal of Ir-1, which had an emission resembled the phosphorescence observed in thin film. The easily formed pyrene-stacking configuration would most probably limit their device performance at a higher concentration. Moreover, the fabricated organic light-emitting diodes (OLEDs) using these materials achieved considerable device performance at a low doping concentration of 0.5 wt %. This work provides an approach for reasonably designing large fused-ring-substituted quinoxaline ligands of iridium complexes.

12.
Environ Sci Technol ; 54(14): 8739-8749, 2020 07 21.
Artigo em Inglês | MEDLINE | ID: mdl-32551609

RESUMO

Organic soil is an important transient reservoir of mercury (Hg) in terrestrial ecosystems, but the fate of deposited Hg in organic forest soil is poorly understood. To understand the dynamic changes of deposited Hg on forest floor, the composition of stable Hg and carbon (C) isotopes in decomposing litters and organic soil layer was measured to construct the 500 year history of postdepositional Hg transformation in a subtropical evergreen broad-leaf forest in Southwest China. Using the observational data and a multiprocess isotope model, the contributions of microbial reduction, photoreduction, and dark reduction mediated by organic matter to the isotopic transition were estimated. Microbial reduction and photoreduction play a dominant role in the initial litter decomposition during first 2 years. Dark redox reactions mediated by organic matter become the predominant process in the subsequent 420 years. After that, the values of Hg mass dependent fractionation (MDF), mass independent fractionation (MIF), and Δ199Hg/Δ201Hg ratio do not change significantly, indicating sequestration and immobilization of Hg in soil. The linear correlations between the isotopic signatures of Hg and C suggest that postdepositional transformation of Hg is closely linked to the fate of natural organic matter (NOM). Our findings are consistent with the abiotic dark reduction driven by nuclear volume effect reported in boreal and tropical forests. We recommend that the dark reduction process be incorporated in future model assessment of the global Hg biogeochemical cycle.


Assuntos
Mercúrio , Biomassa , China , Ecossistema , Monitoramento Ambiental , Florestas , Isótopos , Mercúrio/análise , Isótopos de Mercúrio/análise , Solo
13.
Chemistry ; 25(25): 6385-6391, 2019 May 02.
Artigo em Inglês | MEDLINE | ID: mdl-30834610

RESUMO

One pair of isomers, centrosymmetric anti-Py-1 and axisymmetric syn-Py-2, was designed and synthesized with an acceptor-donor-acceptor (A-D-A) structure by choosing dithienocyclopentapyrene with four 4-hexylphenyl side chains as the D unit, and 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene) malononitrile as the A unit. In-depth structure-property relationship studies revealed that the isomers have similar UV/Vis absorption, fluorescence emission, and energy levels but significant differences in molecular shape, polarity, and charge mobility. Solution-processed bulk-heterojunction (BHJ) small-molecule organic solar cells with Py-1 as the electron-acceptor material and PTB7-Th as the electron-donor material exhibit a power conversion efficiency (PCE) of 6.07 %, or 60 % higher than that of Py-2 (3.7 %), which could be mainly attributed to the higher and more balanced hole/electron mobilities and better phase separation of the Py-1-based active layer.

14.
Chemphyschem ; 20(3): 470-481, 2019 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-30479051

RESUMO

We performed a joint theoretical and experimental study on sixteen Ir(III) complexes bearing a similar molecular platform of bis(2-phenylbenzothiozolato-N,C2' ) iridium(III) (acetylacetonate) by grafting -OCH3 group and/or -CN group on different positions of the C-related arene moiety of the C ^ N ligand (C-ring). Our results reveal that the introduction of -CN renders an overall drop in the FMO energy levels while a reverse increase is observed for -OCH3 . The ortho- and para-sites of the C-ring are more effective substitution positions to modulate the HOMO energy level due to the fact that the electronic density of HOMO mainly locates at them while the meta-site would induce a stronger impact on LUMO since the electronic density of LUMO mainly distributes over the position. Utilizing the synergistic effects of the substituents and the substituted positions, a wide color-tuning range from 479 nm to 637 nm was achieved, which covers nearly the whole window of visible spectrum. In particular, the tri-substituted Ir35mo4cn complex (λem max =637 nm) may be a potential candidate for high efficiency red OLEDs materials due to its greatly enhanced absorption processes, relatively higher 3 MLCT (%), lower ΔES1-T1 , enlarged separation between 3 MLCT/π-π* and 3 MC d-d states, and good hole and particle-transporting performances. Finally, six representative complexes were synthesized and their spectra were determined, which confirm the reliability of our computational strategy.

15.
Environ Sci Technol ; 53(2): 651-660, 2019 01 15.
Artigo em Inglês | MEDLINE | ID: mdl-30501171

RESUMO

The mechanism of elemental mercury (Hg0) re-emission from vegetation to the atmosphere is currently poorly understood. In this study, we investigated branch-level Hg0 atmosphere-foliage exchange in a pristine evergreen forest by systematically combining Hg isotopic composition, air concentration and flux measurements to unravel process information. It is found that the foliage represents a diurnally changing sink for atmospheric Hg0 and its Hg content increases with leaf age and mass. Atmospheric Hg0 is the dominant source of foliar Hg and the involvement of HgII is not supported by isotopic evidence. Upon Hg0 uptake, maturing foliage becomes progressively enriched in lighter Hg isotopes and depleted in odd mass isotopes. The measured isotopic composition of foliage Hg and isotopic shift caused by Hg0 evasion from foliage supports that Hg0 emitted from foliage is derived from Hg previously metabolized and bound in the leaf interior then subsequently recycled after reduction, and not merely a retroflux of recently deposited Hg0 on foliar surface. An isotopic differential mass balance model indicates that the proportion of foliar Hg0 efflux to uptake gradually increase from emergence to senescence with an average flux ratio of 30%.


Assuntos
Monitoramento Ambiental , Mercúrio , Atmosfera , Isótopos , Isótopos de Mercúrio
16.
Angew Chem Int Ed Engl ; 58(19): 6280-6284, 2019 May 06.
Artigo em Inglês | MEDLINE | ID: mdl-30865365

RESUMO

Owing to the quite similar chemical properties of H2 O and D2 O, rational molecular design of D2 O optical sensors has not been realized so far. Now purely organic chromophores bearing OH groups with appropriate pKa values are shown to display distinctly different optical responding properties toward D2 O and H2 O owing to the slight difference in acidity between D2 O and H2 O. This discovery is a new and facile strategy for the construction of D2 O optical sensors. Through this strategy, ratiometric colorimetric D2 O sensor of NIM-2F and colorimetric/fluorescent dual-channel D2 O sensor of AF were acquired successfully. Both NIM-2F and AF can not only qualitatively distinguish D2 O from H2 O by the naked eye, but also quantitatively detect the H2 O content in D2 O.

17.
Chemistry ; 24(35): 8747-8750, 2018 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-29663618

RESUMO

A squaraine-based small molecule (USQ-BI) bearing 3H-benzo[e]indoline was synthesized as an electron donor, and the corresponding organic solar cells show power conversion efficiency of 5.35 % with an excellent short circuit current of over 15 mA cm-2 . The hole mobility of USQ-BI was about 5 times (9.57×10-5 vs. 2.00×10-5  cm2 V-1 s-1 ) higher than that of indoline-based squaraine.

18.
Chemistry ; 24(32): 8056-8060, 2018 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-29655182

RESUMO

A series of blue-emissive 7-(diphenylamino)-4-phenoxycoumarin derivatives bearing -CF3 , -OMe, or -N(Me)2 substituents on the phenoxy subunit were synthesized. Although both the -CF3 and -N(Me)2 modifications were found to trigger redshifted fluorescence, the -OMe substitution was demonstrated to exert an unexpected blueshift color-tuning effect toward the deep-blue region. The reason is that the moderate electron-donating -OMe group can endow coumarins with unaltered HOMO but elevated LUMO energy levels. Moreover, the -OMe substitution was found to be beneficial to the thermal stability of these coumarins. Therefore, the trimethoxy-substituted objective compound can act as a high-performance deep-blue organic light-emitting diode (OLED) emitter, and OLED based on it emits deep-blue light with CIE coordinates of (0.148, 0.084), maximum luminance of 7800 cd m-2 , and maximum external quantum efficiency of 5.1 %. These results not only shed light on the molecular design strategy for high-performance deep-blue OLED emitters through color-tuning, but also show the perspective of coumarin derivatives as deep-blue OLED emitters.

19.
Chemistry ; 24(13): 3234-3240, 2018 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-29274097

RESUMO

A series of unsymmetrical arene-1,3-squaraine (USQ) derivatives with two, three, or four hydroxy (-OH) substituents, namely, USQ-2-OH, USQ-3-OH, or USQ-4-OH, respectively, were designed and synthesized, and the effect of the number of hydroxy groups on the optoelectronic properties of USQs were investigated. Despite the three compounds having similar UV/Vis absorption and HOMO energy levels, solution-processed bulk-heterojunction (BHJ) small-molecule organic solar cells with USQ-3-OH as electron-donor materials exhibit the highest power conversion efficiency of 6.07 %, which could be mainly attributed to the higher hole mobility and smaller phase separation. It is also noteworthy that the short-circuit current (Jsc ) of the USQ-3-OH-based device is as high as 14.95 mA cm-2 , which is the highest Jsc values reported for squaraine-based BHJ solar cells to date. The results also indicate that more -OH substituents on squaraine dyes do not necessarily lead to better photovoltaic performance.

20.
Small ; 13(20)2017 05.
Artigo em Inglês | MEDLINE | ID: mdl-28387442

RESUMO

Twisted intramolecular charge-transfer (TICT) fluorogens bearing highly pretwisted geometries and readily-fine-tuned charge-transfer characters are quite promising sensor and electroluminescence (EL) materials. In this study, by using 4-aryloxy-1,8-naphthalimide derivatives as the molecular framework, it is demonstrated for the first time that a CO bond could serve as the central bond to construct new TICT D-A systems. Photophysical and quantum chemical studies confirm that rotation around central CO bonds is responsible for the formation of a stable TICT state in these compounds. More importantly, owing to the structural adjustability of the aryl moiety and the strong steric interactions between the naphthalimide and the aryl ring systems, these compounds can display readily-fine-tuned TICT characters, hence exhibiting an adjustable solvent polarity threshold for aggregation-induced emission (AIE) activity, and could be AIE-active even in less-polar toluene and nonpolar cyclohexane. Furthermore, these compounds could possess highly-pretwisted ground-state geometries, hence could show good EL performance. The findings reveal a facile but effective molecular constructive strategy for versatile, high-performance optoelectronic TICT compounds.

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