查看更多>>摘要：The Wittig-Horner mediated syntheses of phenothiazines carrying vinylsulfide and vinylselenide motifs attached to the aromatic ring(s) or connected to the central nitrogen atom of the heterocycle, and the subsequent study of their photophysical and electrochemical properties, are reported. These compounds were obtained as mixtures of geometric isomers, in good to excellent yields. To complete the study, a small set of vinylsulfoxide and vinylsulfone derivatives was also prepared from the corresponding oxidized phosphinoxides. The photophysical properties of the compounds were examined in solvents of varying polarity, in which they presented absorption maxima in the UV region, with molar absorptivity coefficients compatible with symmetry-allowed pi-pi* electronic transitions. The heterocyclic derivatives were fluorescent. Compounds bearing vinylsulfide moieties associated to the nitrogen atom of the heterocycle displayed less intense fluorescence than the phenothiazine derivatives carrying vinylchalcogenides bonded to the aromatic ring; the latter also exhibited more red-shifted absorption spectra, and Stokes shifts in the range 6115-8170 cm-1 with weak dependence of solvent polarity. The sulfoxide and sulfones displayed more red-shifted spectra than the corresponding sulfides. The cyclic voltammograms of all derivatives exhibited a common pattern of reversible or quasi-reversible processes in the anodic region, related to the phenothiazine unit.
查看更多>>摘要：Organic solar cells (OSCs) have attracted lots of research attention and significant developments have been achieved in the last decade. Small molecular acceptors (SMAs) have played an important role. During the last five years, non-fullerene small molecular acceptors (NFSMAs) have replaced fullerene ones and become the research focus of OSCs, due to their excellent optoelectronic properties, such as wide and strong absorption, easily adjustable energy levels and stable morphology. This review highlights the recent advances of SMAs, especially NFSMAs including perylenediimide, naphthalenediimide, diketopyrrolopyrrole, indacenodothiophene, and Y6 series. The relationships among molecular structures, optical properties, energy levels, device processing methods and photovoltaic performance are systematically analyzed and summarized. Challenges, strategies and prospects are also discussed. This review may provide new guidances for designing high-performance SMAs.
查看更多>>摘要：Considering the advantages of spiro [fluorene-9,9'-xanthene] (SFX) on facilitating radiative transition and suppressing concentration quenching, a pair of isomers, namely F-BT-F and X-BT-X, were designed and synthesized with benzoic] [1,2,5]thiadiazole (BT) as an acceptor core to bridge fluorene moieties (F-BT-F) or xanthene moieties (X-BT-X) of SFXs. The pair of isomers with D-A-D architecture presented almost the same energy gap in chloroform solution, providing a delicate model to probe the electronic and steric differences between binary structure of SFX. Single-crystal diffractions reveal that SFX-donor units are in antiparallel arrangement on the both sides of the BT core, and X-BT-X molecules have more discrete and ordered packing compared to F-BT-F in crystal phase. Photophysical, electrochemical measurements and DFT calculations manifest that the pair of emitters possess excellent photoluminescence quantum yields up to 95%, and the X-BT-X shows weaker charge-transfer character compared with the F-BT-F, attributed to the strong electron-donating nature and partly interrupted conjugation pathway of xanthene-end relative to fluorene-end. In doped organic light-emitting devices (OLEDs), the F-BT-F and X-BT-X displayed nearly uniform electroluminescence (EL) with the emission peaks at 515 and 518 nm, as well as the maximum external quantum efficiencies (EQEs) approaching 5.0%. In non-doped OLEDs, however, the X-BT-X had more remarkable EL performance with the emission peak at 525 nm, maximum current efficiencies of 14.02 cd A(-1), maximum power efficiencies of 8.81 lm W-1 and maximum EQE of 4.25%, exceeding the efficiency values of 13.75 cd A(-1), 7.71 lm W-1, and 4.08% of F-BT-F based device. By illuminating the electronic and steric features of xanthene moiety, this work opens a new door to construct high-efficiency and low-cost SFX-based fluorescence emitters.
查看更多>>摘要：To study the relationship between chemical structure and switching time of electrochromic polymer materials, four star-shape monomers, 3,6-di(thiophen-2-yl)-9-(4-(thiophen-2-yl)phenyl)-9H-carbazole (M1), 2,7-di(thiophen-2-yl)-9-(4-(thiophen-2-yl)phenyl)-9H-carbazole(M2), 3,6-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-9(4-(thiophen-2-yl) phenyl)-9H-carbazole(M3) and 2,7-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-9-(4-(thiophen-2-yl)phenyl)-9H-carbazole(M4) were designed and synthesized successfully, their chemical structure were characterized by nuclear magnetic resonance (NMR) and high resolution mass spectrum (HRMS). Their resulting polymer films could be obtained by electropolymerization, all the polymer films showed well-defined electrochemical properties except for PM2, the PM3 and PM4 revealed wider electrochemical response due to the existence of EDOT units. The surface morphology results indicated that all the polymer films consisted of many particles, and PM1 and PM3 showed smaller grain than that of PM2 and PM4 due to the different aggregation structure, which might benefit for the transport of doped ions. Electrochromic kinetic studies confirmed such hypothesis furtherly, PM3 revealed fastest switching time (Tc: 0.72 s and Tb: 0.61 s), the reason could be explained by electrochemical impedance spectroscopy, which indicated that PM3 possessed the smallest charge transfer resistance (Rct) and fastest diffusion coefficient values at the oxidation state. We hope these findings will provide a little effect on designing and synthesizing high performance electrochromic materials and devices.
查看更多>>摘要：The incorporation of benzothiazole heterocycles into existing molecular frameworks has resulted in the production of a wide range of multifunctional molecular materials. However, this strategy has not yet been explored for an emerging class of boron difluoride dyes, derived from formazanate ligands, which often exhibit tuneable redox and optical properties. Here, we address this gap in the literature and describe the synthesis and characterization of a series of benzothiazole-substituted BF2 formazanates. The incorporation of benzothiazole resulted in absorption profiles that were shifted to lower energies and reduction events that were shifted to more positive potentials when compared to those of the triphenyl-substituted analogue. These results were corroborated by DFT and TD-DFT calculations that suggest that the incorporation of benzothiazole units results in stabilization of the LUMO level thereby narrowing the HOMO-LUMO gaps of this new family of readily accessible dyes. Fine-tuning of these parameters was demonstrated through variation of the supporting N-aryl substituents appended to the formazanate ligand backbone.
查看更多>>摘要：We demonstrated highly selective and sensitive tetraphenylethene -tetraphosphonic acids for the facile detection of aminoglycoside antibiotic neomycin for the first time. Neomycin was found to effectively induce aggregate formation of (4-(1,2,2-tris(4-phosphonophenyl)vinyl)phenyl)phosphonic acid octasodium salt (TPPE) in aqueous solution. The aggregation-induced emission (AIE) response of TPPE was realized upon addition of neomycin in Milli-Q water at pH 7. The detection mechanism relies on electrostatic and hydrogen bonding interactions. The TPPE-based sensor system exhibited a detection limit 2.088 x 10-10 M of neomycin. Further, we demonstrate use of TPPE system for visual detection of neomycin as thin layer chromatography (TLC) sensor to develop kits for real world applications.
Pelosi, Andre GasparottoZucolotto Cocca, Leandro HenriqueAbegao, Luis M. G.Sciuti, Lucas Fiocco...
7页
查看更多>>摘要：This work investigates the influence of different electron-withdrawing groups (Cl, Br, fluorobenzonitrile), on the two-photon absorption cross-section of six imidazo[4,5-b]pyridine derivatives. The two-photon absorption crosssection spectra were obtained by ultra-fast Z-scan technique from 470 nm up to 700 nm. The Sum-Over-States approach was applied to model the two-photon absorption spectra, using a three-level energy system. Photophysical properties, such as transition dipole moment, the difference of permanent dipole moments, and anisotropy coefficient were determined through the analysis of one-photon absorption spectra, solvatochromism, and fluorescence anisotropy, respectively. Besides, the excited state absorption spectra were measured through ultra-fast transient absorption, allowing the excited state lifetime and spectral position determination. Twophoton absorption cross-sections of about 160 GM were observed when two electron-withdrawing groups are linked to the imidazo[4,5-b]pyridine core, elucidating a path to achieve high optical nonlinearities in imidazopyridine derivatives. Furthermore, a increase in the two-photon cross-section was observed when chloride is linked at the C-6 position (90 GM) instead of the C-5 position (50 GM), which is related to the proximity of a higher excited state.
查看更多>>摘要：The development of dyes with both high initiating efficiency and photobleaching properties is of importance for the photopolymerization of thick materials and still an emerging challenge. Carbazole-based photo-bleachable dyes CMs (CM-1 and CM-2) and CIs (CI-1 and CI-2) as free radical initiators for visible light polymerization were designed and synthesized. Their structures were confirmed by H-1 NMR, C-13 NMR, and HR-MS. Through electron paramagnetic resonance (EPR) analysis and visible light photolysis experiments, the free radical generation mechanisms of CMs and CIs were proposed. CMs and CIs could effectively initiate the photopolymerization of 1, 6-hexanediol diacrylate (HDDA) under LED@455 nm exposure. Among these dyes, CM-2 and CI-2 with carboxylic acid in their structures showed better free radical initiating efficiencies and lower extraction rates. In addition, at a concentration of 2 x 10(-5) mol/L, CM-2/MDEA exhibited the better photopolymerization rates and double bond conversions in comparison to CQ/MDEA systems. Under the irradiation of visible light, in particular, dyes CM-2 and CI-2 could successfully initiate the polymerization of thick films of 12-13 mm to form colorless polymers. Thus, these carbazole-based photo-bleachable dyes have great potential in deep photocuring for the preparation of thick materials.
查看更多>>摘要：Based on the strategy of constructing a new cross-linkable thermally activated delayed fluorescence TADF dendrimer act as the emitter, the blue all-solution-processed organic light-emitting diodes (OLEDs) was developed. Here, two thermally cross-linkable TADF molecules, namely DV-3CzCN and DVCz-3CzCN, are designed and synthesized. Systematic studies demonstrate that the utilization of DVCz-3CzCN can form a stable and uniform thin film by the solution-process, but also effectively suppress the triplet excitons concentration quenching by the intermolecular interaction. Simultaneously, DVCz-3CzCN possesses the sufficient solvent resistance that can afford the subsequently deposition of electron transporting materials by orthogonal solvent. Consequently, the highly efficient blue all-solution-processed device based on DVCz-3CzCN realized a maximum current efficiency (CE), power efficiency (PE) and external quantum efficiency (EQE) of 7.1 cd A(-1), 4.5 lm W-1 and 6.8%, respectively, which is eight times higher in device efficiency than corresponding device with the unencapsulated DV-3CzCN.
查看更多>>摘要：Nitrogen and sulfur co-doped graphene quantum dots (N, S-GQDs) are prepared by using o-phenylendiamine and catechol as raw materials under UV irradiation in dimethyl sulfoxide (DMSO) solution for 2 h. The resultant N, SGQDs show uniform size, good crystallinity and fluorescence stability. The tunable polychromatic luminescence is obtained by adjusting the concentration of N, S-GQDs. Then, N, S-GQDs/HPMC composite material is designed and synthesized, which exhibits light responsive optical switching performance owing to micro-aggregation efficacy of N, S-GQDs to transform light into heat and drive the phase transition of hydroxypropyl methyl cellulose (HPMC). Therefore, the prepared N, S-GQDs/HPMC with excellent solar modulation ability can easily switch between opaque and transparent states depending on weather condition. In the end, the thermoresponsive property of N, S-GQDs/HPMC endows it with good performance as functional materials matrix.
NSTL
Elsevier