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排序方式: 共有396条查询结果,搜索用时 288 毫秒
111.
Mallick A Haldar B Maiti S Bera SC Chattopadhyay N 《The journal of physical chemistry. B》2005,109(30):14675-14682
Photophysical properties of 3-acetyl-4-oxo-6,7-dihydro-12H-indolo[2,3-a]quinolizine (AODIQ), a bioactive molecule, has been investigated in well-characterized, monodispersed biomimicking nanocavities formed by sodium bis(2-ethylhexyl)sulfosuccinate (AOT) in heptane using steady-state and picosecond time resolved fluorescence and fluorescence anisotropy. The emission behavior of AODIQ is very much dependent upon the water/surfactant mole ratio (W), i.e., on the water pool size of the reverse micellar core. AODIQ exhibits a sharp decrease in fluorescence anisotropy with increasing W, implying that the overall motional restriction experienced by the molecule is decreased with increased hydration. Some of the depth-dependent relevant fluorescence parameters, namely, fluorescence maxima and fluorescence anisotropy (r), have been monitored for exploiting the distribution and microenvironment around the probe in the reverse micelles. Fluorescence spectral position and fluorescence quenching studies suggest that the probe does not penetrate into the reverse micellar core; rather it binds at the interfacial region. Quantitaive estimates of the micropolarity and microviscosity at the binding sites of the probe molecule have been determined as a function of W. 相似文献
112.
Dafei Yuan Mohammad A. Awais Valerii Sharapov Xunshan Liu Andriy Neshchadin Wei Chen Mrinal Bera Luping Yu 《Chemical science》2020,11(41):11315
A critical issue in developing high-performance organic light-emitting transistors (OLETs) is to balance the trade-off between charge transport and light emission in a semiconducting material. Although traditional materials for organic light-emitting diodes (OLEDs) or organic field-effect transistors (OFETs) have shown modest performance in OLET devices, design strategies towards high-performance OLET materials and the crucial structure–performance relationship remain unclear. Our research effort in developing cross-conjugated weak acceptor-weak donor copolymers for luminescent properties lead us to an unintentional discovery that these copolymers form coiled foldamers with intramolecular H-aggregation, leading to their exceptional OLET properties. An impressive external quantum efficiency (EQE) of 6.9% in solution-processed multi-layer OLET devices was achieved.Coiled foldamers with intramolecular H-aggregation in semi-ladder copolymers lead towards the highest EQE of 6.9% in solution-processed multi-layer OLETs. 相似文献
113.
R. N. Bera N. Cumpstey P. L. Burn I. D. W. Samuel 《Advanced functional materials》2007,17(7):1149-1152
Intermolecular interactions play a crucial role in the performance of organic light‐emitting diodes (OLEDs). Here we report the photophysical and electroluminescence properties of a fac‐tris(2‐phenylpyridyl)iridium(III ) cored dendrimer in which highly branched biphenyl dendrons are used to control the intermolecular interactions. The presence of fluorene surface groups improves the solubility and enhances the efficiency of photoluminescence, especially in the solid state. The emission peak of the dendrimer is around 530 nm with a PL quantum yield of 76 % in solution and 25 % in a film. The photophysical properties of this dendrimer are compared with a similar dendrimer with the same structure but without the fluorene surface groups. Dendrimer LEDs (DLEDs) are prepared using each dendrimer as a phosphorescent emitter blended in a 4,4′‐bis(N‐carbazolyl)biphenyl host. Device performance is improved significantly by the incorporation of an electron‐transporting layer of 1,3,5‐tris(2‐N‐phenylbenzimidazolyl)benzene. A peak external quantum efficiency of 10 % (38 Cd A–1) for the dendrimer without surface groups and 13 % (49.8 Cd A–1) for the dendrimer with fluorene surface groups is achieved in the bilayer LEDs. 相似文献
114.
Synthesis of isonucleosides 13 , 14 , 16 , and 17 , bearing an exocyclic methylidene group at the sugar moiety, starting from a 3‐keto sugar is described. The keto compound was converted to the methylene‐sugar 10b (Scheme 1), which was coupled with nucleobases by means of the Mitsunobu reaction. The coupling reaction with adenine and 8‐azaadenine produced both the N9‐ and N3‐nucleosides (see 13 and 14 , resp.; Scheme 2). The structures of 13a and 14a were confirmed by single‐crystal X‐ray data. Synthesis of the pyrimidine compounds was also approached from the β‐amino sugar 20 that was prepared using a Gabriel‐synthesis methodology (Scheme 3). 相似文献
115.
Growth,characterization and interfacial reaction of magnetron sputtered Pt/CeO2 thin films on Si and Si3N4 substrates
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Growth of magnetron sputtered Pt/CeO2 thin films on Si and Si3N4 were characterized by X‐ray diffraction (XRD), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and X‐ray photoelectron spectroscopy (XPS). Interaction of Pt/CeO2 films with Si on Si and Si3N4 substrates was extensively investigated by XPS. XRD studies show that films are oriented preferentially to (200) direction of CeO2. XPS results show that Pt is mainly present in +2 oxidation state in Pt/CeO2/Si film, whereas Pt4+ predominates in Pt/CeO2/Si3N4 film. Concentration of Pt4+ species is more than four times on Si3N4 substrate as compared with that on Si. Ce is present as both +4 and +3 oxidation states in Pt/CeO2 films deposited on Si and Si3N4 substrates, but concentration of Ce3+ species is more in Pt/CeO2/Si film. Interfacial reaction between CeO2 and Si substrate is controlled in the presence of Pt. Pt/Ce concentration ratio decreases in Pt/CeO2/Si3N4 film upon successive sputtering, whereas this ratio decreases initially and then increases in Pt/CeO2/Si film. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
116.
117.
Manindranath Bera Prasant Kumar Nanda Uday Mukhopadhyay Debashis Ray 《Journal of Chemical Sciences》2004,116(3):151-158
Low-temperature stoichiometric Schiff base reaction in air in 3:1 mole ratio between benzaldehyde and triethylenetetramine
(trien) in methanol yields a novel tetraaza μ-bis (bidentate) acyclic ligand L. It was characterized by elemental analysis, IR, EI mass and NMR (1H and13C) spectra. The formation of a five-membered imidazolidine ring from the ethylenediamine backbone as a spacer-cumbridging
unit gives rise to a new type of imidazolidine-bridged ligand. A geometric optimisation was made of the synthesized ligand
and its complexes by the method of molecular mechanics (MM2) method in order to establish the stable conformations. This hitherto
unknown tetraaza acyclic ligand affords new cationic dicopper(I/I) and dicopper(II/II) complexes in good yield. Dicopper(II/II)
complex displays weakd-d transition bands in the visible region, while dicopper(I/I) complex displays strong MLCT band in the same region. Both the
dinuclear complexes are of non-intimate nature and show interesting solution electrochemical behaviour. EPR spectral study
of μ-bis (imidazolidino) bridged dicopper(II/II) complex also supports the non-communicative nature of the two copper centres within
the same molecule 相似文献
118.
Summary Methods are proposed for the gravimetric determination of zinc and mercury with benzimidazole at pH ranges of 8.4–10.0 and 9.0–10.0, respectively. Using suitable masking agents zinc has been separated from a large number of diverse ions. Thermograms of the zinc and mercury complexes reveal that they are extraordinarily stable up to 520° and 340°C.
The work was carried out at Chemistry Department, Jadavpur University, Calcutta-32, India. 相似文献
Zusammenfassung Zur gravimetrischen Bestimmung von Zink oder Quecksilber wird die Fällung mit Benzimidazol bei pH 8,4–10,0 bzw. 9,0–10,0 empfohlen. Zink kann bei Verwendung geeigneter Maskierungsmittel mit guter Genauigkeit von zahlreichen Fremdionen abgetrennt werden. Durch thermogravimetrische Untersuchungen wurde festgestellt, daß die Zn-bzw. Hg-Komplexe bis zu 520 bzw. 340° C beständig sind.
The work was carried out at Chemistry Department, Jadavpur University, Calcutta-32, India. 相似文献
119.
120.
Experiments were performed at X band with GaAs f.e.t.s used as mixer elements. These studies show that an f.e.t. mixer may exhibit a conversion gain approaching that of the corresponding amplifier. Conversion gains as high as 6 dB were measured. Low noise and high signal-handling capabilities were also demonstrated. 相似文献