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A new class of donor–bridge–acceptor (D−π–A) π-conjugated light-emitting molecules comprising carbazole as donor and maleimide (Cbz-MI, Cbz-MI(d)), phthalimide (Cbz-Pth) as acceptor units with phenyl ring as spacer have been synthesized in good yields. These compounds exhibit high quantum yield with three distinct emission colors yellowish-green (Cbz-MI), bright yellow Cbz-MI(d), and sky blue (Cbz-Pth) in the solid state. Single-crystal X-ray and quantum chemical calculations reveals that twisting of the phenyl rings with high torsional angle on maleimide and phthalimide units reduce the effective inter-chromophore electronic coupling, furnish dramatic changes in their photophysical properties in solution and solid states. Intriguingly, Cbz-MI(d)and Cbz-Pthexhibits a unique aggregation-induced blue-shifted emission (AIBSE) due to restricted intramolecular rotation (RIR) process, while Cbz-MIshows red-shifted emission in the solid state. The solvatochromic study reveal that combined RIR and excited state migration augment AIE (aggregation-induced emission) properties. The electrochemical properties reveal that Cbz-MIexhibits high oxidation propensity while Cbz-Pthshows low reduction values. Subsequently, organic light-emitting diodes (OLEDs) were fabricated with a simple three-layer device containing Cbz-Pthand Cbz-MI(d)as emitting layers. Cbz-MI(d)exhibits high performance yellow OLED with an external quantum efficiency exceeding ∼4.1% and a brightness exceeding ∼73915 cd/m2, which is among the best performance reported for bright yellow fluorescence organic light-emitting diodes.

The objective of this study is to report the results of dielectric properties and dielectric breakdown strength (DBS) of PbO-B2O3-SeO2:Ho2O3(PBSH) glass ceramics as functions of Au2O3content and to correlate the results with spectroscopic properties. PBSH glass ceramics with traces of Au2O3were fabricated and characterized with different techniques that include positron annihilation spectroscopy (PAS). Several dielectric parameters and DBS were studied as functions of Au2O3concentration. Observed increase of ε′with Au2O3content was attributed to a hike in the space charge polarization (scp) due to the increased concentration of structural imperfections. Dipolar relaxation phenomenon exhibited by electric moduli was analyzed using Cole-Cole plots. σac(a c, conductivity) showed an increasing tendency with Au2O3content. Such increase was attributed to the polaronic exchange between two structural groups of SeO2. Inferences drawn from dielectric and DBS studies were found to be in agreement with different spectroscopic properties of these glass ceramics.

A series of fluoranthene derivatives (F1–F5) varied with nature and type of substituents were synthesized viaDiels–Alder reaction followed by in situdecarbonylation. The solid state structures have been established through single crystal X-ray diffraction (XRD). The presence of extended conjugation and having two alkyloxy chains on phenyl rings induces flexibility to orient opposite to each other and interacts with another fluoranthene unit with weak π–π interactions and show unique supramolecular arrangements. The envisaged photophysical and DFT studies demonstrated that HOMO–LUMO levels were effectively tuned by different substituents with an optical band gap from 3.44 to 3.88 eV provoked to examine as sensitive fluorescent chemosensors for the detection of nitroaromatic compounds (NACs). The sensitivity toward the detection of NACs was evaluated through fluorescence quenching in solution (aqueous and non-aqueous) and solid state (vapor and contact mode). Fluorescence studies demonstrated that electron transfer occurs from the electron rich fluoranthene fluorophores to the electron deficient NACs by the dominant static quenching mechanism and the quenching process is reversible. It was found that the detection sensitivity increases with extent of conjugation on fluoranthene unit. The contact mode approach using thin layer silica chromatographic plates exhibits a femtogram (1.15 fg/cm2) detection limit for trinitrotoluene (TNT) and picric acid (PA), while the solution state fluorescence quenching shows for PA detection at the 2–20 ppb level. The sensing performance of fluoranthene thin films to NACs in aqueous solution reveals that fluorophores are highly selective towards the detection of PA. The smart performances of thin film fluorophores with high photostability have great advantage than those of conjugated polymers with superior sensitive detection of PA in groundwater.

In this work, we have synthesized a series of TDPP derivatives with different alkyl groups such as n-hexyl (−C6H13) 3a, 2-ethylhexyl (-(2-C2H5)C6H12) 3b, triethylene glycol mono methyl ether (-(CH2CH2O)3cH3, TEG) 3c, and octadodecyl (-(8-C8H17)C12H22) 3d. N,Ndialkylation of thiophene-diketopyrrolopyrrole (TDPP, 1) strongly influences its solubility, solid state packing, and structural order. These materials allow us to explicitly study the influence of alkyl chain on solid state packing and photophysical properties. TDPP moiety containing two different alkyl groups 3e(TEG and 2-ethylhexyl) and 3f(TEG and n-hexyl) were synthesized for the first time. The absorption spectra of all derivatives exhibited a red shift in solid state when compared to their solution spectra. The type of alkyl chains leads to change in the optical band gaps in solid state. The fluorescence study reveals that TDPP derivatives have strong π–π interaction in the solid state and the extent of bathochromic shift is due to combination of intramolecular interaction and formation of aggregates in solid state. This behavior strongly depends on the nature of alkyl chain. The presence of strong C–H···O inter chain interactions and CH−π interactions in solid state exhibits strong influence on the photophysical properties of TDPP chromophore.

This study consists of comprehensive investigations on dielectric permittivity (ε′), electric moduli (M′, M″), impedance (Z), and conductivity (σac) spectra over broad regions of frequency and temperature of lead zirconium silicate glass ceramics mixed with different concentrations of Fe2O3. The observed increase in dielectric permittivity with the content of Fe2O3is attributed to the increasing presence of iron ions in octahedral positions. Electric moduli plots with frequency (ω) and temperature (T) exhibit dipolar effects. These effects are quantitatively analyzed by Cole–Cole plots; the analysis indicates the distribution of relaxation times. Probable dipoles for these effects are identified and discussed. AC conductivity (σac) shows a rising trend with an increase in Fe2O3beyond 0.2 mol%, and this increase is attributed to the polaron exchange among Fe2+and Fe3+ions. The conduction mechanism is well explained using a polaron tunneling model in the middle‐frequency and high‐temperature regions. In this study comprehensive investigations on dielectric permittivity (ε′), electric moduli (M′, M″), impedance (Z), and conductivity (σac) spectra over broad regions of frequency and temperature of lead zirconium silicate glass ceramics mixed with different concentrations of Fe2O3are made.