Controlling nano- and microfilament morphology by strategically placing chiral centers in the side chains of bent-core molecules.

Self-assembled lamellar nano- and microfilaments formed by select types of bent-core molecules are prime examples of the interplay between molecular conformation and morphological chirality. Here, we demonstrate how the strategic placement of chiral centers at C-1 and/or C-3 in the terminal alkyloxy side chains, largely based on a priori calculations of molecular conformation, leads to the predictable formation of increasingly complex nano- and microfilament morphologies. Adding to the previously described diversity of twisted and writhed filament types, we here demonstrate and explain the formation and coexistence of flat nanoribbons, nanocylinders, or nano- as well as microfilaments where the morphology spontaneously changes along the filament long axis. For some these more exotic types of filament morphology, helical multilayer filaments suddenly unwind to form flat nanoribbons that also twist again under preservation (not perversion) of the helical twist sense. Moreover, the morphologies formed by this series of molecules now allows us to demonstrate the complete transformation from flat multilayer ribbons over microfilaments and helical-wrapped nanocylinders to helical nanofilaments depending on the number and position of chiral centers in the aliphatic side chains.

Novel Self-Assembling Supramolecular Phenanthro[9,10-a]phenazine Discotic Liquid Crystals: Synthesis, Characterization and Charge Transport Studies.

The incorporation of heteroatoms in the chemical structure of organic molecules has been identified as analogous to the doping process adopted in silicon semiconductors to influence the nature of charge carriers. This strategy has been an eye-opener for material chemists in synthesizing new materials for optoelectronic applications. Phenanthro[9,10-a]phenazine-based mesogens have been synthesized via a cyclo-condensation pathway involving triphenylene-based diketone and o-phenyl diamines. The incorporation of phenazine moiety as discussed in this paper, alters the symmetric nature of the triphenylene. The phenanthro[9,10-a]phenazine-based mesogens exhibit hole mobility in the order of 10-4 cm2/Vs as measured by the space-charge limited current (SCLC) technique. The current density in the SCLC device increases with increasing temperature which indicates that the charge transport is associated with the thermally activated hopping process. This report attempts to elucidate the self-organization of asymmetric phenanthro[9,10-a] phenazine in the supramolecular liquid crystalline state and their potential for the fabrication of high-temperature optoelectronic devices. However, the low charge carrier mobility can be one of the challenges for device performance.

Temperature-dependent hole mobility in pyrene-thiophene-based room-temperature discotic liquid crystals.

π-Conjugated pyrene-thiophene-based room-temperature discotic liquid crystals armed with four peripheral aliphatic chains are reported to study their potential use in a hole-transporting organic semiconductor. The charge carrier mobility studies using the ToF method revealed room temperature hole mobility in the order of 10-4 cm2 V-1 s-1 for both mesogens. However, the mobility values for compound 1a were observed in the order of 10-3 cm2 V-1 s-1 at high temperatures. Such molecular systems can potentially be used in nonlinear organic electronic applications.

First examples of room-temperature discotic nematic liquid crystals exhibiting ambipolar charge carrier mobilities.

Four new room-temperature nematic liquid-crystalline (LC) dimers consisting of a wedge-shaped 3,4,5-tridecyloxy gallic ester molecule linked to either cyanobiphenyl, cholesteryl, pentaalkynylbenzene or triphenylene based moieties are reported. Dimers with pentaalkynylbenzene and triphenylene moieties in their room-temperature discotic nematic (ND) mesophase show ambipolar charge carrier mobilities of the order of 10-5 cm2 V-1 s-1 and 10-3 cm2 V-1 s-1, respectively, as measured using a time-of-flight (ToF) technique.

Luminescent Conductive Columnar π-Gelators for Fe(II) Sensing and Bio-Imaging Applications.

The high demand and scarcity of luminescent, photoconductive, and transparent gels necessitate its finding as they are potential components in photonic devices such as solar cell concentrators where optical losses via scattering and reabsorption require to be minimized. In this direction, we have reported highly transparent, blue luminescent as well as photoconductive gels exhibiting the hole mobility of 10-3 cm2/V s at ambient temperature as investigated by the time-of-flight technique. The π-driven self-standing supergels were formed using triazole-modified phenylene-vinylene derivatives as gelators in a nonpolar solvent. Different microscopic studies revealed its entangled network of interwoven fibrilar self-assembly and anisotropic order in the gel state. Supramolecular assembly of xerogels, studied by small- and wide-angle X-ray scattering (SAXS/WAXS) suggesting their local columnar hexagonal (Colh) superstructure, is beneficial for conducting gels. Rheological measurements direct the stiffness and robustness of the organogels. In addition, the gelators were developed as a sensing platform for the ultrasensitive detection of Fe(II) ions at ppb level. 1H nuclear magnetic resonance (NMR) titrimetric studies revealed that the interaction of the H-atom of triazole units with Fe(II) is responsible for quenching of blue fluorescence. Also, one of the gelators was successfully applied in bio-imaging using the pollen grains of the Hibiscus rosa-sinensis plant.

Continuous Flow Reactor for the Controlled Synthesis and Inline Photocatalysis of Antibacterial Ag2 S Nanoparticles.

The present study is focused on the integration of microreactors to synthesize visible light active nanophotocatalysts for inline photocatalytic degradation of organic dye and antibacterial activity. A wire-assisted and a rapid laser micromachining technique has been employed for the fabrication of polydimethylsiloxane (PDMS) and poly(methyl methacrylate) (PMMA)-based microreactors, respectively. By varying the design and chemical reagents involved, different sizes of visible light active Ag2 S nanoparticles were prepared via a continuous microfluidics approach using fabricated microreactors. When polyvinylpyrrolidone (PVP) was utilized as the capping agent during the reaction, smaller particles of the size of ~ 15 nm were observed. The photocatalytic performance of these nanoparticles has been evaluated inline by employing the single-inlet planar microreactor as a function of flow rate and channel length. The photocatalyst durability test and a comparative photocatalytic efficiency study between the microreactor and the conventional beaker reactor have also been carried out. Under visible light, these nanoparticles exhibit a remarkable enhancement of ~ 94.5% in the inline microreactor-based photocatalytic degradation of methylene blue dye. The slower the flow rate and longer the channel length, gradual enhancement in the performance has been observed. Also, these nanoparticles express an antibacterial effect with very high efficacy even at very low (2 mg mL-1 ) concentration toward the inhibition of Escherichia Coli.

Hydrothermally Tailored Three-Dimensional Ni-V Layered Double Hydroxide Nanosheets as High-Performance Hybrid Supercapacitor Applications.

Here, we report a facile and easily scalable hydrothermal synthetic strategy to synthesize Ni-V layered double hydroxide (NiV LDH) nanosheets toward high-energy and high-power-density supercapacitor applications. NiV LDH nanosheets with varying Ni-to-V ratios were prepared. Three-dimensional curved nanosheets of Ni0.80V0.20 LDH showed better electrochemical performance compared to other synthesized NiV LDHs. The electrode coated with Ni0.80V0.20 LDH nanosheets in a three-electrode cell configuration showed excellent pseudocapacitive behavior, having a high specific capacity of 711 C g-1 (1581 F g-1) at a current density of 1 A g-1 in 2 M KOH. The material showed an excellent rate capability and retained the high specific capacity of 549 C g-1 (1220 F g-1) at a current density of 10 A g-1 and low internal resistances. Owing to its superior performance, Ni0.80V0.20 LDH nanosheets were used as positive electrode and commercial activated carbon was used as negative electrode for constructing a hybrid supercapacitor (HSC) device, having a working voltage of 1.5 V. The HSC device exhibited a high specific capacitance of 98 F g-1 at a current density of 1 A g-1. The HSC device showed a higher energy density of 30.6 Wh kg-1 at a power density of 0.78 kW kg-1 and maintained a high value of 24 Wh kg-1 when the power density was increased to 11.1 kW kg-1. The performance of NiV LDHs nanosheets indicates their great potential as low-cost electrode material for future energy-storage devices.