Bottom-Up On-Surface Synthesis of Two-Dimensional Graphene Nanoribbon Networks and Their Thermoelectric Properties.

Graphene, the one-atom-thick two-dimensional (2D) carbon material, has attracted tremendous interest in both academia and industry due to its outstanding electrical, mechanical, and thermal properties. For electronic applications, the challenging task is to make it as a semiconductor. The bottom-up synthesis of semiconducting one-dimensional (1D) nanometer-wide graphene strips, namely, graphene nanoribbons (GNRs), has attracted much attention owing to its promising electronic, optical, and magnetic properties. In this regard, we report the fabrication of cove-type 2D GNR networks (GNNs) via the interconnection of 1D self-assembled GNRs on the surface of Au(111). The cove-type 2D GNRs networks (GNNs) were fabricated from the GNR, 5-CGNR-1-1, synthesized using the precursor of DBSP. Annealing of high-density self-assembled GNRs on the surface of Au(111) through two-zone chemical vapour deposition (2Z CVD) successfully generated a 2D interconnected structure with high yield via the fusion and ladder coupling reactions of GNR chains. In order to validate the later fusion reaction, we have also synthesized the GNR, 7-AGNR-1-1, using the precursor of DBBA. The GNNs, which consist of hybridized metallic-like and semiconducting GNRs, are a new class of carbon-based materials. Further, we applied this material for thermoelectric (TE) applications and found a very low cross-plane thermal conductivity of 0.11 Wm-1 K-1 , which is one of the lowest value among the carbon-based materials as well as inorganic semiconductors, while maintaining the cross-plane electrical conductivity of 188 S m-1 .

An easy route to red emitting homoleptic IrIII complex for highly efficient solution-processed phosphorescent organic light-emitting diodes.

A thiophene-phenylquinoline-based homoleptic Ir(III) complex, [Ir(Th-PQ)(3)], has been synthesised by a simple route and utilised as a dopant in solution-processed phosphorescent organic light-emitting diodes (PhOLEDs). It shows the current efficiency of approximately 26 cd A(-1) and the external quantum efficiency of about 21 %, which are the highest values reported to date for PhOLEDs prepared by solution-process.

An electron transporting unit linked multifunctional Ir(III) complex: a promising strategy to improve the performance of solution-processed phosphorescent organic light-emitting diodes.

An oxadiazole based electron transporting (ET) unit was glued to the heteroleptic Ir(III) complex (TPQIr-ET) and used as a dopant for phosphorescent organic light-emitting diodes (PhOLEDs). It shows superior device performance than the dopant without the ET unit (TPQIr) due to the balanced charge carrier injection by the ET unit.

Colorimetric detection of fluoride ion by 5-arylidenebarbituric acids: dual interaction mode for fluoride ion with single receptor.

Two 5-arylidenebarbituric acid derivatives (IH and IM) have been synthesized by the Knoevenagel condensation of barbituric acid with 4-N,N-dimethylamino benzaldehyde and studied for anion sensing activities. Both receptors sense fluoride ion with high selectivity and sensitivity and the sensing action has been demonstrated by naked eye detection, UV-visible absorption, and fluorescence spectral changes in the presence of F(-). Indeed, the F(-) sensing mechanism for receptor IH depends on F(-) ion concentration. While at higher concentrations F(-) forms strong hydrogen bonding interaction with the N-H proton of the receptor, at lower concentrations sensing is influenced by the deprotonation of the methylene proton, followed by the chemical reaction, which is also confirmed by the (1)H-NMR technique. On the other hand, when replacing the N-H proton with a methyl group, IM does not show any concentration dependent behaviour with F(-). The F(-) concentration dependent sensing is attributed to the changes in the receptor-anion interaction equilibrium, where at higher F(-) concentrations, F(-) interacts with the receptor through hydrogen bonding and at lower concentrations it induces a chemical reaction.

Benzoselenadiazole fluorescent probes--near-IR optical and ratiometric fluorescence sensor for fluoride ion.

A highly selective and sensitive near-IR optical sensor, benzoselenadiazole based diarylamine (TBS-HN), for fluoride (F(-)) has been designed and synthesized. TBS-HN also shows turn-on ratiometric fluorescence signaling in the presence of F(-) by inhibiting the excited state intramolecular proton transfer (ESIPT) processes.

[60]Fulleropyrrolidines bearing π-conjugated moiety for polymer solar cells: contribution of the chromophoric substituent on C60 to the photocurrent.

Two fullerene-terthiophene dyads without hexyl chains (3T-C60) and with hexyl chains (3TH-C60) on the terthiophene substituent are synthesized by 1,3-dipolar cycloaddition of corresponding azomethine ylides to C60. The cyclic voltammetry studies indicate no apparent electronic communication between the terthiophene pendent group and the fulleropyrrolidine core in the ground state. However, a significant florescence quenching is observed for 3T-C60 and 3TH-C60, compared to their fluorescent terthiophene (3T) and 3TH precursors, respectively, suggesting the occurrence of strong intramolecular electron/energy transfers in the photoexcited state. Furthermore, these new fulleropyrrolidine derivatives are applied as electron acceptors to fabricate poly(3-hexylthiophene) (P3HT) based bulk heterojunction solar cells. The incident photon-to-current efficiency (IPCE) value of the P3HT/3T-C60 device is significantly higher than that of the P3HT/PCBM cell in wavelengths of 350-420 nm. This finding provides direct evidence for the contribution of 3T excitons to the photocurrent. Replacing 3T-C60 with 3TH-C60 effectively improves the morphology of the photoactive layer and widens the window of optimal D/A ratios, raising the power conversion efficiency (PCE) from 2.14% to 2.54%. Importantly, these devices exhibit superior stability of PCE against high-temperature aging.