Anthracene-Pentacene Dyads: Synthesis and OFET Characterization.

The synthesis of a series of unsymmetrical derivatives of pentacene appended with functionalized anthracene moieties is reported. These anthracene-pentacene dyads have been characterized by UV-vis spectroscopy and cyclic voltammetry to examine their electronic properties. X-ray crystallographic analysis was used to examine the solid-state features of anthracene-pentacene dyads 1 a-d with H-, F-, Cl-, and Br- substituents on the 9-position of anthracene, and shows that the packing arrangement of anthracene-pentacene derivatives 1 b,d,e are remarkably similar irrespective of the presence of fluoride, bromide or methyl substituents. The pentacene-anthracene dyads have been incorporated into OTFTs to evaluate their semiconducting properties. The pentacene derivative 1 b shows ambipolar behavior using AlOx C14 PA as the gate dielectric (electron and hole mobilities of 7.6 ⋅ 10-3 and 1.6 ⋅ 10-1  cm2 V-1 s-1 ), while performance of all derivatives was poor using p-doped Silicon as the substrate. These studies highlight the importance of thin-film formation over molecular structure.

Enhancing the Dispersibility of TiO2 Nanorods and Gaining Control over Region-Selective Layer Formation.

We demonstrate that the dispersibility and reactivity of core-shell TiO2 nanorods (NRs) can be controlled significantly through functionalization with a combination of ligands based on phosphonic acid derivatives (PAs). Specifically, a glycol based PA allows dispersion of the NRs in methanol (MeOH). On the other hand, incorporating an alkyne terminated PA in the ligand shell of the NRs allows for a copper-catalyzed alkyne-azide cycloaddition (CuAAC) reaction with an azide-patterned aluminum oxide (AlOx) substrate and forms a region-selectively deposited film of NRs. We clearly demonstrate that the quality of the NR films correlates strongly with the stability of the NR dispersions in the reaction medium. In particular, tuning the concentration of alkyne PA in the ligand shell inhibits aggregation of the NRs on the substrate, while reactivity for the CuAAC reaction is maintained. The surface coverage with NRs fits the Langmuir model. This study illustrates that surface functionalization of AlOx substrates can be effectively and conveniently controlled through enhancing the dispersibility of the NRs using mixed ligand shells.

Green processing of metal oxide core-shell nanoparticles as low-temperature dielectrics in organic thin-film transistors.

TiO2 , Fe3 O4, AlOx , ITO (indium tin oxide), and CeO2 nanoparticles are tailored to exhibit excellent dispersability in deionized water and alcohols. The latter provides an ecofriendly solution for processing metal oxide nanoparticles at a neutral pH. Water-processed dielectrics from the metal oxide nanoparticles are incorporated into organic thin-film transistors fabricated on rigid and flexible substrates.

Region-Selective Deposition of Core-Shell Nanoparticles for 3D Hierarchical Assemblies by the Huisgen 1,3-Dipolar Cycloaddition.

A method for the region-selective deposition of nanoparticles (NPs) by the Huisgen 1,3-dipolar cycloaddition is presented. The approach enables defined stacking of various oxide NPs in any order with control over layer thickness. Thereby the reaction is performed between a substrate, functionalized with a self-assembled monolayer of an azide-bearing phosphonic acid (PA) and aluminum oxide (AlO(x)) NPs functionalized with an alkyne bearing PA. The layer of alkyne functionalized AlO(x) NPs is then used as substrate for the deposition of azide-functionalized indium tin oxide (ITO) NPs to provide a binary stack. This progression is then conducted with alkyne-functionalized CeO2 NPs, yielding a ternary stack of NPs with three different NP cores. The stacks are characterized by AFM and SEM, defining the region-selectivity of the deposition technique. Finally, these assemblies have been tested in devices as a dielectric to form a capacitor resulting in a dramatic increase in the measured capacitance.

An unsymmetrical pentacene derivative with ambipolar behavior in organic thin-film transistors.

Three new unsymmetrical anthracenyl-pentacene derivatives have been synthesized, characterized using X-ray crystallography, and used as semiconductors in OTFTs. For one derivative, ambipolar charge carrier transport was observed with a hole mobility of 0.2 cm(2) V(-1) s(-1) and an electron mobility of 0.03 cm(2) V(-1) s(-1).