Nanoaggregates from oligothiophenes and oligophenylenes: a systematic growth survey

Abstract

The growth of nanoscopic oligophenylene and oligothiophene aggregates on muscovite mica by vacuum deposition has been investigated. In the case of para-phenylenes a dipole assisted self assembly generation of needle-like aggregates is observed on mica. At optimum fiber growth temperature phenylene aggregates grow in most cases without a layer of upright oriented molecules. In contrast, vacuum deposition of oligothiophenes results simultaneously in fibers of laying molecules as well as islands of upright molecules. Since both phenylenes and thiophenes are strongly polarizable but differ in the lattice parameters of the resulting crystalline overlayers a direct comparison between the two classes of molecules allows us to study the role of epitaxy on the growth of nanoaggregates. Besides straight aggregates we also observe thiophene rings on water and methanol treated mica surfaces, which consist of radially oriented, laying molecules.

Organic Nanofibers from Chloride-Functionalized p-Quaterphenylenes

“…Assuming a similar herringbone packing of the molecules for CLP4 as for a quaterphenylene functionalized by fluor atoms, the easiest growing axis of the aggregates (i.e., the long needle axis) is approximately perpendicular to the long molecular axis and along the layers of parallel molecules. A similar behavior has been observed for many rodlike molecules like, e.g., p- phenylenes, , thiophenes, and thiophene/phenylene co-oligomers . Different angles β Mol can easily be explained by different contact faces of the bulklike needles with the substrate, cf.…”

Nucleation and growth of thin films of rod-like conjugated molecules

“…A model system demonstrating this is the deposition of para-Sexiphenyl onto muscovite mica surfaces. Several groups have shown that for a large number of rod-like molecules-such as 6P, 5A, and 6T-nanofibers formed by flat-lying molecules are the dominant morphology on clean mica surfaces [54,[86][87][88][89][90][91]. In figure 6, typical morphologies obtained by atomic force microscopy (AFM) of 6P films grown on mica are presented.…”

Tailoring the growth of p-6P nanofibres using ultrathin Au layers: an organic–metal–dielectric model system

“…Para-hexaphenyl (p-6P), a conjugated oligomer, has interesting potential for application as, e.g., the active layer in organic light emitting diodes [1] or organic nanolasers [2] because of its intense blue luminescence. On substrates like muscovite mica [3,4], phlogopite mica [5], TiO 2 (110) [6], and on alkali halides [7,8] and for certain growth conditions, p-6P does not form a continuous film like on GaAs [9] but condenses into long aggregates, so called 'nanofibres' or 'nanoneedles' [8,10]. For the shorter para-quaterphenyl (p-4P) molecules, needles on clean and carbon covered Au(111) surfaces and on polycrystalline Au foil have been observed [11][12][13].…”