Shandong Xu

Molecular Superlattices Induced by Alkyl Substitutions in Self-Assembled Triphenylene Monolayers

The configuration of the superlattices, formed from liquid-crystalline molecules on a graphite surface, are controllable through their alkyl substituents. This control may be attributed to the interplay of molecular steric interaction and the 2 D crystallization of alkyl chains. Two such lattices, as observed by STM, are shown in the accompanying graphic (C12- and (inset) C14-substituted molecules).

Photoinduced organic nanowires from self-assembled monolayers

The self-assembled diacetylene molecular monolayer was prepared on highly oriented pyrolitic graphite and observed by scanning tunneling microscopy. Upon applying ultraviolet irradiation, the self-assembled conjugated polydiacetylene nanowires resulting from photoinduced topochemical reaction of diacetylene molecules were obtained. Control of the spacings between nanowires was achieved by a simple coadsorption method. The result presented here may supply a general method to obtain spacing-controllable organic nanowires.

The two-dimensional self-assembled n-alkoxy-substituted stilbenoid compounds and triphenylenes studied by scanning tunneling microscopy

Abstract We present a comparison of the assembling behavior of two series discotic molecules, n -alkoxy-substituted stilbenoid compounds ( E , E , E )-1,3,5- Tris [2-(3,4,5-trialkoxyphenyl) ethenyl] benzenes ( n TEB, n =12, 14, 16 and 18) and n -alkoxy-substituted triphenylenes, 2,3,6,7,10,11-hexakisalkoxytriphenylenes (H n T, n =9, 12, 14, 16, 18 and 20), on highly oriented pyrolytic graphite surface using scanning tunneling microscopy. Characteristic two-dimensional self-assembly structures, hexagonal structures and linear array structures, were observed with different alkyl chain length for both series of molecules. While linear lamellae structure prevails for long alkyl substituted species of both series, the hexagonal assembly pattern differs significantly. It was evident that 12TEB develops center-void hexagonal structures and H12T adopts center-filled hexagons. The difference of the assembling structure could be attributed to the steric effect associated with molecular cores.

STM observation of 1,3,5-triazines bearing rod-like benzeneazonaphthalene moieties monolayers self-assembled on graphite surface

A series of 1,3,5-triazines incorporating benzeneazonaphthalene moieties have been synthesized and STM observations have clarified the geometrical configuration of the self-assembled molecules on a graphite surface.

Towards total dissolution of full length unmodified carbon nanotubes (CNT) and its application to fabrication of ultra-thin CNT films at the water/air interface

In this study, we report the observation of dissolution of unmodified full-length CNTs using liquid state alkane at elevated temperatures. The dissolved CNTs were examined by UV-vis absorption and fluorescence spectroscopy, and SEM methods. The results obtained support the existence of the CNT component in the solution. Furthermore, a condensed ultra-thin film of carbon nanotubes, which were not treated by ultrasonic agitation and acid to avoid damaging the nanotubes, was fabricated on a pure water subphase. The film is stable at least up to 60 mN m−1. The TEM images on the film show that individual carbon nanotubes and carbon nanotube bundles are indeed present in the film.

2D self-assembling of 4, 5-didodecylthiolphthalonitrile on graphite surface

An important precursor 4,5-didodecylthiolphthalonitrile DCP for synthesis of phthalocyanines Pcs and subphthalocyanines SubPcs was synthesized and the assembling structure of this molecule on the basal plane of highly oriented pyrolytic graphite HOPG surface was characterized using the scanning tunneling microscopy (STM) in ambient conditions. In high-resolution images of the molecules, we found that the arrangement of the cyano groups forms a “head-to-head” configuration to keep the stability of the entire system. The mismatch of the DCP molecules with the substrate lattice has also been observed in the experiment.