Imaging ofC70intramolecular structures with scanning tunneling microscopy

Abstract

Adsorption of pure C7p and its mixture with C«on the Cu(111)1X 1 surface was investigated by using scanning tunneling microscopy. The pure C7p monolayer was found to form the 4X4-commensurate superlattice, similar to the case of pure C6p after a brief annealing at approximately 320 C. The individual C7p molecules take the upright position with the long axis perpendicular to the surface. Introducing C6p s in the C7p layer allows some of the C7p molecules to take the lying-down position with the long axis parallel to the (110) direction of the surface. By comparing with theoretical simulations, we propose that C7p molecules in the C7p-C6p mixture cease their internal rotation and are ratcheted with one of the hexagonal rings around the equator facing down the Cu(111) surface.Since the discovery of C6Q and larger fullerenes, ' and their synthesis in a macroscopic quantity, efforts have been made to try to image the molecular structures with various kinds of methods, including scanning tunneling microscopylspectroscopy (STMiSTS). However, due to the rapid intrinsic rotation of individual C6Q s in the bulk phase, only a few have succeeded in imaging their molecular structures by adsorbing C6Q molecules on Au, Si(100), and Si(111) surfaces.Most recently, it was found that the Cu(111) surface serves as a good substrate to observe the intramolecular structures of C6Q, since the small lattice misfit (-2%) between the nearest-neighbor (NN) distance for C6o in bulk phase (10.0 A) and four times the NN distance for the Cu(111)1X1 surface (10.2 A) and a reasonable strong interaction help the C60's ratcheted at the threefold hollow site and force them to cease their rotation.The observed bias voltage dependence of the STM images for the case of C6o/Cu (111)4 X 4 convincingly demonstrated that the STM images indeed represent the local electronic structures, in good agreement with those calculated by Kawazoe et al. using the local-density approximation. C7Q is the second most abundant fullerene, and is known to take an ellipsoidal shape. STM studies of C7Q adsorption and thin-film growth on the GaAs(110) (Ref. 10) and Au(111) (Ref. 11) surface confirm its ellipsoidal structure and form close-packed arrangements. The NN distance of C7o in bulk phases (both fcc and hcp) is measured to be 10.6 A, ' which is 4% larger than four times the Cu-Cu NN distance (10.2 A) on the Cu(111)1X 1 surface. Therefore, it is likely that pure C7Q s also form the 4 X 4 reconstruction on the Cu(111) surface, by taking the upright position with one of the pentagon rings facing the Cu surface and their long axes perpendicular to the surface. Under this configuration, the intermolecular dis-0 tance can be 10.2 A, identical to that for pure C6Q adsorption. When C6Q is coadsorbed with C7Q molecules on the Cu(111) surface, it may be possible to find a situation where some of the C7Q molecules take a lying-down position with the long axis parallel to the surface, due to readjustment of the surface stress and the adsorbateadsorbate interactions. These speculat...

Adsorption and Dynamics of Long‐Range Interacting Fullerenes in a Flexible, Two‐Dimensional, Nanoporous Porphyrin Network

“…However, the real conformation is likely to be different as deduced from the slightly different distances and brightness of the protrusions in the STM image (b). ported by Wang et al [32] This difference may be caused by the relatively weak adsorption energy of the fullerenes in the present porphyrin framework compared to the stronger metal-fullerene interaction in the above-mentioned reports, which forces the C 70 molecules to adsorb steadily with the long side parallel to the surface. This indicates that the fullerenes in the pores of the supramolecular assembly of 1 are able to vibrate and rotate at 298 K, which is confirmed by their averaged round appearance on the time scale of STM measurements.…”

Electrochemical STM investigation of C70, C60/C70 mixed fullerene and hydrogenated fullerene adlayers on Au(111) prepared using the electrochemical replacement method

“…In particular, much attention has been given to scanning tunneling microscopy (STM) studies of fullerene adlayers on various substrates. Since the pioneering work on STM imaging of fullerenes by Wilson et al [1] and Wragg et al [2], a large number of real space STM imaging studies of fullerene molecules have been performed in ultrahigh vacuum (UHV) at low temperature [3][4][5][6][7] and room temperature [1,[8][9][10][11][12][13][14][15][16][17][18][19][20], in air [2,21,22], and in situ STM conducted in organic solvents [23][24][25] and aqueous solution [26][27][28][29][30]. Adlayers of C 60 [1,[3][4][5][6][7][8][9][10][11][12][13][14][18][19][20]…”

“…Mostly, fullerene adlayers and films have been prepared through a variety of ''sophisticated" dry processes under UHV, such as vapor deposition [1][2][3][4][5][6][7][8][9][10][11][12][14][15][16][17][18][19] and molecular beam epitaxy (MBE) [13,20]. Wet processes such as the spontaneous adsorption of fullerenes from organic solvent [23][24][25]32,33,35,38,39], solution evaporation [26], and the transfer of Langmuir (L) films from the air-water interface (Langmuir-Blodgett (LB) technique) [21,22,[27][28][29][30][31] have also proven equally successful.…”

ECSTM study of adsorption of C60, C70, C86 and Y@C82 on Au(111)

“…It indicates that C 70 molecules take an upright position with the long axis perpendicular to the surface and continue to rotate along their long axis [15]. The molecular rows in most domains are essentially parallel with the 3 direction.…”

“…The nearest neighbouring distance of C 70 in the bulk phase is measured to be 10.6 Å [14]. Yurov et al investigated the adsorption of C 70 on the Cu(111)(1 × 1) surfaces employing STM under UHV conditions [15]. The pure C 70 monolayer was found to form the 4 × 4-commensurate structure as a close-packed hexagonal lattice, after a brief annealing at approximately 320 °C.…”