Gold nanopariticles, formed by a controllable reduction of tetrachlorauric acid (HAuCl4) and subsequently coated by a self-assembled monolayer (SAM) of 3-mercaptopropionc acid (MPA) molecules, were used to investigate lateral single-electron tunneling (L-SET) using an ultrahigh vacuum four probe technique with gold electrodes on SiO2/Si (100) at low temperature 16 k, and were also used to test ultraviolet absorption. X-ray photoelec tron speclroscopy (XPS) has been used to confirm the gold particles coated by a SAM of MPA. Scanning tunneling microscopy (STM) imaging showed that the coated parlicles were dispersed in diameter size and spherical in shape. Experimental data from electrial transport measurements are in well agreement with semi-classical predietions for correlated L-SET and permit estimations of the electrical resistance and capacitance in a multi-tunnel systed composed of various tunnel junctions. Ultraviolet absorption spectra showed a small blue shift for the smaller particle, and the phenomena of blue shift caused by quantum size effect were also discussed.

Three triple-helical hairpin DNAs with substitution of 5-bromocytosine for cytosine in different strands have been investigated by molecular mechanics and Raman spectroscopy. The stability of the three substituted triplexes were compared with the corresponding unsubstituted triplex DNA by the molecular mechanics method. Base stacking interactions and strand]strand interactions of each triplex were analyzed in detail. Sugar conformations in these triplexes have been determined by both vibrational spectroscopy and molecular dynamics simulation. The hairpin triplexes with substitution occurring in strand I or both in strands I and III have the main sugar conformation of C39-endo, while the triplex with substitution occurring in strand III is the combination of C39-endo and C29-endo sugar conformation. Theoretical results are basically in agreement with experiments. Q 1999 Elsevier Science B.V. All rights reserved.

We describe in this paper the fabrication of two-and one-dimensional nano-structures with organic molecular beam epitaxy (OMBE) principle based on controlled self-assembly by using adsorbate-ubstrate and intermolecular interactions that are important in molecular fabrication. Cu(100) single crystal was used as substrate in fabricating molecular nanostructures. Scanning tunneling microscopy (STM) experiments confirmed that Zn-tetra-[3,5-di-t-butylphenyl]porphyrin molecules can be used to fabricate both monolayer and molecular wire on Cu(100) surface simultaneously, and the latter is arranged on the terrace edges. We herein briefly discuss the selectivity in terms of a mechanism in which the highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) of the molecules interact with the surface.

Highly conductive and transparent indium tin oxide (ITO) thin films, each with a thickness of 100 nm, were deposited on glass and Si(100) by direct current (DC) magnetron sputtering under an argon (Ar) atmosphere using an ITO target composed of 95% indium oxide and 5% tin oxide for photon-STM use. X-ray diffraction, STM observations, resistivity and transmission measurements were carried out to study the formation of the films at substrate temperatures between 40 and 400 ◦C and the effects of thermal annealing in air between 200 and 400 ◦C for between 1 and 5 h. The film properties were highly dependent on deposition conditions and on post-deposition film treatment. The films deposited under an Ar atmosphere pressure of 1.7×10−3 Torr by DC power sputtering (100W) at substrate temperatures between 40 and 400 ◦C exhibited resistivities in the range 3.0–5.7×10−5 Ωm and transmissions in the range 71%–79%. After deposition and annealing in air at 300◦C for 1 h, the films showed resistivities in the range 2.9–4.0×10−5 Ωm and transmissions in the range 78%–81%. Resistivity and transmission measurements showed that in order to improve conductive and transparent properties, 2 h annealing in air at 300 ◦C was necessary. X-ray diffraction data supported the experimental measurements of resistivity and transmission on the studies of annealing time. The surface roughness and film uniformity improve with increasing substrate temperature. STM observations found the ITO films deposited at a substrate temperature of 325 ◦C, and up to 400 ◦C, had domains with crystalline structures. After deposition and annealing in air at 300 ◦C for 1 h the films still exhibited similar domains. However, after deposition at substrate temperatures from 40 ◦C to 300 ◦C, and annealing in air at 300◦C for 1 h, the films were shown to be amorphous. More importantly, the STM studies found that the ITO film surfaces were most likely to break after deposition at a substrate temperature of 325 ◦C and annealing in air at 300◦C for 2 or 3 h. Such findings give some inspiration to us in interpreting the effects of annealing on the improvement of conductive and transparent properties and on the transition of phases. In addition, correlations between the conductive/transparent properties and the phase transition, the annealing time and the phase transition, and the conductive/transparent properties and the annealing time have been investigated.

We dissolved 1-iodo-4-nitrobenzene in various solvents, including ethanol, benzene, toluene and dimethylacetamide, and prepared solution with different concentration from 10-2 M to 10-5 M. Epitaxial Au(111) film and graphite were used as substrates. Scanning tunneling microscope (STM) was used to observe structures of 1-iodo-4-nitrobenzene molecules on those substrates. Experimentally, we found that 1-iodo-4-nitrobenzene molecules constructed nanowires on graphite surface at room temperature in air. The mechanism of formation of nanowire is briefly discussed in this paper.