Double-ended alkanedithiols, 1,9-nonanedithiol and 1,5-pentanedithiol, formed self-assembled monolayers (SAMs) on Au(l11) substrates and were used to adsorb silver ions from an ethanolic solution of silver nitrate and formed Ag–dithiol–Au multilayer structures. Ellipsometry, contact angle measurement and X-ray photoelectron spectroscopy (XPS) confirmed that the alkanedithiol molecules formed SAMs with only one-ended thiol groups attached to the Au substrates, which was supported by molecular mechanics calculation. XPS and X-ray Auger electron spectroscopy (XAES) indicated that silver ions were deposited onto the SAMs from the solution by the chemical reaction of silver nitrate with another-ended thiol groups of the SAMs. Atomic force microscopy (AFM) was used to observe SAMs and multilayer structures.

Self-assembled monolayers (SAMs) of 1,5-pentanedithiol and 1,9-nonanedithiol on Au (111) surfaces were used to adsorb copper ions (Cu2C) from an ethanolic solution of cupric chloride (CuCl2) by chemical interaction of thiol groups and copper ions assembling multilayer structures. Ellipsometry, contact angle measurement and X-ray photoelectron spectroscopy (XPS) confirmed that the alkanedithiol molecules formed SAMs with only one-ended thiol groups attached to the gold surface, leaving the other-ended thiol groups free, which is supported by the molecular mechanics calculation. XPS and X-ray Auger electron spectroscopy (XAES) not only indicate that copper ions deposited onto SAMs from the solution by the chemical reaction of copper ions with ended free thiol groups of SAMs, but more importantly demonstrate that copper is present in the C1 oxidation state in the multilayer system. Atomic force microscopy (AFM) was used to observe SAMs and multilayer structures.

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.

The conformational transitions (helix-coil transitions) of three hairpin triple helices, models 5’.(A-G), + 5’-(T-C),-T,- (hrC-T), [CY]. S-&G), + 5’-(T-h’C),-T,-(C-T), [YC] and 5’.(A-G), + 5’-(T-h’C),-T,-(h’C-T), [YY], are characterized in this work by UV spectroscopy. Melting of these triplexes is biphasic. and the profiles are used to obtain the thermodynamic parameters. The thermodynamic properties of the hairpin triplex are Tm= 19.45°C and Δ Hvh, = 293. I2 kJ molt-’ for CY, Tm= 22.85°C and Δ Hvh, = 256.63 kJ mol- ’ for YC and Tm = 28.47 °Cand ΔHvh, = 234.68 kJ molt ’ for YY at pH 4.4. Those of the duplex are Tm = 30.5O°C and AH,, = 427.09 kJ molt-’ for CY, Tm= 32.96°C and Δ Hvh, = 374.47 kJ molt ’ for YC and Tm = 33.24°C and Δ Hvh, = 329.67 kJ mol- ’ for YY at pH 4.4. The distinct transitions of triplex to duplex and duplex to single strands are analyzed win g the nearest-neighbor Ising model. Electrostatic effects on each conformation are also analyzed. 0 1997 Elsevier Science B.V.

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.