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Seemingly contradicting results raised a debate over the ability of DNA to transport charge and the nature of the conduction mechanisms through it. We developed an experimental approach for measuring current through DNA molecules, chemically connected on both ends to a metal substrate and to a gold nanoparticle, by using a conductive atomic force microscope. Many samples could be made because of the experimental approach adopted here, which enabled us to obtain reproducible results with various samples, conditions, and measurement methods. We present multileveled evidence for charge transport through 26-bp-long dsDNA of a complex sequence, characterized by S-shaped current-voltage curves that show currents >220 nA at 2 V. This significant observation implies that a coherent or band transport mechanism takes over for bias potentials leading to high currents (>1 nA). molecular electronics | scanning probe microscopy | nanoelectronics

A simple low-vacuum mass spectrometer (LVMS) operating in the milliTorr pressure range was developed. The instrument resolves masses by time-of-flight measurements and employs a high-gain, fast-response detector that can operate at these pressures. This instrument allows simultaneous determination of mass and collision cross sections of the ions with the bath gas. Here we demonstrate the LVMS's abilities to determine total collision cross sections for the collisions of organic ions with three background gases, He, [N.sub.2], and S[F.sub.6]. As a demonstration of the system capabilities, the unimolecular interconversion of photochemically produced [C.sub.7][[H.sub.7].sup.+] to the tropylium ion structure is investigated.

Dicarboxylic acids chemisorb on the GaAs surface, with binding appreciably stronger for the di- than for the monocarboxylic acids. This was concluded from results of an investigation of the kinetics of adsorption of these acids onto GaAs(100) surface. A two-site mechanism is used to describe the chemisorption of dicarboxylic acids on GaAs (100), unlike the one-site mechanism for benzoic acid adsorption. Absorption kinetics was directly measured using a new electrical method, wherein the current through a GaAs/(Al,Ga)As-based device is measured. Results agree with Fourier transform infrared spectroscopy absorption equilibrium data.

The electron transfer through an organized organic monolayer of alkyl chains adsorbed on a silicon wafer has been studied. The silicon was used as an electrode in a three-electrode electrochemical cell, and the current versus voltage response was measured. The results show that when the chains in the monolayer are in the 'all trans' configuration, the charge transfer efficiency is higher than when the chains have a 'gauche' configuration. A mechanism rationalizing all the observations is suggested., Electron transfer (ET) processes involving organic molecules are relevant to many biological systems, like vision and photosynthesis (1). Therefore, these processes have been studied in much detail, both theoretically (2)(3)(4)(5) [...]

Magnetolithography is applied to chemically pattern the inside of tubes. The new capability has helped in performing sequential processes within the tubes and many enzymatic reactions are shown.

A combination of the high-resolution electron energy loss spectroscopy (HREELS) and XPS studies is used to study the interactions of the self-assembled monolayers of DNA with electrons. The monolayers are shown to be well-organized, displaying sharp vibrational peaks.

The effect of diffusion through a gel medium on the competition between a single specific reaction and a larger number of weak nonspecific interactions is examined. The effectiveness of the method is shown by the high selectivity obtained both in the adsorption of DNA to a surface and in DNA hybridization to preadsorbed single-strand oligomer on a surface.

Empirical evidence supporting the existence of a new optical absorption band observed when monolayers of alkylthiol are self-assembled on gold substrate is presented. The intensity of the new band has correlated well with the density of molecules and the quality of the organization of the monolayer.

XPS studies are conducted to show that when monolayers of single-stranded ssDNA are formed from NaCl buffer and washed thoroughly, no Na(super +) is detected. Results reveal that in ssDNA absorbed on gold substrate, the concentration of metallic cations is far below the value required to fully neutralize the DNA molecules, and since the layer is not charged, DNA is believed to be neutralized mainly by protons.

Modeling of surface properties has become popular in various industries since the achievements of modern technology has allowed for precise design and substrate patterning even at the atomic level. Nowadays, [...]