Biomedical subjects

Mykola Kondratenko

Publications and source records attributed to Mykola Kondratenko.

3 recordsLinked to original sources

PubMed2006

Rectifying diodes from asymmetrically functionalized single-wall carbon nanotubes.

Asymmetrically functionalized single-wall carbon nanotubes (SWNTs) have been prepared by a covalent reaction of an 11-mercaptoundecanol-modified Au surface with oxidized SWNT cylinders. While one end of the tubes is attached to gold substrate via ester groups, the free carboxylic substituents on the other end can be either ionized (CO2-) or esterified (CO2Et), creating a donor-acceptor asymmetric and acceptor-acceptor symmetric SWNT, respectively. Study of the SWNT monolayer conductance in Hg drop junction experiments reveals a pronounced diode-like behavior for donor-SWNT-acceptor junctions, while acceptor-SWNT-acceptor junctions are electrically symmetric.

Electric Conductivity↗

PubMed2005

Self-assembly and multistage redox chemistry of strong electron acceptors on metal surfaces: polynitrofluorenes on gold and platinum.

Nitrofluoren-9-one and nitrofluoren-9-dicyanomethylene electron acceptors 7, 8, and 11 functionalized with a terminal thioctic acid unit have been synthesized from 2,4,5,7-tetranitrofluorenone. The self-assembled monolayers (SAMs) of these compounds on gold, formed via gold-sulfur interaction, have been fully characterized by electrochemical, FTIR, ellipsometry, and contact angle measurements. Cyclic voltammetry of SAMs reveals two reversible single-electron reduction waves for fluorenone derivatives 7a,b and 11, and three single-electron reductions for the dicyanomethylene-fluorene 8b, providing the first observation of a radical trianion species in SAMs. The tendency of the thioctic anchor to form multilayers via disulfide links is noted.

Electrochemistry↗

PubMed2005

The first studies of a tetrathiafulvalene-sigma-acceptor molecular rectifier.

Langmuir-Blodgett monolayers of a donor-acceptor diad TTF-sigma-(trinitrofluorene) (8) with an extremely low HOMO-LUMO gap (0.3 eV) have been used to create molecular junction devices that show rectification behavior. By virtue of structural similarities and position of molecular orbitals, 8 is the closest well-studied analogue of the model Aviram-Ratner unimolecular rectifier (TTF-sigma-TCNQ). Compressing the monolayer results in aligning the molecules, and is followed by a drastic increase in the rectification ratio. The direction of rectification depends on the electrodes used and is different in n-Si/8/Ti and Au/8/C16H33S-Hg junctions. The molecular nature of such behavior was corroborated by control experiments with fatty acids and by reversing the rectification direction with changing the molecular orientation (Au/D-sigma-A versus Au/A-sigma-D).

Journal Article↗