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1.
Nanoscale ; 16(31): 14879-14898, 2024 Aug 13.
Article in English | MEDLINE | ID: mdl-39037702

ABSTRACT

Molecular logic gates (MLGs) are molecules which perform logic operations. They can potentially be used as building blocks for nano-sized computational devices. However, their physical and functional integration is a difficult task which remains to be solved. The problem lies in the field of signal exchange between the gates within the system. We propose using non-adiabatic excitation transfer between the gates to address this problem while absorption and fluorescence are left to communicate with external devices. Excitation transfer was studied using the modified Bixon-Jortner-Plotnikov theory with the example of the 3H-thioxanthene-TTF-dibenzo-BODIPY covalently linked triad. Several designs of the molecule were studied in a vacuum and cyclohexane. It was found that the molecular logic system has to be planar and rigid to isolate radiative interfaces from other gates. Functioning of these gates is based on dark πσ*-states in contrast to bright ππ*-states of radiative interfaces. There are no fundamental differences between ππ* → πσ* and ππ* → ππ* transitions for cases when an exciton hops from one gate to another. The rates of such transitions depend only on an energy gap between states and the distance between gates. The circuit is highly sensitive to the choice of solvent which could rearrange its state structure thereby altering its behavior. According to the obtained results, non-adiabatic transfer can be considered as one of the possible ways for transmitting a signal between MLGs.

2.
Phys Chem Chem Phys ; 22(43): 25243-25254, 2020 Nov 21.
Article in English | MEDLINE | ID: mdl-33135705

ABSTRACT

Using an exciton as a carrier was examined as a possible solution to the problem of signal transmission between molecular logic gates. A tetrathiafulvalene chain was chosen as a model for a molecular logic system and its distinct logic states were described as excitons located at certain tetrathiafulvalene units. The parameters of the exciton transfer between the units of the chain were studied. The transfer rate between the two adjacent units was calculated using the Plotnikov-Bixon-Jortner theory basing on molecular parameters calculated using TD-DFT. The order of electronic states was studied at the MCQDPT and TD-DFT levels of theory. It was found that certain functional groups in the chain can make exciton transfer faster than its recombination. The exciton can effectively carry a signal through the chain, which in turn can be enlarged and modified.

3.
Nanomaterials (Basel) ; 10(4)2020 Apr 01.
Article in English | MEDLINE | ID: mdl-32244608

ABSTRACT

We studied the tribological properties of amorphous molybdenum sulfide (MoSx) thin-film coatings during sliding friction in an oxidizing environment at a low temperature (-100 °C). To obtain films with different sulfur contents (x ~ 2, 3, and 4), we used reactive pulsed laser deposition, where laser ablation of the Mo target was performed in H2S at various pressures. The lowest coefficient of friction (0.08) was observed during tribo-testing of the MoS3 coating. This coating had good ductility and low wear; the wear of a steel counterbody was minimal. The MoS2 coating had the best wear resistance, due to the tribo-film adhering well to the coating in the wear track. Tribo-modification of the MoS2 coating, however, caused a higher coefficient of friction (0.16) and the most intensive wear of the counterbody. The MoS4 coating had inferior tribological properties. This study explored the mechanisms of possible tribo-chemical changes and structural rearrangements in MoSx coatings upon contact with a counterbody when exposed to oxygen and water. The properties of the tribo-film and the efficiency of its transfer onto the coating and/or the counterbody largely depended on local atomic packing of the nanoclusters that formed the structure of the amorphous MoSx films.

4.
Biofizika ; 60(1): 32-7, 2015.
Article in Russian | MEDLINE | ID: mdl-25868338

ABSTRACT

An image of fragmented sequence of biopolymer molecules by example of bacterial DNA in vivo (in atmosphere air) was received by scanning tunneling microscopy. An air adsorbate (mainly water vapors) that covers the molecule's surface gives rise to local tunnel conductivity and by virtue of adsorption selectivity indirectly reflects local conductance of fragments that consist of different rows of various atoms, supporting their tunnel conductivity. Having processed experimental data fragment images are obtained with scaled-up topography characteristics for their further identification.


Subject(s)
DNA, Bacterial/chemistry , DNA, Bacterial/ultrastructure , Microscopy, Scanning Tunneling/methods
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