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A new step in the nanoworld


Електронні знімки (СЕМ) нанокомпозиту ПАНІ / Таун - МД

Miniaturization of modern electronic equipment is truly impressive. Today nanotechnologist are working under creation of electronic circuits elements of about 50 nanometers and are close to the creation of experimental models of individual organic molecules. For example, the use of such devices in electronics allow increasing the power of computer processors in hundreds of times.

For this purpose, nanotubes and fullerenes are used, but the more promising may be semiconductor nanodiamonds that are currently obtained by explosive technology or surface coating. However, the nanodiamonds have many issues that hinder their practical application. Industrial nanodiamonds vary in size, contain significant amounts of graphite, the surface of these crystals is heterogeneous. Meanwhile nanotechnology need homogeneous material, ie material with particles of the same shape and size. Furthermore, for the precision chemical binding of molecules, the needed substituent must be injected in the nanodiamond molecule in certain position, or, as chemists say, selectively functionalize the molecule.

Adamantine carbon skeleton is a diamond unit cell, free valence of which is occupied by hydrogen atoms, ie it is the smallest hydrogenated diamond. Recently, researchers of the company “Shevron” identified from petroleum hydrocarbons, which are represented as two, three, four and up to ten condensed adamantine fragments. In fact, these hydrocarbons are hydrogenated nanodiamonds of 2.4 nanometers in size. They are called “diamondoids” and they cause interest for nanotechnology.

Today, the efforts of chemists, physicists, geochemists from Ukraine, Germany and USA were combined to use diamondoinds in nanotechnology. One of the most difficult problems in diamondoind’s chemistry are controlled introduction of functional groups in the certain molecule’s position, because of the increasing size of the molecule, the number of replacement options increases.

For several decades, scientists of the Department of Organic Chemistry and Technology of organic substances (OC and TOS) explore methods of synthesis, properties, reactivity, mechanisms of transformation and use of adamantine and cyclic homogues. Currently, this Department is the world’s leader in this area and at the OC and TOS Departments, where in detail were examined the mechanisms of functionalization of the frame hydrocarbons, were found the conditions of selective functionalization of the diamodoids. Under the guidance of prof. A.A. Fokin in collaboration with a number of Western universities were developed new methods for introducing various functional groups, and as a result the first samples of selectively functionalized nanodiamonds were received to study their electronic properties.

Already the first results of the studying the properties obtained from derivatives of the diamondoids appeared to be promising. Was found, that functionalized nanodiamonds able to sorb from the solution to the surface of silver or gold forming a self-assembled ordered monolayers. These new materials have been studied in detail in the Laboratory of advanced materials in Stanford University, National Laboratory of advanced light sources at Berkeley and at the Lawrence Livermore National Laboratory (USA). It was found that monolayer of the functionalized diamondoid (thickness of 1.5 nm) becomes negative properties of affinity for electrons and photons of about 1 eV, with very low energy losses. Such negative electron affinity has not been experimentally known to organic molecules.

The results of this research are in the article of the world’s highest-rated magazine Science, 2007, t.316, p.1460 (by the way, this publication is the first involving Ukrainian chemists in this magazine). This discovery promises the widespread use of self-assembled diamondoinds’ monolayers in nanotechnology to create flat panel displays, microwave amplifiers, vacuum microelectronic devices, X-ray detectors, solid state lighting, in electronic microscopy, electron-beam lithography and so on.

Oct 19, 2007 || By O.H.Yurchenko, Dr. Sci.

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