Defects in nanoparticles - news one

Physical properties of metal nanoparticle are very strongly differ more often from properties of volume samples of the same stuff (for example, reduction of the dimensions of a particle leads to reduction of its fusion temperature). Technologists have learnt to make nanoparticles the various dimensions, the form and a chemical compound. And here to monitor number and phylum of defects in nanoparticles they are not able yet. Therefore in a question on influence of defects on characteristics nanoparticle till now there are many white maculae. Meanwhile it is known, that presence of defects can lead to rather essential change of properties nanoparticles. For example, defective golden nanoparticles are more stable thermodynamically.

Fig. 1. Growth nontwinned and twinned nanoparticles silver from various precursors.
 

Employees University of Maryland (USA) have developed technology which allows to make a controllable mode nanoparticleы the silver, having the identical dimension, but thus being either monocrystalline, or containing a considerable quantity of doubles – ranges with various orientation of crystallographic axes. Section borders between such ranges are defects of the special sort (so-called twinning defects). This technology is based on use for synthesis nanoparticle the various polymerous precursors, namely – trifenilphosphin’s silver (PPh3) 33Ag-R with different functional bunches R = Cl, and R = NO3. If at R = NO3) from blastemals grow twinned LF, at R = Cl – nontwinned (fig. 1 see.).

It is bound to specific feature of ions Cl to quench education of doubles. The average dimension both that, and others nanoparticles has compounded 10.5 nanometers.

Researches have shown, that physical and chemical properties of these two phylums nanoparticle is essential differ. For example, at interaction with selenium from nontwinned nanoparticles turned out hollow nanoparticles Ag2Se, and from twinned – continuous unimodal nanoparticles. This results from the fact that difference of diffusion coefficients of atoms Ag and Se on a crystalline lattice promotes formation of vacancies (which clump as a result and forms a lumen in LF), whereas atoms Se moving not on a lattice, and on borders of doubles, easily inpour into ranges Ag parted by these borders therefore it is formed unimodal nanoparticles Ag2Se. Further, in twinned nanoparticles much faster refrigerating of an electron subsystem after influence of laser impulse (owing to a transmission of energy to a lattice) takes place. It means that borders of doubles enhance an electron-fononnoe interaction which, hence, can be regulated by change of concentration of defects in nanoparticles. It is curious, that the elasticity module nontwinned nanoparticles (defined on the season of their radial fluctuations after an irradiating the laser) has appeared on third less, than at twinned nanoparticles (it, however, it will be compounded with data of atomic power microscopy available in the literature on augmentation of fastness silver nanolines after twinning). On the contrary, a research of optical characteristics has shown that the reverberatory response of noncommunicative surface plasmons in crystalline nanoparticles is much stronger. And as the surface plasmon is very sensitive to a choronomic environment nontwinned nanoparticles approach for use in sensors of gases is better. Thus, optimum degree of deficiency nanoparticles is defined by that, where exactly these nanoparticles will be used also what particularly devices collect to produce on their basis. Somewhere nanocrystallinity it is good, and somewhere and is not present …