ИСТИНА

There are many methods for preparation of silicon nanocrystals (ncSi) and any of these methods has both advantages and shortcomings. Synthesis in liquid media is attractive due to the fact that the obtained dispersions of ncSi in organic solvents are promising for preparation of ncSi layers on supports. We studied reduction of SiBr4 and Si(OEt)4 by sodium, potassium and NaBH4 in glyme, diglyme or diethyl ether at the presence of ionic liquids (IL) 1-alkyl-3-methyl- imidazolium iodide (alkyl = methyl, buthyl, decyl). Cation of IL is reduced to carbene which reacts with the surface of ncSi thus stabilizing silicon nanoparticles and reducing dangling bonds. We found out that size distribution of ncSi stabilized with 1,3-dimethylimidazol-2-ylidene is in range 2-7 nm with the maximum at 3 nm, but the maximum for ncSi covered with 1-buthyl-3-methylimidazol-2-ylidene is at 1.4 nm and 1-decyl-3-methylimidazol-2-ilidene prevents formation of ncSi due to steric hindrance of ligands. Potassium and sodium reduce Si(Hal)4 and cation of Ils via the different mechanisms. Potassium reduces 1,3-dimethylimidazolium to corresponding ylidene, which reacts with the surface of ncSi, but sodium does not reduce cation of IL separately. However, stabilization of ncSi by imidazole-2- ylidenes occurs in a mixture of SiBr4 with sodium and IL. The most unexpected result is reduction of Si(OEt)4 in a mixture with IL by NaBH4 solution in diglyme giving ncSi stabilized with imidazole-2-ilidene. Synthesis in liquid media gives good yield, it is fast and convenient for mass production. The results of electron microscopy and electron diffraction, SAXS, photoluminescence spectra , NMR etc. will be demonstrated. Ionic liquids are very efficient for demonstration of the surface states of nanosilicon. Ionic liquids stabilize nanosilicon particles very efficiently, thus photoluminesce and cathodoluminescence was observed for a long time.Research was supported by grant RFBR 11- 03-01071.