%0 Journal Article
%T The Surface of Nanoparticle Silicon as Studied by Solid-State NMR
%A Rebecca A. Faulkner
%A Joseph A. DiVerdi
%A Yuan Yang
%A Takeshi Kobayashi
%A Gary E. Maciel
%J Materials
%D 2013
%I MDPI AG
%R 10.3390/ma6010018
%X The surface structure and adjacent interior of commercially available silicon nanopowder ( np-Si) was studied using multinuclear, solid-state NMR spectroscopy. The results are consistent with an overall picture in which the bulk of the np-Si interior consists of highly ordered (※crystalline§) silicon atoms, each bound tetrahedrally to four other silicon atoms. From a combination of 1H, 29Si and 2H magic-angle-spinning (MAS) NMR results and quantum mechanical 29Si chemical shift calculations, silicon atoms on the surface of ※as-received§ np-Si were found to exist in a variety of chemical structures, with apparent populations in the order (a) ( Si每O每) 3 Si每H > (b) ( Si每O每) 3 SiOH > (c)ˋ(HO每) n Si( Si) m(每O Si) 4ˋmˋn ＞ (d) ( Si每O每) 2 Si(H)OH > (e) ( Si每O每) 2 Si(每OH) 2 > (f)ˋ( Si每O每) 4 Si, where Si stands for a surface silicon atom and Si represents another silicon atom that is attached to Si by either a Si每 Si bond or a Si每O每 Si linkage. The relative populations of each of these structures can be modified by chemical treatment, including with O 2 gas at elevated temperature. A deliberately oxidized sample displays an increased population of ( Si每O每) 3 Si每H, as well as ( Si每O每) 3 SiOH sites. Considerable heterogeneity of some surface structures was observed. A combination of 1H and 2H MAS experiments provide evidence for a substantial population of silanol ( Si每OH) moieties, some of which are not readily H-exchangeable, along with the dominant Si每H sites, on the surface of ※as-received§ np-Si; the silanol moieties are enhanced by deliberate oxidation. An extension of the DEPTH background suppression method is also demonstrated that permits measurement of the T 2 relaxation parameter simultaneously with background suppression.
%K silicon
%K nanoparticles
%K 29Si NMR
%K solid-state NMR
%K surface characterization
%U http://www.mdpi.com/1996-1944/6/1/18