29Si high resolution solid state nuclear magnetic resonance spectroscopy of porous silicon

Pietraβ, T.; Bifone, Angelo; Roth, Robert; Koch, Vanessa; Alivisatos, A. Paul; Pines, Alexander

doi:10.1016/0022-3093(96)00144-5

Cited by 25 publications

(18 citation statements)

References 31 publications

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“…, and (2) the study of high-surface-area materials (~10 2 m 2 g −1 ) by solid-state nuclear magnetic resonance (NMR) [13,14,15,16,17,18,19]. The surface of single crystal silicon has been extensively examined by the former approach but has been inaccessible to NMR, because there is an insufficient number of nuclei at the surface to overcome NMR’s inherently low sensitivity.…”

Section: Introductionmentioning

confidence: 99%

The Surface of Nanoparticle Silicon as Studied by Solid-State NMR

et al. 2012

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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–O–)3Si–H > (b) (Si–O–)3SiOH > (c) (HO–)nSi(Si)m(–OSi)4−m−n ≈ (d) (Si–O–)2Si(H)OH > (e) (Si–O–)2Si(–OH)2 > (f) (Si–O–)4Si, where Si stands for a surface silicon atom and Si represents another silicon atom that is attached to Si by either a Si–Si bond or a Si–O–Si linkage. The relative populations of each of these structures can be modified by chemical treatment, including with O2 gas at elevated temperature. A deliberately oxidized sample displays an increased population of (Si–O–)3Si–H, as well as (Si–O–)3SiOH 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–OH) moieties, some of which are not readily H-exchangeable, along with the dominant Si–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 T2 relaxation parameter simultaneously with background suppression.

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Section: Introductionmentioning

confidence: 99%

The Surface of Nanoparticle Silicon as Studied by Solid-State NMR

et al. 2012

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“…It is widely accepted that as prepared PSiPs exhibit Si–H bonds on the surface [37]. The FTIR spectrum of freshly-etched PSiPs (Figure 6), reflects the presence of these species.…”

Section: Resultsmentioning

confidence: 93%

Visible Light Assisted Organosilane Assembly on Mesoporous Silicon Films and Particles

et al. 2019

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Porous silicon (PSi) is a versatile matrix with tailorable surface reactivity, which allows the processing of a range of multifunctional films and particles. The biomedical applications of PSi often require a surface capping with organic functionalities. This work shows that visible light can be used to catalyze the assembly of organosilanes on the PSi, as demonstrated with two organosilanes: aminopropyl-triethoxy-silane and perfluorodecyl-triethoxy-silane. We studied the process related to PSi films (PSiFs), which were characterized by X-ray photoelectron spectroscopy (XPS), time of flight secondary ion mass spectroscopy (ToF-SIMS) and field emission scanning electron microscopy (FESEM) before and after a plasma patterning process. The analyses confirmed the surface oxidation and the anchorage of the organosilane backbone. We further highlighted the surface analytical potential of 13C, 19F and 29Si solid-state NMR (SS-NMR) as compared to Fourier transformed infrared spectroscopy (FTIR) in the characterization of functionalized PSi particles (PSiPs). The reduced invasiveness of the organosilanization regarding the PSiPs morphology was confirmed using transmission electron microscopy (TEM) and FESEM. Relevantly, the results obtained on PSiPs complemented those obtained on PSiFs. SS-NMR suggests a number of siloxane bonds between the organosilane and the PSiPs, which does not reach levels of maximum heterogeneous condensation, while ToF-SIMS suggested a certain degree of organosilane polymerization. Additionally, differences among the carbons in the organic (non-hydrolyzable) functionalizing groups are identified, especially in the case of the perfluorodecyl group. The spectroscopic characterization was used to propose a mechanism for the visible light activation of the organosilane assembly, which is based on the initial photoactivated oxidation of the PSi matrix.

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“…The overlapping of some characteristic bands in the FTIR spectra makes the univocal identification of GPTMS difficult. In order to overcome this issue, we used SSNMR spectroscopy and assigned the peaks on the basis of the correlation of the chemical shifts with those observed on functionalized silicates [31][32][33][34][35][36][37]. Figure 4a shows the 29 Si NMR spectra of the GPTMS-functionalized PSi compared with freshly formed PSi.…”

Section: Surface Bound Gptms On Psi Particlesmentioning

confidence: 99%

“…Figure 4a shows the 29 Si NMR spectra of the GPTMS-functionalized PSi compared with freshly formed PSi. In the first one, the chemical shift of the dominant signal is centered at −96 ppm, with a line width (full width at half maximum, FWHM) of 20 ppm, which can be assigned to SiH or SiH2 structural elements [32].…”

Section: Surface Bound Gptms On Psi Particlesmentioning

confidence: 99%