Rapid chemography of porous silicon undergoing hydrolysis

Abstract

Communications ADVANCED MATERIALSmaterials can be visualized in terms of different connectivity patterns of the dimer building blocks. This topological idea is illustrated in Figure 5 b,c for the R-SnS-1 and R-SnS-3 structure types. Periodic arrays of interconnected Sn,S, broken-cube clusters result from this kind of assembly scheme. The unique three-coordinate capping sulfide sites of adjacent Sn,S, cluster units, which are found to alternate up then down around the 24-atom and 32-atom ring pores of the R-SnS-1 and R-SnS-3 structure types, respectively, are found to be a natural consequence of the interlinking of (Sn,SJ4" building blocks in the patterns shown in Figures 1 and 5.A cautionary note is in order at this juncture in the discussion of the mode of formation of the R-SnS-n materials. Although the crystallization and structure determination of such species as (CHAH),Sn,S,, (TMA),Sn,S,, and (DAB-COH),Sn(S,), are interesting and informative, and spectroscopic evidence has been found for (SII,S,)~@ dimers in the mother liquors of the R-SnS-n preparations, their actual relationship, if any, to the reactions and mechanisms involved in the formation of the R-SnS-n materials could be circumstantial and must currently be regarded as interesting and motivation for further work on this system. Work is continuing that is aimed at probing the nature and chemistry of the gas, solution, and solid phase species present at various stages in the R-SnS-n syntheses in order to clarify the matter further. Esperimen tal I ( VC H I4~rlugsgetellr~haJr nzbH D-69469 Wemherm, 1994 0935-964819411111-0868 $ 5 00+ 2510

Quantification and Reduction of the Residual Chemical Reactivity of Passivated Biodegradable Porous Silicon for Drug Delivery Applications

“…As-etched pSi can generate darkening on a photographic plate within 10 minutes exposure (28). When as-etched pSi and 800 • C passivated (rotary furnace, 16 hours) pSi were exposed for 4 hours at 100% humidity, only as-etched pSi showed a dark spot while the oxidized sample showed no image, indicating that the rate of silane emission from this sample is much slower or negligible (Fig 6).…”

“…Porous silicon releases low levels of gaseous silanes in humid air which create images on photographic plates through reduction of the silver halide in a photographic emulsion [28]. The low levels of monosilane emission are thought to be primarily due to hydrolysis of Si-H 3 bonds, so relatively high concentrations of hydrides on the surface will cause the chemographic effects to be more pronounced for as-etched material than oxide-passivated or derivatized porous silicon surfaces [29].…”

Porous silicon in drug delivery devices and materials☆

“…For drug delivery this introduces a complication in that the drug may not release from the linker, resulting in a modified version of the drug being introduced into the body. In addition, a drug may be susceptible to attack by silane generated during the degradation of the porous Si scaffolding [52] or by residual reactive species on the porous Si material itself [31]. Any studies involving porous Si (or with nanomaterials in general) need to incorporate activity assays to ensure that the released drug has not become inactivated.…”

“…(1)-(3). The surface of porous Si contains Si-H, SiH 2 , and SiH 3 species that can readily convert to silane [52,53]. Silane is chemically reactive (Eq.…”

Porous Silicon Formation by Anodization

“…The storage conditions of anodized layers must be carefully considered, especially so for large quantities, as it has been shown that silane gas can be generated and released as the material reacts with ambient air (Canham et al 1994b). Chapter "▶ Chemical Reactivity and Surface Chemistry of Porous Silicon" of this handbook provides a comprehensive survey of such reactions.…”