Size Control of Porous Silicon-Based Nanoparticles via Pore-Wall Thinning

Abstract

Photoluminescent silicon nanocrystals are very attractive for biomedical and electronic applications. Here a new process is presented to synthesize photoluminescent silicon nanocrystals with diameters smaller than 6 nm from a porous silicon template. These nanoparticles are formed using a pore-wall thinning approach, where the as-etched porous silicon layer is partially oxidized to silica, which is dissolved by a hydrofluoric acid solution, decreasing the pore-wall thickness. This decrease in pore-wall thickness leads to a corresponding decrease in the size of the nanocrystals that make up the pore walls, resulting in the formation of smaller nanoparticles during sonication of the porous silicon. Particle diameters were measured using dynamic light scattering, and these values were compared with the nanocrystallite size within the pore wall as determined from X-ray diffraction. Additionally, an increase in the quantum confinement effect is observed for these particles through an increase in the photoluminescence intensity of the nanoparticles compared with the as-etched nanoparticles, without the need for a further activation step by oxidation after synthesis.

Adaptive Cavitation Ultrasonication for Large-Scale Preparation of Porous Silicon Nanoparticles

“…4 For these applications, various surface chemistries, 5 drug-or imaging agent-encapsulation strategies, 6 and particle size control methods have been explored to enable or extend the utility of pSiNPs. 7 The process used to prepare pSiNPs, involving electrochemical anodization of high-purity single-crystal silicon wafers, provides very precise control of nanostructure in the material. 8 Despite the improved in vitro and in vivo performance of the material, one of the major challenges of pSiNPs is their high cost relative to other nanoparticle systems, such as sol−gel-derived mesoporous silica nanoparticles, polymer nanoparticles, or liposomes.…”

“…Biological applications of porous silicon nanoparticles (pSiNPs) include drug delivery systems, , bioimaging, and biosensing . For these applications, various surface chemistries, drug- or imaging agent-encapsulation strategies, and particle size control methods have been explored to enable or extend the utility of pSiNPs . The process used to prepare pSiNPs, involving electrochemical anodization of high-purity single-crystal silicon wafers, provides very precise control of nanostructure in the material .…”

Preserving surface area and porosity during fabrication of silicon aerocrystal particles from anodized wafers

“…Examples are the porosity determining drug payload and the surface area determining sensor limit of detection. Nevertheless, in most studies concerning USF of pSi [7,[9][10][11][12][13][14], yields are not provided. Table 1 shows data from two exceptions, together with results from this study.…”

Pore Wall Thinning of Mesoporous 4H‐SiC by Sacrificial Oxidation

“…In sacrificial oxidation, the dimensions within the as‐etched porous SiC are further reduced during oxidation by consuming SiC and the subsequent HF dip step removes the grown SiO 2 . In recent work for porous Si, nanoparticles smaller than 6 nm were obtained from porous Si after pore wall thinning using an oxidation step followed by sonication which was otherwise difficult to achieve with sonication alone. It was hypothesized that the surface energy barrier to form particles increases with reducing particle size and eventually sonication would not be sufficiently powerful to reduce the dimensions further.…”