Contact Pin-Printing onto Porous Silicon for Creating Microarrays with High Chemical Diversity

Abstract

We explore the size and spatial microheterogeneity of contact pin-printed spots formed on porous silicon (pSi). Glycerol was contact printed at room temperature onto as-prepared, hydrogen-passivated pSi (ap-pSi) using 50 or 200 µm diameter solid pins. The pSi was then subjected to a strong oxidizing environment (gaseous O) and washed to remove the glycerol masks. The glycerol-free regions were converted to oxidized pSi (ox-pSi); the glycerol-coated regions were protected from O, but not entirely. The final array is described as circularly shaped "ap-pSi" regions on a field of ox-pSi. When comparing the areas outside and inside the glycerol-masked pSi spots, one finds dramatic differences in the Si-O-Si, SiH (x = 1-3) and OSiH (y, x = 1-3) levels with a spatially dependent continuum of compositions across the spot diameter. Experimental conditions could be adjusted to tune the final ap-pSi spot diameter and edge widths from 90 µm to 520 µm and 20 µm to 130 µm, respectively. The resulting ap-pSi spot diameter is explained by using molecular kinetic theory and time-dependent glycerol imbibement into the pSi within a one-dimensional Darcy's law model.

Interplay Between Silicon Nanocrystal Size and Local Environment Within Porous Silicon on the Analyte-Dependent Photoluminescence Response

“…2c to aid in subsequent discussions. These observations highlight the heterogeneity we have observed in the past 16–19 and we set out to identify its root causes.

Figure 2.Total PL intensity maps (665–775 nm) from a pSi specimen.

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“…14,15 Over the years, our research group has been developing pSi-based PL sensors and sensor arrays. 16–19 During these research activities, we have noticed that the PL response across a pSi specimen can exhibit significant variability. This has led us to question the relationship between the silicon nanocrystallite (SiNC) size, size distribution, and local environment surrounding the SiNC and the analyte-induced PL response from pSi-based sensor platforms.…”