title: 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 O3) 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 O3, 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, SiHx(x = 1-3) and OySiHx(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.
authors.affiliation: Department of Chemistry, Natural Sciences Complex, SUNY-Buffalo, USA.
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Horner
authors.affiliation: PPG Industries Inc., USA.
authors.forename: Nadine D
authors.initials: ND
authors.lastname: Kraut
authors.affiliation: Lenape Valley Regional High School, USA.
authors.forename: Caley A
authors.initials: CA
authors.lastname: Richardson
authors.affiliation: Department of Chemistry and Biochemistry, Mellon Hall of Sciences, Duquesne University, USA.
authors.forename: Bernandie
authors.initials: B
authors.lastname: Jean
authors.affiliation: Department of Chemistry, Natural Sciences Complex, SUNY-Buffalo, USA.
authors.forename: Alyssa M
authors.initials: AM
authors.lastname: Rook
authors.affiliation: Department of Chemistry, Natural Sciences Complex, SUNY-Buffalo, USA chefvb@buffalo.edu.
authors.forename: Frank V
authors.initials: FV
authors.lastname: Bright
keywords: Porous silicon; contact pin-printing; infrared; infrared imaging; microarrays; ozone; photoluminescence; porosity