Ionic Liquids Can Permanently Modify Porous Silicon Surface Chemistry.

To develop ionic liquid/porous silicon (IL/pSi) microarrays we have contact pin-printed 20 hydrophobic and hydrophilic ionic liquids onto as-prepared, hydrogen-passivated porous silicon (ap-pSi) and then determined the individual IL spot size, shape and associated pSi surface chemistry. The results reveal that the hydrophobic ionic liquids oxidize the ap-pSi slightly. In contrast, the hydrophilic ionic liquids lead to heavily oxidized pSi (i.e., ox-pSi). The strong oxidation arises from residual water within the hydrophilic ILs that is delivered from these ILs into the ap-pSi matrix causing oxidation. This phenomenon is less of an issue in the hydrophobic ILs because their water solubility is substantially lower.

Exploiting the 3-Aminopropyltriethoxysilane (APTES) autocatalytic nature to create bioconjugated microarrays on hydrogen-passivated porous silicon.

Porous silicon (pSi) based microarrays are attractive because pSi: (i) can be modified in many ways, (ii) possesses a high surface area, and (iii) exhibits strong photoluminescence (PL). These characteristics make pSi-based microarrays candidates for a host of applications including sensing, optoelectronic devices, and photodetectors. Microarray fabrication requires a high-throughput approach to produce chemically modified, spatially isolated spots on a particular substrate. The most stable platforms are characterized by covalent attachment to the substrate. In this paper we exploit the autocatalytic nature of 3-aminopropyltriethoxysilane (APTES) to contact pin-print APTES directly onto as prepared, H-passivated pSi (ap-pSi) without the need for a formal oxidation step. We assess the APTES-derived spots by using PL and Fourier transform infrared spectroscopy (FT-IR) imaging and determine the spot size and spatial homogeneity. All APTES-derived spots exhibited two distinct regions; a silanized core surrounded by an oxidized halo. By decreasing the APTES concentration and increasing the acid concentration, the oxidized halo size decreased by 60%; however, the silanized core diameter remains APTES and acid concentration independent. Bioconjugation can be achieved to all APTES-derived features; however, the highest biomolecule loading was realized by using pure APTES. Together these experiments demonstrate an easy and simple strategy for creating protein microarrays on pSi.