(a) Vapor deposition of APS on the Si substrate. (b) Patterning of the photoresist film by photolithography and then using oxygen plasma to remove the APS from the regions not protected by the photoresist. (c) Functionalization of the surrounding Si substrate by PEG-silane and removal of the photoresist covering amine-terminated patterns. (d) Selective assembly of single-stranded thiolated DNA on APS patterns. (e) Assembly of first layer of DNA-1conjugated Au nanoparticles on APS patterns. (f) Assembly of second layer of nanoparticles on the first nanoparticle layer.
(a) Two layers of gold nanocrystals assembled on silicon surfaces connected via complementary strands of single-stranded DNA, with APS patterns surrounded by a PEG coating. (b) Magnified view of the image of in (a). The inset on the top right corner of shows a zoomed-in view of a satellite structure of two layers of gold nanoparticles. (c) Gold nanoparticles assembled on APS patterns surrounded by bare silicon, with substantial nonspecific adsorption occurring on silicon.
Histogram for quantitative comparison of different chemical patterning techniques. Fabrication process index “1” refers to aminosilane/PEG patterning developed in this research, “2” refers to gold/OTS-based patterning (Ref. 16), and “3” refers to aminosilane/bare silicon patterning.
(a) Assembly of DNA-functionalized gold nanoparticles on APS-patterned, PEG-passivated coated silicon substrates, with unclean native oxide used for the PEG coating process. The bottom half (slightly brighter region) is the PEG-coated surface, where a substantial amount of nonspecific adsorption is observed. (b) Nanoparticle assembly of APS/PEG patterned substrates when the PEG coating is exposed to normal atmospheric conditions for before performing nanoparticle assembly.
Quantitative analysis of nonspecific adsorption on silicon substrates for the fabrication conditions in Fig. 4. Process index “1” is for Fig. 4(a) and index “2” for Fig. 4(b).
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