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(Color online) Schematic of selective adsorption of TBF via Ti-aptamer to a Ti pattern on a SiO2 layer. According to the literature,13 positively charged arginine and negatively charged aspartic acid residues are supposed to bond with -O− and -OH2 + sites on a Ti surface, respectively. The inserted SEM image shows the selectively positioned Fe2O3 NPs at the Ti pattern on a SiO2 substrate using TBFs.
SEM images of Fe2O3 NPs on Ti-decorated SiO2 surfaces at Ti coverages (Θ) of (a) 0.03, (b) 0.05, (c) 0.08, and (d) 1.00 (i.e., 3-nm-thick Ti film). SEM observation was carried out after removing outer TBF proteins by UV/O3 treatment. White dots represent the individual Fe2O3 cores, which correspond to TBF adsorption sites.
(Color online) Changes in (a) average adsorption density of Fe2O3 NPs and (b) zeta potential of Ti-decorated SiO2 surfaces under 50 mM Tris-HCl buffer solution adjusted to pH 8.0 as a function of the surface Ti coverage (Θ). The zeta potential reveals the average electric potential of the Ti-decorated SiO2 surface. An increased Ti coverage led to the positive shift of the zeta potential, indicating the generation of positively charged sites arising from oxidized Ti atoms.
(Color online) Absorption behavior of TBFs including Fe2O3 NPs on various SiO2 surfaces. SEM images of Fe2O3 NPs on (a) the reference thermal oxide, (b) sputter-deposited SiO2, (c) after annealing at 350 °C for 10 min, and (d) subsequent UV/O3 treatment at 110 °C for 20 min after the anneal treatment. (e) Summary of adsorption density of Fe2O3 NPs and the measured zeta potential of the SiO2 surfaces under 50 mM Tris buffer at pH 8.0.
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