We electrostatically placed a single ferritin molecule on a nanometric 3-aminopropyltriethoxysilane (APTES) pattern that was on an oxidized Si substrate. The numerical analysis of the total interaction free energy for ferritin predicted that a quadrilateral array of 15nm diameter APTES nanodisks placed at intervals of 100nm would accommodate a single molecule of ferritin in each disk under a Debye length of 14nm. The experiments we conducted conformed to theoretical predictions and we successfully placed a single ferritin molecule on each ATPES disk without ferritin adsorbing on the SiO2 substrate surface.
High-density cage-shaped proteins with inorganic cores were selectively adsorbed as a monolayer onto a 3-aminopropyltriethoxysilane (APTES) layer on a Si substrate. The electrostatic interaction between the protein and substrate surface was studied and it was proven that protein adsorption density depends on the quantitative balance of surface charge on the substrate and protein. The combination of a highly positive APTES layer and moderately negative ferritin, Fer-4, achieved an adsorption density of 7:6 Â 10 11 cm À2 and the combination of the APTES layer and Listeria ferritin (Lis-fer) reached an adsorption density of 1:3 Â 10 12 cm À2 . The adsorption process including the reduced charge of Lis-fer due to denaturation further enhanced the adsorption density up to 1:5 Â 10 12 cm À2 , whereas no Lis-fer was adsorbed onto the SiO 2 surface under the same conditions. This new technique makes it possible to produce a nanodot monolayer with a density higher than 1 Â 10 12 cm À2 , which can be applied to floating nanodot gate memories.
A monolayer of inorganic nanoparticles (NPs) was fabricated on a silicon wafer using a cage-shaped protein, ferritin, which can sequester several kinds of inorganic NP in their cavities. Ferritins were bound electrostatically in aqueous condition to the silicon wafer which was modified with aminosilane molecules. The obtained sample was heat-treated at 500°C under oxygen gas, and the protein moiety and aminosilane were completely eliminated. The obtained NP monolayer showed no aggregation or sintering. This new method can be used to produce a dispersed inorganic NP monolayer on a silicon substrate as designed, which could be used as a nanodot array in floating nanodot gate memories.
An array of high-density 1.8×1012 cm-2 floating nanodots was embedded within a metal–oxide–semiconductor (MOS) capacitor using a cage-shaped protein supramolecule, Listeria ferritin (Lis-fer). A monolayer of Lis-fer with a 4.5 nm ferrihydrite core was adsorbed on a 3 nm tunneling SiO2 layer on a p-Si substrate by 3-aminopropyl-triethoxysilane (APTES) surface modification. The outer protein was selectively removed and the obtained cores were covered with a 20-nm-thick control SiO2 layer and an aluminum electrode. The MOS capacitor was annealed in reducing gas (H2:N2=10:90%), and the embedded cores were reduced to conductive nanodots. The capacitance–voltage characteristics of the MOS capacitor measured at 1 MHz by applying a DC bias voltage from -5 to +5 V showed a clear hysteresis. This result indicates that the array of nanodots produced and positioned by Lis-fer has the ability for electron confinement.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.