This paper reports the characteristics of folding‐based electrochemical DNA sensors fabricated on recessed nanodisk‐array electrodes (RNEs). The RNEs were based on gold substrates coated with polystyrene‐block‐poly(methylmethacrylate)‐derived thin films (30 nm thick) comprising vertically‐oriented cylindrical nanopores (14, 20 or 30 nm in diameter). RNE‐based sensors were fabricated by modifying the underlying gold surface with a stem‐loop DNA probe with a terminal methylene blue (MB) tag. The electrochemical responses of such RNE‐based sensors to complementary single‐stranded 17‐mer DNA were compared with those of film‐free counterparts using cyclic voltammetry. RNE‐based sensors exhibited signal suppression at a significantly lower target DNA concentration than film‐free sensors, possibly due to the manipulated dynamic properties of the MB tag as suggested by its apparent electron transfer rate constant and/or enhanced hybridization within the nanopores. These results indicate that RNEs provide unique platforms for developing folding‐based electrochemical sensors with improved sensitivity.

This paper reports the applicability of a dimethyl sulfoxide (DMSO) solution of stannous acetate (Sn(OAc) 2 /DMSO) for sensitization in electroless deposition (ELD). Silver ELD was examined on nanostructured surfaces derived from polystyrene-blockpoly(methylmethacrylate) via sensitization with an aqueous or DMSO solution of Sn(OAc) 2 or SnCl 2 , activation with aqueous Ag[(NH 3 ) 2 ] + , followed by immersion in an aqueous solution containing [Ag(NH 3 ) 2 ] + and tartrate. Sensitization with 0.5 mM Sn(OAc) 2 /DMSO led to the preferential deposition of silver nanoparticles (Ag-NPs) on the nanoscale ridges of the polymer film upon 10-minute ELD. In contrast, Ag-NPs were negligibly deposited on the polymer film sensitized with 0.5 mM SnCl 2 /DMSO. Conventional sensitization solutions based on aqueous SnCl 2 (SnCl 2 /H 2 O) required a much higher Sn(II) concentration (≥5 mM) for sensitization of the polymer surface. X-ray photoelectron spectroscopy results supported the stoichiometric formation of Ag 0 from Sn(II) in the activation step on the polymer surface sensitized with Sn(OAc) 2 /DMSO as with 50 mM SnCl 2 /H 2 O. Sn(OAc) 2 /DMSObased sensitization was inefficient on thiolate self-assembled monolayers. The efficient sensitization of the polymer surface with Sn(OAc) 2 /DMSO was explained by the reduction of hydroxide formation by the use of the organic solution and efficient partitioning of Sn(OAc) 2 into the solvent-swollen surface region of the polymer film.