Do-It-Yourself Pyramidal Mold for Nanotechnology.

The handcrafted fabrication of a pyramidal mold on a silicon wafer for nanopatterning was investigated. This process started with the manual delivery of an aqueous glycerol solution onto the SiO/Si wafer using a micropipette and subsequent drying to form a hemisphere whose diameter is in the range of hundreds of micrometers. A coating of polystyrene (PS) onto this wafer generates a circular hole caused by dewetting.

Programmable Electrochemical Rectifier Based on a Thin-Layer Cell.

A programmable electrochemical rectifier based on thin-layer electrochemistry is described here. Both the rectification ratio and the response time of the device are programmable by controlling the gap distance of the thin-layer electrochemical cell, which is easily controlled using commercially available beads. One of the electrodes was modified using a ferrocene-terminated self-assembled monolayer to offer unidirectional charge transfers via soluble redox species.

H(+)-Assisted fluorescent differentiation of Cu(+) and Cu(2+): effect of Al(3+)-induced acidity on chemical sensing and generation of two novel and independent logic gating pathways.

A novel Schiff base probe exhibited strong 'turn-ON' fluorescence for Cu(2+) at 345 nm, Al(3+) at 445 nm, and Cu(+) at 360 nm in the presence of Al(3+) in organic solvent (acetonitrile), which allowed for construction of molecular logic gates 'INH' and '1:2 DEMULTIPLEXING.' H(+) generated from Al(3+) contributed greatly to Cu(+) chemosensing based on a redox non-innocence mechanism.

A hydrogel pen for electrochemical reaction and its applications for 3D printing.

A hydrogel pen consisting of a microscopic pyramid containing an electrolyte offers a localized electroactive area on the nanometer scale via controlled contact of the apex with a working electrode. The hydrogel pen merges the fine control of atomic force microscopy with non-linear diffusion of an ultramicroelectrode, producing a faradaic current that depends on the small electroactive area. The theoretical and experimental investigations of the mass transport behavior within the hydrogel reveal that the steady-state current from the faradaic reaction is linearly proportional to the deformed length of the hydrogel pen by contact, i.

Subcellular neural probes from single-crystal gold nanowires.

Size reduction of neural electrodes is essential for improving the functionality of neuroprosthetic devices, developing potent therapies for neurological and neurodegenerative diseases, and long-term brain–computer interfaces. Typical neural electrodes are micromanufactured devices with dimensions ranging from tens to hundreds of micrometers. Their further miniaturization is necessary to reduce local tissue damage and chronic immunological reactions of the brain.

Enhanced adhesion of preosteoblasts inside 3D PCL scaffolds by polydopamine coating and mineralization.

In tissue engineering, fabrication of 3D scaffolds with well-defined, inter-connected pores followed by culture of mammalian cells is a typical approach. In practice, however, hydrophobicity of scaffold surfaces is not suitable for cells to be adhered because of poor wettability. Especially, infiltration followed by adhesion of cells inside hydrophobic scaffolds remains as a challenge.

Synthesis of gold coated magnetic microparticles and their application for electrochemical glucose sensing by the enzymatically precipitated prussian blue.

An enzyme stimulated deposition of prussian blue onto the gold-coated magnetic microparticles is described. We propose to synthesize the continuous outer gold layer on the magnetic particle for a gold working electrode and its superparamagnetic property. In-depth characterization of the gold shell formation was studied with scanning electron microscopy, energy-dispersive X-ray spectroscopy, cyclic voltammetry.

Synthetic, 119Sn NMR spectroscopic, electrochemical, and reactivity study of organotin A3 corrolates including chiral and ferrocenyl derivatives.

Various R/Ar-functionalized tin 5,10,15-tris(pentafluorophenyl)corrolate derivatives are reported herein including the first ferrocenyltin corrolate species. The isopropyl, sec-butyl-, 2-methyl-n-butyl-, phenyl-, 2-thienyl-, and ferrocenyltin species have been prepared and characterized through (1)H, (13)C, and (119)Sn HMQC NMR spectroscopy, mass spectrometry, UV-vis and photoluminescent spectroscopy, and cyclic voltammetry studies. J(C/H-Sn) NMR spectroscopic couplings and ring-current effects (upfield shifting) were determined for the R-Sn axial hydrogen and carbon atoms.

Aptamer based electrochemical sensor system for protein using the generation/collection mode of scanning electrochemical microscope (SECM).

To detect the target molecules, aptamers are currently focused on and the use of aptamers for biosensing is particularly interesting, as aptamers could substitute antibodies in bioanalytical sensing. So this paper describes the novel electrochemical system for protein in sandwich manner by using the aptamers and the scanning electrochemical microscope (SECM). For protein detection, sandwich system is ideal since labeling of the target protein is not necessary.

Electrochemical detection of biomolecule with mixed self-assembled monolayers of ferrocene-undecanethiol.

Thiol self-assembled monolayers (SAMs) have been widely used as a modification method to immobilize biomolecules to gold surfaces. However, the additional layers of SAM and biomolecules make electron transfer difficult, leading to a large overpotential in electrical signal. Electron transfer mediation is the most popular solution to overcome the problem of the overpotential for an electrochemical biosensor.

Ordered polymeric microhole array made by selective wetting and applications for electrochemical microelectrode array.

In this paper, we report the microelectrode array fabrication using selective wetting/dewetting of polymers on a chemical pattern which is a simple and convenient method capable of creating negative polymeric replicas using polyethylene glycol (PEG) as a clean and nontoxic sacrificial layer. The fabricated hole-patterned polypropylene film on gold demonstrated enhanced electrochemical properties. The chemical pattern is fabricated by microcontact printing using octadecanethiol (ODT) as an ink on gold substrate.

Nanosieving of anions and cavity-size-dependent association of cyclodextrins on a 1-adamantanethiol self-assembled monolayer.

In this paper, we studied charge transfer through a self-assembled monolayer (SAM) of 1-adamantanethiol on gold. Charge transfer through the 1-adamantanethiol SAM depended on the type of anion present when [Fe(CN)6]3- was used as a redox probe. The sluggish charge transfer process was monitored by cyclic voltammetry using the relatively large and hydrophobic perchlorate and hexafluorophosphate ions as the supporting electrolyte.

Synthetic, cyclic voltammetric, structural, EPR, and UV-Vis spectroscopic studies of thienyl-containing meso-A(2)B-cor(Cr(V)=O) systems: consideration of three interrelated molecular detection modalities.

We report eight new A(2)B-type (M(n+)) corrolate compounds (two structural studies) that include the oxo[5,15-bis(pentafluorophenyl)-10-R-corrolatochromium(V)] [R = 2-/3-thienyl (1a/2a), 3-thianaphthyl (3a)] species. The first examples of meso-A(2) (thienyl)- and Cr-A(2)B-corrole types are represented herein. Characterization includes cyclic voltammetry, electron paramagnetic resonance, 2D ((1)H and (13)C) NMR, and UV-vis spectroscopy, mass spectrometry, and elemental analysis.

An electrochemical immunosensor using p-aminophenol redox cycling by NADH on a self-assembled monolayer and ferrocene-modified Au electrodes.

Redox cycling of enzymatically amplified electroactive species has been widely employed for high signal amplification in electrochemical biosensors. However, gold (Au) electrodes are not generally suitable for redox cycling using a reducing (or oxidizing) agent because of the high background current caused by the redox reaction of the agent at highly electrocatalytic Au electrodes. Here we report a new redox cycling scheme, using nicotinamide adenine dinucleotide (NADH), which can be applied to Au electrodes.

Label-free aptasensor for platelet-derived growth factor (PDGF) protein.

A label-free aptasensor for platelet-derived growth factor (PDGF) protein is reported. The aptasensor uses mixed self-assembled monolayers (SAMs) composed of a thiol-modified PDGF binding aptamer and 6-mercaptohexanol (MCH) on a gold electrode. The SAMs were characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV) before and after binding of the protein using [Fe(CN)(6)](3-/4-), a redox marker ion as an indicator for the formation of a protein-aptamer complex.

Characterization and electrocatalytic properties of Prussian blue electrochemically deposited on nano-Au/PAMAM dendrimer-modified gold electrode.

Gold electrode was modified with 3-mercaptopropionic acid (MPA) and further reacted with poly(amidoamine) (PAMAM) dendrimer (generation 4.0) then attached the nano-Au to obtain films on which Prussian blue (PB) was electrochemically deposited to afford much wider pH adaptive range, much better electrochemical stability and excellent electrochemical response. The microstructure and electrochemical behavior of Au/MPA/PAMAM/nano-Au/PB electrode were investigated by scanning electron microscopy (SEM) and cyclic voltammetry.

Protein micropatterning based on electrochemically switched immobilization of bioligand on electropolymerized film of a dually electroactive monomer.

We demonstrate a protein micropatterning method based on electropolymerization of a monomer with two electroactive units, hydroquinone monoester and disulfide, which enables electrochemical ON-OFF switching for immobilization of bioligands on electrodes modified with the electropolymerized film.

Sieving behaviour of nanoscopic pores by hydrated ions.

In this study, for the first time, the anion dependency of Ag-deposition on self-assembled monolayers (SAMs) with alkyl chains long enough to meet the densely packed and well-organized surface is reported. Irrespective of pH, types of terminal groups of the SAMs, and the convective mass transfer condition, SAM structures show the "sieving behaviour" to the Ag deposition by the composition of the electrolytes.

An electrochemical immunosensor using ferrocenyl-tethered dendrimer.

We report here an enzyme-amplified, sandwich-type immunosensor for detecting the biospecific interaction between an antibody and antigen using redox mediation. We employed biotin/anti-biotin IgG as a model immunosensing pair. Partially ferrocenyl-tethered dendrimer (Fc-D), whose ferrocene moiety acts as a redox mediator, was immobilized to the electrode surface by covalent binding between the dendrimer amines and the carboxylic acids of a self-assembled monolayer.

pH-Dependent rectification in self-assembled monolayers based on electrostatic interactions.

Asymmetric electrostatic interactions dependent on pH between the redox molecules and the terminal group on the top of the self-assembled monolayer (SAM) afford control of the electron transfer property of the SAM having the imidazole terminal group.

Anion exchange-promoted Ru3+/2+ redox switch in self-assembled monolayers of imidazolium ions on a gold electrode.

1,3-Dialkylimidazolium salts, known as one of the ionic liquids, are very attractive molecules because their physicochemical properties can easily be tuned by the variation of the alkyl appendages of the imidazolium cations and counteranions. In this paper we report that the self-assembled monolayers (SAMs) terminating in 1,3-dialkylimidazolium salts with various counteranions [except Fe(CN)6(3-)] on a gold substrate exhibited a selective electron-transfer toward redox-probe molecules: the electron transfer occurred in the presence of Fe(CN)6(3-) (anionic redox-probe molecule) but did not occur in the presence of Ru(NH3)6(3+) (cationic redox-probe molecule). The SAM having Fe(CN)6(3-) as an anion showed the electron-transfer toward Ru(NH3)6(3+), and the Ru3+/2+ redox-switchable SAM was generated by reversible anion exchange between Fe(CN)6(3-) and SCN (or OCN-).

Electrochemically induced and controlled one-step covalent coupling reaction on self-assembled monolayers.

We report on a novel covalent coupling method using electrochemical activation of hydroquinone monoester self-assembled monolayers. The reaction generates benzoquinone as a good leaving group, followed by nucleophilic acyl substitution with a primary amine to form an amide in high yield. The method allows the site-selective and the reaction-controlled positioning of biotin on the individually addressable microelectrode array and, subsequently, density-differentiated patterning of streptavidin on the biotin surfaces.

Electrochemical detection of DNA hybridization using biometallization.

We demonstrate the amplified detection of a target DNA based on the enzymatic deposition of silver. In this method, the target DNA and a biotinylated detection DNA probe hybridize to a capture DNA probe tethered onto a gold electrode. Neutravidin-conjugated alkaline phosphatase binds to the biotin of the detection probe on the electrode surface and converts the nonelectroactive substrate of the enzyme, p-aminophenyl phosphate, into the reducing agent, p-aminophenol.