Photochemically controlled electrochemical deposition and dissolution of Ag0 nanoclusters on au electrode surfaces.

A photoisomerizable thiolated nitrospiropyran SP, (1a), monolayer is assembled on a Au electrode by the primary deposition of thiolated nitromerocyanine isomer 1b as a monolayer on the electrode, followed by the irradiation of the surface with visible light, lambda > 475 nm. The surface coverage of nitrospiropyran units (1a) on the electrode is 2 x 10-10 mole cm-2. Irradiation of the electrode with UV light, 320 nm < lambda < 360 nm, results in the nitromerocyanine, MR, monolayer on the electrode that binds Ag+ ions to the phenolate units.

Proteins modified with DNAzymes or aptamers act as biosensors or biosensor labels.

Hybrid systems composed of a glucose oxidase (GOx)/peroxidase-mimicking DNAzyme, and of microperoxidase-11 (MP-11)/anti-thrombin aptamer were synthesized. The hybrid systems were employed as amplifying labels for the colorimetric or chemiluminescence detection of an enzyme functions, and thrombin analysis, respectively. In the GOx/DNAzyme system, the GOx-mediated oxidation of glucose led to the formation of H(2)O(2), and this activated the oxidation of ABTS to a colored product, or to the generation of chemiluminescence in the presence of luminol.

Concatenated logic gates using four coupled biocatalysts operating in series.

The assembly of three concatenated enzyme-based logic gates consisting of OR, AND, XOR is described. Four biocatalysts, acetylcholine esterase, choline oxidase, microperoxidase-11, and the NAD+-dependent glucose dehydrogenase, are used to assemble the gates. Four inputs that include acetylcholine, butyrylcholine, O2, and glucose are used to drive the concatenated-gates system.

Electrical contacting of redox proteins by nanotechnological means.

Redox enzymes in bioelectronic devices usually lack direct electrical contact with electrodes, owing to the spatial separation of their redox centers from the conductive surfaces by the protein shells. The reconstitution of apo-enzymes on cofactor-functionalized nanostructures associated with electrodes provides a means to align the biocatalysts on the conductive surface and to electrically contact redox enzymes with electrodes. The reconstitution of apo-enzymes on cofactor-functionalized gold nanoparticles or carbon nanotubes has led to effective electrical communication between the redox proteins and the electrodes.

Cyclic control of the surface properties of a monolayer-functionalized electrode by the electrochemical generation of Hg nanoclusters.

Hg(2+) ions are bound to a 1,4-benzenedimethanethiol (BDMT) monolayer assembled on a Au electrode. Electrochemical reduction of the Hg(2+)-BDMT monolayer to Hg(+)-BDMT (at E degrees =0.48 V) and subsequently to Hg(0)-BDMT (at E degrees =0.

Logic gates and elementary computing by enzymes.

Different selected enzymes, glucose oxidase (GOx), catalase (Cat), glucose dehydrogenase (GDH), horseradish peroxidase (HRP), and formaldehyde dehydrogenase (FDH), are used alone or coupled to construct eight different logic gates. The added substrates for the respective enzymes, glucose and H(2)O(2), act as the gate inputs, while the biocatalytically generated gluconic acid or NADH are the output signals that follow the operation of the gates. Different enzyme-based gates are XOR, INHIBIT A, INHIBIT B, AND, OR, NOR, Identity and Inverter gates.

Biomolecule-nanoparticle hybrid systems for bioelectronic applications.

Recent advances in nanobiotechnology involve the use of biomolecule-nanoparticle (NP) hybrid systems for bioelectronic applications. This is exemplified by the electrical contacting of redox enzymes by means of Au-NPs. The enzymes, glucose oxidase, GOx, and glucose dehydrogenase, GDH, are electrically contacted with the electrodes by the reconstitution of the corresponding apo-proteins on flavin adenine dinucleotide (FAD) or pyrroloquinoline quinone (PQQ)-functionalized Au-NPs (1.

An electrochemical/photochemical information processing system using a monolayer-functionalized electrode.

An electroactive and photoisomerizable monolayer associated with a Au electrode acts as a Write-Read-Erase information processing system and as a flip-flop Set/Reset memory element.

Controlling the direction of photocurrents by means of CdS nanoparticles and cytochrome c-mediated biocatalytic cascades.

Cathodic or anodic photocurrents are generated by a monolayer of CdS nanoparticles in the presence of the oxidized or reduced states of cytochrome c, respectively, and the photocurrents are amplified by enzyme-generated biocatalytic cascades mediated by cytochrome c.

Two coupled enzymes perform in parallel the 'AND' and 'InhibAND' logic gate operations.

The coupled activation of two enzymes: glucose dehydrogenase (GDH) and horseradish peroxidase (HRP), is used to construct the parallel-operating AND and InhibAND logic gates. The added substrates for the respective enzymes, glucose and H(2)O(2), act as the gate inputs, while the biocatalytically generated NADH and gluconic acid provide the output signals that follow the operations of the gates. The two gates are generated in the same vial, thus allowing the logic operations to take place in parallel, and the simultaneous readout of the functions of the gates.

Magneto-switchable single-electron charging of Au-nanoparticles using hydrophobic magnetic nanoparticles.

Reversible magneto-switchable quantum charging of a Au nanoparticle array associated with a Au electrode is observed in the presence of hydrophobic magnetic nanoparticles attracted to the functionalized electrode surface.

Controlling chemical reactivity at solid-solution interfaces by means of hydrophobic magnetic nanoparticles.

Hydrophobic magnetic nanoparticles are employed to reversibly regulate the hydrophobic/hydrophilic properties of surfaces and to control the electrochemistry and bioelectochemistry at chemically modified electrodes. Selective bioelectrocatalytic transformations at relay-functionalized electrodes are accomplished by the magnetic attractions of the hydrophobic magnetic nanoparticles with coadsorbed hydrophobic redox relays to the electrode. The selective activation of one of two biocatalysts solubilized in the aqueous electrolyte solution in the absence or presence of hydrophobic magnetic nanoparticles results in the specific activation of bioelectrocatalytic processes.

Switchable surface properties through the electrochemical or biocatalytic generation of Ag0 nanoclusters on monolayer-functionalized electrodes.

The electroswitchable and the biocatalytic/electrochemical switchable interfacial properties of a Ag(+)-biphenyldithiol (BPDT) monolayer associated with a Au surface are described. Upon the application of a potential corresponding to -0.2 V the Ag(+)-BPDT is reduced to the Ag(0)-BPDT interface, and silver nanoclusters are generated on the interface.

A quinone-functionalized electrode in conjunction with hydrophobic magnetic nanoparticles acts as a "Write-Read-Erase" information storage system.

Integration of hydrophobic magnetic nanoparticles with a quinone-functionalized Au electrode in a water-toluene two-phase assembly yields a "Write-Read-Erase" information processing system.

Temperature-dependent and friction-controlled electrochemically induced shuttling along molecular strings associated with electrodes.

The temperature and solvent composition dependence of the electrochemically stimulated rate of shuttling of the redox-active cyclophane, cyclobis(paraquat-p-phenylene), on a molecular string has been studied. The molecular string includes a pi-donor diiminebenzene-site that is associated on one side with an electrode, and stoppered on the other side with an adamantane unit. The cyclophane rests on the pi-donor site, owing to stabilizing pi-donor-acceptor interactions.

Reconstitution of apo-glucose dehydrogenase on pyrroloquinoline quinone-functionalized au nanoparticles yields an electrically contacted biocatalyst.

An electrically contacted glucose dehydrogenase (GDH) enzyme electrode is fabricated by the reconstitution of the apo-GDH on pyrroloquinoline quinone (PQQ)-functionalized Au nanoparticles (Au-NPs), 1.4 nm, associated with a Au electrode. The Au-NPs functionalized with a single amine group were attached to the Au surface by 1,4-benzenedithiol bridges, and PQQ was covalently linked to the Au-NPs.

Hydrophobic magnetic nanoparticles induce selective bioelectrocatalysis.

Hydrophobic magnetic nanoparticles were used to sense selectively lactate and glucose at the same applied potential.

Magnetoswitchable reactions of DNA monolayers on electrodes: gating the processes by hydrophobic magnetic nanoparticles.

Biorecognition and biocatalytic reactions of DNA monolayers, such as hybridization, polymerization, and hydrolytic digestion, were followed in situ by chronocoulometry and Faradaic impedance spectroscopy. Hydrophobic magnetic nanoparticles attracted to, and retracted from, the electrode surface by an external magnetic field were used to activate and inhibit the DNA-monolayer reactions, respectively. The attraction of the magnetic nanoparticles to the electrode surface generated a hydrophobic thin film on the surface that is not permeable for the water-soluble components required for the DNA-monolayer reactions.

Magnetoswitchable electrochemistry gated by alkyl-chain-functionalized magnetic nanoparticles: control of diffusional and surface-confined electrochemical processes.

Magnetic nanoparticles consisting of undecanoate-capped magnetite (average diameter ca. 5 nm) are used to selectively gate diffusional and surface-confined electrochemical reactions. A two-phase system consisting of an aqueous buffer solution and a toluene phase that includes the suspended undecanoate-capped magnetic nanoparticles is used to control the interfacial properties of the electrode surface.

Magnetic field effects on bioelectrocatalytic reactions of surface-confined enzyme systems: enhanced performance of biofuel cells.

The effect of a constant magnetic field on bioelectrocatalytic transformations of three different enzyme assemblies linked to electrodes is examined and correlated with a theoretical magnetohydrodynamic model. The systems consist of surface-reconstituted glucose oxidase (GOx), an integrated lactate dehydrogenase/nicotinamide/pyrroloquinoline quinone assembly (LDH/NAD+ -PQQ), and a cytochrome c/cytochrome oxidase system (Cyt c/COx) linked to the electrodes. Pronounced effects of a constant magnetic field applied parallel to the electrode surface are observed for the bioelectrocatalyzed oxidation of glucose and lactate by the GOx-electrode and LDH/NAD+ -PQQ-electrode, respectively.