92 research outputs found
Untersuchung von Wechselwirkungen zwischen mikrostrukturierten Enzymen mittels elektrochemischer Rastermikroskopie (SECM)
Wechselwirkungen zwischen lateral mikrostrukturierten Enzymen sind fĂŒr die Entwicklung von Biosensoren von Bedeutung. Die elektrochemische Rastermikroskopie (SECM) eignet sich sowohl zur Strukturierung als auch zur lokalen ReaktivitĂ€tscharakterisierung von OberflĂ€chen:
Mittels lokaler elektrochemischer Desorption im Direktmodus des SECM können Strukturen in vorhandene selbstorganisierte Alkanthiolatmonolagen (SAM) auf Gold geschrieben werden. Diese Monolagen können sowohl flĂ€chig abgeschieden als auch durch Microcontactprinting (”CP) strukturiert aufgebracht sein. In diesen freigelegten Strukturen lĂ€Ăt sich ein z.B. mit S-AcetylthioessigsĂ€ure-N-hydroxysuccinimidylester (SATA) SH-funktionalisierte Enzyme kovalent immobilisieren.
Verbunden mit der Möglichkeit, eine GoldoberflĂ€che mittels ”CP groĂflĂ€chig zu mikrostrukturieren und anschliessend an die verbleibenden freien GoldflĂ€chen ĂŒber ein aminofunktionalisiertes Thiol ein Enzym (z.B. Meerrettich Peroxidase, HRP) kovalent zu koppeln, ergibt sich ein einfacher Weg zu lateral mikrostrukturierten Anordnungen von Enzymen. In den vorgestellten Experimenten wurden die Enzyme Glucoseoxidase (GOD) und Meerettich Peroxidase (HRP) verwendet.
Zur Untersuchung der enzymatischen AktivitĂ€t eignet sich besonders der Generator-Kollektor-Modus des SECM. Je nach Wahl der experimentellen Parameter kann die AktivitĂ€t eines einzelnen Enzyms in der Mikrostruktur bzw. die AktivitĂ€t von HRP in AbhĂ€ngigkeit der der GOD sichtbar gemacht werden. Solche Anordnungen sind geeignet zur UnterdrĂŒckung von Interferenzen in miniaturisierten Multienzym-Mikrostrukturen
Controlling the supramolecular assembly of redox active dendrimers at molecular printboards by scanning electrochemical microscopy
Redox-active ferrocenyl (Fc)-functionalized poly(propylenimine) (PPI) dendrimers solubilized in aqueous media by complexation of the Fc end groups with ÎČ-cyclodextrin (ÎČCD) were immobilized at monolayers of ÎČCD on glass (âmolecular printboardsâ) via multiple hostâguest interactions. The directed immobilization of the third-generation dendrimerâÎČCD assembly G3-PPIâ(Fc)16â(ÎČCD)16 at the printboard was achieved by supramolecular microcontact printing. The redox activity of the patterned dendrimers was mapped by scanning electrochemical microscopy (SECM) in the positive feedback mode using [IrCl6]3- as a mediator. Local oxidation of the Fcâdendrimers by the microelectrode-generated [IrCl6]2- resulted in an effective removal of the Fcâdendrimers from the host surface since the oxidation of Fc to the oxidized form (Fc+) leads to a concomitant loss of affinity for ÎČCD. Thus, SECM provided a way not only to image the surface, but also to control the binding of the Fc-terminated dendrimers at the molecular printboard. Additionally, the electrochemical desorption process could be monitored in time as the dendrimer patterns were gradually erased upon multiple scan
Highly stable, reactive and ultrapure nanoporous metallic films
Nanoporous metals possess unique properties attributed to their high surface
area and interconnected nanoscale ligaments. They are mostly fabricated by wet
synthetic methods involving solution-based dealloying processes whose purity is
compromised by residual amounts of the less noble metal. Here, we demonstrate a
novel dry synthesis method to produce nanoporous metals, which is based on the
plasma treatment of metal nanoparticles formed by physical vapor deposition.
Our approach is general and can be applied to many metals including non-noble
ones. The resultant nanoporous metallic films are impurity-free and possess
highly curved ligaments and nanopores. The metal films are remarkably robust
with many catalytically active sites, which is highly promising for
electrocatalytic applications.Comment: 40 pages (including 13 pages of supplementary information), 5
figures, submitte
Soft Microelectrode Linear Array for Scanning Electrochemical Microscopy
A linear array of eight individual addressable microelectrodes has been developed in order to perform highthroughput scanning electrochemical microscopy (SECM) imaging of large sample areas in contact regime. Similar to previous reports, the soft microelectrode array was fabricated by ablating microchannels on a polyethylene terephthalate (PET) film and filling them with carbon ink. Improvements have been achieved by using a 5 ÎŒm thick Parylene coating that allows for smaller working distances, as the probe was mounted with the Parylene coating facing the sample surface. Additionally, the application of a SECM holder allows scanning in contact regime with a tilted probe, reducing the topographic effects and assuring the probe bending direction. The main advantage of the soft microelectrode array is the considerable decrease in the experimental time needed for imaging large sample areas. Additionally, soft microelectrode arrays are very stable and can be used several times, since the electrode surface can be regenerated by blade cutting. Cyclic voltammograms and approach curves were recorded in order to assess the electrochemical properties of the device. An SECM image of a gold on glass chip was obtained with high resolution and sensitivity, proving the feasibility of soft microelectrode arrays to detect localized surface activity. Finite element method (FEM) simulations were performed in order to establish the effect of diffusion layer overlapping between neighboring electrodes on the respective approach curves
Seeing Big with Scanning Electrochemical Microscopy
Specialized microelectrode probes fabricated in a soft polymer film now make it possible to use scanning electrochemical microscopy to image the reactivity of large, corrugated, tilted, and dry surfaces
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