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Reactivity mapping with electrochemical gradients for monitoring reactivity at surfaces in space and time.

Krabbenborg SO, Nicosia C, Chen P, Huskens J - Nat Commun (2013)

Bottom Line: Because reaction kinetics is different at surfaces compared with solution, frequently, solution-characterization techniques cannot be used.For both systems, the kinetic data were spatially visualized in a two-dimensional reactivity map.In the case of the copper(I)-catalysed azide-alkyne 1,3-dipolar cycloaddition, the reaction order (2) was deduced from it.

View Article: PubMed Central - PubMed

Affiliation: Molecular Nanofabrication Group, MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, Enschede 7500 AE, The Netherlands.

ABSTRACT
Studying and controlling reactions at surfaces is of great fundamental and applied interest in, among others, biology, electronics and catalysis. Because reaction kinetics is different at surfaces compared with solution, frequently, solution-characterization techniques cannot be used. Here we report solution gradients, prepared by electrochemical means, for controlling and monitoring reactivity at surfaces in space and time. As a proof of principle, electrochemically derived gradients of a reaction parameter (pH) and of a catalyst (Cu(I)) have been employed to make surface gradients on the micron scale and to study the kinetics of the (surface-confined) imine hydrolysis and the copper(I)-catalysed azide-alkyne 1,3-dipolar cycloaddition, respectively. For both systems, the kinetic data were spatially visualized in a two-dimensional reactivity map. In the case of the copper(I)-catalysed azide-alkyne 1,3-dipolar cycloaddition, the reaction order (2) was deduced from it.

No MeSH data available.


Micron-scale surface imine gradient formation by a solution pH gradient.(a) Schematic representation of the electrochemical generation, via the electrolysis of water between interdigitated electrodes, of a solution pH gradient, which is transferred to a surface gradient by means of acid-catalysed imine hydrolysis resulting in a gradient of a surface-bound rhodamine dye. (b) Fluorescence microscopy images showing an overview (centre) and zoom-ins of (top) the generated, surface-bound, imine gradient at the anode (low pH) and of (bottom) an unchanged boundary at the cathode (high pH) after applying the pH gradient for 240 min, 1.6 V, 1 mM, pH 7.1, phosphate buffer and 100 mM Na2SO4 (50 μm electrodes, 100 μm gap). Scale bar, 50 μm; 3 μm (zoom-in). (c) Fluorescence intensity profiles visualizing the rhodamine dye gradients directly after hydrolysis close to the anode at different reaction times (raw data).
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f2: Micron-scale surface imine gradient formation by a solution pH gradient.(a) Schematic representation of the electrochemical generation, via the electrolysis of water between interdigitated electrodes, of a solution pH gradient, which is transferred to a surface gradient by means of acid-catalysed imine hydrolysis resulting in a gradient of a surface-bound rhodamine dye. (b) Fluorescence microscopy images showing an overview (centre) and zoom-ins of (top) the generated, surface-bound, imine gradient at the anode (low pH) and of (bottom) an unchanged boundary at the cathode (high pH) after applying the pH gradient for 240 min, 1.6 V, 1 mM, pH 7.1, phosphate buffer and 100 mM Na2SO4 (50 μm electrodes, 100 μm gap). Scale bar, 50 μm; 3 μm (zoom-in). (c) Fluorescence intensity profiles visualizing the rhodamine dye gradients directly after hydrolysis close to the anode at different reaction times (raw data).

Mentions: Figure 2a shows the schematic representation of the imine hydrolysis in an electrochemically produced pH gradient in solution. An amine-functionalized rhodamine dye is immobilized by imine bond formation onto an aldehyde monolayer29 at a glass surface in between the electrodes of an interdigitated microelectrode array. On top of the full monolayer of the rhodamine dye, a pH gradient is applied3031. The pH gradient is generated via the electrolysis of water, thus generating H+ and OH− at the anode and cathode, respectively. A phosphate buffer was used to stabilize the pH gradient30.


Reactivity mapping with electrochemical gradients for monitoring reactivity at surfaces in space and time.

Krabbenborg SO, Nicosia C, Chen P, Huskens J - Nat Commun (2013)

Micron-scale surface imine gradient formation by a solution pH gradient.(a) Schematic representation of the electrochemical generation, via the electrolysis of water between interdigitated electrodes, of a solution pH gradient, which is transferred to a surface gradient by means of acid-catalysed imine hydrolysis resulting in a gradient of a surface-bound rhodamine dye. (b) Fluorescence microscopy images showing an overview (centre) and zoom-ins of (top) the generated, surface-bound, imine gradient at the anode (low pH) and of (bottom) an unchanged boundary at the cathode (high pH) after applying the pH gradient for 240 min, 1.6 V, 1 mM, pH 7.1, phosphate buffer and 100 mM Na2SO4 (50 μm electrodes, 100 μm gap). Scale bar, 50 μm; 3 μm (zoom-in). (c) Fluorescence intensity profiles visualizing the rhodamine dye gradients directly after hydrolysis close to the anode at different reaction times (raw data).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3644076&req=5

f2: Micron-scale surface imine gradient formation by a solution pH gradient.(a) Schematic representation of the electrochemical generation, via the electrolysis of water between interdigitated electrodes, of a solution pH gradient, which is transferred to a surface gradient by means of acid-catalysed imine hydrolysis resulting in a gradient of a surface-bound rhodamine dye. (b) Fluorescence microscopy images showing an overview (centre) and zoom-ins of (top) the generated, surface-bound, imine gradient at the anode (low pH) and of (bottom) an unchanged boundary at the cathode (high pH) after applying the pH gradient for 240 min, 1.6 V, 1 mM, pH 7.1, phosphate buffer and 100 mM Na2SO4 (50 μm electrodes, 100 μm gap). Scale bar, 50 μm; 3 μm (zoom-in). (c) Fluorescence intensity profiles visualizing the rhodamine dye gradients directly after hydrolysis close to the anode at different reaction times (raw data).
Mentions: Figure 2a shows the schematic representation of the imine hydrolysis in an electrochemically produced pH gradient in solution. An amine-functionalized rhodamine dye is immobilized by imine bond formation onto an aldehyde monolayer29 at a glass surface in between the electrodes of an interdigitated microelectrode array. On top of the full monolayer of the rhodamine dye, a pH gradient is applied3031. The pH gradient is generated via the electrolysis of water, thus generating H+ and OH− at the anode and cathode, respectively. A phosphate buffer was used to stabilize the pH gradient30.

Bottom Line: Because reaction kinetics is different at surfaces compared with solution, frequently, solution-characterization techniques cannot be used.For both systems, the kinetic data were spatially visualized in a two-dimensional reactivity map.In the case of the copper(I)-catalysed azide-alkyne 1,3-dipolar cycloaddition, the reaction order (2) was deduced from it.

View Article: PubMed Central - PubMed

Affiliation: Molecular Nanofabrication Group, MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, Enschede 7500 AE, The Netherlands.

ABSTRACT
Studying and controlling reactions at surfaces is of great fundamental and applied interest in, among others, biology, electronics and catalysis. Because reaction kinetics is different at surfaces compared with solution, frequently, solution-characterization techniques cannot be used. Here we report solution gradients, prepared by electrochemical means, for controlling and monitoring reactivity at surfaces in space and time. As a proof of principle, electrochemically derived gradients of a reaction parameter (pH) and of a catalyst (Cu(I)) have been employed to make surface gradients on the micron scale and to study the kinetics of the (surface-confined) imine hydrolysis and the copper(I)-catalysed azide-alkyne 1,3-dipolar cycloaddition, respectively. For both systems, the kinetic data were spatially visualized in a two-dimensional reactivity map. In the case of the copper(I)-catalysed azide-alkyne 1,3-dipolar cycloaddition, the reaction order (2) was deduced from it.

No MeSH data available.