Formation of Molecular Gradients on Bipolar Electrodes

Ulrich, Christian; Andersson, Olof; Nyholm, Leif; Björefors, Fredrik

doi:10.1002/anie.200705824

Cited by 124 publications

(89 citation statements)

References 23 publications

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“…We attribute the disappearance of SERS peaks to the electrochemical removal of the molecules. It is known for thiol-functionalized molecules that the electrochemical desorption occurs at around −0.7 V, [20,31] which fits with our equivalent local potential generated by bipolar electrochemistry. Second, negatively charged dAMP can be repelled by a negative bias from the surface, resulting in an undetectable level of dAMP in the observed SERS spectra.…”

Section: Doi: 101002/adom201600907supporting

confidence: 86%

“…Such investigation techniques include electrochemiluminescence, [17] electrochemical corrosion microscopy, [18] epifluoresence, [19] and surface plasmon resonance spectroscopy, [20] which are ultimately restricted by the diffraction of light. Here, working toward subwavelength detection, we propose the use of SERS to study the local potentials.…”

Section: Communicationmentioning

confidence: 99%

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Probing Local Potentials inside Metallic Nanopores with SERS and Bipolar Electrochemistry

Chang

Willems

et al. 2017

Advanced Optical Materials

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CommuniCation(1 of 6) 1600907 considerable attention. In addition to being used as electrodes, optical nanostructures for extraordinary light transmission, [8] fluorescence, [9] and surface-enhanced Raman spectroscopy (SERS) [10] have demonstrated additional detection and/or control capabilities. For these optical techniques, metal layers are usually unbiased, so-called floating electrode mode, whereas applying a bias voltage may induce a potential drop over the floating metallic nanopore because of its high resistance. In the field of macroscale fluidics, a sufficient DC voltage difference between the floating metal layer and the solution enables the activation of oxidation and reduction reactions. [11,12] However, on the nanoscale, the study on the local potential and electrochemical effects on floating metallic nanopores remains challenging.Local potential and related electrochemistry on floating metal electrodes has been termed "bipolar electrochemistry" [12,13] In an unbiased state, bipolar electrochemistry requires either highly confined electric fields or extremely high concentration-gradients adjacent to bipolar electrodes [14][15][16] to drive reactions and investigate optical properties. Such investigation techniques include electrochemiluminescence, [17] electrochemical corrosion microscopy, [18] epifluoresence, [19] and surface plasmon resonance spectroscopy, [20] which are ultimately restricted by the diffraction of light. Here, working toward subwavelength detection, we propose the use of SERS to study the local potentials. [21][22][23][24][25] To simultaneously align localized SERS hot spots with fluidic focus for high spatial resolution and high specificity, [26] our technique probes the local potential and characterizes nanoscale bipolar electrochemical effects on metallic nanopores for the first time. Figure 1a depicts a schematic of the experiments on the metallic nanopores. The nanopore chip was mounted into a custom-made flow cell, separating the electrolyte into two reservoirs. Next, a 785 nm laser was tightly focused at the nanopore cavity. The electrical potential was applied to the top side of the membrane as shown in Figure 1a, and the other side was connected to ground. This defines the applied bias direction for positive and negative values in the experiments. A doublesided gold (MM) nanopore is used for the demonstration of bipolar electrochemical SERS. To maximize the plasmonic enhancement effect and subsequent SERS signals at 785 nm, It is essential to understand the local potential distribution of solid-state nanopores in nanofluidic systems. However, applying gate voltage or adding external electrical probes tends to disturb the electric field and/or flow patterns. To solve this problem, an approach is described to monitor the local potential using electrochemical surface enhanced Raman spectroscopy (EC-SERS) in two types of nanocavity pores: doubled-sided gold nanopores (MM nanopores) and single-sided gold nanopores with a dielectric passivation layer on the backside (MD nanopor...

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Section: Doi: 101002/adom201600907supporting

confidence: 86%

Section: Communicationmentioning

confidence: 99%

Probing Local Potentials inside Metallic Nanopores with SERS and Bipolar Electrochemistry

Chang

Willems

et al. 2017

Advanced Optical Materials

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“…Bipolar electrochemistry, [26][27][28][29][30] is a relatively new research topic which nevertheless has attracted significant attention as a means of fabricating molecular gradients on surface, [31] redox gradients within conducting polymer layer, [32] template-less metal-organic frameworks, [33] and, very recently, anodic TiO 2 nanotube arrays containing size gradients [25]. The present free-standing TiO 2 nanotube electrodes, which are employed as monolithic electrodes in Li-ion batteries, contain extended (i.e.…”

Section: Introductionmentioning

confidence: 99%

Hybrid Energy Storage Devices Based on Monolithic Electrodes Containing Well-defined TiO2 Nanotube Size Gradients

Wei

Björefors

Nyholm

2015

Electrochimica Acta

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“…16 Although bipolar electrochemistry can be conceived as a straightforward fabrication technique of various potential induced surface gradients, only a few papers describe its use for this purpose. Björefors et al used bipolar electrochemistry-triggered desorption of self-assembled monolayers for the formation of molecular gradients on gold, 17 Shannon et al reported the bipolar electrodeposition for the fabrication of Au-Ag and CdS solid-state gradients, 18 and Inagi and Fuchigami used bipolar doping to fabricate gradually-doped conducting polymers. 19 In the present paper, we combine for the first time anodization and bipolar electrochemistry in order to fabricate in a few minutes and in a wireless manner self-assembled TiO 2 NT surfaces, which are comprised of NT gradients with tunable length and diameter and we show how these gradients can be used for the rapid screening of the TiO 2 NT properties.…”

Section: Introductionmentioning

confidence: 99%

Bipolar anodization enables the fabrication of controlled arrays of TiO₂ nanotube gradients

Loget

Hahn

et al. 2014

J. Mater. Chem. A

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We report here a new concept, the use of bipolar electrochemistry, which allows the rapid and wireless growth of self-assembled TiO 2 NT layers that consist of highly defined and controllable gradients in NT length and diameter. The gradient height and slope can be easily tailored with the time of electrolysis and the applied electric field, respectively. As this technique allows obtaining in one run a wide range of self-ordered TiO 2 NT dimensions, it provides the basis for rapid screening of TiO 2 NT properties. In two examples, we show how these gradient arrays can be used to screen for an optimized photocurrent response from TiO 2 NT based devices such as dye-sensitized solar cells.

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Formation of Molecular Gradients on Bipolar Electrodes

Cited by 124 publications

References 23 publications

Probing Local Potentials inside Metallic Nanopores with SERS and Bipolar Electrochemistry

Probing Local Potentials inside Metallic Nanopores with SERS and Bipolar Electrochemistry

Hybrid Energy Storage Devices Based on Monolithic Electrodes Containing Well-defined TiO2 Nanotube Size Gradients

Bipolar anodization enables the fabrication of controlled arrays of TiO₂ nanotube gradients

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Formation of Molecular Gradients on Bipolar Electrodes

Cited by 124 publications

References 23 publications

Probing Local Potentials inside Metallic Nanopores with SERS and Bipolar Electrochemistry

Probing Local Potentials inside Metallic Nanopores with SERS and Bipolar Electrochemistry

Hybrid Energy Storage Devices Based on Monolithic Electrodes Containing Well-defined TiO2 Nanotube Size Gradients

Bipolar anodization enables the fabrication of controlled arrays of TiO2 nanotube gradients

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Product

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Bipolar anodization enables the fabrication of controlled arrays of TiO₂ nanotube gradients