Flexible Nanoporous Gold Electrodes for Electroanalysis in Complex Matrices

Khan, Robert Ahmed; Yadavalli, Vamsi K.; Collinson, Maryanne M.

doi:10.1002/celc.201900894

Cited by 10 publications

(3 citation statements)

References 53 publications

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“…[1][2][3][4][5][6][7] More recently, however, there has been renewed interest in the use of metallic redox electrodes and the measurement of mixed potentials. [8][9][10][11][12][13][14][15][16][17][18] Unlike membrane-based electrodes, redox processes (electron transfer) are involved and the measurements taken are not necessarily selective toward one specific ion. Of utmost importance is the rate of electron transfer of the different species present in the solution as well as their concentrations among other factors.…”

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confidence: 99%

The Measurement of Mixed Potentials Using Platinum Decorated Nanoporous Gold Electrodes

Islam¹,

Branigan²,

Ullah³

et al. 2022

J. Electrochem. Soc.

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Potentiometric redox sensing in solutions containing multiple redox molecules was evaluated using in-house constructed nanoporous gold (NPG)-platinum (Pt) and unmodified NPG electrodes. The NPG-Pt electrode was fabricated by electrodepositing Pt into the nanoporous framework of a chemically dealloyed NPG electrode. By varying the concentration of the Pt salt and the electrodeposition time, different amounts of Pt were introduced. Characterization by SEM shows the pore morphology doesn’t change with the addition of Pt and XPS indicates the electrodes contain ∼2.5–24 wt% Pt. Open-circuit potential (OCP) measurements in buffer and solutions containing ascorbic acid, cysteine, and/or uric acid show that the OCP shifts positive with the addition of Pt. These results are explained by an increase in the rate of the oxygen reduction reaction with the addition of Pt. The overall shape of the potentiometric titration curves generated from solutions containing one or more bioreagents is also highly dependent on the amount of Pt in the nanoporous electrode. Furthermore, the generation of OCP vs Log [bioreagent] from the results of the potentiometric experiments shows an ∼2-fold increase in sensitivity can result with the addition of Pt. These results indicate the promise that these electrodes have in potentiometric redox sensing.

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confidence: 99%

The Measurement of Mixed Potentials Using Platinum Decorated Nanoporous Gold Electrodes

Islam¹,

Branigan²,

Ullah³

et al. 2022

J. Electrochem. Soc.

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“…In addition, the peak current densities for all samples have a linear relationship with the square root of scan rate (Figure S22d) showcasing that the EOR by mesoporous Au NPs is a diffusion-controlled process. 70,71 In this case, the diffusion efficiency of each catalyst is represented by the slope. As the slope value increases with the decrease of the size of the particle, it suggests that the electron and mass transfer on the mesoporous Au NPs is improved when the size of the particle is smaller.…”

Section: Estimating Reactivity and Accessibility Of Au Pores Via Elec...mentioning

confidence: 95%

Symmetry-Breaking Plasmonic Mesoporous Gold Nanoparticles with Large Pores

et al. 2022

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Creating free-standing gold nanoparticles (Au NPs) with large pores is desirable because the exterior and interior voids can enhance electrocatalytic activity, mass transport, and optical extinction properties. However, the high mobility and significant positive reduction potential of Au precursors make it challenging to create Au NPs with pores of sufficient size to strongly interact with light. We demonstrate a method to synthesize mesoporous Au NPs with large, tunable pores. L-Cysteine acts as a metallogelator to form a dense, less mobile Au(I)−thiolate precursor that traps aggregated block copolymer micelles and facilitates the reduction of mesoporous Au NPs. Electron tomography measurements showed that the pores were distributed throughout the interior and exterior of the particle. Electrochemical methods were used to estimate the chemical reactivity of the surface active sites and estimate the accessible surface area of the pores to ensure that the metal surfaces were maximally accessible to the environment. The 3D models generated by tomography were then used to simulate their optical properties. Mesoporous Au NPs support multipolar plasmon resonances that penetrate deep into the interior pores of the NP. A simple model indicates that porosity affects the local optical conductivity of the NP by subdividing it into tiny nanoscale junctions that redshift the plasmon modes without changing the overall size or shape of the NPs. Large pores promote symmetry breaking, causing the quadrupolar and dipolar modes to overlap and form strongly hybridized plasmon modes. In the context of photocatalysis, porosity-induced symmetry breaking is advantageous because strong electric fields of the plasmon are colocalized along concave/convex features where step-edges and kinks in the atomic structure generate numerous catalytic active sites. Plasmon-enhanced photodegradation of metanil yellow was used to demonstrate the superior photocatalytic properties of meso Au NPs versus nonporous Au NPs.

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“…Nanoporous gold (NPG) electrodes prepared by dealloying gold leaf have proven to be promising materials for electrochemical measurements due to their high surface area and ability to increase electron transfer rates for kinetically sluggish reactions [ 48 , 49 , 50 ]. They have also been shown to be a useful tool to make electrochemical measurements in complex solutions containing known biofouling agents [ 51 , 52 ]. This occurs through a unique biosieving-like mechanism where small redox molecules can enter into the nano-sized pores to exchange electrons while much larger proteins cannot [ 51 ].…”

Section: Introductionmentioning

confidence: 99%

Potentiometric Biosensing of Ascorbic Acid, Uric Acid, and Cysteine in Microliter Volumes Using Miniaturized Nanoporous Gold Electrodes

et al. 2020

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Potentiometric redox sensing is a relatively inexpensive and passive approach to evaluate the overall redox state of complex biological and environmental solutions. The ability to make such measurements in ultra-small volumes using high surface area, nanoporous electrodes is of particular importance as such electrodes can improve the rates of electron transfer and reduce the effects of biofouling on the electrochemical signal. This work focuses on the fabrication of miniaturized nanoporous gold (NPG) electrodes with a high surface area and a small footprint for the potentiometric redox sensing of three biologically relevant redox molecules (ascorbic acid, uric acid, and cysteine) in microliter volumes. The NPG electrodes were inexpensively made by attaching a nanoporous gold leaf prepared by dealloying 12K gold in nitric acid to a modified glass capillary (1.5 mm id) and establishing an electrode connection with copper tape. The surface area of the electrodes was ~1.5 cm2, providing a roughness factor of ~16 relative to the geometric area of 0.09 cm2. Scanning electron microscopy confirmed the nanoporous framework. A linear dependence between the open-circuit potential (OCP) and the logarithm of concentration (e.g., Nernstian-like behavior) was obtained for all three redox molecules in 100 μL buffered solutions. As a first step towards understanding a real system, the response associated with changing the concentration of one redox species in the presence of the other two was examined. These results show that at NPG, the redox potential of a solution containing biologically relevant concentrations of ascorbic acid, uric acid, and cysteine is strongly influenced by ascorbic acid. Such information is important for the measurement of redox potentials in complex biological solutions.

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Flexible Nanoporous Gold Electrodes for Electroanalysis in Complex Matrices

Cited by 10 publications

References 53 publications

The Measurement of Mixed Potentials Using Platinum Decorated Nanoporous Gold Electrodes

The Measurement of Mixed Potentials Using Platinum Decorated Nanoporous Gold Electrodes

Symmetry-Breaking Plasmonic Mesoporous Gold Nanoparticles with Large Pores

Potentiometric Biosensing of Ascorbic Acid, Uric Acid, and Cysteine in Microliter Volumes Using Miniaturized Nanoporous Gold Electrodes

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