Electrochemistry of a Single Attoliter Emulsion Droplet in Collisions

Kim, Byung Kwon; Kim, Jiyeon; Bard, Allen J.

doi:10.1021/ja512065n

Cited by 127 publications

(177 citation statements)

References 25 publications

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“…Molecular structure of (A) 5,10,15,20-tetraphenyl-21H,23H-porphine zinc (ZnTPP), (B) ferrocene (Fc), (C) decamethyl ferrocene (DMFc), and (D) 5,10,15,20-tetraphenyl-21H,23H-porphine copper(II) (CuTPP).electrolysis of the redox molecule in a single emulsion droplet demonstrated similar behavior to the bulk electrolysis in which the current decayed exponentially with time 15,16. The model assumes that the droplet attaches itself to the colliding surface upon collision, opening up and exposing its contents to a small disk electrode for electrolysis.…”

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confidence: 96%

“…The electrochemical study of single-collision events has been applied to a wide range of hard nanoparticles (NPs), including metals (Pt, Ag, Au, Cu, Ni), 2−7 metal oxides (IrO 2 , TiO 2 , CeO 2 , SiO 2 ), 8−11 and organic NPs (indigo, polystyrene, and relatively large aggregates of fullerene). 12−14 Collisions of soft particles have also been investigated, such as toluene 15 and nitrobenzene droplets, 16 liposomes, 17 viruses, 18 vesicles, 19 and single macromolecules. 20 Understanding single emulsion droplet collisions may also be of interest to many industrial applications (food processing, petroleum, and detergent industries).…”

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confidence: 99%

“…We further explored the reduction electrochemistry inside a single emulsion droplet containing 7,7,8,8-tetracyanoquinodimethane (TCNQ), an ionic liquid, and nitrobenzene. 16 From these single emulsion collision results, we can obtain the collision frequency, size distribution, and i−t decay behavior of the emulsion droplets. These results will contribute to a better understanding of the collision of other types of single "soft" particles (liposomes and vesicles) on an UME, as demonstrated in previous papers.…”

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confidence: 99%

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Analyzing Benzene and Cyclohexane Emulsion Droplet Collisions on Ultramicroelectrodes

Deng

Dick

et al. 2015

Anal. Chem.

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We report the collisions of single emulsion oil droplets with extremely low dielectric constants (e.g., benzene, ε of 2.27, or cyclohexane, ε of 2.02) as studied via emulsion droplet reactor (EDR) on an ultramicroelectrode (UME). By applying appropriate potentials to the UME, we observed the electrochemical effects of single-collision signals from the bulk electrolysis of single emulsion droplets. Different hydrophobic redox species (ferrocene, decamethyl-ferrocene, or metalloporphyrin) were trapped in a mixed benzene (or cyclohexane) oil-in-water emulsion using an ionic liquid as the supporting electrolyte and emulsifier. The emulsions were prepared using ultrasonic processing. Spike-like responses were observed in each i-t response due to the complete electrolysis of all of the above-mentioned redox species within the droplet. On the basis of these single-particle collision results, the collision frequency, size distribution, i-t decay behavior of the emulsion droplets, and possible mechanisms are analyzed and discussed. This work demonstrated that bulk electrolysis can be achieved in a few seconds in these attoliter reactors, suggesting many applications, such as analysis and electrosynthesis in low dielectric constant solvents, which have a much broader potential window.

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Analyzing Benzene and Cyclohexane Emulsion Droplet Collisions on Ultramicroelectrodes

Deng

Dick

et al. 2015

Anal. Chem.

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“…[1][2][3] An interesting approach for observing the electrochemical properties of catalytic NPs is to monitor their impact (or landing) from solution onto a collector electrode, as introduced by Bard et al, 4,5 and developed by several groups. [6][7][8][9][10][11][12] In order to resolve such impacts, the use of a small-sized ultramicroelectrode (UME) is mandatory to reduce both background currents and the impact frequency. To enhance the impact signal to background current, electrode surfaces have been modified with Hg or Bi 7 and borondoped diamond 12 has also been used as an UME material.…”

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Time-Resolved Detection and Analysis of Single Nanoparticle Electrocatalytic Impacts

et al. 2015

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ABSTRACT:There is considerable interest in understanding the interaction and activity of single entities, such as (electro)catalytic nanoparticles (NPs), with (electrode) surfaces. Through the use of a high bandwidth, high signal/noise measurement system, NP impacts on an electrode surface are detected and analyzed in unprecedented detail, revealing considerable new mechanistic information on the process. Taking the electrocatalytic oxidation of H2O2 at ruthenium oxide (RuOx) NPs as an example, the rise time of currenttime transients for NP impacts is consistent with a hydrodynamic trapping model for the arrival of a NP with a distancedependent NP diffusion-coefficient. NP release from the electrode appears to be aided by propulsion from the electrocatalytic reaction at the NP. High frequency NP impacts, orders of magnitude larger than can be accounted for by a single pass diffusive flux of NPs, are observed that indicate the repetitive trapping and release of an individual NP that has not previously recognized. The experiments and models described could readily be applied to other systems and serve as a powerful platform for detailed analysis of NP impacts.An important frontier in electrochemistry is measuring the behavior of individual nano-entities such as nanoparticles (NPs), nanowires and nanorods and relating this to other properties such as size, structure and electronic characteristics, so as to develop fundamental understanding and rational applications. 1-3 An interesting approach for observing the electrochemical properties of catalytic NPs is to monitor their impact (or landing) from solution onto a collector electrode, as introduced by Bard et al.,4,5 and developed by several groups. [6][7][8][9][10][11][12] In order to resolve such impacts, the use of a small-sized ultramicroelectrode (UME) is mandatory to reduce both background currents and the impact frequency. To enhance the impact signal to background current, electrode surfaces have been modified with Hg or Bi 7 and borondoped diamond 12 has also been used as an UME material. Alternatively, scanning electrochemical cell microscopy (SECCM) functioning as an ultramicro-electrochemical cell system offers particularly low background currents by reducing the area of the collector electrode, as well as offering the widest range of support electrodes. This is because the electrochemical cell is formed by meniscus confinement, rather than electrode encapsulation (Figure 1). 13 Despite these innovations, detailed analysis of the form of the current-time profile which is the primary signal for the landing (and detachment) of a single NP on an electrode has not yet been forthcoming, but would represent a huge advance towards understanding the impact process. Herein, we are able to analyze this process as never before and deduce key information on the NP arrival and release process from individual impact transients. Moreover, we show that impact frequencies can be orders of magnitude higher than expected based on single pass diffusion due to the repetitiv...

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“…[22,23] These attempts facilitate single particle studies for revealing the electron transfer process.H owever, both single-nanoparticle electrochemistry and the nanoparticle-related practical applications still face several challenges.First, the normal electrode dimension (for example,U ME) brings high-current noise,w hich submerges the important current fluctuations from dynamic interactions. [25] Ther elated detection mechanism with ah igh current and temporal resolution would further help understand the intrinsic feature of the individual nanoparticle and interactions between nanoentities. Theu ncontrollable interface could induce inconsistencies in the current response for each electrode.T his disadvantage may increase the possibility for inconsistent single-nanoparticle interactions with the electrodes,c ausing discrepancy for each measurement.…”

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confidence: 99%

A 30 nm Nanopore Electrode: Facile Fabrication and Direct Insights into the Intrinsic Feature of Single Nanoparticle Collisions

Gao

Ying

et al. 2017

Angew Chem Int Ed

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Clarifying the hidden but intrinsic feature of single nanoparticles by nanoelectrochemistry could help understand its potential for diverse applications. The uncontrolled interface and bandwidth limitation in the electrochemical measurement put the obstacle in single particle collision. Here, we demonstrate a well-defined 30 nm nanopore electrode with a rapid chemical-electrochemical fabrication method which provides a high reproducibility in both size and performance. A capacitance-based detection mechanism is demonstrated to achieve a high current resolution of 0.6 pA ±0.1 pA (RMS) and a high the temporal resolution of 0.01 ms. By utilizing this electrode, the dynamic interactions of every single particle in the mixture could be directly read during the collision process. The collision frequency is two orders of magnitude higher than previous reports, which helps reveal the hidden features of nanoparticles during the complex and multidimensional interaction processes.

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Electrochemistry of a Single Attoliter Emulsion Droplet in Collisions

Cited by 127 publications

References 25 publications

Analyzing Benzene and Cyclohexane Emulsion Droplet Collisions on Ultramicroelectrodes

Analyzing Benzene and Cyclohexane Emulsion Droplet Collisions on Ultramicroelectrodes

Time-Resolved Detection and Analysis of Single Nanoparticle Electrocatalytic Impacts

A 30 nm Nanopore Electrode: Facile Fabrication and Direct Insights into the Intrinsic Feature of Single Nanoparticle Collisions

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