Transport and chemistry at electroactive interfaces studied using line-imaging Raman spectroscopy

Schwartz, Daniel T.; Haight, S.M.

doi:10.1016/s0927-7757(00)00512-4

Cited by 7 publications

(5 citation statements)

References 17 publications

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“…Principle component regression, a multivariate method, was used to quantify concentrations from each spectrum. Raman imaging (27) and multivariate analysis (28) were similar to those re-ported. By rastering the optical sampling volume horizontally through the flow cross section, two-dimensional concentration images were constructed.…”

Section: Experimental Details and Data Analysissupporting

confidence: 75%

Microfluidics without microfabrication

Lutz

Chen

Schwartz

2003

Proc. Natl. Acad. Sci. U.S.A.

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Microfluidic devices create spatially defined, chemically controlled environments at microscopic dimensions. We demonstrate the formation and control of microscopic hydrodynamic and chemical environments by impinging a low-intensity acoustic oscillation on a cylindrical electrode. The interaction of small-amplitude (<203 m), low-frequency (<515 Hz) fluid oscillations with a submillimeter cylinder creates four microscopic eddies that circulate adjacent to the cylinder. This steady flow is known as acoustic streaming. Because the steady circulation in the eddies has closed streamlines, reagent dosed from the electrode can escape the eddies only by slow molecular diffusion. As a result, reagent dosing rates of 10 nmol͞s produce eddy concentrations as high as 8 mM, without a correspondingly large rise in bulk solution composition. Imaging Raman spectroscopy is used to visualize the eddy concentration distribution for various acoustic oscillation conditions, and point Raman spectra are used to quantify eddy compositions. These results, and corresponding numerical simulations, show that each eddy acts as a microchemical trap with size determined by acoustic frequency and the concentration tuned via reagent dosing rate and acoustic amplitude. Low-intensity acoustic streaming flows can serve as microfluidic elements without the need for microfabrication.

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Section: Experimental Details and Data Analysissupporting

confidence: 75%

Microfluidics without microfabrication

Lutz

Chen

Schwartz

2003

Proc. Natl. Acad. Sci. U.S.A.

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“…8, curve a), which is better than the stable CNT-PANI-NiHCF film reported by Lin et al [10] Even after 1500 and 3000 cycles, the NiHCF nanotubes still retained 92.2 % and 82.9 % of their ion-exchange capacity, respectively. As reported by Schwartz and his co-worker, [16] the oxidation state of the iron centers within the nickel hexacyanoferrate thin film could be readily modulated between the ferric and ferrous states in a freshly prepared film. However, repeated cycling results in an irreversible loss of capacity as the iron centers no longer are able to efficiently switch into the ferric state.…”

Section: Full Papermentioning

confidence: 65%

Highly Stable Nickel Hexacyanoferrate Nanotubes for Electrically Switched Ion Exchange

Chen

Xia

2007

Adv Funct Materials

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Nickel hexacyanoferrate (NiHCF) nanotubes are fabricated by an electrokinetic method based on the distinct surface properties of porous anodic alumina. By this method, nanotubes can be formed rapidly with the morphologies faithfully replicating the nanopores in the template. The prepared nanotubes were carefully characterized using SEM and TEM. Results from IR, UV, EDX, and electrochemical measurements show that the NiHCF nanotubes exist only in the form of K2Ni[Fe(CN)6]. Because of this single composition and unique nanostructure, NiHCF nanotubes show excellently stable cesium‐selective ion‐exchange ability. The capacity for electrodes modified with NiHCF nanotubes after 500 potential cycles retains 95.3 % of its initial value. Even after 1500 and 3000 cycles, the NiHCF nanotubes still retain 92.2 % and 82.9 %, respectively, of their ion‐exchange capacity.

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“…Ferricyanide oxidant concentrations were quantified using Raman imaging spectroscopy , analyzed by principal component regression . Two-dimensional Raman images of the OH-stretching region from water (not shown) were used to locate the cylinder and to position optical sampling volumes in the eddy core and in the bulk solution.…”

Section: Methodsmentioning

confidence: 99%

Characterizing Homogeneous Chemistry Using Well-Mixed Microeddies

2006

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Well-mixed reaction volumes are often sought in engineered microchemical devices and can be an important feature of naturally occurring physicochemical processes such as pitting corrosion. Steady streaming eddies can serve as well-mixed, easily controlled microliter chemical reactors for characterizing homogeneous chemical reactions. Here, steady streaming eddies are produced by oscillating a liquid-filled cuvette around a stationary cylindrical electrode (radius 406 microm, length 1.6 cm) at audible frequencies (75 Hz). Oxidant (ferricyanide) electrochemically dosed at small rates (

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Transport and chemistry at electroactive interfaces studied using line-imaging Raman spectroscopy

Cited by 7 publications

References 17 publications

Microfluidics without microfabrication

Microfluidics without microfabrication

Highly Stable Nickel Hexacyanoferrate Nanotubes for Electrically Switched Ion Exchange

Characterizing Homogeneous Chemistry Using Well-Mixed Microeddies

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