Multiplex Infrared Spectroscopy Imaging for Monitoring Spatially Resolved Redox Chemistry

IR spectroscopy is an excellent method for understanding surface redox chemistry. However, obtaining sufficient spatial resolution to analyze in situ surface redox reactions is difficult because the aqueous sampling environments provide some challenges for IR spectroscopy. These challenges arise bec...

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Bibliographic Details
Published in:Analytical chemistry (Washington) 2018-02, Vol.90 (3), p.1487-1491
Main Authors: Macedo, Lucyano J. A, Crespilho, Frank N
Format: Article
Language:English
Subjects:
Aqueous electrolytes
Calcium fluoride
Charge transfer
Chemistry
Electrochemical potential
Electrochemistry
Focal plane devices
Infrared imaging
Infrared imaging systems
Infrared spectroscopy
Iron
Redox reactions
Sampling
Spatial discrimination
Spatial resolution
Spectroscopy
Spectrum analysis
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Summary:IR spectroscopy is an excellent method for understanding surface redox chemistry. However, obtaining sufficient spatial resolution to analyze in situ surface redox reactions is difficult because the aqueous sampling environments provide some challenges for IR spectroscopy. These challenges arise because of the vibrational contribution of water. In this letter, we demonstrate a solution to this problem, where the key development enabling the coupling of spectromicroscopy with electrochemical measurements is a CaF2/electrolyte/Au sandwich IR-sensitive sample holder that acts as an electrochemical cell. In this system, there is a very thin layer of aqueous electrolyte (∼10 μm), and it is possible to monitor, in real time, the vibrational maps and changes to the Au surface modified with iron­(II, III) hexacyanoferrate­(II, III) by varying the electrochemical potential. By selecting specific vibrational modes with a focal plane array detector, which allows the simultaneous collection of IR spectra from 4096 microscopic regions, chemical maps showing the surface changes were obtained and analyzed using color, providing new insights into how the charge transfer processes affect the chemical composition in specific 2D spatially resolved regions.
ISSN:0003-2700
1520-6882
DOI:10.1021/acs.analchem.7b04438