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An, Kwangjin
Advanced Nanocatalysis Lab (An Lab)
Research Interests
  • Nanoparticle catalytsts, catalytic activity, selectivity, and stability, strong metal-support interactions, biofuel conversion

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Sum Frequency Generation Vibrational Spectroscopy of Colloidal Platinum Nanoparticle Catalysts: Disordering versus Removal of Organic Capping

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Title
Sum Frequency Generation Vibrational Spectroscopy of Colloidal Platinum Nanoparticle Catalysts: Disordering versus Removal of Organic Capping
Author
Krier, James M.Michalak, William D.Baker, L. RobertAn, KwangjinKomvopoulos, KyriakosSomorjai, Gabor A.
Keywords
Active surface sites; Capping agent; Catalytic nanoparticle; Catalytic reactions; Colloidal platinum; Hydrogen gas; Nano-meter scale; Nanoparticle catalysts; Nanoparticle sizes; Organic capping; Organic capping agents; Organic ligands; Polyvinyl pyrrolidone; Pt nanoparticles; Reaction conditions; SFG vibrational spectroscopy; Size and shape; Solvent cleaning; Strong signal; Sum Frequency Generation vibrational spectroscopies; Surface intermediates; UV cleaning
Issue Date
2012-08
Publisher
AMER CHEMICAL SOC
Citation
JOURNAL OF PHYSICAL CHEMISTRY C, v.116, no.33, pp.17540 - 17546
Abstract
Recent work with nanoparticle catalysts shows that size and shape control on the nanometer scale influences reaction rate and selectivity. Sum frequency generation (SFG) vibrational spectroscopy is a powerful tool for studying heterogeneous catalysis because it enables the observation of surface intermediates during catalytic reactions. To control the size and shape of catalytic nanoparticles, an organic ligand was used as a capping agent to stabilize nanoparticles during synthesis. However, the presence of an organic capping agent presents two major challenges in SFG and catalytic reaction studies: it blocks a significant fraction of active surface sites and produces a strong signal that prevents the detection of reaction intermediates with SFG. Two methods for cleaning Pt nanoparticles capped with poly (vinylpyrrolidone) (PVP) are examined in this study: solvent cleaning and UV cleaning. Solvent cleaning leaves more PVP intact and relies on disordering with hydrogen gas to reduce the SFG signal of PVP. In contrast, UV cleaning depends on nearly complete removal of PVP to reduce SFG signal. Both UV and solvent cleaning enable the detection of reaction intermediates by SFG. However, solvent cleaning also yields nanoparticles that are stable under reaction conditions, whereas UV cleaning results in aggregation during reaction. The results of this study indicate that solvent cleaning is more advantageous for studying the effects of nanoparticle size and shape on catalytic selectivity by SFG vibrational spectroscopy. © 2012 American Chemical Society.
URI
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DOI
10.1021/jp303363m
ISSN
1932-7447
Appears in Collections:
ECHE_Journal Papers
Files in This Item:
JPCC 2012,166,17540, SFGVS of Colloidal Platinum NPCatalysts; Disordering versus Removal of Organic Capping.pdf Download

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