skip to main content

Explore Research Products in the NSF-PAR

  • NSF Public Access
  • Search Results
  • Rational design and synthesis of bifunctional metal nanocrystals for probing catalytic reactions by surface-enhanced Raman scattering
Title: Rational design and synthesis of bifunctional metal nanocrystals for probing catalytic reactions by surface-enhanced Raman scattering
This report highlights recent progress in the rational design, synthesis, and applications of bimetallic nanocrystals with integrated SERS and catalytic activities. The ultimate goal is to develop bifunctional nanocrystals as a SERS probe for monitoring a catalytic reaction in situ . We first introduce seeded growth as a facile and powerful route to the syntheses of bifunctional nanocrystals with catalytic activities arising from Au or Pd, in addition to plasmonic properties originating from Ag or Au. Specifically, we discuss two distinctive pathways, namely conformal and site-selected deposition of a second metal on the surface of a noble-metal nanocrystal seed, for the fabrication of bifunctional nanocrystals with controlled composition and morphology. We then discuss the application of these bifunctional nanocrystals as unique probes for in situ SERS monitoring of the Au or Pd-catalyzed reduction of 4-nitrothiophenol to 4-aminothiophenol by NaBH 4 and the Ag-catalyzed oxidation of 4-aminothiophenol to trans -4,4′-dimercaptoazobenzene by the O 2 from air. We conclude this review with perspectives on the future development.  more » « less
Award ID(s):
1708300
NSF-PAR ID:
10063805
Author(s) / Creator(s):
; ;
Date Published:
Journal Name:
Journal of Materials Chemistry C
Volume:
6
Issue:
20
ISSN:
2050-7526
Page Range / eLocation ID:
5353 to 5362
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ( , ChemNanoMat)
    Abstract

    We report the synthesis of bifunctional Ag@SiO2/Au nanoparticles with an “islands in the sea” configuration by titrating HAuCl4solution into an aqueous suspension of Ag@SiO2core–shell nanocubes in the presence of NaOH, ascorbic acid, and poly(vinyl pyrrolidone) at pH 11.9. The NaOH plays an essential role in generating small pores in the SiO2shellin situ, followed by the epitaxial deposition of Au from the Ag surface through the pores, leading to the formation of Au islands (6–12 nm in size) immersed in a SiO2sea. By controlling the amount of HAuCl4titrated into the reaction system, the Au islands can be made to pass through and protrude from the SiO2shell, embracing catalytic activity toward the reduction of 4‐nitrophenol to 4‐aminophenol by NaBH4. While the Ag in the core provides a strong surface‐enhanced Raman scattering activity, the SiO2sea helps maintain the Au component as compact, isolated, and stabilized islands. The Ag@SiO2/Au nanoparticles can serve as a bifunctional probe to monitor the stepwise Au‐catalyzed reduction of 4‐nitrothiophenol to 4‐aminothiophenol by NaBH4and Ag‐catalyzed oxidation of 4‐aminothiophenol totrans‐4,4′‐dimercaptoazobenzene by the O2from air in the same reaction system.

     
    more » « less
  2. ; ( , Angewandte Chemie)
    Abstract

    Bifunctional nanocrystals with integrated plasmonic and catalytic activities hold great promise for analyzing chemical reactions by in situ surface‐enhanced Raman spectroscopy. This Minireview gives a brief introduction to the general strategies for designing such nanocrystals, followed by four typical examples, including their fabrication, characterization, and potential limitation. We then use the reduction of 4‐nitrothiophenol and oxidation of 4‐aminothiophenol as two model systems to demonstrate the capabilities of these bifunctional nanocrystals to monitor chemical reactions for the elucidation of reaction mechanisms and measurement of kinetics. We conclude with perspectives on further development of these bifunctional nanocrystals into a viable platform for investigating other types of catalytic reactions.

     
    more » « less
  3. ; ( , Angewandte Chemie International Edition)
    Abstract

    Bifunctional nanocrystals with integrated plasmonic and catalytic activities hold great promise for analyzing chemical reactions by in situ surface‐enhanced Raman spectroscopy. This Minireview gives a brief introduction to the general strategies for designing such nanocrystals, followed by four typical examples, including their fabrication, characterization, and potential limitation. We then use the reduction of 4‐nitrothiophenol and oxidation of 4‐aminothiophenol as two model systems to demonstrate the capabilities of these bifunctional nanocrystals to monitor chemical reactions for the elucidation of reaction mechanisms and measurement of kinetics. We conclude with perspectives on further development of these bifunctional nanocrystals into a viable platform for investigating other types of catalytic reactions.

     
    more » « less
  4. ; ; ; ; ; ( , ChemNanoMat)
    Abstract

    Aromatic azo compounds are high‐value chemicals extensively used as pigments, drugs, and food additives, but their production typically requires stoichiometric amounts of environmentally unfriendly metals or nitrites. There is an urgent need to develop a dual catalytic system capable of reducing nitroaromatics to aromatic amines, followed by their oxidation to azo compounds. Here we report such a dual catalyst based on Ag@Pd‐Ag core‐frame nanocubes for the stepwise conversion of 4‐nitrothiophenol totrans‐4,4′‐dimercaptoazobenzene under ambient conditions. Our in situ surface‐enhanced Raman spectroscopy study reveals three sequential processes that include the Pd‐catalyzed reduction of 4‐nitrothiophenol to 4‐aminothiophenol by hydrogen, a period during which the 4‐aminothiophenol remain unchanged until all hydrogen has depleted, and the Ag‐catalyzed oxidation of 4‐aminothiophenol totrans‐4,4′‐dimercaptoazobenzene by the O2from air. This work will lead to an environmentally friendly and sustainable approach to the production of aromatic azo compounds.

     
    more » « less
  5. ; ; ; ; ( , Nanoscale)
    We report a facile route to the synthesis of Ag@Au–Pt trimetallic nanocubes in which the Ag, Au, and Pt atoms are exposed at the corners, side faces, and edges, respectively. Our success relies on the use of Ag@Au nanocubes, with Ag 2 O patches at the corners and Au on the side faces and edges, as seeds for the site-selective deposition of Pt on the edges only in a reaction system containing ascorbic acid (H 2 Asc) and poly(vinylpyrrolidone). At an initial pH of 3.2, H 2 Asc can dissolve the Ag 2 O patches, exposing the Ag atoms at the corners of a nanocube. Upon the injection of the H 2 PtCl 6 precursor, the Pt atoms derived from the reduction by both H 2 Asc and Ag are preferentially deposited on the edges, leading to the formation of Ag@Au–Pt trimetallic nanocubes. We demonstrate the use of 2,6-dimethylphenyl isocyanide as a molecular probe to confirm and monitor the deposition of Pt atoms on the edges of nanocubes through surface-enhanced Raman scattering (SERS). We further explore the use of these bifunctional trimetallic nanoparticles with integrated plasmonic and catalytic properties for in situ SERS monitoring the reduction of 4-nitrothiophenol by NaBH 4 . Upon the removal of Ag via H 2 O 2 etching, the Ag@Au–Pt nanocubes evolve into trimetallic nanoboxes with a wall thickness of about 2 nm and well-defined openings at the corners. The trimetallic nanoboxes embrace plasmon resonance peaks in the near-infrared region with potential in biomedical applications. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email