TY - JOUR
T1 - Observing the Overgrowth of a Second Metal on Silver Cubic Seeds in Solution by Surface-Enhanced Raman Scattering
AU - Zhang, Yun
AU - Liu, Jingyue
AU - Ahn, Jaewan
AU - Xiao, Ting Hui
AU - Li, Zhi Yuan
AU - Qin, Dong
N1 - Funding Information:
This work was supported in part by the National Science Foundation (CHE-1412006), start-up funds from the Georgia Institute of Technology and 3M nontenured faculty award. Part of the research was performed at the Institute of Electronics and Nanotechnology. Y.Z. acknowledges the International Postdoctoral Exchange Fellowship from the China Postdoctoral Council. J.L. acknowledges the support of NSF (CHE-1465057) and the use of facilities in the John M. Cowley Center for High Resolution Electron Microscopy at ASU.
Publisher Copyright:
© 2017 American Chemical Society.
PY - 2017/5/23
Y1 - 2017/5/23
N2 - We report the development of an isocyanide-based molecular probe for in situ characterizing the overgrowth of a second metal on silver nanocrystal seeds in solution by surface-enhanced Raman scattering (SERS). As the first demonstration, we elucidate that the vibrational frequency of 2,6-dimethylphenyl isocyanide (2,6-DMPI) can serve as a distinctive reporter for capturing the nucleation of Pt on the edges of Ag nanocubes in the aqueous solution containing a Pt precursor, ascorbic acid, and poly(vinylpyrrolidone) under ambient conditions. Our success relies on the difference in stretching frequency for the NC bond when the isocyanide group binds to the Ag and Pt atoms. Specifically, σ donation from the antibonding σ∗ orbital of the -NC group to the d-band of Ag would strengthen the NC bond, blue shifting the stretching frequency. In contrast, π-back-donation from the d-band of Pt to the π∗ antibonding orbital of the -NC group would weaken the NC bond, leading to a red shift of stretching frequency. Therefore, it is feasible to in situ characterize the outermost surface that consists of both newly deposited Pt atoms and remaining Ag atoms by following the stretching frequencies and intensities of 2,6-DMPI in real time. Because the SERS hot spots on the edges of Ag nanocubes coincide with the {110} facets preferred for the nucleation of Pt atoms, this technique is capable of resolving 27 Pt atoms being deposited on each edge of a 39 nm Ag nanocube in the original growth solution. Collectively, in situ SERS, with its consummate sensitivity to molecular structure and bonding of isocyanide-based molecular probe, could elucidate the mechanistic details involved in the seeded overgrowth of a catalytically significant metal, such as Pt, Pd, Ir, Rh, and Ru, on the surface of a Ag or Au nanocrystal seed.
AB - We report the development of an isocyanide-based molecular probe for in situ characterizing the overgrowth of a second metal on silver nanocrystal seeds in solution by surface-enhanced Raman scattering (SERS). As the first demonstration, we elucidate that the vibrational frequency of 2,6-dimethylphenyl isocyanide (2,6-DMPI) can serve as a distinctive reporter for capturing the nucleation of Pt on the edges of Ag nanocubes in the aqueous solution containing a Pt precursor, ascorbic acid, and poly(vinylpyrrolidone) under ambient conditions. Our success relies on the difference in stretching frequency for the NC bond when the isocyanide group binds to the Ag and Pt atoms. Specifically, σ donation from the antibonding σ∗ orbital of the -NC group to the d-band of Ag would strengthen the NC bond, blue shifting the stretching frequency. In contrast, π-back-donation from the d-band of Pt to the π∗ antibonding orbital of the -NC group would weaken the NC bond, leading to a red shift of stretching frequency. Therefore, it is feasible to in situ characterize the outermost surface that consists of both newly deposited Pt atoms and remaining Ag atoms by following the stretching frequencies and intensities of 2,6-DMPI in real time. Because the SERS hot spots on the edges of Ag nanocubes coincide with the {110} facets preferred for the nucleation of Pt atoms, this technique is capable of resolving 27 Pt atoms being deposited on each edge of a 39 nm Ag nanocube in the original growth solution. Collectively, in situ SERS, with its consummate sensitivity to molecular structure and bonding of isocyanide-based molecular probe, could elucidate the mechanistic details involved in the seeded overgrowth of a catalytically significant metal, such as Pt, Pd, Ir, Rh, and Ru, on the surface of a Ag or Au nanocrystal seed.
KW - SERS
KW - bimetallic nanocrystals
KW - heterogeneous nucleation
KW - seeded growth
KW - site-selective deposition
KW - surface-enhanced Raman scattering
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U2 - 10.1021/acsnano.7b01924
DO - 10.1021/acsnano.7b01924
M3 - Article
C2 - 28437068
AN - SCOPUS:85019953597
SN - 1936-0851
VL - 11
SP - 5080
EP - 5086
JO - ACS nano
JF - ACS nano
IS - 5
ER -