Ag-Clad Au Nanoparticles: Novel Aggregation, Optical, and Surface-Enhanced Raman Scattering Properties
| Autor: | R. Griffith Freeman, Katherine C. Grabar, and Michael A. Jackson, Michael J. Natan, Michael B. Hommer |
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| Rok vydání: | 1996 |
| Předmět: | |
| Zdroj: | The Journal of Physical Chemistry. 100:718-724 |
| ISSN: | 1541-5740 0022-3654 |
| DOI: | 10.1021/jp951379s |
| Popis: | Ag-coated Au colloidal particles have been prepared by reduction of Ag+ in the presence of preformed Au colloids. The composition of the Au100-xAgx particles was varied from x = 0 to 80. SERS spectra of pyridine, p-nitroso-N,N‘-dimethylaniline (p-NDMA), and trans-1,2-bis(4-pyridyl)ethylene (BPE) have been obtained with these colloids. At monolayer Ag coverages (x < 10), the optical spectra of Ag-coated Au particles are indistinguishable from uncoated Au particles. However, the SERS behavior of aggregated colloids with 647.1 nm excitation is extremely dependent upon the Ag:Au ratio. Very small amounts of Ag (x ≤ 5) lead to an increase in SERS intensity, but further increases lead to complete loss of signal. For p-NDMA and pyridine, these data can be explained by Ag inhibition of adsorbate-induced aggregation. The initial increase in SERS intensity results from production of smaller aggregates that exhibit a surface plasmon band in better alignment with the excitation wavelength; higher ratios of Ag elimina... |
| Databáze: | OpenAIRE |
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