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Surface‐Enhanced Raman Scattering on Silver Nanoparticles in Different Aggregation Stages
Author(s) -
Kneipp Katrin,
Kneipp Harald
Publication year - 2006
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1560/ijc_46_3_299
Subject(s) - chemistry , raman scattering , excitation , crystal violet , surface plasmon resonance , plasmon , silver nanoparticle , nanoparticle , molecule , colloid , raman spectroscopy , scattering , chemical physics , nanotechnology , optoelectronics , optics , materials science , medicine , physics , electrical engineering , organic chemistry , pathology , engineering
Enhancement factors of surface‐enhanced Raman scattering (SERS) are compared for crystal violet attached to 15–60‐nm‐sized colloidal silver particles in various aggregation stages using 830 nm and 407 nm laser excitation. Enhancement factors on the order of 10 6 –10 7 have been measured at 407 nm excitation for molecules adsorbed on spatially‐isolated silver spheres exhibiting strong, sharp, single‐sphere plasmon resonance at 395 nm. Extremely large SERS enhancement factors on the order of 10 14 are obtained at near infrared excitation for molecules on clusters built from colloidal particles. The SERS enhancement factor is demonstrated to be independent of the size of the clusters. The increase of SERS enhancement factors by 7–8 orders of magnitude by the formation of aggregates, as well as the extremely small density of “hot sites” exhibiting this high level of enhancement, provide further strong arguments for the electromagnetic origin of the hot spots and for strongly enhanced local optical fields as a key effect in SERS at an extremely high enhancement level.