期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2010
卷号：107
期号：33
页码：14530-14534
DOI：10.1073/pnas.1007524107
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The size-dependence of surface plasmon resonances (SPRs) is poorly understood in the small particle limit due to complex physical/chemical effects and uncertainties in experimental samples. In this article, we report an approach for synthesizing an ideal class of colloidal Ag nanoparticles with highly uniform morphologies and narrow size distributions. Optical measurements and theoretical analyses for particle diameters in the d {approx} 2-20 nm range are presented. The SPR absorption band exhibits an exceptional behavior: As size decreases from d {approx} 20 nm it blue-shifts but then turns over near d {approx} 12 nm and strongly red-shifts. A multilayer Mie theory model agrees well with the observations, indicating that lowered electron conductivity in the outermost atomic layer, due to chemical interactions, is the cause of the red-shift. We corroborate this picture by experimentally demonstrating precise chemical control of the SPR peak positions via ligand exchange.
关键词：Mie theory ; nanoparticle ; extinction ; chemical interaction ; sensing
