SCREENING AND ENRICHMENT OF METAL NANOPARTICLES WITH NOVEL OPTICAL-PROPERTIES

A rapid screening and enrichment method is reported for exploring the size and shape diversities (libraries) of nanometer-scale colloidal pa rticles. With the use of surface-enhanced Raman scattering, a new clas s of metal nanoparticles has been identified from heterogeneous silver colloids. These particles are relatively large, faceted nanocrystals that are able to enhance the efficiencies of surface optical processes by as much as 14-15 orders of magnitude. The population of these nove l nanoparticles is only about 0.1-1% in standard colloid preparations but can be enriched to about 10-15% by size-selective fractionation. T his new class of nanoparticles could find potential uses in optoelectr onic devices, ultrasensitive chemical sensors, and single-molecule det ection.