Comparison of the plasmonic performances between lithographically fabricated and chemically grown gold nanorods.

Noble metal nanostructures, especially gold nanocrystals, have attracted intensive interest due to their rich plasmonic properties and enormous potential technological applications. The preparation process of gold nanocrystals can strongly affect their plasmonic properties and therefore their performances in various applications. Chemically synthesized colloidal gold nanocrystals are usually employed in biomedical fields, while lithographically fabricated ones are highly preferred for constructing optical meta-structures. A detailed careful comparison of the plasmonic performances between lithographical and chemical metal nanostructures is strongly desired for using them for different applications. Herein, we experimentally measured and quantitatively compared the plasmonic properties, including longitudinal localized surface plasmon wavelengths (LLSPWs) and plasmon peak widths, scattering intensities, and local electric field enhancements, of lithographically fabricated and chemically grown gold nanorods. The lithographical nanorods exhibit much weaker scattering, largely broadened spectral widths, and considerably reduced electric field enhancements. Electrodynamic simulations suggest that the reduction in the plasmonic performance of the lithographical nanorods is caused mainly by the use of an adhesive metal layer and slightly by their polycrystalline nature. Our quantitative comparison results will be very helpful in guiding the selection of proper types of metal nanostructures for targeted technological applications.