Hierarchical self-assembly of 1D and 2D ordered silver nanoparticle arrays on block copolymer templates

A new approach, based on the low-energy nanoclusters with controlled size obliquely deposited onto the block copolymer templates at low coverage, for obtaining 1D and 2D ordered nanoparticle arrays has been reported in this paper. Tapping-mode AFM is employed to characterize the morphology of samples. It is revealed that silver nanoparticles form ordered linear arrays and 2D ordered arrays. At the same time the interparticles distance of the ordered arrays is comparable to the particle size. Optical absorption spectra indicate that the surface plasmon resonance (SPR) of the silver nanoparticle linear arrays occurs at about 444.5 nm and 2D ordered silver nanoparticle arrays occurs at 436.1 nm, manifesting a red shift of 21.4 nm and 13 nm respectively compared to the SPR absorption of silver nanoparticles deposited on a fused quartz substrate. It is mainly due to the interaction of silver nanoparticles with the exciting light at their surface plasmon frequency and electrodynamic interactions between silver nanoparticles. Surface-enhanced Raman spectroscopy(SERS) spectra show the electric field enhancement that occurs in the vicinity of interacting silver nanopraticles. This templating approach thus provides an alternative method to transcend resolution in nanolithography and achieve well ordered nanostructures.