Toward hyperuniform disordered plasmonic nanostructures for reproducible surface-enhanced Raman spectroscopy.
We report on the self-assembling of clusters of gold-nanoparticles (Au-NPs) directed by the phase separation of poly(styrene)-b-poly(methylmethacrylate) (PS-b-PMMA) block-copolymer (BCP) on indium tin oxide coated glass, which induces the onset of vertical lamellar domains. After thermal evaporation of gold on BCP, Au-NPs of 4 nm are selectively included into PS-nanodomains by thermal annealing, and then clustered with large density of hot spots (> 10(4) μm(2)) in a random two-dimensional pattern. The resulting nanostructure exhibits near-hyperuniform long-range correlations. The consequent large degree of homogeneity of this isotropic plasmonic pattern gives rise to a highly reproducible Surface-Enhanced Raman Scattering (SERS) enhancement factor over the centimeter scale (std. dev. ∼ 10% over 0.25 cm(2)). We also discuss the application of a static electric field for modulating the BCP host morphology. The electric field induces an alignment of Au-NP clusters into ordered linear chains, exhibiting a stronger SERS activity, but reduced SERS spatial reproducibility.
Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Monte S. Angelo, Via Cintia 80126, Napoli, Italy.
C
C
De Rosa
F
F
Auriemma
C
C
Diletto
R
R
Di Girolamo
A
A
Malafronte
P
P
Morvillo
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G
Zito
G
G
Rusciano
G
G
Pesce
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A
Sasso