Hierarchical Self-assembly of Silver Nanocluster Arrays on Triblock Copolymer Templates

Abstract

Poly(styrene-b-butadiene-b-styrene) (SBS) triblock copolymer templates which present in-plane cylinders of polystyrene (PS) aligned parallel to the plane of the substrate have been prepared by a solvent-induced order-disorder phase transition method. Silver nanoclusters have been obliquely deposited onto the SBS copolymer templates at low coverage, utilizing the directed low-energy cluster beam deposition (LECBD) method. The morphology of the samples has been characterized by a tapping-mode AFM. It is shown that the silver nanoclusters form ordered linear arrays and the intercluster distance within each individual linear array is comparable to the cluster size. Optical absorption spectra indicate that the surface plasmon resonance (SPR) of the silver nanocluster linear arrays occurs at about 444.5 nm, manifesting a red shift of approximately 21.4 nm compared to the SPR absorption of silver nanoclusters deposited on a fused quartz substrate. This is attributed mainly to the near-field electrodynamic interactions between the silver nanoclusters. This hierarchical approach to create ordered nanostructures transcends the spatial limits of lithography and provides a promising route to achieve well-ordered cluster-based nanostructures.

Investigation of 1D Siliver Nanoparticle Arrays for Use as Molecule Concentration‐Specific SERS Substrates

“…A constant laser power of 100 W was used for the SERS measurement. aligned parallel to the substrate, similar to those found in our previous investigations [11]. The orientational order of the cylinders can cover several tens of lattice constant, which is around 38 nm as measured from the AFM image.…”

“…It has been demonstrated previously that evaporating metal onto a phase-separated block copolymer film resulted in selective decoration of one of the blocks [10,22]. When silver nanoparticles are deposited onto the triblock copolymer SBS thin films, they are selectively absorbed onto the PB domains, forming regular arrays of nanoparticles [11]. Due to the high stability of the nanoparticles preformed in gas phase and the limited diffusive mobility and coalescence of silver nanoparticles on the PB blocks, nanochains of particles with fairly narrow size distribution and uniform interparticle spacing are produced.…”

“…Triblock copolymer poly(styrene-b-butadiene-b-styrene) (SBS) films with self-assembled nanopatterns were used as templates to selectively adsorb the deposited silver nanoparticles on the polybutadiene (PB) phase [11,19]. The films were prepared by spin coating toluene solutions of 4 wt% SBS (weight-averaged molecular weight M = 140000 Da, polydispersity index PDI = 1.2, polystyrene (PS) weight fraction PS = 0.3, Aldrich Chemical Inc.) onto fused quartz glasses at about 2500 rpm for 30 s, followed by solvent annealing in a toluene vapor atmosphere with an extremely slow toluene evaporation rate (∼0.001 mL/h) at room temperature.…”

“…Recently, block copolymer self-assembled nanopatterns were used as templates to fabricate high density regular arrays of metal nanoparticles [10][11][12]. Excellent structure uniformity in the interparticle gap distance and the size of the nanoparticles in the array could be obtained in a large area, and high SERS enhancement factor with good reproducibility was demonstrated [13][14][15][16][17][18].…”

Photochemical fabrication of hierarchical Ag nanoparticle arrays from domain-selective Ag+-loading on block copolymer templates

“…Recently, block copolymer templates have drawn much attention owing to their great capability to self-assemble into well-ordered nanopatterns. Shi et al 13 also demonstrated that silver nanoclusters obliquely deposited onto polystyrene-block-polybutadiene-block-polystyrene triblock copolymer templates can be hierarchically assembled to form ordered linear arrays of nanoparticles. 5 For example, Ag, Au and Pt nanoscale patterns driven by polystyrene-block-poly(2-vinylpyridine)block-poly(ethylene oxide) triblock copolymer and PS-b-P4VP diblock copolymer templates 6,7 were prepared by galvanic displacement on semiconductor surfaces.…”