Size Effect of 3D Aggregates Assembled from Silver Nanoparticles on Surface‐Enhanced Raman Scattering

Abstract

The size influence of 3D silver nanoparticle aggregates on surface-enhanced Raman scattering (SERS) is investigated. Micrometer- and nanometer-sized wells prepared on a polydimethylsiloxane (PDMS) surfaces are filled with cetyltrimethylammonium bromide (CTAB)-coated silver nanoparticles. A concentration of CTAB around its critical micelle concentration is used not only to form a bilayerlike structure around the nanoparticles and thus generate nanometer-sized gaps in the aggregates, but also to improve the compatibility of the surface charge properties of the silver nanoparticles with the surface of PDMS and thus successfully fill the wells by assembly of silver nanoparticles into 3D structures. A resonance-free enhancement factor of 10(7) can be easily achieved on larger aggregates, and the enhancement factor increases with decreasing size of the 3D aggregates, which is contrary to reported studies on conventional silver clusters. We find that the number of silver nanoparticles in the 3D aggregate should be less than 200-300 for optimal SERS performance.

Oligonucleotide-Mediated Au–Ag Core–Shell Nanoparticles

“…The bands at 580, 1512, 730, 502 cm −1 were chosen for the calculation for Cy5, rhodamine 6G, adenine and TAMRA, respectively. In our previous studies, we used rhodamine 6 to estimate the enhancement factor on the surfaces we prepared [40,41]. A bulk Raman spectrum of 0.1 M rhodamine 6G was used for comparison.…”

Dealloying Ag–Al Alloy to Prepare Nanoporous Silver as a Substrate for Surface‐Enhanced Raman Scattering: Effects of Structural Evolution and Surface Modification

“…So far, many nanostructured metal materials have been tested as SERS substrates. [1][2][3][4][5][6][7][8][9][10][11][12] It has been shown that the SERS enhancement factor depends on the size, morphology, and assembly of the nanoparticles. The ability to prepare a nanostructured array with controlled particle size and interparticle distance would allow one to control the resonance frequency of the localized surface plasmon and to opportunely match it with the incident laser wavelength, resulting in larger SERS enhancements.…”

Tunable SERS Platforms from Small Nanoparticle 3D Superlattices: A Comparison between Gold, Silver, and Copper

“…For example, the manufacture of SERS substrates by using colloidal particle deposits can produce great enhancements but is hardly reproducible. In contrast, electron‐beam lithography allows the design of regular nanostructure arrangements with a high resolution and fair reproducibility, but the smallest achievable gaps between nanostructures are generally limited to 10 nm . A possible alternative consists of molecular‐mediated assemblies of colloids that enable fine tuning of the interparticle junction (down to 1 nm) through the choice of the bridging molecules.…”

“…In contrast, electronbeam lithography allows the design of regular nanostructure arrangements with ah igh resolution and fair reproducibility, but the smallest achievable gaps between nanostructures are generally limited to 10 nm. [16,17] Ap ossible alternative consists of molecular-mediated assemblies of colloidst hat enablef ine tuningo ft he interparticle junction (down to 1nm) [18] through the choice of the bridging molecules. However,t hese systems provedt ob em etastable because aggregation or dissociation phenomenaa re difficult to control.…”