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Title: Sputtering growth of seed Au nanoparticles for nanogap-assisted surface-enhanced Raman scattering (SERS) biosensing
Authors: Fu, C.Y.
Dinish, U.S.
Rautela, S.
Goh, D.W.
Olivo, M. 
Keywords: Biosensing
Gold nanoparticle
Surface enhanced Raman scattering
Issue Date: 2011
Citation: Fu, C.Y., Dinish, U.S., Rautela, S., Goh, D.W., Olivo, M. (2011). Sputtering growth of seed Au nanoparticles for nanogap-assisted surface-enhanced Raman scattering (SERS) biosensing. Proceedings of SPIE - The International Society for Optical Engineering 8204 : -. ScholarBank@NUS Repository.
Abstract: Gold-coated array patterned with tightly-packed nanospheres was developed as a substrate base for constructing SERSenriched nanogaps with Au-nanoparticles (GNPs). Using 1,2-ethanedithiol as a linker, Au-NPs (φ=17-40nm) were anchored covalently on the sphere-array. Thin Au layer was sputtered on the substrate to mask the citrate coating of GNPs that could demote the sensing mechanism. The negatively-charged GNP surface warrants the colloidal stability, but the resulting repulsive force keeps the immobilized NPs apart by about 40nm. The attained gap size is inadequately narrow to sustain any intense enhancement owing to the near-field nature of SERS. Minimal amount of NaCl was then added to slightly perturb the colloidal stability by reducing their surface charge. Notably, the interparticle-gap reduces at increasing amount of salt, giving rise to increased packing density of GNPs. The SERS enhancement is also found to exponentially increase at decreasing gap size. Nevertheless, the minimum gap achieved is limited to merely 7nm. Excessive addition of salt would eventually induce complete aggregation of particles, forming clustered NPs on the array. A simple sputtering-growth approach is therefore proposed to further minimize the interparticle gap by enlarging the seeded NPs based on mild sputtering. The SEM images confirm that the gap below 7nm is achievable. With advent of the colloidal chemistry, the combined salt-induced aggregation and sputtering-growth techniques can be applied to engineer interparticle gap that is crucial to realize an ultrasensitive SERS biosensor. The proposed two-step preparation can be potentially adopted to fabricate the SERS-enriched nanogaps on the microfluidics platform. © 2011 SPIE.
Source Title: Proceedings of SPIE - The International Society for Optical Engineering
ISBN: 9780819488459
ISSN: 0277786X
DOI: 10.1117/12.903639
Appears in Collections:Staff Publications

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