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Proceedings Paper

Sputtering-growth of seeded Au nanoparticles for nanogap-assisted surface-enhanced Raman scattering (SERS) biosensing
Author(s): Chit Yaw Fu; Dinish U.S.; Shashi Rautela; Douglas Wenda Goh; Malini Olivo
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Paper 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 (=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.

Paper Details

Date Published: 23 December 2011
PDF: 9 pages
Proc. SPIE 8204, Smart Nano-Micro Materials and Devices, 82041O (23 December 2011);
Show Author Affiliations
Chit Yaw Fu, National Univ. of Ireland, Galway (Ireland)
Singapore Bioimaging Consortium (Singapore)
Dinish U.S., Singapore Bioimaging Consortium (Singapore)
Shashi Rautela, Singapore Bioimaging Consortium (Singapore)
Douglas Wenda Goh, Singapore Bioimaging Consortium (Singapore)
Malini Olivo, National Univ. of Ireland, Galway (Ireland)
Singapore Bioimaging Consortium (Singapore)
Royal College of Surgeons Ireland (Ireland)

Published in SPIE Proceedings Vol. 8204:
Smart Nano-Micro Materials and Devices
Saulius Juodkazis; Min Gu, Editor(s)

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