Engineering Nanoparticle Cluster Arrays for Bacterial Biosensing: The Role of the Building Block in Multiscale SERS Substrates

• Published in: Advanced functional materials 2010-08, Vol.20 (16), p.2619-2628
• Main Authors: Yang, Linglu, Yan, Bo, Premasiri, W. Ranjith, Ziegler, Lawrence D., Negro, Luca Dal, Reinhard, Björn M.
• Format: Article
• Language: English
• Subjects: Bacterial Pathogens; Gold Nanoparticles; Nanoparticle Cluster Arrays; Nanoplasmonics; Photonic Plasmonic Crystals
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201000630

Noble metal nanoparticle cluster arrays (NCAs) are a novel class of engineered substrates for surface enhanced Raman spectroscopy (SERS), in which the noble metal nanoparticles interact on multiple length scales to create a multiscale E‐field cascade enhancement. In this work the role of the building block for the NCA performance is quantified. Periodic NCAs with constant cluster diameter (D = 200 nm) but variable nanoparticle diameter (d) and intercluster separation (Λ) were assembled on glass and their optical response and SERS enhancement were systematically characterized as a function of D, Λ, and d. An increase of d from 40 to 80 nm and simultaneous decrease of Λ from 200 to 50 nm led to an improvement of the ensemble averaged SERS enhancement factor by a factor of up to ∼8. The coefficient of variation (cv) of the enhancement factors (G) is significantly lower for the d = 80 nm NCAs than for the d = 40 nm and d = 60 nm NCAs. Optimized (D = 200 nm, Λ = 50 nm, d = 80 nm) NCAs show the overall highest signal reproducibility of all investigated NCAs and random nanoparticle substrates and achieve effective single cell detection sensitivity. Nanoparticle cluster arrays (NCAs) are two dimensional photonic plasmonic crystals (see a and b) that sustain electromagnetic interactions on multiple length scales. In this study, NCAs are assembled from different building blocks (40, 60, 80 nm gold spheres and 40/5, 40/10 core‐satellite nanostructures, and their SERS performance is evaluated. The 80 nm NCAs lead to the overall highest SERS enhancement and reproducibility both for small molecules and for monolayers of bacteria (c). Effective single cell SERS sensitivity is demonstrated for optimized NCAs.