**4. Conclusions and outlook**

Molecular self-assembly using amphiphilic copolymers and colloids derived thereof can deliver nanoplasmonic interfaces with high spatial resolutions, with control over geometric variables in steps of only a few nanometers. The approach enables metal nanoarrays with spatial coherence between features, orthogonal control over the different geometric attributes, and standard deviations below 10%. These characteristics can be leveraged to better understand and predict the optical properties of these arrays, allowing rational routes to maximize plasmonic sensing performance. The self-assembly parameters at both the template production and pattern transfer stages could be rigorously controlled to ensure high uniformity, reproducibility, and scalability of the resulting plasmonic arrays on full wafers. The correlation of the geometry ⇔ optical ⇔ SERS performance was demonstrated with a combination of experiments and numerical simulations. Plasmonic nanoarrays presenting a large number of gap hot spots, with gap distances down to sub-10 nm length scale, are possible to obtain in case of nanoparticle cluster arrays and nanopillar arrays. The homogeneously distributed hot spots over large areas present an opportunity to not only detect but also quantify the concentration of analytes, with large dynamic range with promisingly low limits of detection. Among the key challenges for future developments is to identify configurations that naturally drive the co-localization of analytes with EM hot spots to achieve maximize plasmonic signal enhancements. Further, the efforts to enhance EM fields solve only a part of the sensing challenge. In addition to maximizing the EM enhancements, the surface needs to be tailored to maximize analyte interactions and their concentrations on the surface.

Yet another challenge is the application of plasmonic arrays for biosensing. The high spatial resolutions sought for maximizing EM enhancements at gap or curvature hot spots are not compatible with the spatial requirements to accommodate large biomolecules like proteins. Further, the sensitivity of the plasmonic sensor extends typically to only a few nanometers from the surface. This is a challenge considering that the size of biomolecular interactions can already be a few tens of nanometers, for example, for an immunosandwich assay. Further, the plasmonic sensor needs to be adapted to work in complex media, for which the surface

**127**

*Nanoplasmonic Arrays with High Spatial Resolutions, Quality, and Throughput…*

functionalization to avoid non-specific binding would also consume part of the sensitive space above the plasmonic interface. While the plasmonic sensors have held high promise for highly sensitive, fast responding, and portable configurations, they need significant transversal development cutting across topics beyond fabrication, physics, and photonics, to ensure reliable devices that address emerging

Funding received from National Research Fund of Luxembourg (FNR) via the project PLASENS (C15/MS/10459961) and FNR-PRIDE (FNR PRIDE/15/10935404)

, Pierre Michel Adam<sup>2</sup>

1 Materials Research and Technology Department, Luxembourg Institute of Science

Nanotechnology, Department (PM2N), Nanotechnologies, Light, Nanomaterials and Nanotechnology team (L2N), University of Technology of Troyes (UTT),

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

3 Faculty of Science, Engineering and Technology, Swinburne University of

\*Address all correspondence to: sivashankar.krishnamoorthy@list.lu

, Saulius Juodkazis3

*DOI: http://dx.doi.org/10.5772/intechopen.89064*

analytical challenges.

**Acknowledgements**

is gratefully acknowledged.

**Author details**

Rishabh Rastogi1

Troyes Cedex, France

, Matteo Beggiato1

\*

2 Institute Charles Delaunay CNRS, Physics, Mechanics, Materials and

and Sivashankar Krishnamoorthy1

and Technology, Belvaux, Luxembourg

Technology, Hawthorn, VIC, Australia

provided the original work is properly cited.

*Nanoplasmonic Arrays with High Spatial Resolutions, Quality, and Throughput… DOI: http://dx.doi.org/10.5772/intechopen.89064*

functionalization to avoid non-specific binding would also consume part of the sensitive space above the plasmonic interface. While the plasmonic sensors have held high promise for highly sensitive, fast responding, and portable configurations, they need significant transversal development cutting across topics beyond fabrication, physics, and photonics, to ensure reliable devices that address emerging analytical challenges.
