Embedded plasmonic nanostructures: synthesis, fundamental aspects and their surface enhanced Raman scattering applications

Abstract

The unique physical and tunable optical properties of noble metal nanoparticles (NPs) provides the opportunity to develop new sensing platforms with enhanced capabilities in the specific detection of a variety of small molecules. While noble metal NPs are interesting as nanomaterials, future and practical applications as high-performance novel functional materials will require the use of these NPs embedded in suitable host materials. This review details how embedded noble metal NPs and the local environment influence the sensing properties for potential application in nano-biotechnology, ultrasensitive chemical and biochemical detection by surface enhanced Raman scattering (SERS) nanotechnology. Although the synthesis and potential applications of noble metal NPs based SERS substrates have been reviewed previously, there is a growing interest in synthesis and functionalisation of embedded noble metal NPs and their applications as SERS substrates. This topic has been rarely reviewed in literature. In particular, we review the highly active solid and thin film SERS substrates such as polymer and glass substrates embedded with noble metal NPs. We also discuss their optical properties due to the localised surface plasmon resonance and enhanced local electromagnetic field which are responsible for enhanced SERS activity with emphasis on their fundamental and technological applications. This review also includes a new class of promising porous coordination polymeric SERS substrates (a metal-organic framework) embedded with noble metal NPs. The review first explains many fundamental key concepts of SPR and SERS enhancement as well as factors affecting these properties in the case of embedded NPs. This then summarises methods for the fabrication of highly reproducible and robust SERS substrates embedded with NPs followed by their SERS application in detection of several chemical and biological molecules. The article also describes the recent developments in the fabrication of these SERS substrates embedded with noble metal NPs from conventional chemical routes to physical methods including novel ion beam techniques.

Keywords:

• noble metal nanoparticles
• embedded nanostructures
• localised surfaced plasmon resonance (LSPR)
• surface enhanced Raman scattering (SERS)
• solid SERS substrates

Acknowledgement

We are grateful to the editor for kind approval and consideration of this review article. The authors would like to acknowledge the authors of the related work and their supports in the past. The authors would like to thank materials Science group at IUAC (New Delhi), and researchers at KIST, (South Korea), where some of the experiment work was performed also reported in this review. The author (JP) would like to acknowledge UFS, South Africa for the postdoctoral fellowship and DST, India for prestigious INSPIRE faculty award (INSPIRE/04/2015/002452).