Coupled noble metal nanostructures for high-performance surface-enhanced spectroscopies

Abstract

This chapter gives a brief introduction to the whole thesis. Following a concise overview of previous researches, the problems existed in previous studies and the three hypotheses made in this work are stated. Then the objectives and scopes, the outline of this thesis, and the main findings and the significances of this work are listed. (3) To investigate the effects of the SPPs of the underlying metal film on the hot spots in MNOMF. To optimize the electric field enhancement in MNOMF for high-performance SES. 1.3 Dissertation overview The thesis consists of 7 chapters. Chapter 1 is the introduction, including the problem statement, hypotheses, research objectives and scopes, the dissertation overview, and the findings and significances. Chapter 2 gives a comprehensive literature review, including the SPRs of noble metal nanostructures, SES, noble metal nanostructures with hot spots, and methods to optimize the hot spots in metallic nanostructures for high-performance SES. Following the literature review, the research gaps are listed and the PhD in context of literature is provided. Chapter 3 introduces the theoretical method used in this study, including the introduction of Maxwell's curl equations and the finite-difference time-domain (FDTD) method. Chapter 4 investigates the hot spots in Au SNPDs. The influences of the SNPD configurations, the spherical core diameters, the hollow nanoshell core, and the polarization angle on the hot spots in Au SNPDs are studied. A methodology to achieve both huge "hot spots volume" and high electric field intensity in dimers is proposed. Chapter 5 investigates the optical properties of Au crossed T-T SDDs. The "hot spots volume" and electric field enhancement in crossed T-T SDD are compared with those in disk dimer. The effects of glass substrate, disk diameter, tip width, tip length, structure thickness, gap size between two crossed tips, the longitudinal overlap distance between two crossed tips, and the polarization direction on the hot spots in crossed T-T SDDs are comprehensively investigated.