Nanoantenna structures for the detection of phonons in nanocrystals

Abstract

We report a study of the infrared response by localized surface plasmon resonance (LSPR) modes in gold micro- and nanoantenna arrays with various morphologies and surface-enhanced infrared absorption (SEIRA) by optical phonons of semiconductor nanocrystals (NCs) deposited on the arrays. The arrays of nano- and microantennas fabricated with nano- and photolithography reveal infrared-active LSPR modes of energy ranging from the mid to far-infrared that allow the IR response from very low concentrations of organic and inorganic materials deposited onto the arrays to be analyzed. The Langmuir–Blodgett technology was used for homogeneous deposition of CdSe, CdS, and PbS NC monolayers on the antenna arrays. The structural parameters of the arrays were confirmed by scanning electron microscopy. 3D full-wave electromagnetic simulations of the electromagnetic field distribution around the micro- and nanoantennas were employed to realize the maximal SEIRA enhancement for structural parameters of the arrays whereby the LSPR and the NC optical phonon energies coincide. The SEIRA experiments quantitatively confirmed the computational results. The maximum SEIRA enhancement was observed for linear nanoantennas with optimized structural parameters determined from the electromagnetic simulations. The frequency position of the feature’s absorption seen in the SEIRA response evidences that the NC surface and transverse optical phonons are activated in the infrared spectra.

Infrared metamaterial for surface-enhanced infrared absorption spectroscopy: pushing the frontier of ultrasensitive on-chip sensing

“…[73][74][75][76][77] Therefore, it is an effective way to improve the EF of SEIRA by optimizing metamaterial structure design. [78,79] Specifically, reducing the distance between the metamaterial pattern units can enhance the near-field intensity, which is attributed to the near-field interaction caused by the attractive electromagnetic force. [48] In 2013, Aouani et al fabricated a broadband log-periodic trapezoidal nanoantenna with a minimum gap of 20 nm between units by using the EBL method (Figure 3(a)).…”

Optically and electrically driven nanoantennas

“…This work explores the minimum number of tags required for obtaining a SERS signal under operation conditions. Moving further towards the (near-) infrared regime, different antennas are employed in a surface-enhanced infrared absorption (SEIRA) configuration [45]. Here the aim is to detect low concentrations of semiconductor nanocrystals through maximum local enhancement of their optical phonon response.…”