Confinement on the optical response in h-BNCs: Towards highly efficient SERS-active 2D substrates

Marcos Mandado; Nicolás Ramos-Berdullas

doi:10.1016/j.saa.2021.120451

Confinement on the optical response in h-BNCs: Towards highly efficient SERS-active 2D substrates

Spectrochim Acta A Mol Biomol Spectrosc. 2022 Feb 5:266:120451. doi: 10.1016/j.saa.2021.120451. Epub 2021 Sep 29.

Authors

Marcos Mandado¹, Nicolás Ramos-Berdullas²

Affiliations

¹ Department of Physical Chemistry, University of Vigo, Lagoas-Marcosende s/n, 36310 Vigo, Spain. Electronic address: mandado@uvigo.es.
² Department of Physical Chemistry, University of Vigo, Lagoas-Marcosende s/n, 36310 Vigo, Spain.

PMID: 34627018
DOI: 10.1016/j.saa.2021.120451

Abstract

Several experimental and theoretical studies have shown that 2D hybrid structures formed by boron, nitrogen and carbon atoms (h-BNCs) possess a highly tunable linear and non-linear optical responses. Recent advances towards the controlled synthesis of these unique structures have motivated an important number of experimental and theoretical work. In this work, the confinement on the optical response induced by boron-nitride (BN) strings in h-BNC 2D structures is investigated using time-dependent density functional theory (TDDFT) and electron density response properties. The number of surrounding BN strings (N_BN) necessary to "isolate" the optical modes of a carbon nanoisland (nanographene) from the remaining substrate has been characterized in two different nanoisland models: benzene and pyrene. It was found that for N_BN ≥ 3 the excitation wavelengths of the optically active modes remain constant and the changes in the transition densities, the ground to excited state density differences and their associated electron deformation orbitals are negligible and strongly confined within the carbon nanoisland. Using a water molecule as model system, Raman enhancement factors of 10 [6] for the water vibrational modes are obtained when these electromagnetic "hot spots" are activated by an external electromagnetic field. The high tunability of the optical absorption bands of nanographenes through changes in size and morphology makes h-BNCs be perfect materials to construct platforms for surface enhancement Raman spectroscopy (SERS) for a wide range of laser sources.

Keywords: Computational chemistry; Graphene; SERS; White graphene; h-BNC.