Optical biosensing platforms based on Ga-graphene plasmonic structures on Cu, quartz and SiO₂/Si substrates

Abstract

Ga nanoparticles (GaNPs) produced by thermal evaporation or epitaxial methods on graphene sheets present strong plasmonic effects that can couple to graphene phonons. In this work, GaNPs are deposited on graphene monolayers supported on Cu, quartz, and SiO2/Si substrates. The use of graphene increases the interparticle distance and improves the size uniformity. The enhancement of G and 2D graphene Raman lines is analyzed for the different substrates under excitation at 633 and 532 nm. The plasmonic effects are investigated using spectroscopic ellipsometry, finding a strong resonant mode at energies between 1.7 and 2.0 eV and an incidence angle of 55.6°. Finally, the heterogeneous surfaces are functionalized for the preparation of optical biosensors exposing the surface to 3,3′‐dithiodipropionic acid di(N‐succinimidyl ester) (DTSP). A significant energy shift of the ellipsometric signal on the Ga/graphene surfaces is observed in comparison to Ga/Si surfaces. Sketch of GaNPs atop graphene and biofunctionalizing agent (DTSP). Dip in the Psi ellipsometric function, and associated step in the Delta function, found around the GaNPs–graphene coupling resonance at an incident angle of 55.6°.

Photoluminescence enhancement of monolayer MoS2 using plasmonic gallium nanoparticles

“…32,35 Indeed, some studies have previously reported Ga NP evaporation on graphene showing SERS of the D, G and 2D bands thanks to the coupling between both materials. 36,37 Herein, the optical characteristics of 2D MoS 2 monolayers with and without Ga NPs are studied. We provide direct evidence of the effect of the Ga NPs on the MoS 2 by observing a PL enhancement as a function of the NP radius.…”

Plasmonic coupling in closed-packed ordered gallium nanoparticles

“…surface enhanced Raman spectroscopy (SERS) [27][28][29] , surface enhanced fluorescence 30,31 , Li-ion batteries 32 , waveguiding 33,34 , optical switching 35,36 , phase-change memories 37 or the development of biosensors for the detection of different diseases 38,39 .…”

“…With the aim to advance in these applications, several recent works have reported different approaches that have improved the size distributions of Ga NPs using IR light 40,41 , corrugated Cu films 29 , polymer nanostructured templates 42 and even 2D materials 31 . Although in all the cases the NPs were aligned and the size distributions were more homogeneous, NPs of different sizes still coexist.…”

Plasmonics for Biosensing

“…It has been applied as a gas sensor [128] and used for vibrational spectroscopy [129]. Graphene has also been used to combine with other metal materials [130,131]. By adding graphene on top of a thin layer of Au, the sensitivity was improved to 10 −18 M for single-stranded DNA using phase interrogation [132].…”