Versatile Analytical Platform Based on Graphene-Enhanced Infrared Attenuated Total Reflection Spectroscopy

Abstract

Graphene, with its unique properties including atomic thickness, atomic uniformity, and delocalized π bonds, has been reported as a promising alternative material versus noble metals for surface-enhanced spectroscopies. Here, a simple and effective graphene-enhanced infrared absorption (GEIRA) strategy was developed based on infrared attenuated total reflection spectroscopy (IR-ATR). The IR signals of a broad range of molecules were significantly enhanced using graphene-decorated diamond ATR crystal surfaces versus conventional ATR waveguides. Utilizing rhodamine 6G (R6G) as the main model molecule, the experimental conditions were optimized, and potential enhancement mechanisms are discussed. Aqueous sample solutions were directly analyzed utilizing graphene dispersions, which eliminates harsh experimental conditions, tedious sample pretreatment, and sophisticated fabrication/patterning routines at the ATR waveguide surface. The GEIRA approach presented here provides simple experimental procedures, convenient operation, and excellent reproducibility, promoting a more widespread usage of graphene in surface-enhanced infrared absorption spectroscopy.

Resolved Infrared Spectroscopy of Aqueous Molecules Employing Tunable Graphene Plasmons in an Otto Prism

“…Finally, the graphene plasmonic nanostructure can be fabricated using the nanoprinting technique. Compared with the SEIRAS measurement in a traditional transmission configuration, such an ATR configuration allows us to detect the target molecules dissolved even in strongly infrared absorbing media, such as water, because of the shallow penetration depth (i.e., few micrometers) of infrared light into the surrounding media. − Especially, the near-field enhancement of graphene plasmons could further shrink the original evanescent wavelength, which minimizes the optical path to an extreme subwavelength level and significantly suppresses the signal from the bulk water molecules.…”

Graphene-Based Surface Enhanced Vibrational Spectroscopy: Recent Developments, Challenges, and Applications

“…52 Apart from EM, potential CM for enhancing infrared signatures induced by graphene should not be neglected. 43 In the following, typical examples of graphene-based SEIRA (a.k.a., graphene-enhanced infrared absorption; GEIRA) are highlighted.…”

“…Hence, in situ analysis of aqueous solution is enabled, and the IR-signatures of species present in the vicinity of the ATR waveguide surface decorated with appropriate signal-enhancing structures can be probed. 43,66 Zheng et al proposed an IR biosensor for aqueous-phase molecules based on chemically doped graphene and an ATR element (Figure 3a). 67 A boron-doped graphene (BG) nanodisk array deposited at the surface of a ZnSe ATR prism was fabricated by nanosphere lithography (NSL).…”

“…Hu et al have established a versatile and practical graphene-enhanced infrared absorption (a.k.a., GEIRA) platform for analyzing aqueous solutions by taking advantage of an ATR sensing configuration and the unique properties of graphene. 43 Graphene dispersions were first drop-casted and dried at the surface of a diamond ATR prism prior to adding the sample solution (Figure 3b), which required only a few microliters of both graphene dispersion and sample solution. While this procedure may readily be automated using an appropriate microfluidic system, the simplicity and convenience of the manipulation versus conventional graphene-transfer-involving procedures is immediately evident.…”

“…11,30,39−41 For example, graphene shows excellent adsorption affinities toward aromatic molecules and components attributed to its high surface-to-volume ratio and delocalized π bonds, thereby suggesting significant adsorption/enrichment capacities for appropriate analytes. 42,43 Moreover, graphene may effectively quench the photoluminescence of fluorescent molecules via resonance energy transfer processes and thus significantly reducing or even eliminating the photoluminescence background underneath SERS spectra. 44 Graphene is also supporting highly confined surface plasmon waves at mid-infrared frequencies with low attenu-ation loss, thus resulting in stronger light−matter interactions in SEIRA.…”