Graphene-enhanced plasmonic nanohole arrays for environmental sensing in aqueous samples

Abstract

The label-free nature of surface plasmon resonance techniques (SPR) enables a fast, specific, and sensitive analysis of molecular interactions. However, detection of highly diluted concentrations and small molecules is still challenging. It is shown here that in contrast to continuous gold films, gold nanohole arrays can significantly improve the performance of SPR devices in angle-dependent measurement mode, as a signal amplification arises from localized surface plasmons at the nanostructures. This leads consequently to an increased sensing capability of molecules bound to the nanohole array surface. Furthermore, a reduced graphene oxide (rGO) sensor surface was layered over the nanohole array. Reduced graphene oxide is a 2D nanomaterial consisting of sp2-hybridized carbon atoms and is an attractive receptor surface for SPR as it omits any bulk phase and therefore allows fast response times. In fact, it was found that nanohole arrays demonstrated a higher shift in the resonance angle of 250–380% compared to a continuous gold film. At the same time the nanohole array structure as characterized by its diameter-to-periodicity ratio had minimal influence on the binding capacity of the sensor surface. As a simple and environmentally highly relevant model, binding of the plasticizer diethyl phthalate (DEP) via π-stacking was monitored on the rGO gold nanohole array realizing a limit of detection of as low as 20 nM. The concentration-dependent signal change was studied with the best performing rGO-modified nanohole arrays. Compared to continuous gold films a diameter-to-periodicity ratio (D/P) of 0.43 lead to a 12-fold signal enhancement. Finally, the effect of environmental waters on the sensor was evaluated using samples from sea, lake and river waters spiked with analytically relevant amounts of DEP during which significant changes in the SPR signal are observed. It is expected that this concept can be successfully transferred to enhance the sensitivity in SPR sensors.

Plasmon properties and hybridization effects in silicene

“…Recent studies have thoroughly characterized the plasmon dispersions * antonello.sindona@fis.unical.it in MG [17][18][19][20][21][22] and some other graphene-related materials, such as bilayer graphene (BLG) [23,24] and graphene nanoribbons (GNRs) arranged in regular planar arrays,which, unlike MG, offer geometrically controllable band gaps [25][26][27]. Further advances are expected from the analysis of nanocarbon-metal interfaces together with associated application developments in biological sensing, optical signal processing and quantum information technology [3,[28][29][30][31][32].…”

Durable Antimicrobial Behaviour from Silver-Graphene Coated Medical Textile Composites

“…It increases if an additional thin layer of high dielectric constant material is over-coated, and decreases for a lower dielectric constant material [74]. Thus, for Ag-rGO, the synergistic plasmonic effects between AgNP and the rGO network, and the differing dielectric constants between the two components, affects the character of the SPR signal [52]. Typically, solely a silver presence is said to suffer from chemical instability that leads to oxidation and results in an SPR red-shift and dampening.…”

“…rGO has recently been used to sequester metal NP to obtain materials with multi-faceted applications, while the encapsulation of NP within polymer substrates is thought to reduce NP-loss by washing or wiping the surface [50,51]. Such systems based on plasmonic nanostructures and graphene are known as 'plasmon-graphene hybrids' [52].…”

LSPR immuno-sensing based on iso-Y nanopillars for highly sensitive and specific imidacloprid detection

“…Refractive index (RI) variations due to the deposition of molecules on the metallic surface can be simply and promptly revealed by evaluating the red shift of the wavelength associated with the transmitted light minimum, allowing a quantitative label-free analysis. [19][20][21][22] Compared with other plasmonic approaches, LSPR sensing does not require temperature control or complicated coupling optical systems and, moreover, it allows the design of cheap portable prototype devices (costs less than $5000). 23 The most sensitive region to RI changes is in close proximity to the metal surface; indeed the electromagnetic field quickly decreases over a 10-15 nm distance from the plasmonic area.…”