Pillararene-Based Supramolecular Plasmonic Thin Films for Label-Free, Quantitative and Multiplex SERS Detection
journal contributionposted on 19.07.2017, 00:00 by Verónica Montes-García, Borja Gómez-González, Diego Martínez-Solís, José M. Taboada, Norman Jiménez-Otero, Jacobo de Uña-Álvarez, Fernando Obelleiro, Luis García-Río, Jorge Pérez-Juste, Isabel Pastoriza-Santos
Novel plasmonic thin films based on electrostatic layer-by-layer (LbL) deposition of citrate-stabilized Au nanoparticles (NPs) and ammonium pillararene (APA) have been developed. The supramolecular-induced LbL assembly of the plasmonic nanoparticles yields the formation of controlled hot spots with uniform interparticle distances. At the same time, this strategy allows modulating the density and dimensions of the Au aggregates, and therefore the optical response, on the thin film with the number of AuNP-APA deposition cycles. Characterization of the AuNP-APA hybrid platforms as a function of the deposition cycles was performed by means of visible–NIR absorption spectroscopy, and scanning electron and atomic force microscopies, showing larger aggregates with the number of cycles. Additionally, the surface enhanced Raman scattering efficiency of the resulting AuNP-APA thin films has been investigated for three different laser excitations (633, 785, and 830 nm) and using pyrene as Raman probe. The best performance was shown by the AuNP-APA film obtained with two deposition cycles ((AuNP-APA)2) when excited with a 785 laser line. The optical response and SERS efficiency of the thin films were also simulated using the M3 solver and employing computer aided design models built based on SEM images of the different films. The use of host molecules as building blocks to fabricate (AuNP-APA)2) films has enabled the ultradetection, in liquid and gas phase, of low molecular weight polyaromatic hydrocarbons, PAHs, with no affinity for gold but toward the hydrophobic APA cavity. Besides, these plasmonic platforms allowed achieving quantitative detection within certain concentration regimes. Finally, the multiplex sensing capabilities of the AuNP-APA)2 were evaluated for their ability to detect in liquid and gas phase three different PAHs.