An aptamer based SERS sensor was developed to detect picomolar concentrated ochratoxin solutions using an OPLS model.

Optical forces are used to aggregate plasmonic nanoparticles and create SERS–active hot spots in liquid. When biomolecules are added to the nanoparticles, high sensitivity SERS detection can be accomplished. Here, we pursue studies on Bovine Serum Albumin (BSA) detection, investigating the BSA–nanorod aggregations in a range from 100 µM to 50 nM by combining light scattering, plasmon resonance and SERS, and correlating the SERS signal with the concentration. Experimental data are fitted with a simple model describing the optical aggregation process. We show that BSA–nanorod complexes can be optically printed on non-functionalized glass surfaces, designing custom patterns stable with time. Furthermore, we demonstrate that this methodology can be used to detect catalase and hemoglobin, two Raman resonant biomolecules, at concentrations of 10 nM and 1 pM, respectively, i.e., well beyond the limit of detection of BSA. Finally, we show that nanorods functionalized with specific aptamers can be used to capture and detect Ochratoxin A, a fungal toxin found in food commodities and wine. This experiment represents the first step towards the addition of molecular specificity to this novel biosensor strategy.

Scanning-probe-assisted mid-infrared nano-spectroscopy is employed to reveal the polaritonic dispersion of individual MIM (metal-insulator-metal) square patch antennas whose modes can be strongly coupled to a mid-infrared intersubband transition. The patch antenna side length L sets the resonances between λ = 5.5 μm and 12.5 μm. The active region consists of a highly doped AlInAs/InGaAs/AlInAs single quantum well that presents an intersubband transition at 1190 cm⁻¹ (λ = 8.4 μm). When the patch antenna optical resonance approaches and matches the intersubband transition frequency (L ∼ 1.8 μm), a clear anticrossing behavior—evidence of strong coupling—is observed in the near-field scattering phase spectra of individual antennas. The measured Rabi splitting is 4.5 THz. The near-field scattering spectra agree with the far-field extinction spectra acquired on arrays of identical antennas.