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.

The preparation and characterization of a hybrid composite, based on carbon cloth (CC) matrix functionalized with two-dimensional (2D) MoS₂ flakes and MoO₃, and its use for developing an electrochemical sensor for the determination of riboflavin (RF) is here reported. The 2D-MoS₂-MoO₃CC composite was prepared by depositing 2D-MoS₂ nanosheets, obtained by liquid phase exfoliation (LPE), on the surface of a carbon cloth fiber network, previously functionalized with a layer of molybdenum oxide (α-MoO₃) by radio-frequency magnetron reactive sputtering technique. The 2D-MoS₂-MoO₃CC composite was characterized by scanning electron microscopy and energy dispersive X-ray analysis (SEM-EDX), and Raman spectroscopy. An electrochemical sensor has been then fabricated by fixing a slice of the 2D-MoS₂-MoO₃CC composite on the working electrode of a screen-printed carbon electrode (SPCE). The 2D-MoS₂-MoO₃-CC/SPCE sensor display good electrochemical characteristics which have been exploited, for the first time, in the electroanalytical determination of riboflavin (RF). The sensitivity to RF, equal to 0.67 µA mM⁻¹ in the linear range from 2 to 40 µM, and a limit of detection (LOD) of 1.5 µM at S/N = 3, demonstrate the promising characteristics of the proposed 2D-MoS₂-MoO₃-CC/SPCE electrochemical sensor for the determination of riboflavin.