Ultra-uniform high-quality plasmonic metasurfaces through electrostatic self-assembly of gold nanoparticles on chemically unmodified glass.

We present a novel method for the fabrication of ultra-uniform metasurfaces through the direct electrostatic self-assembly of positively charged gold nanoparticles (AuNPs) on chemically unmodified glass. The method was successfully applied to two types of ultra-uniform AuNPs like nanospheres and nanocubes differing in shape, size, and cationic surfactant ligands, proving the versatility of the proposed methods. Unlike previous studies, we found that the AuNP clustering was due to improper drying of the metasurfaces after the deposition and not to instability of the colloids.

Plasmon-enhanced fluorescence and electrochemical aptasensor for SARS-CoV-2 Spike protein detection.

In this work, we combined plasmon-enhanced fluorescence and electrochemical (PEF-EC) transduction mechanisms to realize a highly sensitive dual-transducer aptasensor. To implement two traducers in one biosensor, a novel large-scale nanoimprint lithography process was introduced to fabricate gold nanopit arrays (AuNpA) with unique fringe structures. Light transmitting through the AuNpA samples exhibited a surface plasmon polariton peak overlapping with the excitation peak of the C7 aptamer-associated fluorophore methylene blue (MB).

Multifunctional Core@Satellite Magnetic Particles for Magnetoresistive Biosensors.

Magnetoresistive (MR) biosensors combine distinctive features such as small size, low cost, good sensitivity, and propensity to be arrayed to perform multiplexed analysis. Magnetic nanoparticles (MNPs) are the ideal target for this platform, especially if modified not only to overcome their intrinsic tendency to aggregate and lack of stability but also to realize an interacting surface suitable for biofunctionalization without strongly losing their magnetic response. Here, we describe an MR biosensor in which commercial MNP clusters were coated with gold nanoparticles (AuNPs) and used to detect human IgG in water using an MR biochip that comprises six sensing regions, each one containing five U-shaped spin valve sensors.