Spatial Sensitivity of Immobilized Gold Nanoparticles on Glass

Spatial Sensitivity of Immobilized Gold Nanoparticles on Glass 

The penetration depth of the electromagnetic field due to surface plasmons has been extensively studied for planar SPR. The electromagnetic field in planar SPR decays exponentially from the surface, and the SPR sensor responds to the refractive index change upto 200 nm from the surface. In contrast to planar SPR, there is less information available on the sensing depth of metal nanoparticles. The electromagnetic field due to SPR in nanoparticles depends on the metal composition, size and shape of the nanoparticles. A few experimental results available for 14 and 15 nm diameter gold nanoparticles indicate that the sensing distance is 20-25 nm from the surface of the nanoparticles. Theoretical studies by Schatz and co-workers have shown that the 

The previous discussion has focused on the fabrication, characterization and optimization of the transducer. Here, we discuss, coupling of the biomolecular detector to the optical transducer to create a functional nanoSPR biosensor. The two important steps in coupling the biological detector to the optical transducer are presentation of the receptor on the nanoparticle surface and biomolecular binding between receptor and analyte. It has been shown that the density and spatial distribution of the receptor on the surface influences the effective binding affinity of the biomolecular recognition interaction as well as the surface density of the biomolecular complex, so that 

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