| New gold nanostructures were prepared through a modified nanosphere lithography method. The structures, obtained by self-assembly of polystyrene microspheres and gold colloids in multilayers and subsequent removal of polystyrene, consist of nanohole/nanorings, distributed uniformly among gold nanoparticles on a silanized glass substrate. The size of the hole corresponds to the footprint of the polystyrene microspheres that were in contact with the glass substrate before dissolution. Sensing is based on the spectral measurement (in transmission mode) of the position of the Au localized surface plasmon resonance band in the ultraviolet-visible (UV-Vis) spectrum. Experiments were conducted with small molecules as well as with proteins (fibrinogen, Amyloid beta-derived diffusible ligands (ADDLs), and AT5G07010.1, a plant protein from Arabidopsis thaliana) incubated on a functionalized substrate and have shown a higher sensitivity for platforms with 100 and 200 nm holes, compared to those having larger (500 and 700 nm) holes; for example, by using a platform with 100 nm holes, a concentration as low as 4.3x10-7 M of the plant protein (AT5G07010.1) could be detected. The biorecognition of the plant protein and the corresponding antibody has been shown by the broadening of the localized surface plasmon resonance band and the presence of a new band around 600-620 nm. It is believed that this band originates in interparticle localized surface plasmon resonance coupling, when biorecognition forces the functionalized particles into close proximity. |
