Fabrication of a substrate for Ag-nanorod metal-enhanced fluorescence using the oblique angle deposition process

Abstract

Metal-enhanced fluorescence (MEF) is a powerful technology to improve the sensitivity of fluorescence analysis by allowing fluorophores to interact with enhanced electromagnetic fields generated by the localised surface plasmon resonance effects of metallic nanostructures. To apply MEF technology to disposable DNA or protein microarray analysis, metallic nanostructures need to be fabricated on the full area of a glass slide at low cost. In this reported work an oblique angle deposition process was used to fabricate Ag nanorods on the whole area of a 25 x 75 mm(2) glass slide to serve as an inexpensive and large-area MEF substrate. To examine the feasibility of the proposed substrate and maximise signal enhancement, Ag nanorods with different lengths were deposited on glass slides. Different concentrations of streptavidin-conjugated Cy5 in phosphate buffered saline were spotted onto the Ag nanorods and bare glass substrates, and the fluorescence signals were measured and compared. Longer Ag nanorods improved the fluorescence enhancement factor because of a higher surface plasmon resonance effect and the large surface area of the nanostructure with a high aspect ratio. A maximum enhancement factor of -23 was obtained from Ag nanorods that were 1000 nm long with comparable uniformity with the glass substrate.