Silver nanoparticles embedded in glass by ion exchange method for biosensor applications

Aalto University, P.O. Box 11000, FI-00076 Aalto www.aalto.fi Author Ya Chen Name of the doctoral dissertation Silver nanoparticles embedded in glass by ion exchange method for biosensor applications Publisher School of Electrical Engineering Unit Department of Microand Nanosciences Series Aalto University publication series DOCTORAL DISSERTATIONS 125/2012 Field of research Photonics Manuscript submitted 1 June 2011 Date of the defence 26 October 2012 Permission to publish granted (date) 23 September 2012 Language English Monograph Article dissertation (summary + original articles) Abstract This thesis focuses on the fabrication of silver nanoparticles (Ag NPs) embedded in glasses and their applications for surface enhanced Raman spectroscopy (SERS).This thesis focuses on the fabrication of silver nanoparticles (Ag NPs) embedded in glasses and their applications for surface enhanced Raman spectroscopy (SERS). Firstly, Ag NPs are produced in microscope slides and high iron float glasses by ion exchange with thermal treatment. These two kinds of glasses contain a different percentage of iron oxide, which acts as the reducing agent in a silver reduction process. The study shows that the iron content in the Fe2+ form is more important than that in the Fe3+ form for the silver reduction. It is also demonstrated that Ag NP aggregates embedded in high iron float glasses can make them as SERS-active substrates. Secondly, Ag NPs are formed in high quality Corning 0211 glasses by a masked ion exchange and a two-step ion exchange. Ag NPs are deposited just under the mask edge due to the electrolytic deposition taking place in the masked ion exchange process. They form into Ag NP patterns according to the mask pattern. With the two-step ion exchange, uniform nanoparticle clusters over large areas are embedded in glass due to the galvanic replacement reaction and the electrolytic deposition. When applying a photolithographic mask in either the first step of an Ag+ ion exchange or the second step of a K+ ion exchange process, the two-step ion exchange can also enable the patterning of areas with particles having desired shapes and sizes. The SERS performance of the particles formed by these two methods is also demonstrated. The presented methods based on ion exchange are simple and potentially low-cost processes for large scale fabrication of SERS-active substrates. Furthermore, the two methods used to fabricate Ag NPs in the high quality Corning 0211 glass are ideal options in the development of integrated sensor chips by combining optical waveguides and microfluidics with the formed nanoparticles.