Silver Nanoislands for Plasmonic Detection of Proteins

Extended Abstract Deposition of metallic nanostructures on an optically transparent substrate is an important process step in the fabrication of localized surface plasmon biosensors. Various methods of deposition of nanostructures on substrates are thermal and e-beam deposition or sputtering and heat treatment, selfassembly through convective process, etc. (Alet et al., 2008; Szunerits et al., 2008; Gaspar et al., 2013). We have previously reported a novel method of formation of gold nanoislands on glass substrate by convective assembly and post-deposition annealing (Ozhikandathil et al., 2012; Ozhikandathil et al., 2012; Ozhikandathil and Packirisamy, 2012; Ozhikandathil and Packirisamy, 2014). The gold nanoisland sensor was tested for the detection of bovine growth hormone with the detection limit as low as 5ng/ml. In this work, a simple and novel method of manufacturing silver nanoislands is described. The colloidal silver nanoparticle solution was prepared by reducing ion by sodium borohydride. The surface of the glass substrate has been activated by oxygen plasma treatment. The manufacturing of silver nanostructure involves two steps, namely, convective assembly and post-deposition annealing. The silver nanoclusters was deposited by convective assembly at temperatures between 70 to 100 C. The convective assembly resulted in silver nanoclusters on the glass substrate. The nanocluster morphology was transformed to widely separated nanoislands by post-deposition annealing. The size distribution and optical absorbance properties of nanoislands is characterized by scanning electron microscopy and UVVisible spectroscopy, respectively. The nanoclusters shown in Figure 1(a) are found to have a wide optical absorbance spectrum due to the strong interparticle field coupling effects. The nanoclsuter morphology was tuned to nanoislands as shown in Figure 1(b) by annealing at above 500 C. The size of nanoislands is found to be in the range of 50 to 200nm.