Sensing characteristics of NIR localized surface plasmon resonances in gold nanorings for application as ultrasensitive biosensors.
The optical responses of 75-150 nm diameter gold nanorings to changes in local refractive index have been quantified by near-infrared extinction spectroscopy and compared to DDA calculations and an analytical approach. The "bulk" refractive index sensitivities of gold nanorings are substantially (>5 times) larger than those of nanodisks with similar diameters. Nanorings retain a significantly larger sensitivity than nanodisks at the same spectral position, demonstrating a clear shape dependence that may correlate to a systematic difference in the influence of the dielectric substrate. The nanoring bulk refractive index sensitivity scales linearly with plasmon peak position. The spectral sensitivity to thin films of alkanethiols gave a shift of approximately 5.2 nm/CH2 unit while bulk sensitivities as high as 880 nm/RIU were observed, the highest such reported sensitivities. Both bulk and thin dielectric film sensitivities correlated well with theory. Real-time label-free monitoring of protein binding via molecular recognition was demonstrated.
Larsson
Elin M
EM
Department of Applied Physics, Chalmers University of Technology, S-41296 Göteborg, Sweden.
Alegret
Joan
J
Käll
Mikael
M
Sutherland
Duncan S
DS
D015374:Biosensing Techniques; D006046:Gold / Q000737:chemistry*; D049329:Nanostructures; D012680:Sensitivity and Specificity; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D020349:Surface Plasmon Resonance / Q000379:methods*
D006046:Gold