Optical Waveguide-Based Biosensors Using Noble Metal Nanoparticles - From Bioimaging to Biosensors: Noble Metal Nanoparticles in Biodetection - page 95

versus RI of the surrounding medium, a linear it ( R = 0.9940) is
observed. From the plot, a RIR of 1.5 × 10 −4 RIU and a slope of 4.6
AU/RIU is estimated. To further increase the sensitivity of the PW-
PPR sensors, it has been shown that single-mode planar waveguide
structures are more sensitive by a few orders of magnitude than
their thicker multimode counterparts. 84,85 However, direct coupling
is extremely dificult for single-mode planar waveguide structures.
Buried grating coupler have been suggested because the beam input
and collection optics are located behind the waveguide and are
completely isolated from the liquid sample and thus are much more
amendable to a sensor format. 86
Figure 5.5 Schematic representation of the experimental setup for the
PW-PPR biosensor to make measurements: A, laser; B, gold
nanoparticles-modiied glass slide; C, microluidic channel; D,
top cover; E, photodiode; F, liquid inlet; G, liquid outlet. The
biosensing chip (B) consists of gold nanoparticles (C-1) and
immobilized receptor molecules (C-2), which bind with analyte
molecules (C-3) in the microluidic channel (C).
Figure 5.6 Temporal response of a DNP-functionalized PW-PR sensor
with injection of a 1 × 10 −4 g/mL anti-DNP solution.