Electron beam lithography (EBL) was used to directly pattern periodic gold nanodot arrays on optical fiber tips. Localized surface plasmon resonance of the E-beam patterned gold nanodot arrays on optical fiber tips was utilized for biochemical sensing. The advantage of the optical fiber based localized surface plasmon resonance (LSPR) sensors is the convenience to work with and work in harsh environments. An optical fiber tip LSPR refractive index sensor of 196 nm per refractive index unit (RIU) sensitivity has been demonstrated. The affinity sensing property of the fiber tip sensor was demonstrated using biotin/streptavidin as the receptor/analyte. The detection limit for streptavidin was determined to be 6 pM.
A hand-held dissolved oxygen optical sensor based on solid-state electronics and
highly oxygen-sensitive luminescence material has been developed. Oxygen-sensitive
dye absorbed on silica gel particles was dispersed in a 0.2 mm homogenous silicone
rubber film (optode membrane) and coated on a 580 nm long-pass filter. The O2-sensitive
dye was excited by an ultra-bright blue light-emitting diode and the emission
intensity was captured by a silicon photodiode. The long-pass filter efficiently
reduced the scattered light from the light source. The emission signal of the
optode membrane was converted to the voltage signal which was processed by a
single-chip Micyoco controller, and the dissolved oxygen concentration was
automatically displayed on a liquid crystal display unit. The developed hand-held
optical sensor is a single-piece device which can provide instant and reliable
dissolved oxygen measurement. The sensor showed good repeatability,
photostability and long-term stability. Satisfactory results were obtained
when its analytical performance was compared with that of a typical
Clark-type amperometric oxygen electrode. The developed oxygen optical
sensor possesses the advantages of portability, low cost and long lifetime.
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