Hg2+ Optical Fiber Sensor Based on LSPR with PDDA-Templated AuNPs and CS/PAA Bilayers

An optical fiber localized surface plasmon resonance (LSPR) sensor was proposed and experimentally demonstrated to detect Hg2+ ions by functionalizing the optical fiber surface with gold nanoparticles (AuNPs) and chitosan (CS)/poly acrylic acid (PAA) bilayers. A flame-brushing technology was proposed to post-process the polydimethyl diallyl ammonium chloride(PDDA)-templated nanoparticles, avoiding the aggregation of AuNPs and achieving well-dispersed AuNPs arrays. LSPR stimulated by the AuNPs is sensitive to changes in the refractive index induced by Hg2+ ions absorption on the CS/PAA bilayers. Experimental results demonstrated that the LSPR peak wavelength linearly shifts with the concentrations of Hg2+ ions from 1 to 30 μM with a sensitivity of around 0.51 nm/ppm. The sensor also exhibits good specificity and longtime stability.

Fabrication and Characterization of Surface Plasmon Resonance Sensor with Tapered Optical Fiber Structure

Improvement of tapered fiber sensor by introducing gold thin layer for facilitating surface plasmon resonance (SPR) generation has been studied. The design of structure has been investigated to generate SPR effectively by a finite element method. The particular interest in this problem is the conditions that determine the formation of evanescent field and the interrogation of the transmission intensity change due to the evanescent field absorption. The fabrication of the tapered fiber was conducted by a technique based on flame brushing. The gold nanolayer was then deposited onto the surface of tapered fiber by sputtering technique. Qualitative agreement between the modeling and experiment results found. The results suggest that a compact sensor based on this structure may be useful for biochemical sensors.

DETECTION OF DIFFERENT CONCENTRATIONS OF URIC ACID USING TAPERED SILICA OPTICAL SENSOR COATED WITH ZINC OXIDE (ZNO)

The working principle of measurement of output power from silica optical sensor for the detection of different concentrations of uric acid is demonstrated. The fabricated sensors used single mode silica optical fibers (SOF) which were tapered using flame brushing technique to achieve a waist diameter of 32 µm and tapering length of 2 mm. The tapered fiber were then coated with ZnO nanostructures using sol–gel immersion method. The concentration of the uric acid is measured in volume parts per million (ppm) for a concentration change from 0 ppm to 500 ppm by tapered SOF coated with ZnO and non-coated sensors. The peak voltage increases linearly for coated and non-coated from 214 mV to 268 mV and 270 mv to 344 mV, respectively. Sensitivity was measured with 0.11 mV/ppm and 0.15 mV/ppm, respectively. In addition, the results show that the linearity of the sensors is 94.56% and 97.78%, respectively. Simple in fabrication and low in cost, this sensor can detect concentration changes of uric acid in a fast and convenient way with high stability and sensitivity. Thus, this sensor will be very promising in chemical and biomedical applications.