Detection of nickel ions using mach-zehnder inteferometric sensor coated with carbon nanotubes & chitosan & poly(acrylic acid)

• Main Author: Maa, Han Lun
• Other Authors: Chan Chi Chiu
• Format: Final Year Project
• Language: English
• Published: 2017
• Subjects: DRNTU::Engineering::Bioengineering
• Online Access: http://hdl.handle.net/10356/70966
• Institution: Nanyang Technological University

Heavy metal ions in drinking water is hazardous to human health. Notably, nickel would cause respiratory problems, DNA damage, and more. Before consuming unknown water sources, detection of these metal ions is necessary. A heavy metal ion optical fiber sensor based on Mach-Zehnder interferometer (MZI) formed by using cascading with two coating-functionalized taper fibers was proposed and experimentally demonstrated. The tapered fiber sensor with approximate sensing length of 1mm and waist diameter of 30µm was coated using layer-by-layer technique. This allows carbon nanotubes/ chitosan and poly(acrylic acid) to be stacked on each other, creating multiple bilayers that increase chelating sites for nickel ions to attach on. As the heavy metal ions got absorbed by the coating, transmission spectrum of MZI changes due to refractive index variation of the coating. By modulating the intensity of the spectrum, concentration of heavy metal ions can be measured. Results shown that the design is suitable to detect low concentration nickel ions, from 0.3mM to 0.8mM, with sensitivity of 50.879dB/mM. It is also capable of detecting tin ions, with sensitivity of 11.782dB/mM. On top of this, the interferometric sensor is able for limited reuse, with negligible influence from temperature, making it a suitable choice for heavy metal ions detection in water bodies.