Effects of Acid Dopants Toward Application of Polyaniline in Optical Interferometer Sensor for Lead Detection

Ong, Jing Yi (2018) Effects of Acid Dopants Toward Application of Polyaniline in Optical Interferometer Sensor for Lead Detection. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

Text Ong Jing Yi_Full Text.pdf Restricted to Registered users only Download (2MB)

Abstract

Vast amount of lead (Pb) pollution has been caused by the growth of industries such as paint, lead smelting and battery recycling. Conventional methods including Atomic Absorption Spectrometry (AAS), Laser Induced Breakdown Spectrometry (LIBS) and Anodic Stripping Voltammetry (ASV) were used to detect Pb in waste water, but it causes a lot of disadvantages. Therefore, a novel polyaniline (PAni) coated optical fiber sensor with Mach-Zehnder interferometer (MZI) set-up was developed to overcome the pitfalls of conventional sensing methods in Pb detection. PAni with different aniline (Ani) to diethylhexyl sulfosuccinate sodium salt (AOT) ratio (5:3, 5:5 and 5:7) and different acid dopants (HCl, H2SO4 and H3PO4) were synthesized by using chemical oxidation reaction. All of the PAni were characterized by using FTIR, UV-Vis and electrical conductivity studies. Supporting data from FTIR, UV-VIS and electrical conductivity studies have confirmed the chemical interaction between PAni and Pb during sensing application. Among all PAni, PAni-HCl possesses the highest electrical conductivity (4.225 × 10-1 S/cm) due to the lowest pH that allows strong electron withdrawing property which provide more mobile carbocation and thus having a higher conductivity. Among all PAni, PAni-H2SO4 possesses the highest sensitivity (0.0927) due to the two steps dissociations of H2SO4 which protonate larger amount of amine and imine groups that are able to yield more active sites and enhance Pb detections. Partially positive Pb2+ will be attacked by the partially negative N atom of amine and imine groups of PAni. Among all Pani, PAni-H2SO4 coated optical fiber shows the best performance with the highest sensitivity of 0.0927, fast response time of 11 s and the limit of detection (LOD) which is lower than 10 ppm. The performance of this novel PAni-coated optical fiber is comparable to the conventional methods in lead detections with the response time longer than 3 min and the LOD range of 0.02 ppb to 5.00 ppm.