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Title:	Chitosan-graphene oxide surface plasmon resonance sensor based on Au/Ag/Au nanostructure for lead (II) ion detection
Authors:	Nur Hasiba Kamaruddin (P59613)
Supervisor:	Ahmad Ashrif A Bakar, Assoc. Prof. Dr.
Keywords:	Ion detection Sensor Nanostructure Wastewater Universiti Kebangsaan Malaysia -- Dissertations
Issue Date:	26-Oct-2017
Description:	Heavy metal contamination in groundwater has become one of the public health concerns due to its detrimental effect to living organisms. Therefore, various detection techniques have been deployed to monitor the concentration of this effluent in one of its sources which is the wastewater. Surface plasmon resonance (SPR) sensor is an appealing alternative because it offers a more convenient detection technique with an adequate sensitivity compared to the conventional ones. SPR sensors utilise the evanescent field at the metal-dielectric interface which acts as the 'probing tip' to detect the changes in the refractive index due to the analyte-ligand interactions in the dielectric layer. While many popular studies manipulate the material of the dielectric layer which contains the ligands of an SPR sensor, the novelty of this research lies in the metal layer. The main objective of this research is to extend the linearity range and saturation point of the conventional Gold (Au)/Chitosan-Graphene Oxide (CS-GO) SPR sensor in detecting lead (II) (Pb2+) ions by incorporating the combination of Silver (Ag) and Au multi-metallic nanostructure. Preliminary results show that the multi-metallic nanostructure is capable to enhance the evanescent field thus allows for further detection of refractive index changes caused by the increased Pb2+ ion concentration hence the linearity range and saturation point could be extended. The Ag/CS-GO, Ag/Au/CS-GO and Au/Ag/Au/CS-GO SPR sensors were fabricated on glass substrates then analysed to obtain their physical characteristics. SPR experimental set-up based on Kretschmann's configuration was used to test the CS-GO SPR sensors upon exposure of air, deionised water and Pb2+ ions of 0.1 ppm, 0.5 ppm, 1 ppm, 3 ppm and 5 ppm where the performance parameters such as sensitivity, linearity range, saturation point, repeatability, detection accuracy (DA) and signal-to-noise ratio (SNR) were computed. The characterisation analysis of the samples exhibit that the Ag, Ag/Au and Au/Ag/Au nanostructures were successfully deposited onto the glass substrates according to the designated thickness while the CS-GO nanocomposite was effectively synthesised and immobilised onto them. The experimental results show that both Ag/Au and Au/Ag/Au nanostructures are capable to extend the linearity range and saturation point of the conventional Au/CS-GO SPR sensor. Apparently, Au/Ag/Au nanostructure seems to be more effective because not only the linearity range and saturation point have been extended beyond 5 ppm but the shift in the SPR angle has also increased by approximately 0.4 ° for 0.1 - 1 ppm of Pb2+ ions than those produced by the Au/CS-GO SPR sensor. The repeatability of the Au/Ag/Au/CS-GO SPR sensor is also excellent based on the small relative standard deviation (RSD) of 0.03-0.16. The outstanding performance owes to the enhanced evanescent field provided by the inner Ag layer which contributes to a more stable 'probing tip' for further detection of refractive index changes plus the inherited sensitivity of the Au layers. The binding affinity constant, K between the Au/Ag/Au/CS-GO SPR sensor and Pb2+ ion which was derived using the Langmuir isotherm model yielded a value of 7 × 105 M-1. This study proves that the Au/Ag/Au nanostructure is effective to improve the performance of the conventional Au/CS-GO SPR sensor hence should also be practical for other SPR sensors as well.,Ph.D.
Pages:	208
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Engineering and Built Environment / Fakulti Kejuruteraan dan Alam Bina

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