The Study And Application Of Chemical Sensor Based On Gold Nanoparticles

As a type of metallic nanoparticles, gold nanoparticles show some characteristics such as small size effect, extremely large surface to volume ratio, macroscopical quanta size effect, surface effect, and so on. Particularly, gold nanoparticles are attracting intensive scientific interest for their unique properties and potential applications such as photothermal therapy, biosensing, molecular imaging, and catalysis and gene delivery for cancer treatment. Core-shell nanoparticles are of great interests because it can integrate several different functionalities required by the applications into one common nanostructure. In this thesis, chemical sensor and biosensor based on gold nanoparticles have been developed.The developed technique is different from many other conventional methods in that formation of the shell is the result of the core reacting with metal ions and Na2S2O3. Not only the size of generated core-shell nanoparticles but also the core size and shell thickness can be controllable. The plasmon-derived optical resonance can be adjusted with the controllable core-shell nanoparticles. This unique red-shift of the nanoparticle plasmon resonance to wavelengths in the visible and near-infrared regions of the spectrum, a wavelength region of extreme technological interest, may prove to be of tremendous importance for optical applications. In addition, the silver element is the required composition of the resulting core-shell nanoparticles. The nanoparticle-based platform is thus demonstrated to be a highly selective and sensitive nanosensor for silver ions in aqueous media.A type of core-shell nanostructure, Au₂S/AuAgS/Ag₃AuS₂ coated gold nanorods was used as a sensing platform to detect fsNDA. The prepared core-shell nanorods are positively charged due to the adsorption of the positively charged cetyltrimethylammonium bromide (CTAB) cations on their surface. fsDNA can form ternary fsDNA–CTAB–nanorod complexes together with CTAB and nanorod, which provides a useful platform to detect fsDNA through absorption spectra and RLS spectroscopy. In this sensitive core-shell nanorod sensor, CTAB concentration and the nanoparticle dosage play important roles and have been investigated. The fsDNA–CTAB–nanorod complexes induce the great enhancement of RLS intensity of the core-shell GNRs and directly proportional to the concentration of fsDNA, reaching a detection limit of about 10-9 mg/mL.we demonstrate a method to amplify the LSPR signal based on the non-chemical functionalization induced assembly of GNRs and a highly selective and sensitive assay for detection of Hg²⁺ in aqueous solution relying on this GNR assembly has been developed. Firstly, we present Na3PO4 induced assembly of GNRs, a controllable and reversible assembly of GNR through the electrostatic interactions between isolated GNRs, resulting in a significant change of LSPR signal. Then, we take advantage of the strong affinity between Au and Hg, which conduces to a significant blue shift of coupled LSPR plasmon peak due to the formation of amalgamation. The outstanding selectivity and ultra-sensitivity of the method provide a unique way to determine Hg in aqueous solution without previous separation or preconcentration of the original sample.