Morphology Controlling Of Noble Metal Nanomaterials And Their Optical Sensing Properties

In this thesis,noble metal nanomaterials with diverse morphologies,including Au nanospheres,Au nanostars,Au nanorods,Au nanobipyramids,Au nanoprisms,Au nanorings,Au@Ag nanosperes,and Au@Ag nanorods were prepared via chemical reduction method,seed-mediated growth method,and galvanic replacement method.Localized Surface Plasmon Resonance?LSPR?,a kind of unique optical properties of noble metal nanomaterials,was also studied.We further fabricated functional sol-gel silica films coated with Au nanoparticles?Au NPs?or quantum dots?QDs?,in which 3-aminopropyltrimethoxysilane?APS?sol-gel layer was employed as a linker.The optical properties of prepared device and the Plasmon Enhanced Fluorescence Resonance Energy Transfer?FRET?were also discussed.What is more,we also employed Au nanorods?Au NRs?as optical sensors to analyse the disease indicator including enzymes and metal ions.The proposed sensing methods were also applied in the real sample,and various portable sensing devices based on these sensing mechanisms were fabricated.The specific research contents are listed as follows:1.Au nanospheres and Au nanostars were prepared via chemical reduction method.Au nanorods,Au nanobipyramids,and Au nanoprisms were synthesized via seed-mediated growth method.Au nanorings were prepared through galvanic replacement method.The influence of experimental conditions on the morphology of nanomaterials was studied.The relationship between LSPR phenomenon and the shape of nanomaterials was also discussed.2.A layer-by-layer?LbL?self-assembled method has been developed to create the nano architectonics consisted of QDs including hydrophobic CdSe/CdZnS and hydrophilic CdTe and Au NPs through a functional silica layer as a linker on a slide glass.The glass layer was created by the hydrolysis of APS in which the amino group in APS plays an important role for the connection among QDs and Au NPs.UV-vis and PL spectroscopy,scanning electron microscopy?SEM?,and transmission electron microscopy?TEM?were employed to characterize.The result reveals that Au NPs or QDs could be dispersed in the glass slides at a high concentration,and little aggregation.The PL intensity and absorbance is linearly increased with the number of dipping cycles.Furthermore,when the glass layer between Au NPs and CdTe QDs is thin,the PL of the QDs quenched because of the Plasmon-enhanced fluorescence resonance energy transfer.In contrast,the bright PL of the QDs was observed when the glass layer became thick.The LbL self-assembled glass film shows excellent stability and transparency,which can make a promise for application in biochemical,optoelectronic,and clinical diagnosis areas.3.The detection of catalase?CAT?associated withvarious diseases is very important due to it is frequently downregulated in human cancer tissues.Noble metalassistedsensors have achieved rapid development for wide applications but few to detecting catalase.Thus,a novel colorimetric detection has been developed to the selective and rapid visual detection of catalase by using the decelerating etching of Au NRs in the presence of hexadecyltrimethylammonium bromide?CTAB?and SCN^-,which can reduce the redox potential of Au?I?/Au?0?,Au NRs would be etched by H₂O₂ along the longitudinal direction.As a consequence,the color of solutions changed from green to pink accompanied by the LSPR extinction peak shifted to short wavelength.In contrast,the etching process would be prohibited in the presence of catalase.As a result,the color and LSPR extinction peak of Au NRs remained unchanged.Furthermore,an Au NRs-based sensor is applied to test the paper that could be used in the detection of catalase in real samples.Constructively,this method is highlighted by its selectivity and easy operation compared with previous method.The discussion of mechanism suggested such sensing method has an ideal performance in terms of sensitivity,selectivity,and linearity.4.A colorimetric method is described for the determination of ferric ion(Fe²⁺)with high sensitivity and selectivity.The method is based on catalytic etching of Au NRs In an acid condition,Fe²⁺reacts with H₂O₂ to produce superoxide radical(O₂^·-)that etches gold NR from the low energy surface along the longitudinal directionpreferentially.As a result,the changes of UV-Vis absorbance spectrum and color of gold NR can be measured and also can be detected visually.Under the optimal conditions,the assay has very low detection limit?13.5 nM?and a linear response in the 75 nM to 1?M Fe²⁺concentration range.The method was applied to the determination of Fe²⁺in spiked samples of Fetal Bovin Serum?FBS?and also transferred to a kind of test stripe for use in fast practical applications.5.In this study,a simple visual approach for the colorimetric detection of superoxide dismutase?SOD?activity was developed based on the prohibition to the morphology transition of CTAB-stabilized Au NRs.O₂^·-generated from the reaction between H₂O₂ and Fe²⁺would preferentially etch Au NRs along the longitudinal direction,which leads to remarkable changes of shape and the LSPR absorption band of Au NRs.Thanks to the dismutation of SOD,SOD decomposed O₂^·-into H₂O₂ and O_2.Thus,the etching process was held back.Under the optimal conditions,the sensor reveals excellent selectivity and sensitivity toward SOD?limited detection is 0.25 U?.A linear detection range from 1.4 to 14U was also obtained.The proposed sensing system not only was applied in the serum media,but also was made to a kind of cost-effective sensory agarose hydrogel with vivid color changes.