Construction Of Novel Transition Metal-based Nanozymesand Their Applications In Colorimetric Analysis

Great advancement has been achieved in nanotechnology since the beginning of the21 st century,leading to huge progress in materials science.Nanomaterials with special enzymatic features have shown wide applications in various fields ranging from biosensing,immunoassay,diagnosis and treatment of cancer,to nerve protection,stem cell growth and environmental pollution control.We have systematically explored the transition metal-based nanomaterials varying from noble metal alloy to transition metal sulfides,in order to evaluate their potentials as hydrogen peroxide or mercury ion sensor,in broad areas from milk to cosmetics.This thesis focuses on the construction of novel transition metal-based nanoenzymes and their applications in colorimetric assays,and includes five chapters.1.We have reviewed recent progress in the field of nano-enzyme.The concept,methodologies,applications as well as perspectives of nano-enzyme have been discussed.2.Three-dimensional porous Pt Cu dendrites(HPPt Cu Ds)as a novel type of peroxidase were synthesized.The morphology,structure and composition of HPPt Cu Ds were characterized.Due to the special three-dimensional porous dendritic structure and its electronic effect,HPPt Cu Dsshow unique peroxidase-like activity and can catalyze the reaction between benzidine(TMB)and hydrogen peroxide.Kinetics studies indicate that HPPt Cu Ds show better catalytic capability than Pt and Pt Cu.HPPt Cu Dsbehaves as a highly sensitive H2O2 sensor with a linear range of 0.3-325?M and a detection limit(LOD)of only 0.1 ?M,well below the US Food and Drug Administration(FDA,USA)(0.05 wt%,about 15?M).3.We have developed various Cux Sy nanomaterials with well-controlled morphology and good dispersionby taking advantage of the capability of trivalent aluminum ions to mediate the morphology of Cux Sy nanoparticles and the temperature effect on the size of Cux Sy.The products were characterized by UV and TEM,and their catalytic activities as peroxidases were investigated.TMB and hydrogen peroxide were oxidized to form blue products and Cu1.8S was found to have strong catalytic activity.An assay for the detection of hydrogen peroxide with a linear range of 1-40?M and a minimum detection limit of 0.5?M was achieved by optimizing the conditions of p H,temperature,hydrogen peroxide and catalyst concentration.4.It established a colorimetric assay for the determination of mercury ions by using the promotion effect of peroxidase-mimic thin-layer molybdenum disulfide nanosheets.The encapsulation of nanosheets with negatively charged sodium polystyrene sulfonate reduced the formation of blue oxidative products.When nanoparticles were coated with positively charged diallyldimethylammonium cations,the formation of blue dyes slightly increased.Under the optimum conditions,the enzymatic activity of molybdenum dioxide is mediated by divalent mercury ions(2.0-200 ?M).The detection limit of this assay can reach up to 0.5 ?M,far below the permitted concentration of mercury ionsin cosmetics(1 ppm;ca.5 ?M).This newly developed assay showssupreme sensitivity,selectivity and stability.5.It constructed a MoS2-Au based assayfor highly sensitive and selective colorimetric detection of Hg2+ in tap water.The addition of Hg2+stimulates the peroxidase-like activity of Mo S2-Au nanomaterials,along with lower Km values toward TMB and H2O2.This stimulation effect has been applied directly to detect Hg2+ with a broad linear range of 20 n M to 20 ?M and a detection limit(LOD)of 5 n M.This assay is successfully applied for the determination of Hg2+in tap water with excellent selectivity.