||(a) Platnium Nanoparticles as Oxidase and Peroxidase Mimic and Their |
Application in Heparin Sensing
In our first study, the Pt-NPs were synthesized using an one-pot method and were used to catalyze 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS), 3,3',5,5'-Tetramethylbenzidine (TMB), and dopamine under oxygen. The size of Pt- NPs are approximately 6±1 nm. By using TMB as substrate, the Km and Vmax were obtained 0.9 mM and 0.0042 μM/s, respectively. In order to investigative the process of electrons transfer and whether oxygen is the medium for catalytic reaction on Pt-nanoparticles based system, rotating ring disk electrode and cyclic voltammetry were perform. The results prove that under aerobic conditions, Pt-NPs have highly catalytic activity for TMB, ABTS, and dopamine of redox reaction which occur via four electrons transfer. Therefore, we suggest that Citrate-Pt NPs have the properties of oxidase. We further apply Pt-NPs cooperated with potamine as probe to detect Heparin via the decreased absorbance of TMB which is due to absorption of heparin and potamine linking in Pt-NPs, resulting in the decreased catalytic activity of Pt-NPs for TMB. Linear range is between 1 and 10 nM, detection limit is 0.3 nM. This promising method is successfully applied in detecting Heparin in human serum. Finally, we prove that Citrate-Pt NPs have the properties of peroxidase via the catalytic reaction of TMB, ABTS, and dopamine when hydrogen peroxide exist.
(b) Role of Poly(diallyldimethylammonium chloride) in the Catalytic Reduction
of 4-Nitrophenol by Metal Nanoparticle
Nitroaromatic compounds are widely used in the manufacture of pharmaceuticals、dyes、plasticides、pesticides and explsives, they are dangerous and toxicity for environment. 4-Nitrophenol belong to aromatic nitro-compounds. Due to the stability, 4-Nitrophenol is considered as priority pollutant by EPA. Therefore, it is necessary to develop technology for 4-Nitrophenol in water. In our second study, Au, Pt, Pd NPs were synthesized using PDDA or citric acid. According to the TEM, the size of nanoparticles synthesized by PDDA or citric acid are almost the same. Further, these nanoparticles cooperated with NaBH4 to reduce 4-Nitrophenol and generate 4-Aminophenol. The results reveal that the reaction rates of Au、Pt、Pd NPs synthesized by PDDA were 0.6 min-1、1.8 min-1、3.4 min-1, respectively. Comparatively, the reaction rates of Au、Pt、Pd NPs synthesized by citric acid were 0.1 min-1、0.03 min-1、0.6 min-1, respectively. The catalytic efficiency using Au、Pt、Pd NPs synthesized by PDDA are better than using Au、Pt、Pd NPs synthesized by citric acid. The likely reason is that the positive surface of metal nanoparticles which occurs through electron-transfer processes from metal nanoparticles to PDDA. The positive surface of metal nanoparticles are easier to absorb NaBH4 and 4-Nitrophenolate which is generated by 4-Nitrophenol under alkaline environment. This technology is fast and we can further apply metal nanoparticles synthesized by PDDA for reduction of aromatic nitro-compounds.