Photocatalysis For The Construction Of The SOD Sensor And The Preparation Of Nano-sulfur And Graphene Oxide Composites

During the photosensitzation-based catalysis,the photosensitizer is excited by light with a specific wavelength,it absorbs light energy and transitions from the ground state to the excited state.When the photosensitizer in the excited state returns to the ground state,the released energy will interact with oxygen molecules in the system and thereby,reactive oxygen species?ROS?produces via this process.The photocatalytic reaction can efficiently produce ROS through a simple reaction,which makes it widely used in organic degradation and material modification and has unlimited potential.The process is non-polluting and has low energy consumption,thus considered to be a promising green catalytic oxidation method.In this thesis,a simple and fast superoxide dismutase?SOD?sensor was established by using photocatalytic technology,and the nano-sulfur and graphene composite?GO-S?was successfully prepared by photosensitization method,and the composite material was applied for the removal of heavy metal ions in water.It mainly includes the following two parts:???A photocatalytic biosensor based on Pt-doped graphite phase carbon nitride?g-C₃N₄?was reported for the visual detection of SOD.Under purple light-emitting diode?LED?irradiation,g-C₃N₄ doped with Pt absorbs light energy and catalyzes the formation of·O₂^-,which further oxidizes the dye to a colorless product.In the presence of SOD,it can specifically conver·O₂^-into oxygen and hydrogen peroxide?H₂O₂?,thereby reducing the photo-oxidation of the material,inhibiting the degradation of the dye and producing colors visible to the naked eye.After screening a series of dyes,such as amaranth?AM?,carmine?CA?,sunset yellow?SY?,eosin Y?EY?,malachite green?MG?,rhodamine B?RB?,crystal violet?GV?and bright Blue?BB?,among them,the azo dye amaranth?AM?was proved to be the best indicator of·O₂^-,because the azo bond is easily oxidized by·O₂^-,which greatly reduces the background color.This simple photocatalytic sensor can visually detect SOD in the n M range without the requirement of complex instruments.The linear response range of SOD detection obtained by using spectromestry is 1.5 n M to 4500 n M,and the limit of detection?LOD,3??is 0.3 n M.The sensor has also been successfully used for the unlabeled and no-washing detection of SOD in human serum samples with a good recovery.???Nano-sulfur and nano-sulfur graphene nanocomposites?GO-S?were successfully prepared by photocatalysis.Under the illumination of a green LED lamp,phloxine B?PB?reacts with oxygen molecules to generate singlet oxygen with strong oxidizability,and oxidizes the sulfur ions to sulfur elemental,thus preparing spherical nano-sulfur particles with a particle size of 120-260 nm and good dispersion,the reagents used in this method are cheap and easily available,and the photosensitization preparation of non-sulfur has the advantages of low cost,simple operation,convenience and fast.Similarly,graphene oxide?GO?was added to the photosensitive preparation of nano-sulfur.During the illumination process,due to the strong affinity of the oxygen-containing groups?-OH,-COOH?and sulfur on the surface of GO,the nano-sulfur particles was grown on the surface of GO in situ and successfully prepared GO-S;due to the stronger negative charge of GO modified by nano-sulfur,the electrostatic force is large,and S^2-on the surface of nano-sulfur can be combined with Cu?II?,Cd?II?,Hg?II?and Pb?II?to generate heavy metal sulfide precipitate and adsorb on the surface of the adsorbent,thus greatly improving the ability of GO to remove heavy metal ions.At the same time,the deposition of a large amount of nano-sulfur on the surface of GO increases the original quality of GO,and it is easier to separate after adsorbing heavy metal ions,making the experimental operation more convenient and fast.The best experimental conditions for GO-S adsorption of Cu?II?,Cd?II?,Hg?II?,Pb?II?were obtained;the adsorption characteristics of GO-S for several heavy metals were studied,and the kinetic process of GO-S adsorption of Cu?II?,Cd?II?,Hg?II?,Pb?II?conformed to the quasi-second-order kinetic equation,and the modification of nano-sulfur accelerated the adsorption rate of GO to Cu?II?,Cd?II?,Hg?II?,Pb?II?;Langmuir isotherm adsorption model can well describe the thermodynamic process of GO and GO-S adsorption Cu?II?,Cd?II?,Hg?II?,Pb?II?.Nano-sulfur modification significantly improved GO's adsorption capacity of Cu?II?,Hg?II?,Cd?II?and Pb?II?,the adsorption rate increased from 16%,55%,36.2%,73.5%to 98.4%,96%,95.8%,97.8%;the adsorption mechanism of GO-S was preliminarily analyzed,and the adsorption process of Cu?II?,Cd?II?,Hg?II?,and Pb?II?by GO-S was determined as the result of the synergistic effect of physical adsorption and chemical adsorption,but chemical adsorption was dominant.