| Energy crisis and environmental pollution are becoming more and more serious.It has been an urgent problem to detect and degrade pollutants cleanly and efficiently.Fortunately,surface enhanced Raman spectroscopy(SERS)and photocatalytic degradation technology are effective means to solve the above problems.Due to its unique structure and physical/chemical properties,metal oxide heterojunctions are widely used in photoelectronic,SERS and photocatalysis.Based on metal oxide heterojunctions,their morphology and dispersion can be further controlled or compounded with metal frame materials to improve the photoelectric,SERS and photocatalytic activities of them.The main contents of this dissertation are as follows:First,a novel Sn O2-Mo O3-RGO heterojunction composite was prepared by in-situ induction and calcination of reduced graphene oxide(RGO).The Sn O2-Mo O3 heterojunction anchored on the RGO possessed uniform distribution and small size.Moreover,the nanocomposite contained Sn O2-Mo O3 heterojunction showed lower interfacial resistance,higher absorbance as well as photoelectronic response.As proved by photoluminescence spectra,the enhanced performance was mainly attributed to efficient separation of photogenerated charges and fast electron transfer in the nanocomposite.Moreover,the synergistic effect of the special Sn O2-Mo O3 heterojunction and RGO also played an important role.Then,with Cu2O as the core,Si O2,metal-organic framework(ZIF-8)and Ag nanoparticles are introduced layer by layer to construct a 3D core-shell nanocomposite material(Cu2O@Si O2@ZIF-8@Ag),where the amount of Ag is only 0.5 wt.%.The successful construction of the novel core-shell SERS platform with special structure was confirmed by scanning electron microscopy,transmission electron microscopy,X-ray powder diffraction(XRD),and X-ray photoelectron spectroscopy(XPS).In addition,the Ag nanoparticles on the surface of Cu2O@Si O2@ZIF-8 displayed good dispersibility,small and uniform particle size.Importantly,the nanocomposite exhibited a highly sensitive and stable SERS response toward crystal violet(CV,a dose-related carcinogen)molecules.The considerable SERS enhancement over the nanocomposite was mainly attributed to the special high-density Ag NPs“hot spots”and the powerful enrichment effect of the ZIF-8 shell sustained by the Cu2O@Si O2 core.In particular,even if it was recycled for 5 times or placed in the air for 40 days,Cu2O@Si O2@ZIF-8@Ag still maintained a sensitive SERS response to CV.Additionally,the small amount of silver,good selectivity and stability prove that Cu2O@Si O2@ZIF-8@Ag has great potential in reliable SERS detection.Finally,a metal-organic framework(ZIF-8)and Ag nanoparticles were fabricated layer by layer on the Ti O2 coated Al sheet,and thus a plug-and-play Al-Ti O2-ZIF-8-Ag heterojunction substrate with a sandwich structure was successfully synthesized.The Al-Ti O2-ZIF-8-Ag substrate possessed a low detection concentration of 1×10-9 mol L-1 towards 4-aminothiophenol(4-ATP),and the SERS analytical enhanced factor(AEF)of the Al-Ti O2-ZIF-8-Ag was calculated to 2.6×106,which was higher than other similar comparisons.In particular,Al-Ti O2-ZIF-8-Ag can also selectively detect 4-ATP repeatedly in real water samples containing 4-ATP,indicating that the Al-Ti O2-ZIF-8-Ag was a very active and stable SERS substrate for the monitoring of 4-ATP.Importantly,the substrate exhibited faster and more efficient photocatalytic degradation of 4-ATP.Furthermore,combining photocatalysis and SER performance,XPS,UV-Vis spectroscopy and other means,the SERS and photocatalytic enhancement mechanism of Al-Ti O2-ZIF-8-Ag substrates were proposed.The results of this part proved that this dual-function,low-cost and plug-and-play Al-Ti O2-ZIF-8-Ag sheet has good practical value in the detection and treatment of pollutants in waste water.The design and construction of these heterojunctions with novel structure and superior performance will provide new ideas for the preparation and performance research of other heterojunction composite systems.It will also provide experimental and theoretical reference for exploring the mechanisms of electron transfer and SERS enhancement in other similar systems. |
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