The Detection And Catalysis Of G-C₃N₄/Ag Composites As SERS Substrates For Organic Compounds

Surface-Enhanced Raman Scattering?SERS?is a phenomenon in which when molecules are adsorbed on the surface of rough metal nanoparticles such as gold,silver,copper and some semiconductors,SERS technology can provide the content and structure information of the molecules to be tested,and realize fast and non-destructive ultra-sensitive detection.Graphite-like carbon nitride?g-C₃N₄?is a non-metallic polymer n-type semiconductor material formed by sp² hybridization of carbon and nitrogen atoms.In this paper,two SERS substrates of g-C₃N₄ loaded Ag nanoparticles?Ag NPs?composites were prepared and applied to the detection and photocatalytic degradation of dye molecules RhB and drug ROM.The main research contents of this paper are as follows:a)Two g-C₃N₄ loaded Ag NPs composite materials can be controlled as SERS substrates for dye molecule and drug molecule detectionWe have prepared two g-C₃N₄ loaded Ag NPs nanocomposites.The first method is reducing silver ions by sodium citrate to prepare silver nanoparticles with a particle size of about 50 nm and then assemble them on the surface of g-C₃N₄ nanosheets to produce g-C₃N₄/Ag composites.The other approach is to use?-cyclodextrin??-CD?as a reducing agent to synthesize silver nanoparticles,and then mono-?6-mercapto-6-deoxy?-?-cyclodextrin??-CD?as a stable protective layer covers on the surface of silver nanoparticles to prevent their aggregation.The prepared CD–S–Ag nanoparticles show a size about 26 nm in diameter.The prepared CD-S-Ag NPs are deposited on the surface of g-C₃N₄ to synthesize CD-S-Ag/g-C₃N₄composites.A series of measurements such as UV-Vis,XRD,and Raman are performed to characterize the two materials.g-C₃N₄ nanosheets not only have a highly delocalized?-conjugated system and good adsorption of dye molecules,but also can be used as a carrier of Ag nanoparticles,so that Ag nanoparticles are dispersed uniformly and stably on the g-C₃N₄ their surface,giving the SERS signal excellent stability.The experimental condition of the binding time between the molecule and the substrate is optimized.The effects of pH value on the SERS intensity of the probe molecule are also investigated in detail.As the SERS substrate for SERS detection of RhB dye molecules,the RhB concentration ranges from 1.0×10^-99 to 1.0×10^-66 mol/L.There is a good linear relationship between SERS intensities and RhB concentrations.The linear equation is y=3935log[C_RhB]+36109?R²=0.993?,and the minimum detection limit is 0.39 nmol/L.At the same time,due to the electrostatic interaction between the substrate and the molecule,g-C₃N₄/Ag can enrich cationic dyes and then the dyes can be detected by SERS.CD–S–Ag/g-C₃N₄ is also used as a highly sensitive SERS substrate for detecting illegally added Rosiglitazone Maleate?ROM?in health products.Under the optimal test conditions,ROM can be detected in the concentration range from 4.74 to 237.2?g/mL with a good linear relationship.The linear equation is y=170.32log[C_ROM]+3403?R²=0.992?,and the detection limit is2.37?g/mL.In one word,the two nanocomposites are proven to be highly sensitive SERS substrates.b)Application of two g-C₃N₄ loaded Ag NPs composite materials in photocatalytic degradation of dye molecules and drug moleculesThe deposition of silver nanoparticles on the surface of g-C₃N₄ can improve the photocatalytic activity of the composite.There are two main reasons.One is that the deposition of silver nanoparticles on the surface of g-C₃N₄ can effectively change the electron distribution in the system.With the combination under different Fermi levels of Ag and g-C₃N₄,the Schottky energy barrier can be generated,which can effectively inhibit the recombination of photogenerated electrons and holes and improve the photocatalytic efficiency.On the other hand,the local surface plasmon resonance?LSPR?effect of Ag nanoparticles enhances the absorption under visible light,thereby improving the photocatalytic activity of the composite.In addition,the SPR effect of Ag nanoparticles can induce local electromagnetic field enhancement and improve the utilization efficiency of photocatalysts for visible light.We monitored the photocatalytic degradation process of molecules through SERS technology.g-C₃N₄/Ag and CD-S-Ag/g-C₃N₄ composite materials were used as photocatalysts.With the increase of visible light exposure time,SERS of RhB dye and ROM The characteristic peaks gradually decreased,indicating that the concentration of RhB and ROM continued to decrease with the increase of the visible light exposure time,and reached the degradation equilibrium after 10 and 22 minutes of light exposure,respectively.From the experimental results,it can be seen that both compounds exhibit good photocatalytic effect and have excellent photocatalytic activity.