Study On SERS Substrates Of Chlorella Biological Carbon Spheres

Surface Raman Enhanced Scattering（SERS）is a highly sensitive detection tool that is fast,non-invasive and highly accurate.The detection limit can reach the single-molecule level.It has been widely used in national defense security,medical science,life science,Food safety and environmental protection and other fields.The enhancement mechanism of SERS is divided into electromagnetic field enhancement mechanism（EM）and chemical enhancement mechanism（CM）.At present,most of the research on SERS focuses on the electromagnetic field enhancement mechanism based on precious metal nanomaterials.Research on the electromagnetic field-chemical composite enhancement mechanism is still very much less.The mechanism of pure carbon-based materials as SERS substrates is chemical enhancement,but its sensitivity is not high,and the Raman enhancement factor（EF）is lower than other substrates.However,the carbon-based material itself has excellent adsorption performance and chemical stability.By combining with other noble metal nanomaterials as the support material of the SERS substrate,a composite SERS substrate with excellent performance is obtained.The enhancement mechanism of this substrate includes both carbon-based The chemical enhancement mechanism of materials also includes the electromagnetic field enhancement mechanism of precious metal nanomaterials,and the electromagnetic field enhancement mechanism is dominant.In order for the composite SERS substrate to be widely used,three problems need to be solved.One is that carbon-based materials can adsorb many molecules,how to achieve selective and specific detection;the other is high specific surface area,high conductivity and easy surface The problem of batch preparation of modified carbon-based materials and cost reduction;the third is how to further improve the detection limit of SERS substrates.In this paper,we designed a SERS substrate based on chlorella biochar（CBCS）as a carbon material substrate and composited with precious metal material silver nanoparticles（AgNPs）.The details are as follows:Built a grid-format photobiological culture rack for cultivating chlorella.Each grid is a dark room,which can control the plant tissue culture lights in each dark room.The light intensity and light time refer to the day and night time of the summer solstice in Wuhan,observe the growth of its biomass,and obtain the most suitable light intensity for chlorella growth of 3000 to 4000 lux.Chlorella grown on a large scale using a photobioreactor is used as a raw material for preparing Chlorella biological carbon spheres,design a more efficient chlorella expansion process.The process flow of obtaining Chlorella biological carbon spheres and hollow Chlorella biological carbon spheres by carbonizing Chlorella was designed,and the morphology,conductivity and specific surface area of Chlorella biological carbon spheres after carbonization at different temperatures were discussed.The CBCS@AgNPs SERS substrate was fabricated by assembling the prepared AgNPs on the surface of the Chlorella biological carbon spheres.The SERS detection was performed on the substrate with R6G as the probe molecule,and a stable Raman signal was obtained,with the lowest detection limit reaching 10^-12M,and this substrate has good uniformity and repeatability,and the relative deviation of the intensity of the Raman characteristic peaks does not exceed 10%.In addition,we also proved that the composite substrate has the chemical enhancement mechanism of the Chlorella biological carbon spheres and the electromagnetic field enhancement mechanism dominated by AgNPs,and the Chlorella biological carbon spheres can also separate the incident light from the metal material,which can avoid probe molecules.The photocatalysis also slows down the oxidation process of AgNPs.