Preparation And Characterization Of Raman Reactive Silver Substrate

As a kind of effective analysis detection tools, surface enhanced Raman spectroscopy (SERS) is mainly used in surface science, biological macromolecular conformational analysis, single molecule detection, and environmental science, etc. At present, the SERS technology research mainly embodies in the two aspects:on the one hand, it can realize the separation of mixture and qualitative analysis by the combination of SERS and separation technology; on the other hand, people need to prepare high activity of substrate and expand SERS application field. In this paper, based on hydrothermal synthesis method, we used the sodium borohydride reduction method, the hydrolysis of urea homogeneous precipitation method and sodium citrate reduction method to have the success of the synthesis of different shape and size of the silver substrates and the characterization. Results indicate that silver substrates prepared by above method have these characters, such as the preparation of low cost, simple process, less environmental pollution used reagent, ease of use and preservation, stronger Raman enhancement effect and good stability. The main research content includes the following three parts:Part one:the synthesis of silver substrates by sodium borohydride reduction methodWe prepared silver substrates on titanium plates, with different proportions of silver nitrate and ammonia solution (system A) and different concentration of NaBfH4 (system B) as reaction liquid, respectively. Based on the surface enhanced Raman spectra research of R6G, they have different degrees of enhancement effect. For system A, when the ratio of silver nitrate and ammonia solution is 1:3, the silver substrate has the best Raman enhancement effect; for system B, when the concentration of NaBH4 is 5.00 mmol·L-1, the silver substrate has the best Raman enhancement effect.Part two:the synthesis of silver substrates by hydrolysis of urea homogeneous precipitation methodIn this chapter, we use hydrothermal synthesis methods, silver nitrate as the silver source, urea as the ammonia source, formaldehyde as the reducing agent, CTAB as dispersing and stabilizing agent, pH of the solution is changed due to urea hydrolysis, and silver ion is restored to silver gradually under hydrothermal conditions. Silver substrate prepared under the condition of silver nitrate/urea molar ratio of 1:2 and joining 0.80 mmol·L-1 CTAB has the best Raman enhancement effect. Nano silver in titanium substrate is more stable when the response time is 24 hours. Silver substrate has obvious SERS enhancement effect for R6G from 2×10-5 mol·L-1 to 10-10 mol·L-1, and concentration as low as 10-10 mol·L-1, silver also has certain enhancement for R6G SERS signal. The method is simple and convenient, the material is relatively cheap, the product is stable and easy to save, and it can be directly used for product characterization and SERS detection.Part three:the synthesis of silver substrates by sodium citrate reduction methodIn this chapter, we synthesized Ag/Ti substrate by urea system adding sodium nitrate under hydrothermal conditions, sodium nitrate as a reducing agent. With urea hydrolysis step by step, pH of the solution can be adjusted continuously, and the product NH3 of urea hydrolysis can form complex with Ag+. The synthesized silver substrate has different morphology characteristics due to the change of the concentration of sodium citrate in the experiments, and its Raman active is characterized by R6G. Results show that silver substrate has the strongest Raman signal when the concentration of sodium citrate is 1.00 mmol·L-1.