SERS Study Of Small Organic Molecules Probe

As an important kind of small organic molecule,glycerol can achieve ultra-low friction with a mixed solution of phosphoric acid and so on.But the Raman signal is so weak that could limit its application in exploration of friction coefficient change mechanism.Therefore,it is important to carry out SERS study on glycerol.The purpose of this paper was adopting different methods to prepare SERS substrate in order to enhance the Raman signal.At the same time,the Raman spectra of 5CB and R6G was also tested in order to study the applicability scope of SERS substrate.The research details were as follows:?1?The SERS substrate was prepared by magnetron sputtering and the best experimental scheme was determined:sputtering mixed nanoparticles on glass and removing Al nanoparticles with dilute hydrochloric acid setting sputtering time as 60 s and silver aluminum double target sputtering power ratio as 2:1.Measured on the SERS substrate,the highest Raman enhancement factor of glycerol was 7550 and the limit detection concentration of R6G was about 10^-9 M while the highest Raman enhancement factor on 5CB was only 78.It suggested based on the selectivity,SERS substrate prepared by magnetron sputtering has a good enhancement effect on glycerol and R6G,but a limited enhancement effect on 5CB.?2?The SERS substrate was prepared by chemical reduction and the best experimental conditions were determined:setting chemical reduction reaction time as 96 h,the concentration of silver ammonia solution as the saturation concentration 1.5 M and the volume ratio of APS and toluene as9:10.The highest Raman enhancement factor of glycerol was about 15000and the limit detection concentration of R6G was about 10^-10 M while the highest Raman enhancement factor on 5CB was only 91.It suggested based on the selectivity,SERS substrate prepared by chemical reduction also has a good enhancement effect on glycerol and R6G,but a limited enhancement effect on 5CB.?3?The SERS substrate was prepared by the galvanic cell replacement and the best experimental scheme was determined:dropping the mixed solution of AgNO₃ and CTAB on the zinc sheet to cause the replacement reaction setting the concentration of AgNO₃ as 0.01 M and the concentration of CTAB as 0.005 M.The highest Raman enhancement factor of glycerol was 1680 and the limit detection concentration of R6G was about10^-9 M while the highest Raman enhancement factor on 5CB was only 28.It suggested based on the selectivity,SERS substrate prepared by the galvanic cell replacement also has a good enhancement effect on glycerol and R6G,but a limited enhancement effect on 5CB.?4?The research about repeatability and stability of the SERS substrate indicated that the SERS substrate was good at repeatability,but poor in stability in the air,generally only about 12 h.The preservation effect contrast experiment suggested the preservation effect of TiO₂ as a protective film was better than that of ZnO and vacuum protection method,and the best thickness of TiO₂ was 2 nm.In summary,the SERS substrate prepared by chemical reduction has the best Raman enhancement effect on probe molecules such as glycerol.At the same time,the study indicated that 2 nm TiO₂ nano protective film deposited on the SERS substrate through ALD system could not only improve the stability of the SERS substrate,but also promote the Raman enhancement factor.