介电衬底上利用常压CVD直接生长石墨烯复合纳米银表面增强拉曼研究

Surface-enhanced Raman Spectrum of Nano-silver Composited As-grown Graphene on Dielectric Substrate by APCVD

目的为了进一步完善Ag基表面增强拉曼(SERS)基底,提升其性能,设计了制备SERS基底的新型方法,采用2种方法制备分别得到转移石墨烯纳米银复合SERS基底(Transfer-G/Ag/SiO_(2)基底)和纳米银石墨烯复合基底(Ag/G/SiO_(2)基底),并对2种基底的增强效果从增强因子、热稳定性、重复性的角度进行比较。方法使用常压化学气相沉积(APCVD)在二氧化硅和铜表面同时生长石墨烯,使用多元醇水热法制备纳米银,前者与纳米银复合得到Ag/G/SiO_(2)基底,后者将生长出的石墨烯转移后与纳米银制备得到Transfer-G(Cu)/Ag/SiO_(2)基底,以传统方法制备的Transfer-G/Ag/SiO_(2)基底为对照,评价制备的Ag/G/SiO_(2)基底的增强性能。结果使用拉曼测试平台选用低功率532 nm激光测量10^(-6)mol/L罗丹明6G(R6G)探针分子的SERS拉曼光谱,比较2种基底的性能。计算得到2种基底基于10^(-6)mol/L R6G的增强因子,Transfer-G/Ag/SiO_(2)基底的增强因子为9.93×10^(5),Ag/G/SiO_(2)基底的增强因子为9.23×10^(5)。测试Ag/G/SiO_(2)的稳定性得到,在611、1362、1648 cm^(-1)处特征峰的RSD值分别为9.80%、14.08%、18.18%,数值均低于20%,甚至在611 cm^(-1)和1362 cm^(-1)处的RSD值分别低于10%和15%。结论Ag/G/SiO_(2)基底的SERS效果与传统方法制备的Transfer-G(Cu)/Ag/SiO_(2)基底相比增强效果同样显著,表现在:两者增强因子基本相同,且都具有很好的热稳定性、均匀性和高度重复性。由于使用水热法提高了纳米银的制备效率,并且石墨烯生长避免转移过程,减少对石墨烯的物理损伤和化学药品的化学损伤,确保原位生长石墨烯的质量,进而提高Ag/G/SiO_(2)基底的性能,为快速制备高性能SERS基底提供可行方法。

Raman spectrum is used to feed back the stretching,vibration,and rotation of molecules,thereby transmitting structural information of molecules.The rotation and vibration of each molecular bond are determined by the type of molecule,and different molecules will transmit different signals.Based on such properties,Raman spectrum can be used for molecular identification and determination of substances.However,in practical applications,the concentration of the molecules to be tested is often relatively low,and the scattering intensity is too low for traditional Raman spectrum.Some molecules to be detected also have strong fluorescent signals,which will mask the Raman signal of the molecule.Moreover,traditional Raman has a lower limit of detection,and the limit value is relatively high.The emergence of surface enhanced Raman spectrum(SERS)technology solves the problem of low sensitivity of traditional Raman,which can be detected at the molecular level.SERS substrates are usually fabricated by metal nanoparticles,which can achieve electromagnetic enhancement through localized"hot spots".The composite of metal nanoparticles and graphene is a hot and emerging direction.Among them,nano-silver has the best enhancement effect for SERS substrate.The introduction of graphene makes the SERS substrate more stable and weakens the fluorescence background.However,traditional composite SERS substrates usually use low pressure chemical vapor deposition to fabricate graphene on copper foil,needing to be transferred to combine with nanoparticles.Wet etching and transfer will cause certain damage to the graphene,and there will also be chemicals residues,thus affecting the application effect of graphene.In addition,the graphene transfer is a time-consuming process,which makes the application of graphene cumbersome.Therefore,the work aims to design a novel substrate(Ag/G/SiO_(2))for SERS.Graphene was grown on SiO_(2)dielectric substrate by APCVD,which was free from transfer and combined with nano-silver to prepare SERS substrate.The growth quality of graphene was controlled by adjusting the time of feeding the ethanol carbon source,and the best enhancement effect of graphene under the optimal growth time was explored.In this work,APCVD could improve the growth rate of graphene while ensuring the quality of graphene.Growing graphene directly on SiO_(2)avoided transfer process and reduced damage and chemical pollution to graphene,thus ensuring high-quality applications of graphene.At the same time,the same experimental method was used to prepare graphene on catalytic metal copper foil.After transfer process,a SERS substrate(Transfer-G/Ag/SiO_(2))composited with transferred graphene and nano-silver was prepared,which was used to evaluate the rapidly prepared Ag/G/SiO_(2).The performance of the two substrates was measured by the SERS of a 10^(-6)mol/L R6G probe molecule with a Raman test platform under a low power 532 nm laser.The enhancement factor(EF)of the two substrates was calculated,the EF of the optimal Ag/G/SiO_(2)substrate was 9.23×10^(5),and the EF of the Transfer-G/Ag/SiO_(2)substrate was 9.93×10^(5).The stability of Ag/G/SiO_(2)was tested as well.The RSD values of the characteristic peaks at 611 cm^(-1),1362 cm^(-1)and 1648 cm^(-1)were 9.80%,14.08%and 18.18%,respectively,which were lower than 20%,and even the RSD values at 611 cm^(-1)and 1362 cm^(-1)were lower than 10%and 15%.Compared with Transfer-G(Cu)/Ag/SiO_(2)substrate prepared by traditional methods,the SERS effect of Ag/G/SiO_(2)substrate is also significant,which is shown in the following aspects:The enhancement factors of the two substrates are basically the same,and they both have good thermal stability,uniformity and high repeatability.This improves the performance of Ag/G/SiO_(2)substrate and provides a feasible method for rapid preparation of highperformance SERS substrate.