偶极分子在CVD石墨烯表面的拉曼增强

摘要

选用CVD制备的石墨烯作为拉曼增强的基底，以激光器波长λ＝532 nm的显微拉曼光谱仪对偶极分子DREP分子的石墨烯拉曼增强效应进行了探究。通过对石墨烯上与SiO2片上DREP分子的拉曼强度的对照，发现单纯DREP／SiO2分子浓度很低时，拉曼峰基本不存在，直到达到一定浓度1×10－5 mol・L －1时，其拉曼峰才出现；随着浓度的增加，DREP分子的拉曼信号和荧光信号都增加；而DREP／Graphene／SiO2在1×10－7 mol・L －1时即出现了拉曼信号，随着浓度的增加，拉曼信号增加很快而荧光信号增加并不明显。结果表明石墨烯可实现DREP分子的拉曼增强，并能猝灭荧光背底，提高拉曼信号与荧光信号之比。对比了不同偶极矩的DREP和DR1P分子，表明偶极矩越大，其增强因子越大，增强程度越强。分析了DREP分子在石墨烯上的拉曼增强的机制。DREP分子是尾端接芘的经过改性的偶氮苯分子，其尾端的芘与石墨烯于界面处通过π—π相互作用进行电子转移，改变石墨烯的能级结构使得其发生P型掺杂，发生拉曼增强的机制是化学机制。DREP分子的石墨烯拉曼增强效应有助于我们研究石墨烯以及石墨烯表面拉曼增强机制，比如石墨烯的载流子转移，化学增强机制的原理，以及如何从电磁机制效应分离出化学机制。%The CVD graphene was chosen as the Raman enhancement substrate ,graphene‐enhanced Raman scattering(GERS) of dipolar molecule DREP were explored with a laser wavelengthλ=532 nm of micro‐Raman spectroscopy .Upon comparison of the raman signal of DREP molecular latched to a graphene /SiO2 substrate and to a bare SiO2 substrate ,we found that the Raman signal of pure DREP molecule basically does not exist at low concentrations ,until it reaches a certain concentration of 1 × 10-5 mol・L -1 ,its Raman signal emerging and as the increasing of the concentration ,Raman signal and fluorescence signal all in‐crease .However ,the raman signal of DREP molecular on the grapheme occur at the concentration of 1 × 10-7 mol・L -1 and as the increasing of concentration ,the raman signal increasing quickly but the fluorescence signal is not obvious .The studies were shown that graphene can achieve the Raman signal of DREP molecule enhancement ,and can quench fluorescent backing off ,in‐crease the ratio of Raman signal and fluorescence signals .Comparing the GERS of DREP and DR1P molecules with different mo‐lecular dipole moment ,indicating that the greater the dipole moment ,the greater the enhancement factor ,the degree of enhance‐ment is stronger .Finally ,we analyze the mechanism of Raman enhancement about DREP molecule on the grapheme .The dipole molecular is a pyrene terminal tethered a azobenzene molecular that was modified .There will happen the electron transfer of the pyrene terminal on the graphene interface through π— πinteractions ,changing the energy level of grapheme and leading to a p‐doping .The mechanism of Raman enhancement are chemical mechanisms .The study of GERS of DREP molecular can help the comprehension of grapheme and the mechanism of grapheme enhanced raman scattering ,for example the transfer of grapheme e‐lectron ,the theory of chemical enhancement mechanism and how to separate the chemical enhancement mechanism from electro‐magnetic enhancement mechanism .