Ranishenka Bahdan V, Panarin Andrei Yu, Chelnokova Irina A, Terekhov Sergei N, Mojzes Peter, Shmanai Vadim V
Institute of Physical Organic Chemistry, National Academy of Sciences of Belarus, 13 Surganova Str., Minsk, 220072, Belarus.
B. I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, 68 Nezavisimosti Ave., 220072, Minsk, Belarus.
Beilstein J Nanotechnol. 2021 Aug 16;12:902-912. doi: 10.3762/bjnano.12.67. eCollection 2021.
This work studies the impact of the electrostatic interaction between analyte molecules and silver nanoparticles (Ag NPs) on the intensity of surface-enhanced Raman scattering (SERS). For this, we fabricated nanostructured plasmonic films by immobilization of Ag NPs on glass plates and functionalized them by a set of differently charged hydrophilic thiols (sodium 2-mercaptoethyl sulfonate, mercaptopropionic acid, 2-mercaptoethanol, 2-(dimethylamino)ethanethiol hydrochloride, and thiocholine) to vary the surface charge of the SERS substrate. We used two oppositely charged porphyrins, cationic copper(II) tetrakis(4--methylpyridyl) porphine (CuTMpyP4) and anionic copper(II) 5,10,15,20-tetrakis(4-sulfonatophenyl)porphine (CuTSPP4), with equal charge value and similar structure as model analytes to probe the SERS signal. Our results indicate that the SERS spectrum intensity strongly, up to complete signal disappearance, correlates with the surface charge of the substrate, which tends to be negative. Using the data obtained and our model SERS system, we analyzed the modification of the Ag surface by different reagents (lithium chloride, polyethylenimine, polyhexamethylene guanidine, and multicharged metal ions). Finally, all those surface modifications were tested using a negatively charged oligonucleotide labeled with Black Hole Quencher dye. Only the addition of copper ions into the analyte solution yielded a good SERS signal. Considering the strong interaction of copper ions with the oligonucleotide molecules, we suppose that inversion of the analyte charge played a key role in this case, instead of a change of charge of the substrate surface. Changing the charge of analytes could be a promising way to get clear SERS spectra of negatively charged molecules on Ag SERS-active supports.
本工作研究了分析物分子与银纳米颗粒（Ag NPs）之间的静电相互作用对表面增强拉曼散射（SERS）强度的影响。为此，我们通过将Ag NPs固定在玻璃板上来制备纳米结构的等离子体薄膜，并通过一组带不同电荷的亲水性硫醇（2-巯基乙磺酸钠、巯基丙酸、2-巯基乙醇、2-（二甲氨基）乙硫醇盐酸盐和硫代胆碱）对其进行功能化，以改变SERS基底的表面电荷。我们使用了两种带相反电荷的卟啉，即阳离子铜（II）四（4-甲基吡啶基）卟啉（CuTMpyP4）和阴离子铜（II）5,10,15,20-四（4-磺基苯基）卟啉（CuTSPP4），它们具有相同的电荷值和相似的结构，作为模型分析物来探测SERS信号。我们的结果表明，SERS光谱强度与基底的表面电荷密切相关，甚至直至信号完全消失，而基底表面电荷趋于负性。利用所获得的数据和我们的模型SERS系统，我们分析了不同试剂（氯化锂、聚乙烯亚胺、聚六亚甲基胍和多价金属离子）对Ag表面的修饰。最后，使用标记有黑洞猝灭染料的带负电荷的寡核苷酸对所有这些表面修饰进行了测试。只有向分析物溶液中添加铜离子才能产生良好的SERS信号。考虑到铜离子与寡核苷酸分子的强相互作用，我们推测在这种情况下分析物电荷的反转起到了关键作用，而不是基底表面电荷的变化。改变分析物的电荷可能是在Ag SERS活性载体上获得带负电荷分子清晰SERS光谱的一种有前途的方法。
