School of Pharmacy, Nanjing Medical University , Nanjing, Jiangsu 211166, China.
School of Chemistry and Chemical Engineering, Anhui University , Hefei, Anhui 230601, China.
Anal Chem. 2017 Sep 5;89(17):8836-8843. doi: 10.1021/acs.analchem.7b01267. Epub 2017 Aug 9.
Surface-enhanced Raman scattering (SERS) by use of noble metal nanoparticles has become a powerful tool to determine a low-concentration target by unique spectral fingerprints, but it is still limited to the Raman-inactive and nonresonant biomolecules such as amine acids, proteins, and hormones. Here, we report an Ehrlich reaction based derivative strategy in combination with gold nanoparticles (Au NPs) hotspots for the selective detection of indole-like plant hormones by SERS spectroscopy. Ehrlich reaction of p-(dimethylamino)benzaldehyde (PDAB) with the indole ring chemically transformed plant hormone indole-3-butyric acid (IBA) into a Raman-active and resonant derivative with an extended π-conjugated system in the form of a cation, which produced a new absorption band at 626 nm. On the other hand, cationic IBA-PDAB highly evoked the aggregation of Au NPs with negative citrate ligands to form the effective Raman hotspots and gave rise to the new absorption ranging from 600 to 800 nm. Significantly, the spectral overlap among IBA-PDAB, aggregated Au NPs, and the exciting laser initiated the multiple optical resonances to generate the ultrahigh Raman scattering with a sensitive limit of 2.0 nM IBA. The IBA in the whole sprouts and various parts of pea, mungbean, soybean, and black bean has been identified and quantified. The reported method opens a novel avenue for the SERS detection of Raman-inactive analyte by a proper derivation.
表面增强拉曼散射（SERS）利用贵金属纳米粒子，通过独特的光谱指纹，已成为一种确定低浓度目标物的强大工具，但它仍然仅限于拉曼非活性和非共振生物分子，如氨基酸、蛋白质和激素。在这里，我们报告了一种基于艾利希反应的衍生策略，结合金纳米粒子（Au NPs）热点，用于通过 SERS 光谱选择性检测吲哚类植物激素。对（二甲氨基）苯甲醛（PDAB）与吲哚环的艾利希反应将植物激素吲哚-3-丁酸（IBA）化学转化为具有扩展π共轭体系的拉曼活性和共振衍生物，以阳离子形式存在，在 626nm 处产生新的吸收带。另一方面，阳离子 IBA-PDAB 高度引发带负柠檬酸配体的 Au NPs 聚集，形成有效的拉曼热点，并产生新的吸收范围从 600nm 到 800nm。值得注意的是，IBA-PDAB、聚集的 Au NPs 和激发激光之间的光谱重叠引发了多重光学共振，产生了具有 2.0 nM IBA 超低限的超高拉曼散射。整个豆芽以及豌豆、绿豆、大豆和黑豆的各个部位的 IBA 都已被鉴定和定量。该方法通过适当的衍生，为拉曼非活性分析物的 SERS 检测开辟了一条新途径。
