Department of Chemical and Biochemical Engineering, Gachon University, Seongnam City, Gyeonggi-Do, Republic of Korea.
ACS Appl Mater Interfaces. 2012 Aug;4(8):3923-31. doi: 10.1021/am300750s. Epub 2012 Aug 2.
Gold (Au), silver (Ag), and Ag(core)Au(shell) nanoparticles (NPs) were explored as optical sensing agents for the sensitive detection of dopamine (DA) neurotransmitters in surface-enhanced Raman scattering (SERS) measurements. In these colloidal systems, dopamine (DA) molecules played as a cross-linker between M NPs (Au or Ag NPs), allowing them to reside in the confined junctions (i.e., hot spots) between aggregated NPs. The progressive addition of DA molecules (from 1 × 10(-6) to 1 × 10(-3) M) consequently decreased a primary absorption peak attributed to the characteristic M NPs and generated a secondary absorption peak at longer wavelengths attributed to heavily aggregated M NPs formed by molecular bridging effects of DA molecules at high concentrations. The aggregation degree of M NPs was also dependent on the surface states of Au and Ag NPs, i.e., DA molecules with positive amine groups induced more aggregations of Au NPs in comparison to Ag NPs with less negative charges. As the final outcome, Au NPs demonstrated higher sensitivity in SERS detection of DA at low concentrations (1 × 10(-7) to 1 × 10(-5) M), whereas Ag NPs exhibited the stronger Raman signals of DA molecules at high concentrations (1 × 10(-4) to 1 × 10(-3) M). Besides, Ag(core)Au(shell) NPs with the lowest surface coverage of Au shell exhibited more sensitive and stronger SERS activity for DA molecules than that of singular Au NPs, probably due to the combined contribution by Ag core with strong SERS intensity and Au shell with high SERS sensitivity.
金（Au）、银（Ag）和 Ag（核）Au（壳）纳米粒子（NPs）被探索作为光学传感试剂，用于表面增强拉曼散射（SERS）测量中多巴胺（DA）神经递质的灵敏检测。在这些胶体系统中，多巴胺（DA）分子充当了 M NPs（Au 或 Ag NPs）之间的交联剂，使它们能够存在于聚集 NPs 之间的受限结（即热点）中。随着 DA 分子（从 1×10(-6)到 1×10(-3)M）的逐步添加，与特征 M NPs 相关的主要吸收峰相应减小，并在较长波长处产生二次吸收峰，归因于高浓度下 DA 分子的分子桥接效应导致的大量聚集 M NPs。M NPs 的聚集程度还取决于 Au 和 Ag NPs 的表面状态，即带正电胺基的 DA 分子比带较少负电荷的 Ag NPs 诱导更多的 Au NPs 聚集。最终，Au NPs 在低浓度（1×10(-7)到 1×10(-5)M）下对 DA 的 SERS 检测表现出更高的灵敏度，而 Ag NPs 在高浓度（1×10(-4)到 1×10(-3)M）下表现出 DA 分子更强的 Raman 信号。此外，具有最低 Au 壳覆盖率的 Ag(core)Au(shell)NPs 对 DA 分子表现出比单个 Au NPs 更高的灵敏度和更强的 SERS 活性，这可能是由于 Ag 核具有较强的 SERS 强度和 Au 壳具有较高的 SERS 灵敏度的共同贡献。
