Leng Weinan, Vikesland Peter J
Department of Civil and Environmental Engineering, Institute of Critical Technology and Applied Science (ICTAS), Virginia Tech , 418 Durham Hall, Blacksburg, Virginia 24060-0246, United States.
Langmuir. 2014 Jul 22;30(28):8342-9. doi: 10.1021/la501807n. Epub 2014 Jul 10.
Malachite green isothiocyanate (MGITC) is frequently used as a surface bound Raman reporter for metal nanoparticle-enabled surface enhanced Raman scattering (SERS). To date, however, no study has focused on the application of MGITC for the formation of stable "hot-spot" aggregates for Raman imaging applications. Herein we report a method to produce a series of suspensions of MGITC functionalized gold nanoparticles (MGITC-AuNPs) that at one extreme consist primarily of monomers and at the other extreme as mixtures of multimers and monomers. Monomer and multimer morphologies were characterized by scanning electron microscopy and atomic force microscopy using a reliable spin-coating deposition sampling method. The multimers generally include 2, 3, or 4 individual AuNPs with an average number of 3 ± 1. The number of multimers produced in a given suspension was found to be dependent on the volume and concentration of MGITC initially applied. The surface binding of MGITC to both monomeric and multimeric MGITC-AuNPs was investigated by Raman and SERS, and the degree of aggregation in the multimer suspension was evaluated based upon the measured variation of the MGITC SERS intensity of the AuNPs. Using an estimated extinction coefficient of 1.22 ± 0.41 × 10(11) M(-1) cm(-1) at ≈850 nm for the localized surface plasmon resonance (LSPR) band of the MGITC-AuNP multimers, the multimer concentrations were calculated by Beer's Law.
异硫氰酸孔雀绿（MGITC）经常被用作金属纳米粒子表面增强拉曼散射（SERS）的表面结合拉曼报告分子。然而，迄今为止，尚无研究关注MGITC在形成用于拉曼成像应用的稳定“热点”聚集体方面的应用。在此，我们报告一种制备一系列MGITC功能化金纳米粒子（MGITC-AuNPs）悬浮液的方法，这些悬浮液一端主要由单体组成，另一端则是多聚体与单体的混合物。通过扫描电子显微镜和原子力显微镜，采用可靠的旋涂沉积采样方法对单体和多聚体形态进行了表征。多聚体通常包含2、3或4个单个金纳米粒子，平均数量为3±1。发现给定悬浮液中产生的多聚体数量取决于最初应用的MGITC的体积和浓度。通过拉曼光谱和SERS研究了MGITC与单体和多聚体MGITC-AuNPs的表面结合情况，并根据测量的金纳米粒子MGITC SERS强度变化评估了多聚体悬浮液中的聚集程度。利用MGITC-AuNP多聚体的局域表面等离子体共振（LSPR）带在≈850nm处估计的消光系数1.22±0.41×10(11) M(-1) cm(-1)，根据比尔定律计算了多聚体浓度。
