Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands.
Analyst. 2021 Feb 21;146(4):1281-1288. doi: 10.1039/d0an02103b. Epub 2021 Jan 11.
Surface-enhanced Raman spectroscopy (SERS) is an emerging analytical technique for chemical analysis, which is favourable due to its combination of short measurement time, high sensitivity and molecular specificity. However, the application of SERS is still limited, largely because in real samples the analyte is often present in a complex matrix that contains micro/macro particles that block the probe laser, as well as molecular contaminants that compete for the enhancing surface. Here, we show a simple and scalable spray-deposition technique to fabricate SERS-active paper substrates which combine sample filtration and enhancement in a single material. Unlike previous spray-deposition methods, in which simple colloidal nanoparticles were sprayed onto solid surfaces, here the colloidal nanoparticles are mixed with hydroxyethyl cellulose (HEC) polymer before application. This leads to significantly improved uniformity in the distribution of enhancing particles as the film dries on the substrate surface. Importantly, the polymer matrix also protects the enhancing particles from air-oxidation during storage but releases them to provide SERS enhancement when the film is rehydrated. These SERS-paper substrates are highly active and a model analyte, crystal violet, was detected down to 4 ng in 10 μL of sample with less than 20% point-by-point signal deviation. The filter paper and HEC effectively filter out both interfering micro/macro particles and molecular (protein) contaminants, allowing the SERS-paper substrates to be used for SERS detection of thiram in mud and melamine in the presence of protein down to nanogram levels without sample pre-treatment or purification.
表面增强拉曼光谱（SERS）是一种新兴的化学分析技术，由于其测量时间短、灵敏度高和分子特异性强的特点，因此具有很大的优势。然而，SERS 的应用仍然受到限制，主要是因为在实际样品中，分析物通常存在于复杂的基质中，其中包含微/宏观颗粒会阻挡探针激光，以及分子污染物会与增强表面竞争。在这里，我们展示了一种简单且可扩展的喷涂沉积技术，用于制造 SERS 活性纸基底，该基底将样品过滤和增强结合在单一材料中。与以前的喷涂沉积方法不同，在以前的方法中，简单的胶体纳米粒子被喷涂到固体表面上，而在这里，胶体纳米粒子在应用前与羟乙基纤维素（HEC）聚合物混合。这导致增强颗粒在薄膜干燥在基底表面上时的分布均匀性显著提高。重要的是，聚合物基质还可以在储存过程中保护增强颗粒免受空气氧化，但在薄膜重新水合时释放它们以提供 SERS 增强。这些 SERS 纸基底具有很高的活性，我们以结晶紫为例，在 10 μL 的样品中检测到低至 4 ng 的浓度，且每个点的信号偏差小于 20%。滤纸和 HEC 有效地过滤掉了干扰的微/宏观颗粒和分子（蛋白质）污染物，因此 SERS 纸基底可用于在存在蛋白质的情况下，无需样品预处理或纯化，即可检测泥土中的 thiram 和三聚氰胺，检测限低至纳克级。
