Murugesan Balamurugan, Yang Jyisy
Department of Chemistry, National Chung Hsing University, Taichung 402, Taiwan.
ACS Omega. 2019 Sep 3;4(12):14928-14936. doi: 10.1021/acsomega.9b01686. eCollection 2019 Sep 17.
A new method based on the coffee ring effect was developed for improving the sensitivity, simplicity, and robustness of surface-enhanced Raman scattering (SERS) in determining trace levels of analytes. In this method, a polyvinylpyrrolidone (PVP)-stabilized silver colloidal (AgC) solution was first prepared and mixed with a sample solution. Following deposition of the mixture solution on a solid substrate with a rough surface, a coffee ring was formed once the solvent had evaporated. The formation of a coffee ring not only concentrated the analyte but also reduced the space between silver nanoparticles (AgNPs) to strengthen the hotspot effect, thereby considerably improving SERS sensitivity. To strengthen the coffee ring effect further, the surface roughness of the solid support and PVP content of the AgC solution were investigated. The results indicated that an increase in surface roughness reduced the size of the coffee rings, whereas the addition of PVP not only stabilized the AgNPs but also improved the compactness of the coffee rings. When applying the proposed method to determine the phenylalanine (Phe) level in urine for rapid screening of the phenylketonuria disorder, strong chemical interference from uric acid (UA), which is a major component in urine, was observed. To minimize the interference from UA, ZnO powder was applied to the urine sample to adsorb UA prior to SERS detection. After cleaning by using ZnO, the SERS signals of Phe were revealed for quantitative purposes. Under the optimized conditions, both the sensitivity and reproducibility of SERS measurement considerably improved. Quantitative analyses revealed that the developed method is highly feasible for the rapid determination of Phe in real samples.
开发了一种基于咖啡环效应的新方法，以提高表面增强拉曼散射（SERS）在测定痕量分析物时的灵敏度、简便性和稳健性。在该方法中，首先制备聚乙烯吡咯烷酮（PVP）稳定的银胶体（AgC）溶液，并与样品溶液混合。将混合溶液沉积在具有粗糙表面的固体基质上后，溶剂蒸发后会形成咖啡环。咖啡环的形成不仅浓缩了分析物，还减小了银纳米颗粒（AgNP）之间的间距，以增强热点效应，从而显著提高SERS灵敏度。为了进一步增强咖啡环效应，研究了固体载体的表面粗糙度和AgC溶液的PVP含量。结果表明，表面粗糙度的增加会减小咖啡环的尺寸，而添加PVP不仅能稳定AgNP，还能提高咖啡环的致密性。将该方法应用于尿液中苯丙氨酸（Phe）水平的测定以快速筛查苯丙酮尿症时，观察到尿液中的主要成分尿酸（UA）产生了强烈的化学干扰。为了最小化UA的干扰，在SERS检测前，将ZnO粉末应用于尿液样品以吸附UA。用ZnO清洗后，显示出Phe的SERS信号用于定量目的。在优化条件下，SERS测量的灵敏度和重现性都有显著提高。定量分析表明，所开发的方法对于实际样品中Phe的快速测定非常可行。
