Li Limin, Chin Wee Shong
Department of Chemistry, Faculty of Science, National University of Singapore, 3 Science Drive 3, 117543, Singapore.
ACS Appl Mater Interfaces. 2020 Aug 19;12(33):37538-37548. doi: 10.1021/acsami.0c07178. Epub 2020 Aug 6.
Flexible and transparent surface-enhanced Raman scattering (SERS) substrates have long been sought-after for nondestructive detection of analytes on nonplanar surfaces, but there is still a lack of one convenient and robust way to fabricate such SERS substrates rapidly. Herein, we demonstrate the fabrication of a high-performance SERS substrate consisting of plasmonic Ag nanocube (Ag NC) arrays anchored onto a flexible transparent poly(dimethylsiloxane) (PDMS) membrane. Through a simple organic/water interfacial self-assembly method, arrays of presynthesized Ag NCs are obtained and directly retrieved onto the PDMS membrane without the aid of rigid substrates (e.g., Si wafers or glass slides). The plasmonic Ag NC arrays can produce strong electromagnetic enhancement, achieving high SERS enhancement factor (∼3.43 × 10) and ideal detection capability for methylene blue (MB) and Rhodamine 6G (R6G) at respective trace amounts of 10 and 10 M. Moreover, without the need to transfer from substrate to substrate, the regular Ag NC arrays are kept intact, thereby yielding a good reproducibility (RSD ∼12%). We demonstrate further that our as-fabricated SERS substrate displays ideal selectivity toward different kinds of analyte molecules (R6G, crystal violet (CV), and MB) based on principal component analysis. The PDMS membrane owns excellent transparency and flexibility; thus, the substrate enables the conformal contact with nonplanar surfaces and allows the penetration of a laser to reach the analytes from the reverse side of the substrate. This thus facilitates SERS detection of trace residual crystal violet on fish skin, with limit of detection (LOD) reaching 0.6 ppm. This fabrication method reported here is economical and easily implemented. The robust Ag NCs@PDMS could be readily prepared and stored to meet diverse SERS sensing applications, especially for detection of analytes on irregular nonplanar surfaces.
柔性透明表面增强拉曼散射（SERS）基底长期以来一直是人们所追求的，用于对非平面表面上的分析物进行无损检测，但目前仍缺乏一种方便且可靠的方法来快速制备这种SERS基底。在此，我们展示了一种高性能SERS基底的制备方法，该基底由锚定在柔性透明聚二甲基硅氧烷（PDMS）膜上的等离子体银纳米立方体（Ag NC）阵列组成。通过一种简单的有机/水界面自组装方法，获得了预合成的Ag NC阵列，并直接将其回收至PDMS膜上，无需借助刚性基底（如硅片或载玻片）。等离子体Ag NC阵列能够产生强烈的电磁增强，实现高SERS增强因子（约3.43×10），并对亚甲基蓝（MB）和罗丹明6G（R6G）分别在10和10 M的痕量水平下具有理想的检测能力。此外，无需在不同基底之间转移，规则的Ag NC阵列保持完整，从而具有良好的重现性（相对标准偏差约12%）。我们进一步证明，基于主成分分析，我们制备的SERS基底对不同种类的分析物分子（R6G、结晶紫（CV）和MB）表现出理想的选择性。PDMS膜具有出色的透明度和柔韧性；因此，该基底能够与非平面表面实现共形接触，并允许激光从基底的背面穿透以到达分析物。这便于对鱼皮上的痕量残留结晶紫进行SERS检测，检测限达到0.6 ppm。本文报道的这种制备方法经济且易于实施。坚固的Ag NCs@PDMS能够很容易地制备和储存，以满足各种SERS传感应用，特别是用于检测不规则非平面表面上的分析物。
