Bartschmid Theresa, Farhadi Amin, Musso Maurizio E, Goerlitzer Eric Sidney Aaron, Vogel Nicolas, Bourret Gilles R
Department of Chemistry and Physics of Materials, University of Salzburg, Jakob Haringer Strasse 2A, 5020 Salzburg, Austria.
Institute of Particle Technology, Friedrich-Alexander University Erlangen-Nürnberg, Cauerstrasse 4, 91058 Erlangen, Germany.
ACS Appl Nano Mater. 2022 Aug 26;5(8):11839-11851. doi: 10.1021/acsanm.2c01904. Epub 2022 Aug 15.
Gold nanoparticle/silicon composites are canonical substrates for sensing applications because of their geometry-dependent physicochemical properties and high sensing activity via surface-enhanced Raman spectroscopy (SERS). The self-assembly of gold nanoparticles (AuNPs) synthesized via wet-chemistry on functionalized flat silicon (Si) and vertically aligned Si nanowire (VA-SiNW) arrays is a simple and cost-effective approach to prepare such substrates. Herein, we report on the critical parameters that influence nanoparticle coverage, aggregation, and assembly sites in two- and three-dimensions to prepare substrates with homogeneous optical properties and SERS activity. We show that the degree of AuNP aggregation on flat Si depends on the silane used for the Si functionalization, while the AuNP coverage can be adjusted by the incubation time in the AuNP solution, both of which directly affect the substrate properties. In particular, we report the reproducible synthesis of nearly touching AuNP chain monolayers where the AuNPs are separated by nanoscale gaps, likely to be formed due to the capillary forces generated during the drying process. Such substrates, when used for SERS sensing, produce a uniform and large enhancement of the Raman signal due to the high density of hot spots that they provide. We also report the controlled self-assembly of AuNPs on VA-SiNW arrays, which can provide even higher Raman signal enhancement. The directed assembly of the AuNPs in specific regions of the SiNWs with a control over NP density and monolayer morphology (i.e., isolated vs nearly touching NPs) is demonstrated, together with its influence on the resulting SERS activity.
金纳米颗粒/硅复合材料因其与几何形状相关的物理化学性质以及通过表面增强拉曼光谱（SERS）实现的高传感活性，成为传感应用的典型基底。通过湿化学方法合成的金纳米颗粒（AuNP）在功能化的平面硅（Si）和垂直排列的硅纳米线（VA-SiNW）阵列上的自组装，是制备此类基底的一种简单且经济高效的方法。在此，我们报告了影响纳米颗粒覆盖率、聚集以及二维和三维组装位点的关键参数，以制备具有均匀光学性质和SERS活性的基底。我们表明，平面Si上AuNP的聚集程度取决于用于Si功能化的硅烷，而AuNP的覆盖率可通过在AuNP溶液中的孵育时间进行调节，这两者都直接影响基底性质。特别地，我们报告了几乎相互接触的AuNP链单层的可重复合成，其中AuNP由纳米级间隙隔开，这可能是由于干燥过程中产生的毛细作用力形成的。此类基底用于SERS传感时，由于其提供的高密度热点，会产生均匀且大幅增强的拉曼信号。我们还报告了AuNP在VA-SiNW阵列上的可控自组装，这可提供更高的拉曼信号增强。展示了在SiNW的特定区域中AuNP的定向组装，同时控制NP密度和单层形态（即孤立的与几乎相互接触的NP），以及其对所得SERS活性的影响。
