Brognara Andrea, Bricchi Beatrice R, William Ludovic, Brinza Ovidiu, Konstantakopoulou Maria, Bassi Andrea Li, Ghidelli Matteo, Lidgi-Guigui Nathalie
Dipartimento di Energia, Micro and Nanostructured Materials Laboratory, Politecnico di Milano, via Ponzio 34/3, Milano, I-20133, Italy.
Department of Structure and Nano/-Micromechanics of Materials, Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straße 1, 40237, Düsseldorf, Germany.
Small. 2022 Jun;18(25):e2201088. doi: 10.1002/smll.202201088. Epub 2022 May 26.
The photo-induced enhanced Raman spectroscopy (PIERS) effect is a phenomenon taking place when plasmonic nanoparticles deposited on a semiconductor are illuminated by UV light prior to Raman measurement. Results from the literature show that the PIERS effect lasts for about an hour. The proposed mechanism for this effect is the creation of oxygen vacancies in the semiconductor that would create a path for charge transfer between the analyte and the nanoparticles. However, this hypothesis has never been confirmed experimentally. Furthermore, the tested structure of the PIERS substrate has always been composed of plasmonic nanoparticles deposited on top of the semiconductor. Here, gold nanoparticles co-deposited with porous TiO are used as a PIERS substrate. The deposition process confers the nanoparticles a unique position half buried in the nanoporous semiconductor. The resulting PIERS intensity is among the highest measured until now but most importantly the duration of the effect is significantly longer (at least 8 days). Cathodoluminescence measurements on these samples show that two distinct mechanisms are at stake for co-deposited and drop-casted gold nanoparticles. The oxygen vacancies hypothesis tends to be confirmed for the latter, but the narrowing of the depletion zone explains the long PIERS effect.
光致增强拉曼光谱（PIERS）效应是指在拉曼测量之前，当沉积在半导体上的等离子体纳米颗粒被紫外光照射时发生的一种现象。文献结果表明，PIERS效应持续约一小时。该效应的提出机制是在半导体中产生氧空位，这将为分析物与纳米颗粒之间的电荷转移创造一条路径。然而，这一假设从未得到实验证实。此外，PIERS衬底的测试结构一直是由沉积在半导体顶部的等离子体纳米颗粒组成。在此，将与多孔TiO共沉积的金纳米颗粒用作PIERS衬底。沉积过程赋予纳米颗粒一个独特的位置，即半埋在纳米多孔半导体中。由此产生的PIERS强度是迄今为止测量到的最高强度之一，但最重要的是，该效应的持续时间显著更长（至少8天）。对这些样品的阴极发光测量表明，对于共沉积和滴铸的金纳米颗粒，有两种不同的机制在起作用。氧空位假设倾向于被后者证实，但耗尽区的变窄解释了PIERS效应的长期性。
