Department of Chemistry, University of Bari, Via Orabona 4, 70126 Bari, Italy.
Institute of Nanotechnology, CNR-NANOTEC, c/o Department of Chemistry, University of Bari, Via Orabona 4, 70126 Bari, Italy.
Talanta. 2018 May 15;182:253-258. doi: 10.1016/j.talanta.2018.02.001. Epub 2018 Feb 20.
In this paper, Nanoparticle-Enhanced Laser Induced Breakdown Spectroscopy is applied to transparent samples and gemstones with the aim to overcome the laser induced damage on the sample. We propose to deposit a layer of AuNPs on the sample surface by drying a colloidal solution before ablating the sample with a 532 nm pulsed laser beam. This procedure ensures that the most significant fraction of the beam, being in resonance with the AuNP surface plasmon, is mainly absorbed by the NP layer, which in turn results the breakdown to be induced on NPs rather than on the sample itself. The fast explosion of the NPs and the plasma induction allow the ablation and the transfer in the plasma phase of the portion of sample surface where the NPs were placed. The employed AuNPs are prepared in milliQ water without the use of any chemical stabilizers by Pulsed Laser Ablation in Liquids (PLAL), in order to obtain a strict control of composition and impurities, and to limit possible spectral interferences (except from Au emission lines). Therefore with this technique it is possible to obtain, together with the emission signal of Au (coming from atomized NPs), the emission spectrum of the sample, by limiting or avoiding the direct interaction of the laser pulse with the sample itself. This approach is extremely useful for the elemental analysis by laser ablation of high refractive index samples, where the laser pulse on an untreated surface can otherwise penetrate inside the sample, generate breakdown events below the superficial layer, and consequently cause cracks and other damage. The results obtained with NELIBS on high refractive index samples like glasses, tourmaline, aquamarine and ruby are very promising, and demonstrate the potentiality of this approach for precious gemstones analysis.
本文将纳米颗粒增强激光诱导击穿光谱应用于透明样品和宝石，旨在克服对样品的激光诱导损伤。我们提出在使用 532nm 脉冲激光束烧蚀样品之前，通过干燥胶体溶液在样品表面沉积一层 AuNPs。这一程序确保了光束中与 AuNP 表面等离子体共振的最大部分主要被 NP 层吸收，这反过来又导致击穿发生在 NPs 上而不是样品本身。NPs 的快速爆炸和等离子体感应允许在放置 NPs 的位置处的样品表面部分的等离子体相中进行烧蚀和转移。所使用的 AuNPs 是通过液体中脉冲激光烧蚀（PLAL）在毫 Q 水中制备的，无需使用任何化学稳定剂，以严格控制组成和杂质，并限制可能的光谱干扰（除了 Au 发射线）。因此，通过这种技术，除了来自雾化 NPs 的 Au 发射信号之外，还可以获得样品的发射光谱，同时限制或避免激光脉冲与样品本身的直接相互作用。这种方法对于高折射率样品的激光烧蚀元素分析非常有用，因为未经处理的表面上的激光脉冲否则可能会穿透样品内部，在表面层以下产生击穿事件，并因此导致裂纹和其他损坏。在玻璃、电气石、海蓝宝石和红宝石等高折射率样品上进行 NELIBS 得到的结果非常有前景，证明了这种方法在宝石分析中的潜力。
