Plasmonic nanoantennas are at the core of various optical near-field scanning techniques such as tip-enhanced Raman spectroscopy as they provide the amplification and confinement of the electromagnetic field, which ultimately provides sensitivity and spatial resolution. With a cornucopia of different fabrication methods available, the actual performance of a nanoantenna is often only assessed by whether or not near-field imaging is possible, implying the complete alignment and landing procedure of the scanning probe. We present a semi-quantitative approach to assess the plasmonic enhancement of gold tips via localized surface plasmon resonance (LSPR) enhancement of intrinsic gold photoluminescence without the need for interaction with the sample. As the intensity of the plasmon at the apex decreases, a significant change in the shape of the tip signal spectrum is observed, reflecting itself as a decrease in the R² value (fit quality) for numerical fitting with a Lorentzian, which also provides an approximation for the LSPR wavelength. Our findings suggest that the potential of a tip to perform well as an optical near field antenna may already be assessed in an early stage of the experiment.

中文翻译：

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用于等离子体增强成像技术的金尖端等离子体增强的原位评估

等离子纳米天线是尖端增强拉曼光谱等各种光学近场扫描技术的核心，因为它们提供电磁场的放大和限制，最终提供灵敏度和空间分辨率。随着可用的不同制造方法的聚宝盆，纳米天线的实际性能通常仅通过近场成像是否可行来评估，这意味着扫描探针的完整对准和着陆过程。我们提出了一种半定量方法，通过局部表面等离子体共振 (LSPR) 增强内在金光致发光而不需要与样品相互作用来评估金尖端的等离子体增强。随着顶点处等离子体的强度降低，²值（拟合质量）用于使用洛伦兹函数进行数值拟合，它还提供了 LSPR 波长的近似值。我们的研究结果表明，在实验的早期阶段可能已经评估了尖端作为光学近场天线表现良好的潜力。