We confirm that the unusual purple color of the intermetallic compound AuAl2 is of a plasmonic origin by launching surface plasmons (SPs) in thin AuAl2 films. We measure the SP dispersion relation and also use the films to measure the index of refraction of sucrose solutions using standard SP resonance sensing. We find that the SP energy in planar AuAl2 is approximately 2.1 eV, about 0.4 eV lower than in gold, and the material is highly resistant to oxidation. This is close to what is expected from previously reported measurements of the dielectric function of AuAl2. On this basis, we predict that AuAl2 nanoparticles will a have very strong, spectrally nearly uniform light absorbance about an order of magnitude greater than standard carbon black. Such particles may therefore find applications as obscurants or as an alternative to more complex light-absorbing gold structures in areas such as photothermal therapy or solar steam generation, or in plasmonic catalysis.

中文翻译：

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在紫金 (AuAl2) 中发射低能表面等离子体

我们通过在 AuAl2 薄膜中发射表面等离子体 (SP) 来确认金属间化合物 AuAl2 的不寻常紫色是等离子体起源的。我们测量 SP 色散关系，并使用薄膜使用标准 SP 共振传感测量蔗糖溶液的折射率。我们发现平面 AuAl2 中的 SP 能量约为 2.1 eV，比金低约 0.4 eV，并且该材料具有很强的抗氧化性。这接近于先前报道的 AuAl2 介电函数测量结果的预期。在此基础上，我们预测 AuAl2 纳米粒子将具有非常强的、光谱上几乎均匀的光吸收率，比标准炭黑大一个数量级。