Controlling the overall geometry of plasmonic materials allows for tailoring their optical response and the effects that can be exploited to enhance the performance of a wide range of devices. This study demonstrates a simple method to control the size and distribution of gold (Au) nanoparticles grown on the surface of spaced titanium dioxide (TiO2) nanotubes by varying the deposition time of magnetron sputtering. While shorter depositions led to small and well-separated Au nanoparticles, longer depositions promoted the formation of quasi-continuous layers with small interparticle gaps. The optical spectra of Au/TiO2 nanotubes showed a region of strong absorption (200–550 nm) for all samples and a region of decreasing absorption with an increase of effective Au thickness (550–1100 nm). This behavior led to distinct trends in the Raman signal enhancement of the underlying TiO2 nanotubes depending on the excitation laser wavelength. Furthermore, the quasi-continuous layers formed at higher effective Au thicknesses promoted an amplification of the signal and an improvement in the detection limit of target molecules in surface-enhanced Raman scattering (SERS) experiments. These findings suggest a simple method for designing efficient devices with tailored light absorption and potential applications in detectors and other optical devices.
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机译：控制等离激元材料的整体几何形状可以定制它们的光学响应和效果，从而增强各种设备的性能。本研究展示了一种简单的方法，通过改变磁控溅射的沉积时间来控制在间隔二氧化钛 （TiO2） 纳米管表面生长的金 （Au） 纳米颗粒的大小和分布。较短的沉积会产生小而分离良好的 Au 纳米颗粒，而较长的沉积则促进了具有小颗粒间间隙的准连续层的形成。Au/TiO2 纳米管的光谱显示，所有样品都存在强吸收区域 （200–550 nm），而随着有效 Au 厚度 （550–1100 nm） 的增加，吸收区域降低。这种行为导致底层 TiO2 纳米管的拉曼信号增强出现不同的趋势，具体取决于激发激光波长。此外，在表面增强拉曼散射 （SERS） 实验中，在较高有效 Au 厚度下形成的准连续层促进了信号的放大和靶分子检出限的提高。这些发现为设计具有定制光吸收的高效器件提供了一种简单的方法，并在探测器和其他光学器件中具有潜在的应用。
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