We report a visual detection of Cr(VI) ions using silver-coated gold nanorods (AuNR@Ag) as sensing probes. Au NRs were prepared by a seed-mediated growth process and AuNR@Ag nanostructures were synthesized by growing Ag nanoshells on Au NRs. Successful coating of Ag nanoshells on the surface of Au NRs was demonstrated with TEM, EDS, and UV–vis spectrometer. By increasing the overall amount of the deposited Ag on Au NRs, the localized surface plasmon resonance (LSPR) band was significantly blue-shifted, which allowed tuning across the visible spectrum. The sensing mechanism relies on the redox reaction between Cr(VI) ions and Ag nanoshells on Au NRs. As the concentration of Cr(VI) ions increased, more significant red-shift of the longitudinal peak and intensity decrease of the transverse peak could be observed using UV–vis spectrometer. Several parameters such as concentration of CTAB, thickness of the Ag nanoshells and pH of the sample were carefully optimized to determine Cr(VI) ions. Under optimized condition, this method showed a low detection limit of 0.4 μM and high selectivity towards Cr(VI) over other metal ions, and the detection range of Cr(VI) was tuned by controlling thickness of the Ag nanoshells. From multiple evaluations in real sample, it is clear that this method is a promising Cr(VI) ion colorimetric sensor with rapid, sensitive, and selective sensing ability.

中文翻译：

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Cr（VI）离子的高度灵敏和选择性的视觉检测，基于银涂层金纳米棒的蚀刻。

我们报告使用镀银的金纳米棒（AuNR @ Ag）作为传感探针对Cr（VI）离子的视觉检测。通过种子介导的生长过程制备Au NRs，并通过在Au NRs上生长Ag纳米壳来合成AuNR @ Ag纳米结构。用TEM，EDS和UV-vis光谱仪证明在Au NRs表面成功涂覆了Ag纳米壳。通过增加在金NR上沉积的银的总量，局部表面等离子体激元共振（LSPR）谱带发生了明显的蓝移，从而可以在可见光谱范围内进行调谐。感测机制取决于Cr（VI）离子与Au NRs上的Ag纳米壳之间的氧化还原反应。随着Cr（VI）离子浓度的增加，使用紫外可见分光光度计可以观察到更明显的纵向峰红移和横向峰强度下降。仔细优化了几个参数，例如CTAB的浓度，Ag纳米壳的厚度和样品的pH，以确定Cr（VI）离子。在优化的条件下，该方法显示出0.4μM的低检测限和对其他金属离子对Cr（VI）的高选择性，并且可以通过控制Ag纳米壳的厚度来调整Cr（VI）的检测范围。从实际样品的多次评估中可以明显看出，该方法是一种很有前途的Cr（VI）离子比色传感器，具有快速，灵敏和选择性的传感能力。通过控制Ag纳米壳的厚度来调节Cr（VI）的检测范围。从实际样品的多次评估中可以明显看出，该方法是一种很有前途的Cr（VI）离子比色传感器，具有快速，灵敏和选择性的传感能力。通过控制Ag纳米壳的厚度来调节Cr（VI）的检测范围。从实际样品的多次评估中可以明显看出，该方法是一种很有前途的Cr（VI）离子比色传感器，具有快速，灵敏和选择性的传感能力。