[交流] 求助大神关于金纳米棒的问题

打算合成长径比3.5，长 54.0 ± 2.1 nm 宽 15.9 ± 1nm的金棒，参考的是Catherine J. Murphy之后再13年的一篇文献，具体如下：A solution of 2.5 × 10−4 M HAuCl4 was prepared in 0.1 M aqueous CTAB in a 50 mL centrifuge tube. NaBH4 (600 μL, of a 10 mM stock solution) was added to the gold/CTAB solution (10 mL) with vigorous stirring for 10 min with the help of a stir bar. The resulting seed particles (～3 nm diameter) were used for the synthesis of both short and long gold nanorods. For the short gold nanorods (aspect ratio 3.5), the following were added, in order, to a conical flask: CTAB solution (95 mL of a 0.1 M stock solution), silver nitrate solution (1 mL of a 10 mM stock solution), and HAuCl4 (5 mL of a 10 mM stock solution). An aqueous solution of ascorbic acid (0.55 mL of a 0.1 M stock solution) was then added with gentle mixing. Finally, the gold seed solution (0.12 mL) was added and mixed. The solution was left undisturbed overnight. The colored gold nanorod solution was purified by centrifugation (2×) to remove excess CTAB. The method yielded gold nanorods of length 54.0 ± 2.1 nm and width 15.9 ± 1.1 nm。
合成了四五次，金种为茶叶水的颜色，每部过程当中的颜色也正常，但是最后生长的时候一次巧克力色，一次黄绿色，一次紫红色，并且巧克力色和紫红色都在500多只有一个紫外吸收峰，黄绿色的在400多一个吸收峰，求大神指导！！！！心好累~

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