PDF(Pubmed)
Abstract：
Femtosecond laser ablation of Cu0.70Zn0.30 targets in ethanol led to the formation of periodic surface nanostructures and crystalline CuZn alloy nanoparticles with defects, low-coordinated surface sites, and, controlled by the applied laser fluence, different sizes and elemental composition. The Cu/Zn ratio of the nanoparticles was determined by energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and selected area electron diffraction. The CuZn nanoparticles were about 2-3 nm in size, and Cu-rich, varying between 70 and 95%. Increasing the laser fluence from 1.6 to 3.2 J cm-2 yielded larger particles, more stacking fault defects, and repeated nanotwinning, as evident from high-resolution transmission electron microscopy, aided by (inverse) fast Fourier transform analysis. This is due to the higher plasma temperature, leading to increased random collisions/diffusion of primary nanoparticles and their incomplete ordering due to immediate solidification typical of ultrashort pulses. The femtosecond laser-synthesized often nanotwinned CuZn nanoparticles were supported on highly oriented pyrolytic graphite and applied for ethylene hydrogenation, demonstrating their promising potential as model catalysts. Nanoparticles produced at 3.2 J cm-2 exhibited lower catalytic activity than those made at 2.7 J cm-2. Presumably, agglomeration/aggregation of especially 2-3 nm sized nanoparticles, as observed by postreaction analysis, resulted in a decrease in the surface area to volume ratio and thus in the number of low-coordinated active sites.
摘要：
在乙醇中飞秒激光烧蚀Cu0.70Zn0.30靶导致形成周期性表面纳米结构和具有缺陷的晶体CuZn合金纳米颗粒，低协调地表位点，and,由施加的激光通量控制，不同的大小和元素组成。通过能量色散X射线光谱法测定纳米颗粒的Cu/Zn比，X射线光电子能谱,和选定区域电子衍射。CuZn纳米颗粒的大小约为2-3nm，富含铜，在70%到95%之间变化。将激光通量从1.6增加到3.2Jcm-2产生了更大的颗粒，更多的堆垛层错缺陷，反复获得纳米制胜，从高分辨率透射电子显微镜可以看出，通过(逆)快速傅里叶变换分析。这是由于较高的等离子体温度，导致主要纳米粒子的随机碰撞/扩散增加，并且由于超短脉冲的典型立即固化而导致其不完全有序。飞秒激光合成的通常是纳米晶的CuZn纳米颗粒被负载在高度取向的热解石墨上，并用于乙烯氢化，展示了他们作为模型催化剂的潜力。在3.2Jcm-2下产生的纳米颗粒表现出比在2.7Jcm-2下产生的纳米颗粒更低的催化活性。大概,尤其是2-3nm大小的纳米颗粒的团聚/聚集，正如后反应分析所观察到的，导致表面积与体积之比降低，从而降低了低协调活性位点的数量。
