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One-step femtosecond laser ablation synthesis of sub-3 nm gold nanoparticles stabilized by silica

机译:二氧化硅稳定的亚3 nm金纳米粒子的一步飞秒激光烧蚀合成

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We report the synthesis of silica-gold nanoparticles (silica-Au NPs) using a one-step femtosecond-reactive laser ablation in liquid (fs-RLAL) technique by focusing femtosecond laser pulses onto a silicon wafer immersed in an aqueous KAuCl4 solution. Characterization of the silica-Au NPs revealed two populations of Au NPs: (i) larger, isolated Au NPs with diameter 7.0 +/- 2.0 nm, and (ii) smaller Au NPs (1.9 +/- 0.7 nm) stabilized by an amorphous silica matrix, along with new species of silicon observed from XPS analysis. The silica-Au NPs were catalytically active towards the model reaction of para-nitrophenol reduction by NaBH4. The formation of the two populations of silica-Au NPs is ascribed to reaction dynamics occurring on two distinct timescales. First, the dense electron plasma formed within tens of femtoseconds of the laser pulse initiates reduction of the [AuCl4](-) complex, leading to the formation of larger isolated Au NPs. Second, silicon species ejected from the wafer surface hundreds of picoseconds or later after the initial laser pulse reduce the remaining [AuCl4](-) and encapsulate the growing clusters, forming ultrasmall Au NPs stabilized by the silica matrix. The morphologies of the silica-Au NPs generated from fs-RLAL are distinct from those reported in recent RLAL experiments with nanosecond lasers, reflecting distinct mechanisms occurring on the different pulse duration timescales.
机译:我们报告了通过在液体中的一步飞秒反应性激光烧蚀(fs-RLAL)技术,通过将飞秒激光脉冲聚焦到浸没在KAuCl4水溶液中的硅片上,合成了二氧化硅-金纳米​​颗粒(silica-Au NPs)。二氧化硅-Au NP的表征显示了两个Au NP群体:(i)直径为7.0 +/- 2.0 nm的较大的分离的Au NP,以及(ii)通过非晶态稳定的较小的Au NP(1.9 +/- 0.7 nm)二氧化硅基质,以及从XPS分析中观察到的新型硅。二氧化硅-Au NP对NaBH4还原对硝基苯酚的模型反应具有催化活性。二氧化硅-金纳米​​颗粒的两个种群的形成是由于在两个不同的时间尺度上发生的反应动力学。首先,在激光脉冲的数十飞秒内形成的致密电子等离子体会引发[AuCl4](-)络合物的还原,从而导致形成较大的孤立Au NP。其次,在初始激光脉冲后数百微微秒或更晚从晶片表面喷出的硅物种会减少残留的[AuCl4](-)并封装正在生长的簇,从而形成由二氧化硅基质稳定的超小Au NP。由fs-RLAL生成的二氧化硅-Au NP的形态与最近用纳秒激光进行的RLAL实验报道的形态不同,反映出在不同的脉冲持续时间尺度上发生的不同机理。

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