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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Roles of Free Electrons and H2O2 in the Optical Breakdown-Induced Photochemical Reduction of Aqueous [AuCl4](-)
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Roles of Free Electrons and H2O2 in the Optical Breakdown-Induced Photochemical Reduction of Aqueous [AuCl4](-)

机译：自由电子和H2O2在光学击穿诱导的水溶液[AuCl4]（ - ）中的光化学还原中的作用

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摘要

Free electrons and H2O2 formed in an optical breakdown plasma are found to directly control the kinetics of [AuCl4](-) reduction to form Au nanoparticles (AuNPs) during femtosecond laser-assisted synthesis of AuNPs. The formation rates of both free electrons and H2O2 strongly depend on the energy and duration of the 800 nm laser pulses over the ranges of 10-2400 mu J and 30-1500 fs. By monitoring the conversion of [AuCl4](-) to AuNPs using in situ UVvis spectroscopy during laser irradiation, the first- and second-order rate constants in the autocatalytic rate law, k(1) and k(2), were extracted and compared to the computed free electron densities and experimentally measured H2O2 formation rates. For laser pulse energies of 600 mu J and lower at all pulse durations, the first-order rate constant, k(1), was found to be directly proportional to the theoretically calculated plasma volume, in which the electron density exceeds the threshold value of 1.8 x 10(20) cm(-3). The second-order rate constant, k(2), was found to correlate with the measured H2O2 formation rate at all pulse energies and durations, resulting in the empirical relationship k(2) approximate to H2O20.5. We have demonstrated that the relative composition of free electrons and H2O2 in the optical breakdown plasma may be controlled by changing the pulse energy and duration, which may make it possible to tune the size and dispersity of AuNPs and other metal nanoparticle products synthesized with femtosecond laser-based methods.
机译：发现在光学击穿等离子体中形成的游离电子和H2O2直接控制[Aucl4]（ - ）的动力学，以在飞秒激光辅助合成的剖腹产辅助合成期间形成Au纳米颗粒（AUNP）。自由电子和H2O2的形成速率强烈地取决于800nm激光脉冲的能量和持续时间在10-2400 mu j和30-1500 fs的范围内。通过在激光照射期间使用原位UVVIS光谱法监测[AuCl4]（ - ）转化对AUNP的转化，提取自催化率法，K（1）和K（2）中的第一和二阶率常数，并进行与计算的游离电子密度相比，实验测量的H 2 O 2形成速率。对于600μm的激光脉冲能量，并且在所有脉冲持续时间下更低，发现一阶速率常数K（1）与理论上计算的等离子体体积直接成比例，其中电子密度超过阈值1.8 x 10（20）厘米（-3）。发现二阶率常数K（2）与所有脉冲能量和持续时间的测量的H 2 O 2形成速率相关，导致经验关系K（2）近似到H2O20.5。我们已经证明，可以通过改变脉冲能量和持续时间来控制光学击穿等离子体中的游离电子和H2O2中的相对组成，这可以使得可以调节与飞秒激光器合成的AUNP和其他金属纳米颗粒产品的尺寸和分散度来控制基于基础的方法。

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