Monte Carlo simulation on a gold nanoparticle irradiated by electron beams
Monte Carlo simulation on a gold nanoparticle irradiated by electron beams
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DOI：
10.1088/0031-9155/57/11/3323
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发表时间：
2012-06-07
影响因子：
3.5
通讯作者：
Jaffray, David A.
中科院分区：
文献类型：
--
作者：
Chow, James C. L.;Leung, Michael K. K.;Jaffray, David A.
采用蒙特卡罗模拟方法研究了单能电子束辐照金纳米粒子产生二次电子的过程。用能量分别为50 keV、250 keV、1 MeV和4 MeV的单能电子束分别辐照直径为2、50和100 nm的球形纳米颗粒。使用Geant 4工具包进行MC模拟以确定从GNP发射的二次电子的能量。跟踪了二次电子的平均有效射程和偏转角。计算了二次电子在纳米粒子内外的能量沉积。为了比较，通过用水代替GNP来重复模拟。研究结果表明，二次电子的平均有效射程随着GNP尺寸和电子束能量的增加而增加。对于本研究中使用的电子束能量和GNP尺寸，平均有效范围为纳米颗粒外0.5-15 μ m，这大约在活细胞的尺寸内。根据我们的MC结果，平均偏转角范围为78 - 83度。随着GNP规模的增大，GNP内部的能量沉积比例增大。这与以前使用光子束的研究结果不同。在本研究中，发现对于直径为2nm的最小GNP，二次电子能量沉积比（GNP的能量沉积/水的能量沉积）最高。对于二次电子沉积的能量，我们得出结论，GNP的加入可以增加二次电子在水中的能量沉积，尽管大部分能量被大纳米颗粒（50和100 nm）自吸收。此外，在GNP存在下的电子源似乎并不比光子更好，因为每单位质量的金的二次电子的产率小于水。
This study investigated the secondary electron production from a gold nanoparticle (GNP) irradiated by monoenergetic electron beams using Monte Carlo (MC) simulation. Spherical GNPs with diameters of 2, 50 and 100 nm in water were irradiated by monoenergetic electron beams with energies equal to 50 keV, 250 keV, 1 MeV and 4 MeV. MC simulations were performed using the Geant4 toolkit to determine the energy of the secondary electrons emitted from the GNPs. The mean effective range and deflection angle of the secondary electrons were tracked. Energy depositions inside and outside the nanoparticles due to the secondary electrons were also calculated. For comparisons, simulations were repeated by replacing the GNPs with water. Our results show that the mean effective range of secondary electrons increased with an increase of the GNP size and electron beam energy. For the electron beam energy and GNP size used in this study, the mean effective range was 0.5-15 mu m outside the nanoparticle, which is approximately within the dimension of a living cell. The mean deflection angles varied from 78 to 83 degrees as per our MC results. The proportion of energy deposition inside the GNP versus that outside increased with the GNP size. This is different from the results obtained from a previous study using photon beams. The secondary electron energy deposition ratio (energy deposition for GNP/energy deposition for water) was found to be highest for the smallest GNP of 2 nm diameter in this study. For the energy deposited by the secondary electron, we concluded that the addition of GNPs can increase the secondary electron energy deposition in water, though most of the energy was self-absorbed by the large nanoparticles (50 and 100 nm). In addition, an electron source in the presence of GNPs does not seem to be better than photons as the yield of secondary electrons per unit mass of gold is less than water.