Department of Materials Science and Engineering, University of Washington, Seattle, Washington 98195-2120, United States.
Langmuir. 2012 Nov 20;28(46):16177-85. doi: 10.1021/la303250e. Epub 2012 Nov 7.
The dissipative absorption of electromagnetic energy by 1D nanoscale structures at optical frequencies is applicable to several important phenomena, including biomedical photothermal theranostics, nanoscale photovoltaic materials, atmospheric aerosols, and integrated photonic devices. Closed-form analytical calculations are presented for the temperature rise within infinite circular cylinders with nanometer-scale diameters (nanowires) that are irradiated at right angles by a continuous-wave laser source polarized along the nanowire's axis. Solutions for the heat source are compared to both numerical finite-difference time domain (FDTD) simulations and well-known Mie scattering cross sections for infinite cylinders. The analysis predicts that the maximum temperature increase is affected not only by the cylinder's composition and porosity but also by morphology-dependent resonances (MDRs) that lead to significant spikes in the local temperature at particular diameters. Furthermore, silicon nanowires with high thermal conductivities are observed to exhibit extremely uniform internal temperatures during electromagnetic heating to 1 part in 10(6), including cases where there are substantial fluctuations of the internal electric-field source term that generates the Joule heating. For a highly absorbing material such as carbon, much higher temperatures are predicted, the internal temperature distribution is nonuniform, and MDRs are not encountered.
一维纳米结构在光频下对电磁能的耗散吸收适用于几种重要现象，包括生物医学光热治疗、纳米光伏材料、大气气溶胶和集成光子器件。本文针对沿纳米线轴偏振的连续波激光源垂直照射下具有纳米级直径（纳米线）的无限圆柱体内的温升，提出了封闭解析计算。热源解与数值有限差分时间域（FDTD）模拟和无限圆柱的著名 Mie 散射截面进行了比较。分析表明，最大温升不仅受圆柱的组成和孔隙率的影响，还受形态相关共振（MDR）的影响，这些共振会导致局部温度在特定直径处出现显著峰值。此外，在电磁加热至 10^(-6)时，具有高热导率的硅纳米线表现出极其均匀的内部温度，包括内部电场源项产生焦耳加热时有较大波动的情况。对于像碳这样的高吸收材料，预测的温度要高得多，内部温度分布不均匀，并且不会遇到 MDR。
