从单粒子热不对称到集体控制：用于光热应用的Janus等离子体胶体
From Single-Particle Thermal Asymmetry to Collective Control: Janus Plasmonic Colloids for Photothermal Applications
AI总结：
本文研究了连续波照射下Janus等离子体纳米加热器从孤立粒子到平面随机阵列时热不对称性的变化，建立了阵列平均Janus因子模型，为光热应用中温度分布的设计提供了实用框架。
摘要：
Janus纳米加热器为打破热等离子体加热的空间对称性、在纳米尺度产生定向偏置的热梯度提供了途径。然而，在实际光热场景中，纳米加热器很少作为孤立物体发挥作用，而是在胶体聚集体中运行，其中集体热效应和电磁效应会重塑局部温度分布。本文研究了在连续波照射下，当单个Janus等离子体纳米加热器从孤立粒子转变为平面随机阵列时，其固有热不对称性如何变化。通过耦合电磁和稳态热传递模拟，我们首先量化了单粒子Janus特征仍可检测到的有限空间范围。我们表明，相邻纳米加热器会引入两种相互竞争的效应：一种是几乎对称的集体热背景，它会屏蔽并均化Janus因子；另一种是短程邻域诱导的不对称性，当粒子间距离与单粒子热各向异性的空间范围相当时，这种不对称性会部分补偿上述屏蔽效应。我们推导了阵列平均Janus因子的闭式分析模型，该模型是纳米粒子数量和表面密度的函数。该模型从单粒子量预测了以屏蔽为主的区域，并识别出高密度下与近场邻域诱导贡献相关的偏差。这些结果揭示了连续波操作下生物医学光热应用的核心权衡：集体加热是达到相关温度增量所必需的，但它会通过热均化逐渐消除定向Janus特征。我们的框架为预测和合理设计Janus粒子等离子体聚集体中的空间温度分布提供了实用途径。
英文摘要：
Janus nanoheaters provide a route to break the spatial symmetry of thermoplasmonic heating and generate directionally biased thermal gradients at the nanoscale. However, in realistic photothermal scenarios, nanoheaters rarely act as isolated objects, but rather operate within colloidal assemblies where collective thermal and electromagnetic effects reshape the local temperature landscape. Here, we investigate how the intrinsic thermal asymmetry of a single Janus plasmonic nanoheater is transformed when moving from isolated particles to planar random arrays under continuous-wave illumination. Using coupled electromagnetic and steady-state heat-transfer simulations, we first quantify the finite spatial range over which the single-particle Janus signature remains detectable. We show that neighboring nanoheaters introduce two competing effects: a nearly symmetric collective thermal background that screens and homogenizes the Janus factor, and short-range neighbor-induced asymmetries that partially compensate this screening when interparticle distances become comparable to the spatial extent of the single-particle thermal anisotropy. We derive a closed-form analytical model for the array-averaged Janus factor as a function of nanoparticle number and surface density. The model predicts the screening-dominated regime from single-particle quantities and identifies deviations associated with near-field neighbor-induced contributions at higher densities. These results demonstrate a central trade-off for biomedical photothermal applications in continuous-wave operation: collective heating is required to reach relevant temperature increments, but it progressively erases the directional Janus character by thermal homogenization. Our framework provides a practical route to predict and rationally design the spatial temperature distribution in plasmonic assemblies of Janus particles.
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