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中国物理学会期刊

相干调制振幅投影金纳米棒取向排布的动力学研究

CSTR: 32037.14.aps.74.20251124

Dynamical study on orientation arrangement of gold nanorods via coherent modulation amplitude projection

CSTR: 32037.14.aps.74.20251124
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  • 金纳米棒作为生物医学探针因其可调谐等离激元特性备受关注, 但其亚细胞尺度精准成像受限于衍射极限与现有超分辨技术的高光损伤、外源标记依赖性等瓶颈. 本文提出相干调制振幅投影成像技术, 通过飞秒脉冲对的空间相干调制与振幅-相位协同耦合机制, 低功率激发就可实现金纳米棒取向分布超分辨探测, 同时无需荧光分子标记. 该方法将亚衍射极限信息编码至频域, 利用傅里叶分析同步解析金纳米棒的空间定位、三维取向及局部微环境响应, 规避了荧光分子标记干扰并显著抑制光热效应影响. 实验证实相干调制振幅投影成像通过调控脉冲间延时与相位可精确操控金纳米棒光致发光相干态, 为研究纳米-生物界面动态过程提供了多维度分析工具.

     

    Gold nanorods (AuNRs) have become highly promising biomedical probes due to their tunable plasmonic properties, but their real-time, high-resolution imaging of subcellular behavior, particularly their orientation dynamics reflecting critical nano-bio interactions, is hindered by the diffraction limits and drawbacks of existing super-resolution methods, such as reliance on high-intensity lasers and exogenous labeling. To solve this problem, we develop coherent modulation amplitude projection imaging (CMAPI), a novel label-free technique that uses spatially and temporally modulated pairs of femtosecond pulses to coherently control the two-photon photoluminescence (TPPL) of AuNRs. By using AuNRs as three-level systems with a measurable intermediate state, CMAPI encodes sub-diffraction-limit spatial and orientational information into the frequency domain through precise manipulation of inter-pulse delay, phase, and polarization. Experimental results confirm the nonlinear excitation nature of AuNRs, with single-pulse polarization response following a cos2θ dependence. Under two-pulse excitation, the emission exhibits obvious coherence-dependent behavior: at zero delay, the response is controlled by quantum superposition; under a delay that matches the intermediate state lifetime (0.5 ps), the three-level model accurately describes the response; under a longer delays (10 ps), the system returns to incoherent emission. CMAPI retrieves nanoscale information through Fourier analysis of photon arrival times, producing simultaneous amplitude and phase images that reveal AuNRs’ precise positions (about 60 nm localization precision), in-plane orientations (e.g. quadrant-specific arrangement inferred from phase sign), and local environmental coupling, such as plasmon-induced phase jumps, all under ultralow excitation power (<5 μW/μm2) to avoid light damage. This approach enables visualization of features beyond the diffraction limit, distinguishing multiple AuNRs within a single diffractive spot, as validated by scanning electron microscopy. CMAPI provides a powerful, non-invasive platform for quantifying dynamic biological processes involving anisotropic nanoparticles. These process include conformational shifts during endocytosis, torque transmission in molecular motors, and real-time tracking of nanoscale interactions, thereby offering profound insights into theranostic probe design and fundamental biophysical research.

     

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