Research data supporting [Trapping plasmonic nanoparticles with MHz electric fields]

Figure 1: (A) design of electrode pair and gap. (B) dark-field image of electrode pair showing the 8 µm gap, (C) array of electrode pairs with rectangular pads, (D) PDMS microfluidic chamber layout. (E) experiment setup, showing the sample with the golden electrode pairs, the microfluidic chamber and the glass substrate, as well as the light path and the equivalent circuit representing the connected electronic devices. (F) AuNPs trapped at 3 MHz, shown as a bright spot in the middle of the electrode gap, (G) fabricated sample with upper PDMS microfluidic chambers. Figure 2: (A) Dark field image before applied voltage, (B) upon trapping at electrode edges with voltage on (after 90 s), (C) initially when voltage turned off (100 ms), and (D) after a further 3 s showing diffusion of AuNPs away from electrodes (scale bar is 10 µm). (E) shows the normalized scattered intensity taken from the electrode gap, presented as a percentage of the initial value of each curve, vs rf applied voltage. Arrows show intensity at which scattering from cloud trapping rises by >10% (dashed line) at 1 and 2 MHz. Figure 3: (A) Images of electrode gap at increasing rf frequency and V_p=20 V showing trapping of AuNPs in electrode gap centre, scale bar 10 µm, (B) Applied voltage vs time, (C) frequency vs time, (D) dark-field normalized scattered intensity at λ=600 nm at electrode gap centre (within red circle in A) and (E) average integrated dark-field image intensity (in terms of RGB values) in region around electrode gap. Figure 4: (A) Composite model for AuNP with ionic shell suspended in liquid medium. (B) Real part of Clausius-Mossotti factor Re(K^' ) for shell model with σ_m = 228 μS/c, ε_s=0.1*ε_m=7.9 and various σ_s. (C) Total potential at I=3.8 mM, K' = 0.05 and for varying A_H. (D) Total potential at I=3.8 mM, varying K', A_H = 1eV. (e) Barrier height (defined as the difference between local maximum and local minimum of the potential), (F) position of local minimum vs ionic strength. For all cases ζ = -54 mV (measured with Zetasizer Nano, Malvern Panalytical), ε_m = 79, V_p = 20 V.

图1：(A) 电极对与间隙的设计；(B) 展示8 μm间隙的电极对暗场图像（dark-field image）；(C) 带有矩形焊盘的电极对阵列；(D) PDMS微流控腔（PDMS microfluidic chamber）布局；(E) 实验装置，包含带有金色电极对的样品、微流控腔与玻璃基底，以及光路和代表连接电子设备的等效电路；(F) 于3 MHz下捕获的金纳米颗粒（AuNPs），在电极间隙中央呈现为亮斑；(G) 搭载上层PDMS微流控腔的制备完成样品。图2：(A) 施加电压前的暗场图像；(B) 通电后在电极边缘发生捕获时的图像（90秒后）；(C) 电压刚关闭时的图像（100毫秒时刻）；(D) 再过3秒后的图像，显示金纳米颗粒从电极处扩散开来（比例尺为10 μm）。(E) 为取自电极间隙的归一化散射强度，以各曲线初始值的百分比形式呈现，与射频（radio frequency, rf）施加电压的关系。箭头标注了在1 MHz和2 MHz下，云团捕获的散射强度较初始值提升超过10%（对应虚线）时的强度值。图3：(A) 射频频率递增且峰值电压（peak voltage, V_p）=20 V时的电极间隙图像，显示金纳米颗粒在电极间隙中央被捕获，比例尺10 μm；(B) 施加电压随时间的变化曲线；(C) 射频频率随时间的变化曲线；(D) 电极间隙中央（图A中红色圆圈区域）波长λ=600 nm处的暗场归一化散射强度；(E) 电极间隙周围区域的平均积分暗场图像强度（以RGB值计量）。图4：(A) 悬浮于液体介质中、带有离子壳层的金纳米颗粒复合模型；(B) 壳层模型的克劳修斯-莫索蒂因子（Clausius-Mossotti factor）实部Re(K')，其中σ_m=228 μS/cm，ε_s=0.1×ε_m=7.9且σ_s取不同数值；(C) 离子强度I=3.8 mM、K'=0.05且哈马克常数（Hamaker constant, A_H）取不同值时的总电势；(D) 离子强度I=3.8 mM、K'取不同值且A_H=1 eV时的总电势；(E) 势垒高度（定义为电势的局部最大值与局部最小值之差）；(F) 电势局部最小值的位置随离子强度的变化规律。所有实验条件下，ζ电势均为-54 mV（经由马尔文帕纳科Malvern Panalytical Zetasizer Nano测得），ε_m=79，V_p=20 V。