Allaf Mohammad Amer, Okamoto Koji, Owa Takuto
Nuclear Engineering and Engineering Physics, University of Wisconsin-Madison, Engineering Research Building, 1500 Engineering Drive, Madison, Wisconsin 53705, USA.
Nuclear Professional School, The University of Tokyo, 2-22 Shirakata, Tokai, Ibaraki, 319-1188, Japan.
AIP Adv. 2025 Jun 6;15(6):065109. doi: 10.1063/5.0272623. eCollection 2025 Jun.
Plasmonic heating of gold nanoparticles (GNPs) using pulsed lasers (PLs) enables microbubble generation for imaging, diagnostics, and microfluidics. However, aggregation and photomodification cause inconsistencies (variations) in microbubble formation and distribution, particularly in pool-like environments where GNPs undergo aggregation and photomodification. This study experimentally investigates microbubble generation by heating GNPs (532 nm, nanoseconds PL) of various sizes and concentrations, using high-speed imaging (20 kfps). Results show unpredictable variations in bubble formation area (BFA), even under similar energy absorption. Large individual microbubbles were observed at relatively low energy absorption, primarily due to aggregation. Boiling on the transparent surface occurred in multiple tests, a phenomenon linked to optical pulling forces that deposited GNPs on the surface. This produced well-defined semi-circular bubbles (∼600 m) within 50 s. MB formation was more concentrated near the backward facing surface than along the laser beam, highlighting the role of optical pulling. Dissolved gas release influenced microbubble growth, particularly in samples prone to aggregation. In addition, prior laser pulses impacted BFA through photomodification and aggregation, sometimes reducing BFA despite higher energy absorption. This study provides new insights into the factors influencing microbubble formation and distribution in the plasmonic heating of GNPs. Understanding these mechanisms can help improve the reliability and efficiency of photothermal applications, enabling better control over plasmonic bubble generation for various scientific and technological advancements.
使用脉冲激光（PL）对金纳米颗粒（GNP）进行等离子体加热可产生微泡，用于成像、诊断和微流体。然而，聚集和光改性会导致微泡形成和分布的不一致（变化），特别是在GNP发生聚集和光改性的池状环境中。本研究使用高速成像（20 kfps），通过加热各种尺寸和浓度的GNP（532 nm，纳秒PL），对微泡生成进行了实验研究。结果表明，即使在相似的能量吸收情况下，气泡形成面积（BFA）也存在不可预测的变化。在相对较低的能量吸收下观察到了较大的单个微泡，这主要是由于聚集所致。在多次测试中，透明表面发生了沸腾现象，这一现象与将GNP沉积在表面的光学拉力有关。这在50秒内产生了明确的半圆形气泡（约600米）。微泡形成在朝后的表面附近比沿激光束方向更集中，突出了光学拉力的作用。溶解气体的释放影响了微泡的生长，特别是在易于聚集的样品中。此外，先前的激光脉冲通过光改性和聚集影响BFA，有时尽管能量吸收更高，但BFA仍会减小。本研究为影响GNP等离子体加热中微泡形成和分布的因素提供了新的见解。了解这些机制有助于提高光热应用的可靠性和效率，从而能够更好地控制等离子体气泡的产生，以实现各种科学技术进步。
