Dong Qingchun, An Wei, Zhang Yifan
College of Mechanical Engineering, Tongji University, Shanghai 201804, P. R. China.
Langmuir. 2024 Feb 27;40(8):4198-4206. doi: 10.1021/acs.langmuir.3c03213. Epub 2024 Feb 14.
Ultrashort-pulsed light-induced nanobubbles gain great attention in research fields such as cancer therapy, optical imaging, and drug delivery. However, the mechanism governing the nucleation and growth of nanobubbles remains controversial. In this study, a molecular dynamics simulation combined with near-field electromagnetic theory is developed to investigate the influence of the localized surface plasmon resonance effect (LSPR) on nanobubble nucleation under various time-length pulsed light and to reveal the energy transfer differences during the nanobubble generation process. The results show that when silver nanoparticles (NPs) are irradiated by a 5 ps shorter-pulsed light, the temperature of the water layer adjacent to the nanoparticle surpasses that of the nanoparticle itself and reaches the spinodal temperature. This leads to nanobubbles' rapid nucleation at approximately 20 ps, which is 80 ps earlier than that irradiated by a 100 ps longer-pulsed light. Comparatively, during longer-pulsed light irradiation, a slower increase in both the temperature of the silver NPs and the water layer results in delayed nucleation of nanobubbles. Therefore, the plasmonic nanobubbles (PNBs) were observed around in 74 and 100 ps when irradiated by 50 and 100 ps longer-pulsed light, respectively. Moreover, the result indicates that the LSPR-induced enhanced electric field by shorter-pulsed light (5 ps) is 2.1 × 10 V/m, which can accelerate the motion of water molecules surrounding silver NPs, resulting in rapid generation of nanobubbles. However, the intensities of the resonant electric field drop to 5.6 × 10 and 5.0 × 10 V/m when the duration times of pulsed light are 50 and 100 ps, respectively. These results indicate that the energy transfer mechanism of plasmonic nanobubbles (PNBs) under ultrashort-pulsed light irradiation might be very different from that of thermally mediated nanobubbles (TNBs). This work provides new insights into understanding the generation of PNBs induced by ultrashort-pulsed light.
超短脉冲光诱导的纳米气泡在癌症治疗、光学成像和药物递送等研究领域备受关注。然而，纳米气泡成核和生长的机制仍存在争议。在本研究中，结合近场电磁理论开展了分子动力学模拟，以研究局域表面等离子体共振效应（LSPR）在不同时长脉冲光作用下对纳米气泡成核的影响，并揭示纳米气泡产生过程中的能量转移差异。结果表明，当银纳米颗粒（NPs）受到5皮秒的短脉冲光照射时，与纳米颗粒相邻的水层温度超过纳米颗粒本身的温度并达到亚稳极限温度。这导致纳米气泡在约20皮秒时快速成核，比受到100皮秒长脉冲光照射时早80皮秒。相比之下，在长脉冲光照射期间，银纳米颗粒和水层的温度升高较慢，导致纳米气泡成核延迟。因此，分别受到50皮秒和100皮秒长脉冲光照射时，在74皮秒和100皮秒左右观察到等离子体纳米气泡（PNBs）。此外，结果表明短脉冲光（5皮秒）由LSPR诱导的增强电场为2.1×10 V/m，这可以加速银纳米颗粒周围水分子的运动，导致纳米气泡快速产生。然而，当脉冲光持续时间分别为50皮秒和100皮秒时，共振电场强度分别降至5.6×10和5.0×10 V/m。这些结果表明，超短脉冲光照射下等离子体纳米气泡（PNBs）的能量转移机制可能与热介导纳米气泡（TNBs）的能量转移机制非常不同。这项工作为理解超短脉冲光诱导的PNBs的产生提供了新的见解。
