雷射波長對各式金奈米粒子之光力自組裝的影響

Abstract

本論文研究在顯微鏡中使用線性雷射對金奈米粒子、金奈米桿、金奈米方塊、金奈米片的膠體滴液進行照射，利用電漿子效應使其產生光力自組裝作用，該過程皆在室溫及一大氣壓的環境，並且在無添加任何額外的化學界面活性劑等輔助條件下完成。通過調整雷射光的強度、極化方向和波長等參數，控制奈米結構的排列和運動，從而透過光力及光力矩使各式金奈米結構在水中進行定向性附著的組合。在光力和光力矩的驅動下，促使金奈米結構如同積木般相互組裝拼接，形成較大的自組裝體。當該自組裝體體積逐漸增大後，由於光熱效應使自組裝體整體結構產生改變進行再結晶從原先的多晶體物質轉變為類單晶結構。另外研究也發現在含金奈米片的水溶液中若加入適量的硝酸銀，經雷射照射後，溶液中銀離子產生光化學還原形成銀原子團，實驗觀察到銀奈米粒子會附著於金奈米片上形成雙金屬複合奈米結構，該光化學還原現象與金奈米片的電漿子效應所產生的熱電子有關。 未來應用電漿子增強之光力自組裝、光熱處理及光化學技術於奈米科技和微奈米加工領域是極具潛力，例如，結合光化學法及光力自組裝技術對雷射直寫製程的微米技術值得開發。

This thesis focuses on the study of the optical self-assembly by using linearly polarized laser in a microscope for the irradiation of colloidal droplets containing various gold nanostructures, including gold nanoparticles, gold nanorods, nanocubes, and nanoplates. The goal is to investigate the self-assembly of nanostructures through optical forces induced by the plasmonic effect. Notably, all experiments are conducted under ambient conditions of room temperature and atmospheric pressure, without the use of additional chemical surfactants or auxiliary agents. By carefully adjusting parameters such as laser intensity, polarization direction, and wavelength, precise control over the arrangement and movement of nanostructures is achieved. This enables the directed attachment and assembly of diverse gold nanostructures in water caused by the optical forces and torque. Through the driving optical forces and torques, the gold nanostructures assemble akin to interlocking building blocks, forming larger self-assembled structures. As the self-assembled structures grow in volume, the photothermal effect causes annealing, leading to the transformation of the original polycrystalline material into a quasi-single crystal structure. Additionally, the study also found that the addition of an appropriate amount of silver nitrate to a water solution containing gold nanoplates, followed by laser irradiation, results in photochemical reduction of silver ions and the formation of silver atom clusters. Our experiments show that silver nanoparticles attach to the gold nanoplates to produce bimetal nanocomposites. This photochemical reduction phenomenon is connected to the hot electrons generated from the gold nanoplates due to plasmonic effect. The potential applications of plasmon-enhanced optical self-assembly, photothermal treatment, and photochemical techniques in the field of nanotechnology and micro-nanofabrication are highly promising. For instance, the combination of photochemical methods and optical self-assembly techniques holds great potential for laser direct writing processes in micro-nanometer technology and deserves further exploration.