CW雷射製備三維銀奈米結構及其在SERS的應用

Abstract

我們有系統性地在顯微鏡系統下，以調整CW雷射的波長、功率及照射範圍與時間等參數，以光化學法製作出三維銀奈米結構，在硝酸銀水溶液中加入還原劑，產生微小的銀原子團，並在特定的雷射波長照射下，能夠有效地引發電漿子效應產生表面電漿共振(SPR)，產生的強烈局部電磁場能夠激發銀原子團產生熱電子，促使更多銀離子的光化學還原反應。隨著更多的銀離子被還原成銀原子團或初級的奈米粒子，電漿子效應又進一步產生光力以驅動銀粒子的自組裝，形成較大的次級的枝狀結構。藉由光力和凡得瓦力的共同作用，這些奈米結構會如同模型塊一般進行堆疊與組裝，形成具有明顯主枝與分枝的三維樹枝狀與珊瑚狀結構。結果表明，我們可以透過控制波長或功率等關鍵參數在相同條件下，能生成相似形態和尺寸的三維奈米結構。儘管我們能夠通過雷射掃描的方式在大範圍內生成三維銀奈米結構，但對於如何優化單一銀奈米結構生長的微結構形貌，將是未來的研究重點。 我們進一步以三維銀奈米結構應用於表面增強拉曼散射(SERS)，使用羅丹明6G(R6G)作為探針分子，由於三維樹狀銀奈米結構的表面電漿共振效應，這使得R6G分子在SERS的訊號得以顯著放大，而這些顯著增強的訊號證明了三維銀奈米結構對R6G分子在SERS的作用。總結來說，透過系統性地調整與優化雷射參數，成功製備了三維銀奈米結構，並展示其在SERS應用的巨大潛力。本論文的研究成果不僅為應用三維銀奈米結構在生物醫學和環境監測等領域提供有力支持，也為如何進一步優化三維銀奈米結構，提供了重要的實驗方向。

We systematically adjusted parameters such as the wavelength, power, illumination range, and duration of a CW laser in a microscope system to fabricate three-dimensional (3D) silver nanostructures using a photochemical method. In an aqueous solution of silver nitrate, a reducing agent is added to produce small silver atom clusters. Under illumination with specific laser wavelengths, the plasmonic effect induces surface plasmon resonance (SPR), generating a strong local electromagnetic field that excites the silver atom clusters to produce hot electrons, promoting further photochemical reduction of silver ions. As more silver ions are reduced to silver atom clusters or primary nanoparticles, the plasmonic effect further generates optical forces driving the self-assembly of silver particles into larger secondary dendritic structures. Through the combined action of optical and van der Waals forces, these nanostructures stack and assemble like building blocks, forming distinct main branches and sub-branches into 3D dendritic and coral-like structures. The results indicate that by controlling key parameters such as wavelength and power under the same conditions, we can produce 3D nanostructures of similar morphology and size. Although we can generate 3D silver nanostructures over a large area by laser scanning, optimizing the microstructural morphology of a single silver nanostructure will be the focus of future research.

We further applied the 3D silver nanostructures to surface-enhanced Raman scattering (SERS), using Rhodamine 6G (R6G) as the probe molecule. Due to the surface plasmon resonance effect of the 3D dendritic silver nanostructures, the SERS signal of the R6G molecules was significantly amplified. These enhanced signals demonstrate the effectiveness of the 3D silver nanostructures on the SERS of R6G molecules. In summary, by systematically adjusting and optimizing laser parameters, we successfully fabricated 3D silver nanostructures and demonstrated their great potential in SERS applications. The research findings of this paper not only provide strong support for the application of 3D silver nanostructures in fields such as biomedicine and environmental monitoring but also offer important experimental directions for further optimization of 3D silver nanostructures.