|摘要: ||高表面積之基板在置入奈米銀粒後可形成具層狀堆疊結構體，有效提升表面增強拉曼散射(Surface-enhanced Raman scattering, SERS)的感測性。因此本研究嘗試以平整之高分子基板，經化學溶解方式粗糙化高分子基板，形成之高表面積基板再以化學還原法置入適合SERS量測之銀奈米粒，如此便能形成具多維孔洞結構的SERS基板，大幅改進SERS的量測效果。|
高分子基板的選用必須符合幾個特性，包括價格低廉、具有適合之有機溶劑以及具有適合之官能基可有效吸附銀奈米粒並且達到穩定銀粒的作用。Polycarbonate (PC)和polymethyl methacrylate (PMMA)為具有酯類官能基之高分子材料，符合這些要件，因此本實驗選為高分子底板。高表面積化製備方法以有機溶劑進行前處理，由於溶劑與高分子底板作用會有溶劑殘留之可能性，因此選用之有機溶劑分為兩類，具還原能力如N,N-dimethylformamide (DMF)和acetone以及不具還原能力如chloroform和toluene，探討溶劑種類對於銀奈米粒製備之影響，並將有機溶劑前處理方法分為兩種如單一溶劑前處理法和混和溶劑前處理法，進行高表面積效果和浸泡時間探討。製備完之高表面積高分子材料以場發射掃描式電子顯微鏡(Field-emission scanning electron microscopy, FE-SEM)確認其表面型態。並以硝基硫酚(p-Nitrothiophenol, p-NTP)作為指標分子探討SERS訊號增強效果。
A multi-dimensional structure was formed by a high surface-area substrate treated with silver nanoparticles in order to increase the sensitivity of Surface-Enhanced Raman Scattering (SERS). In this work, planar polymeric plates were roughened with chemical swelling method and used as templates for decoration with silver nanoparticles (AgNPs) to form multi-dimensional SERS substrates.
There were several requirements for the selection of polymeric plates, including low cost, swelling with suitable organic solvents, and with suitable functional groups could adsorb and stabilize AgNPs. Polycarbonate (PC) and polymethyl methacrylate (PMMA) confirmed with the requirements and selected as templates. High surface-area polymeric plates were prepared by organic solvent pretreatment. Since the possibility of organic solvent residues remained on the polymeric plates to impact on AgNPs preparation, the organic solvents divided into organic solvent with reduction ability such as N, N-dimethylformamide (DMF) and acetone or chloroform and toluene without reduction ability. We used two strategies for the preparation of high surface-area polymeric plates, including single organic solvent pretreatment and organic solvent mixture pretreatment. To characterize the morphology of SERS substrates, substrates were monitored by Field-Emission Scanning Electron Microscopy (FE-SEM). Also, p-nitrothiophenol (p-NTP) was used as a probe molecule to optimize the performance of SERS detection.
Results indicate that high surface-area polymeric plates were produced with proper organic solvent pretreatment. Single solvent like DMF, acetone, and chloroform on PMMA plates created network-like structure. But in PC plates, various morphologies could be formed, such as DMF created nanoporous structure whereas acetone created dendritic structure. Mixture of solvents created mixture of structure in both substrates. Substrates were treated with single and mixture of solvents to form high surface-area morphology. Further, the pretreated substrates were treated with DMF to increase the adsorption of AgNPs. With proper pre-treatment of the polymeric plate, the SERS signals improve with close to an order of magnitude compared to flat SERS substrates. With the optimized proper conditions, the prepared substrates offer an enhancement factor larger than 10^6.