2789-6708
2789-6708
ycwen [at] phys.sinica.edu.tw
2789-6708
2789-6708
ycwen [at] phys.sinica.edu.tw
Tseng, Yu-Ping / 886-2-2789-6754
(1) | 西元年:2019 研究人員(中):溫昱傑、拉提雅, 江國揚 研究人員(英):WEN, YU-CHIEH, L. Dalstein and K.-Y. Chiang 研究成果名稱(中):利用相位靈敏式二倍頻光譜技術直接定量水溶液表面電荷 研究成果名稱(英):Direct Quantification of Water Surface Charge by Phase-Sensitive Second Harmonic Spectroscopy 簡要記述(中):帶電荷的水介面主導許多自然現象,也在現今能源轉換或能源儲存元件中扮演重要角色。人們對於帶電水介面的物理模型一般基於一個電雙層結構,其中表面電荷控制介面反應的微觀路徑,因此影響水溶液介面系統的化學、生物性質與功能性。雖然現今已有許多方法可估計水溶液表面電荷,但大多需仰賴熱動力學模型與假設以進行分析,這導致分析結果常具有爭議。本研究工作發展一套相位靈敏式光學二倍頻光譜技術,其可在不進行熱動力學模型、或電雙層結構模型情況下,對水溶液界面電荷進行直接量測。我們不僅證明此新方法的原理,成功展示其應用。並且對於其使用限制提供完整的評估。 簡要記述(英):Our work focuses on characterization of the electrical double layer (EDL) at water interfaces. Such an interfacial charged layer is an essential ingredient for diverse biological and chemical processes and responsible for many modern technologies such as photocatalysis for water splitting and proton-exchange membrane fuel cells. Despite its importance, quantitative characterization of an EDL without crucial model assumption has long been a challenge. Our work is a breakthrough in this direction. We report in this paper a new phase-sensitive second-harmonic-generation (SHG) spectroscopic scheme that allows direct quantification of the surface charge density and surface potential of an EDL for any planar aqueous interface accessible by light, without need of prior interfacial information. This method relies on selective probing of the surface-field-induced reorientation order of water molecules in the EDL (associated with the third-order nonlinear susceptibility of bulk water) and is, hence, independent of the microscopic interfacial structure. For demonstration, we examine a mixed organic-molecule monolayer on water as an example. The surface charge density obtained from our method reveals the manifest effect of the chain-chain interactions between heterogeneous molecules among the monolayer on adsorption of soluble ionic surfactants. This is the first time the surface charge density at heterogeneous organic monolayers on water has ever been directly measured without (thermodynamic, chemical, or electrokinetic) assumption nor isotope replacement.
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