Recovery of Fatty Acid Monolayer by Divalent Salts investigated by Sum-frequency Generation Spectroscopy
- 주제(키워드) Recovery fatty acid monolayer , headgroup deprotonated , sum-frequency generation spectroscopy
- 발행기관 서강대학교 일반대학원
- 지도교수 김도석
- 발행년도 2020
- 학위수여년월 2020. 8
- 학위명 석사
- 학과 및 전공 일반대학원 물리학과
- UCI I804:11029-000000065328
- 본문언어 영어
- 저작권 서강대학교 논문은 저작권보호를 받습니다.
초록/요약
Recovery of fatty acids monolayer at high pH by adding small amount of divalent salt was investigated by surface sensitive sum-frequency generation spectroscopy. Monolayers consisting of fatty acids having relatively short alkyl chains (C14H29COOH (pentadecanoic acid, PDA), C15H31COOH (palmitic acid, PA)) are stable at neutral pH, but become unstable at high pH (pH ~ 11). Further addition of small amount of divalent salt in water was found to recover the monolayer, presumably binding of the divalent cation to the carboxylic headgroup makes the molecule more stable against dissolution into subphase water. This revival of the monolayer was readily seen by pressure-area isotherm measurement or by sum-frequency generation spectrum in the CHx and OH range, at much lower concentration for Mg2+ as compared to Ca2+. More salt than is needed to recover the monolayer reduced the OH intensity in the sum-frequency spectrum due to charge screening effect. In conclusion, these fatty acids could possibly be used to detect trace amount of divalent cations in water.
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