Vibrational sum frequency generation study of fatty amine at air/water interface : A quantitative analysis
- 주제어 (키워드) Langmuir monolayers , Fatty amine , Sum-frequency vibrational spectroscopy , Gouy-Chapman model , Stern , Electric double layer , Possion-Boltzmann equation , Levin’s theory , chemical equilibrium , Specific interactions
- 발행기관 서강대학교 일반대학원
- 지도교수 김도석
- 발행년도 2024
- 학위수여년월 2024. 2
- 학위명 박사
- 학과 및 전공 일반대학원 물리학과
- 실제URI http://www.dcollection.net/handler/sogang/000000077093
- UCI I804:11029-000000077093
- 본문언어 영어
- 저작권 서강대학교 논문은 저작권 보호를 받습니다.
초록
Langmuir monolayers of fatty amine (docosan-1-amine) on different pH solutions and electrolytes were investigated by sum-frequency vibrational spectroscopy. The surface charge density deduced from the sum frequency signal in OH region disagreed with those obtained from the classical Gouy-Chapman model incorporating the chemical equilibrium. A stern layer formation in between the monolayer and the diffuse layer (Guoy-Chapman- Stern model) was suggested to explain the discrepancy. Both neutral and charged amine groups had specific interaction with the anion (HCO3 - and Cl-) in the solution. The specific interaction of the neutral amine (in comparison to the alcohol headgroup) and the anion (OH−) was further investigated at high pH. The modified Poisson-Boltzmann equation incorporating Levin’s theory was used to account for the specific interaction. The hydrogen bonding strength responsible for this specific interaction between the OH and the headgroup was stronger for amine as compared to alcohol.
more목차
Chapter 1. Introduction 1
1.1 General 1
1.2 Charge status measurements 1
1.3 Protonation/deprotonation: Effect of pH 2
1.4 Protonation/deprotonation: Effect of Salt 3
1.5 This work 4
Chapter 2. Theory 6
2.1 Pressure-area isotherm 6
2.2 Background theory of Nonlinear optics 8
2.3 Background theory of Sum frequency 9
2.4 Surface charge density 13
2.5 Theory of electric double layer 17
2.5.1 Classical GC model 19
2.5.2 Gouy-Chapman-Stern (GCS) model 29
2.5.3 Levin's continuum theory 30
Chapter 3. The sum-frequency setup and Sample preparation 36
3.1 Overview of the sum-frequency system 36
3.2 Sample preparation 38
Chapter 4. Experimental results 39
4.1 Peak assignments 39
4.2 Fitting method and obtaining the surface charge density from Ψ 42
4.3 Surface pKa of fatty amine determination 46
4.3 SFG spectra of C22-amine at low pH 48
4.4 SFG spectra of C22-amine at pH 5.7 with varying ionic strength 52
4.5 SFG spectra of the mixtures of C22-amine:C19-alcohol at pH 5.7 with varying ionic strengths 53
4.6 SFG spectra of C22-amine at high pH: specific interaction of R-NH2 with the anions 58
Chapter 5. Summary 62
Reference. 64
