Amino Acids Are Driven to the Interface by Salts and Acidic Environments. Phase State and Thermodynamic Properties of Proxy Sea Spray Aerosol Interfaces Derived from Temperature-Dependent Equilibrium Spreading Pressure. The Journal of Physical Chemistry A 2022, 126 Spectroscopy of Retinoic Acid at the Air–Water Interface. Infrared Reflection–Absorption Spectroscopy of α-Hydroxyacids at the Water–Air Interface. ACS Applied Materials & Interfaces 2023, Article ASAP. Chemical Feedback in the Self-Assembly and Function of Air–Liquid Interfaces: Insight into the Bottlenecks of CO2 Direct Air Capture. Premadasa, Dengpan Dong, Diana Stamberga, Radu Custelcean, Santanu Roy, Ying-Zhong Ma, Vera Bocharova, Vyacheslav S. This article is cited by 53 publications. The polar groups of l-phenylalanine at the surface transition to their deprotonated state at bulk pH values lower than the molecules residing in the bulk, indicating a decrease in their p K a at the surface, and implying an enhanced hydroxide ion concentration in the surface region relative to the bulk. In this work, the polar group vibrations in the surface region are identified spectroscopically in varying bulk pH solutions, and are subsequently compared with the ionization state of the polar groups of molecules residing in the bulk environment. l-phenylalanine has the unique advantage of possessing two different hydrophilic groups, a carboxylic acid and an amine base, which can deprotonate and protonate respectively depending on the ionic environment they experience at the water surface. In this work, infrared reflection–absorption spectroscopy (IRRAS) is used to identify changes in the ionization state of l-phenylalanine in the surface region versus the bulk aqueous solution. The ionization state of organic molecules at the air–water interface and the related problem of the surface pH of water have significant consequences on the catalytic role of the surface in chemical reactions and are currently areas of intense research and controversy.
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