Exploring the Hydration Water Character on Atomically Dislocated Surfaces by Surface Enhanced Raman Spectroscopy.

Area of Science:

• Surface chemistry
• Interfacial phenomena
• Spectroscopy

Background:

• Hydration is crucial for water-substance interactions, especially in biological and interfacial processes.
• Understanding hydration on complex, heterogeneous surfaces like proteins remains challenging.
• Atomic-scale investigation requires specialized platforms for systematic study.

Purpose of the Study:

• To develop a platform for controlled investigation of hydration on heterogeneous surfaces.
• To analyze the impact of surface composition on interfacial water properties.
• To characterize molecular-level interactions at complex interfaces.

Main Methods:

• Fabrication of a heterogeneous self-assembled monolayer system.
• Controllable mixing of hydrophobic and hydrophilic groups.
• Precise distance control of functional groups using methylene spacers.
• Surface-enhanced Raman spectroscopy (SERS) for pKa determination and characterization.

Main Results:

• Demonstrated hydrophobic/hydrophilic mixing ratio-dependent pKa variation of carboxyl groups.
• Observed counterintuitive enhancement of interfacial water dielectric strength with fractional hydrophobic mixing.
• Showed that fractional mixing significantly decreases amide coupling efficiency, indicated by pKa decrease.

Conclusions:

• The developed SERS-based platform enables precise control and characterization of hydration water on heterogeneous surfaces.
• Findings provide insights into interfacial water behavior influenced by surface composition.
• The platform has broad applications in biological and industrial surface science.