Sum frequency generation microscopy of microcontact-printed mixed self-assembled monolayers

Area of Science:

• Surface science
• Chemical imaging
• Spectroscopy

Background:

• Microcontact printing is a method for creating patterned surfaces.
• Self-assembled monolayers (SAMs) are widely studied for surface modification.
• Characterizing chemical heterogeneity in patterned surfaces is challenging.

Purpose of the Study:

• To apply Sum Frequency Generation Imaging Microscopy (SFGIM) for chemical imaging of microcontact-printed surfaces.
• To analyze the chemical composition and distribution of mixed monolayers.
• To compare microcontact printing with traditional immersion methods for SAM formation.

Main Methods:

• Utilizing SFGIM to obtain spatially resolved vibrational spectra.
• Imaging mixtures of C16 thiols with different terminal groups (CH3 and phenyl) on gold.
• Achieving a spatial resolution of approximately 10 micrometers.

Main Results:

• SFGIM successfully imaged chemically distinct regions within the microcontact-printed monolayer.
• Vibrational spectra provided contrast based on the chemical components.
• Significant mixing of molecules from the stamped area and backfilling solution was observed.

Conclusions:

• SFGIM is a powerful tool for high-resolution chemical imaging of patterned surfaces.
• Microcontact printing results in different film characteristics compared to immersion techniques.
• The study demonstrates the capability of SFGIM to detect molecular mixing in complex surface patterns.