Nano Chemical Characterization Uncovers Coating Issues for Monolayer Surface Functionalization

Background

Modifying surfaces to influence subsequent molecular interactions is a powerful technique. By adding functional groups that specific molecules can bind to, researchers can manage how antibodies, enzymes, DNA, bacteria, and viruses interact with a surface [1]. Commonly referred to as surface modification or functionalization, this technique finds applications in diverse industries, including  biotechnology, tissue engineering, biosensors, and the semiconductor industry. The crucial assumption is that functional groups form a critical monolayer for experimental success, as the chemical state of the surface ultimately determines its interactions with other molecules. Therefore, unsuccessful functionalization or the presence of contaminants can introduce confounding variables,making it incredibly challenging to troubleshoot unexpected experimental outcomes. Analytical techniques can be very valuable in ruling out surface modification of the substrate as the cause of any subsequent steps not going as planned.

Analytical Techniques for Monolayers

While understanding the state of a modified surface is critical, characterization at the nanoscale remains a challenge even with advanced microscopy and spectroscopy techniques. Ideally, we need a technique that is non-destructive, operable in ambient conditions, boasts high spatial resolution to detect monolayer gaps, and offers monolayer sensitivity. Popular techniques that are used for materials like this are either ToF-SIMS or XPS. However, ToF-SIMS is a destructive process, and XPS, while also surface sensitive, requires a cumbersome  vacuum environment. Unfortunately, both techniques fall short in spatial resolution. Water contact angle, a common choice, provides a convenient success indicator, but its inability to identify specific surface molecules can lead to a false perception of success. This is where IR-PiFM shines. PiFM’s sub-5 nm spatial resolution and sub-monolayer sensitivity can precisely measuring the IR absorption of organic and inorganic surfaces allows it to excel in characterizing both unprocessed and functionalized surfaces [2]. Its effectiveness is further illustrated by two surface modification case studies, where IR-PiFM successfully confirms the presence of monolayers and shed light on the underlying surface interactions.

Learn More?

Please click on ‘Request Application Note’  and we will send you the full application note: ‘Nano Chemical Characterization Uncovers Coating Issues for Monolayer Surface Functionalization’.