Characterising Nanomaterials Using Inverse Gas Chromatography

In this interview, AZoM talks to Surface Measurement Systems about their inverse gas chromatogrpahy system iGC SEA and how it helps when characterising Nanomaterials

Could you give me a brief overview of the benefits of using inverse gas chromatography?

Inverse Gas Chromatography is a powerful characterization tool used to access a wide range of properties, including surface energetics, Lewis acid-base interactions, works of adhesion/cohesion, surface areas, isotherms, Henry’s constants, heats of sorption, solubility parameters, and surface phase changes.

IGC can be used on a vast array of solid materials, ranging from powders/particulates to fibers to films/coatings.

Why is it better than using contact angle measurement for measuring surface energy?

IGC has many benefits when compared to traditional contact angle measurement for surface energy determination. First, IGC is a gas phase technique, which allows direct surface energy measurement of non-planar, porous, powder, fiber, and irregular shaped surfaces. In contact angle measurements, these surfaces can be challenging, and often impossible to accurately measure with high reliability.

Second, using the Surface Measurement Systems IGC instrument, it is easy to control both the sample temperature and relative humidity. Therefore, researchers can determine the effect of environmental conditions on their materials’ surface properties. Most contact angle instruments do not control both temperature and relative humidity of the sample area.

Finally, contact angle measures only the finite area in contact with the liquid probe. IGC experiments access the entire surface, so the measurements are more representative of the entire surface. Further, in the SMS IGC instrument it is possible to control the vapor to surface ratio. allows the measurement and quantification of energetic heterogeneity. Most ‘real’ surfaces are heterogeneous due to different surface groups, composite structure, impurities, or process-induced disorder.

How does this help when characterizing nanomaterials?

By nature, nanomaterials are not flat, homogenous surfaces. By definition, they will have at least one dimension approaching nanometer length scales. Also, nanomaterials can be produced via many pathways; bottom-up methods like nucleation and crystallization, or top-down methods like mechanical or chemical processing.
 

This leads to materials with different surface groups, particle sizes, shapes, porosity, and aspect ratios. Therefore, nanomaterials are often both physically and energetically heterogeneous. Very often, IGC is the only technique that can accurately and reliably determine the surface energetics of these materials.

What is the importance of measuring isotherms?

Determining the sorption isotherms via IGC can give direct access to multiple parameters; including Henry’s constants, BET surface areas, relative solvent affinities, and sorption mechanisms.

What do surface measurement systems offer that makes this easier?

The SMS IGC was designed from the start to measure vapor-surface interactions over a diverse range of conditions and vapor:surface ratios. For instance, the SMS IGC can measure isotherms and, subsequently, BET surface areas as a function of both temperature and relative humidity.

Traditional BET surface area measurements by volumetric techniques under vacuum and liquid nitrogen temperatures. For some materials, these extreme conditions used by volumetric techniques can cause irreversible phase changes or structural collapse. Studying sorption isotherms over a range of temperatures/humidities can allow investigation of ‘real world’ conditions on material properties.

Also, the SMS IGC system can be preloaded with up to 12 different solvents.  This allows for the automatic collection of up to 12 different isotherms on a single sample without any operator interactions. Researchers can quickly and accurately investigate the effect of probe molecule chemistry, size, and shape on sorption properties.​

How do you stand out from other companies in your field?

First, SMS is founded in science. From the beginning, our company was founded and led by our scientific principles. We develop products that help researchers solve challenging material properties problems. Our scientific support is second-to-none.

SMS is constantly improving the application space of our products. We accomplish this through pioneering research in peer-reviewed journals and collaborating with different research groups across the globe.

Where do you believe that the next developments in the iGCfield lie?

SMS is constantly pushing the boundaries of IGC instrumentation, theory, and applications. One particular future area of interest for SMS is expanded sample temperatures. Our goal is to build instrumentation with higher maximum sample temperatures, that will allow pretreatment and parameter measurement of up to at least 500 °C.

This can be particularly important for high energy and highly porous materials like activated carbons, zeolites, catalysts, and nanoclays. SMS is also pursuing enhanced frontal analysis, which would allow for breakthrough determination. Additionally, SMS is currently enhancing our application knowledge and theory related to solubility parameters.

About Dan Burnett

Dan Burnett is the Director of Science Strategy for Surface Measurement Systems, Ltd. He is located at SMS’s North American headquarters in Allentown, PA.  He received his bachelor’s degree in Professional Chemistry from Eastern Michigan University in 1997.  He received his Ph.D. degree in Chemical Engineering from the University of Michigan in 2001.

Since joining SMS in 2001, he has continued his interests in sorption science and surface chemistry on a range of materials including: pharmaceutical powders, natural and man-made fibers, polymers, films, and food/flavor systems.  Dr. Burnett has authored or co-authored over 25 papers in peer-reviewed journals and presented at numerous national and international conferences.