Episode 5: Nanoscale Chemical Analysis with AFM-IR
Episode 5: Nanoscale Chemical Analysis with AFM-IR
In this episode, Dr. Craig Prater, co-founder and CTO of Photothermal Spectroscopy Corp., shares the story behind the AFM-based infrared spectroscopy technique and its ability to generate unique chemical fingerprints. He speaks about current trends, from multimodal imaging to the investigation of complex systems like protein aggregation in Alzheimer’s and Parkinson’s, highlighting applications in material science, polymer research, and the analysis of semiconductors and composite materials.
Dr. Craig Prater, a pioneer in photothermal spectroscopy, was awarded the Coblentz Society Williams-Wright Award for his contributions to vibrational spectroscopy in 2023.
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AFM-IR: Bridging the Gap Between Imaging and Chemistry at the Nanoscale
AFM-IR is a combination of two well-established techniques, atomic force microscopy and infrared spectroscopy. While AFM excels at achieving high spatial resolution and creating images, it does not provide any information on the chemical identity of the sample.
Knowing what a structure is made of can be just as important as knowing what it looks like.
This challenge is precisely what AFM-IR addresses. By integrating the information about the spatial resolution from AFM with the molecular specificity from infrared spectroscopy, AFM-IR enables simultaneous structural and chemical mapping.
In this recent episode of Conversations on AFM, we spoke with Dr Craig Prater. Dr Prater was a driving force in developing and commercializing AFM-IR and authored more than 140 publications in his career. In this blog, we will talk about the principles behind AFM-IR and its impact across materials science, life sciences, and biomedical research.
What is AFM-IR?
AFM-IR combines two techniques. Firstly, AFM provides nanometre-scale spatial resolution by scanning a sharp tip across a sample surface. Secondly, IR spectroscopy, which identifies chemical species by probing how molecules absorb infrared light at specific vibrational frequencies [1].
When combined in AFM-IR, a tunable infrared laser is directed at the sample beneath the AFM tip. When the laser wavelength matches a molecular vibration, the sample absorbs energy, causing minute heating and expansion. This thermal expansion generates a tiny “kick” detected by the AFM cantilever. By sweeping the laser wavelength and recording cantilever responses, researchers can obtain an infrared absorption spectrum, which acts as a chemical fingerprint.
In practice, this means AFM-IR can both image nanoscale structures and identify their chemical composition, something that can only be achieved by combining both techniques.
From Synchrotrons to Benchtops
Like many breakthroughs, AFM-IR has a fascinating history. Early efforts, such as combining AFM with Fourier transform infrared (FTIR) spectroscopy, proved the concept but lacked the sensitivity and resolution needed. Later, researchers used synchrotron light sources - in huge, multimillion-dollar facilities - to demonstrate nanoscale chemical imaging.
The true commercial breakthrough came when benchtop tunable lasers were integrated with AFM systems. This made the technology accessible to laboratories worldwide, moving AFM-IR from proof-of-concept to a practical, widely adopted tool.
Why Not Just Use Conventional IR?
A natural question is why traditional infrared spectroscopy cannot deliver the same nanoscale insights. The limitation comes from optical diffraction: the spatial resolution of optical techniques is constrained by the wavelength of light [2]. Infrared wavelengths are much longer than visible light, meaning even the sharpest IR microscope images blur at scales of several microns.
AFM-IR overcomes this by using the physical AFM tip - not light - to determine the resolution. This enables measurements with resolutions down to 10-20 nanometres, unlocking structures invisible to conventional IR.
Applications Across Science
The versatility of AFM-IR is one of its greatest strengths. Dr Prater highlighted several fields where the technology has already made an impact:
- Polymers and Composites
Modern polymers often consist of blends and additives. AFM-IR can map the distribution of different chemical species within these complex materials, guiding innovations in packaging, aerospace, and electronics [1]. - Life Sciences
In biomedical research, AFM-IR has been applied to proteins and cells. Particularly exciting are studies of protein misfolding, implicated in neurodegenerative diseases such as Alzheimer’s [3]. - Semiconductors and 2D Materials
In nanotechnology, AFM-IR helps characterise semiconductors, thin films, and layered 2D materials, offering insights into structure-property relationships critical for next-generation devices [1].
Complementary Technologies: OPTIR
Dr Prater also introduced optical photothermal infrared (OPTIR) spectroscopy, a related approach [4]. Instead of using an AFM tip to detect absorption, OPTIR uses a visible probe beam. The resolution is lower, around hundreds of nanometres, but the technique is simpler to operate, more like a standard optical microscope.
To get the most out of the methodology, in some labs, AFM-IR and OPTIR are used together. Where OPTIR maps larger areas quickly, identifying regions of interest, and then AFM-IR zooms in for local high-resolution chemical analysis. This complementary workflow allows researchers to combine breadth with detail.
The application of both methods together is exemplified in studies such as to investigate microplastics in snow [5] or studies of bone mineralisation patterns [6].
The Power of Multimodal Imaging
AFM has always been a multimodal platform, capable of measuring mechanical, electrical, and thermal properties alongside topography. AFM-IR adds chemical identity to this toolkit.
When combined with other techniques, such as fluorescence microscopy, Raman spectroscopy, and even X-ray diffraction, even more complex sample insights can be gained. Multimodal imaging and data integration are current trends in microscopy.
As Dr Prater noted, the more independent channels of information scientists can access and integrate, the deeper their understanding and the greater the potential for scientific discovery.
Looking Ahead
The next challenges are making the technologies faster, easier to use, and more accessible. And while commercialisation of AFM has significantly aided usability, advances in automation, software, and training will further lower the expertise barrier. This will enable more laboratories to use these techniques to their full potential.
For the life sciences in particular, this accessibility is crucial. The ability to probe disease-related proteins or study nanoscale drug delivery systems could translate into tangible improvements in healthcare.
In materials science, better characterisation means better products, from stronger composites to more efficient semiconductors.
Conclusion
AFM-IR represents a turning point in nanoscale analysis. By uniting AFM’s precision with IR spectroscopy’s chemical specificity, it answers the once-unanswerable: what does it look like and what is it made of?
As Dr Prater emphasised, the goal now is to further improve technology and to bring these powerful tools to more researchers, in more fields, worldwide.
You can also download our resource collection to learn more about nanoscale infrared spectroscopy and their application.
References
- A. Dazzi and C. B. Prater, “AFM-IR: Technology and Applications in Nanoscale Infrared Spectroscopy and Chemical Imaging,” Chem. Rev., vol. 117, no. 7, pp. 5146–5173, Apr. 2017, doi: 10.1021/acs.chemrev.6b00448.
- [2] A. C. V. D. dos Santos, N. Hondl, V. Ramos-Garcia, J. Kuligowski, B. Lendl, and G. Ramer, “AFM-IR for Nanoscale Chemical Characterization in Life Sciences: Recent Developments and Future Directions,” ACS Meas. Sci. Au, vol. 3, no. 5, pp. 301–314, Oct. 2023, doi: 10.1021/acsmeasuresciau.3c00010.
- [3] J. Waeytens, V. Van Hemelryck, A. Deniset-Besseau, J.-M. Ruysschaert, A. Dazzi, and V. Raussens, “Characterization by Nano-Infrared Spectroscopy of Individual Aggregated Species of Amyloid Proteins,” Molecules, vol. 25, no. 12, p. 2899, Jan. 2020, doi: 10.3390/molecules25122899.
- [4] C. B. Prater, M. Kansiz, and J.-X. Cheng, “A tutorial on optical photothermal infrared (O-PTIR) microscopy,” APL Photonics, vol. 9, no. 9, p. 091101, Sept. 2024, doi: 10.1063/5.0219983.
- [5] S. L. Belontz, J. Brahney, C. E. Caplan, E. Dillon, T. Yan, and G. Dominguez, “Combining Submicron Spectroscopy Techniques (AFM-IR and O-PTIR) To Detect and Quantify Microplastics and Nanoplastics in Snow from a Utah Ski Resort,” Environ. Sci. Technol., vol. 59, no. 26, pp. 13362–13373, July 2025, doi: 10.1021/acs.est.4c12170.
- [6] T. Ahn et al., “Matrix/mineral ratio and domain size variation with bone tissue age: A photothermal infrared study,” Journal of Structural Biology, vol. 214, no. 3, p. 107878, Sept. 2022, doi: 10.1016/j.jsb.2022.107878.
Interested in learning more about this topic?
You can find detailed applications and technical notes, expert-led webinars, and on-demand instrument and measurement demonstrations in our online resource library. Get instant, full-length access to all resources related to this podcast using the form below.
This resource collection includes:
- 1 full-length guide to Photothermal AFM-IR Spectroscopy
- 2 full length application notes
- 2 full length on-demand webinar recordings
FULL-LENGTH TECHNOTE
A Comprehensive Guide to Photothermal AFM-IR Spectroscopy
An all-inclusive photothermal AFM-IR guide for everyone, from the nanoIR novice to the AFM-IR expert.
FULL-LENGTH APPNOTE
Advantages of Photothermal AFM-IR for Polymer Research
Learn how AFM-IR’s localized chemical characterization provides valuable insights into the macroproperties and functions of polymeric materials.
FULL-LENGTH APPNOTE
High-Performance Nanoscale IR Spectroscopy and Imaging with Dimension IconIR
Explore the comprehensive meaning of “high-performance” AFM-IR, from sensitivity and resolution to probing depth and throughput.
ON-DEMAND WEBINAR RECORDING
Introduction to Nanoscale Infrared Spectroscopy and Imaging with Photothermal AFM-IR
In this webinar, Bruker experts introduce the core principles behind the technique, share key sample considerations, and present a wide application overview spanning polymers, life sciences, environmental and pharmaceutical research, materials, and semiconductors. The session also includes live demonstrations of the Dimension IconIR system featuring PMMA/epoxy analysis.
ON-DEMAND WEBINAR RECORDING
Resonance Enhanced Force Volume AFM-IR: A Powerful New Technique for Nanoscale IR CharacterizationR
In this webinar, Bruker speakers give an overview over REFV AFM-IR, outline how to perform simultaneous multimodal imaging and spectroscopy, introduce new mechanical tracking methods and applications, and perform a live demonstration of this technique using the Dimension IconIR.
