Nanoscale Infrared Spectroscopy

Resonance Enhanced Force Volume (REFV) AFM-IR

Uniquely and easily extends the capabilities and sample range compatibility of resonance-enhanced AFM-IR techniques

The new Resonance Enhanced Force Volume (REFV) AFM-IR mode enables an increased range of unique nanochemical research possibilities, from multiplexed, exhaustive datasets for advanced users to beginner-friendly mechanical tracking and utility on previously challenging samples.

REFV AFM-IR combines the industry-leading sensitivity of Bruker's patented resonance-enhanced AFM-IR detection for nanochemical analysis with a force volume-based cantilever approach — easily extending sample compatibility and measurement capabilities across more applications regardless of the user's prior experience with photothermal AFM-IR technology.

Only REFV AFM-IR provides:

dPS-b-PMMA core-shell sample where PS domains seem to be covered by PMMA shells. The core-shell assembly shown here is only 10–15 nm tall. The absorption measured in REFV AFM-IR at the PMMA carbonyl resonance at 1730 cm-1 locates the PMMA distribution around the nanoparticles. 

Effortlessly Delivering Artifact-Free, Multiplexed Datasets

REFV AFM-IR achieves:

  • Same monolayer sensitivity and <10 nm spatial resolution of Resonance Enhanced AFM-IR nanochemical analysis
  • Lateral force control and soft/fragile sample compatibility of Tapping AFM-IR
  • Easy IR mapping without mechanical artifacts
  • Extended sample compatibility with simultaneous mechanics and frequency-sweep data

“REFV AFM-IR is a powerful new tool for AFM-IR measurements, it removes the lateral forces during the scan and the frequency sweep approach provides a rich data set with the full access to mechanical properties (resonance frequency, Q factor). It is a significant development on existing AFM-IR technology and my preferred technique” 

Dr. Alexandre Dazzi, Inventor of AFM-IR, University of Paris-Saclay

Resonance-Enhanced AFM-IR Measurements on Even More Challenging Samples

Perfecting resonance-enhanced detection

Like Bruker's patented Resonance Enhanced AFM-IR mode (a contact mode technique), REFV AFM-IR is based on resonance-enhanced detection—a method in which the pulse rate of the laser source is set to a resonance frequency of the AFM cantilever, delivering:

  • Monolayer sensitivity
  • <10 nm spatial resolution

Like Bruker's DataCube AFM modes, REFV AFM-IR performs a force-distance spectrum at every pixel with a user-defined dwell time, enabling:

  • Multidimensional nanoscale information at every pixel
  • Full characterization in a single experiment
Schematic showing how REFV AFM-IR works.

Integrating sample-friendly force-volume methods

Unlike standard Resonance Enhanced AFM-IR mode, REFV AFM-IR uses a force-volume method (linear approach/retract) with an adjustable hold (dwell) time. Since the probe is not dragged on the surface, there are no lateral forces, enabling investigations of previously inaccessible samples, such as fragile nanoparticles.

REFV AFM-IR eliminates lateral forces to deliver:

  • Enhanced compatibility with fragile samples
  • Extended compatibility with soft, sticky, or otherwise difficult samples
REFV AFM-IR of an approximately 7 nm thick purple membrane protein.  REFV AFM-IR reveals simultaneous chemical and topographic mapping of the membrane. Point spectroscopy reveals the Amide I and Amide II bands corresponding to the protein with excellent signal-to-noise.

Simultaneously Collect Nanomechanical and Nanochemical Data

With REFV AFM-IR, chemical and mechanical information are collected from the same pixel simultaneously. A rich dataset is gathered from a single scan, eliminating concerns about thermal drift or sample changes between separate scans:

  • Nanochemical analysis is conducted using well-established photothermal AFM-IR principles.
  • Nanomechanics data is extracted from the retract part of the force curve via fitting to established mechanical models
Simultaneous mechanical and chemical mapping of a PS-LDPE polymer blend. Chemical mapping at 1493 cm-1 shows the PS regions that also have a higher modulus, linking the properties together. The capability to use a single probe for nanomechanical and nanochemical imaging simplifies the workflow and provides rich, detailed datasets.

Easily Setup and Use Mechanical Tracking / Compensation

Mapping IR absorption at fixed frequencies can lead to mechanically induced artifacts, inversion (fake) signal, or edge effects. Traditionally, it requires a skilled user and knowledge about sample mechanics to correct for these artifacts.

With REFV AFM-IR, the IR absorption is automatically mapped at the local resonance frequency using software corrections, meaning:

  • True chemistry is accessible for any user and with no sample mechanics knowledge required.
  • Artifact-free nanochemical imaging is available with just the click of a button.
Frequency sweep capabilities on a polymer sample with a contaminant inclusion. The frequency of the mechanical resonance can shift as much as 10 kHz, where not appropriately tracking the frequency can introduce false, mechanical contrast in the IR data. Frequency tracking provides a very easy way of ensuring the maximum accuracy of AFM-IR data. Sample credit: Prof. Philippe Leclére, Mons University.

Access Comprehensive Datasets in a Single Sweep

Conducting a frequency sweep at each measurement point simplifies experiment setup for the user and enables the collection of rich, comprehensive datasets that even go beyond simultaneous nanochemistry and nanomechanics. One complete measurement provides IR imaging, quantitative nanomechanics, contact resonance data, and Q-factor.

REFV AFM-IR uses a single scan to deliver:

  • Nanochemistry from IR spectroscopy and imaging
  • Nanomechanics from force curve analysis
  • Dissipation and stiffness information from contact resonance analysis
Advanced data analysis on a PS-b-PMMA core-shell nanoparticle. The frequency sweep data contains nanomechanical, chemical, and contact resonance (CR) data. By measuring the frequency shift, the contact resonance frequency and Q-factor can be extracted, corresponding to the viscoelastic response of the sample. REFV AFM-IR provides a comprehensive and easy-to-use approach for nanochemical analysis.