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Conventional IR Microspectroscopy
Power of IR microspectroscopy
Spatial resolution limits of IR microspectroscopy
nanoIR - Infrared Nanospectroscopy
Overcoming resolution limits of infrared spectroscopy
Power & limits of AFM
Bringing chemical characterization to AFM
Power of IR microspectroscopy
IR microspectroscopy has already demonstrated itself as a powerful tool for spatial mapping chemical content in a wide variety of applications[1-3], leading to over 15,000 publications in 2009. It has been used to characterize numerous materials critical in industry[4], especially polymeric materials [5-11] . Exciting applications have also been demonstrated in biology,[12] including analysis of plant materials,[13-15], bone[16-21], single cells[22], and strain identification in yeasts[23] and bacteria[24], for example. There have also been many biomedical applications, including applications in pharmaceuticals,[25-27] and medical diagnosis,[28-32]
Spatial resolution limits of IR microspectroscopy
Despite its widespread applications, infrared microspectroscopy has fundamental spatial resolution limits set by both the laws of optics and practical design constraints. Fourier Transform IR spectroscopy is generally limited to a spatial resolution of three times the wavelength of the IR radiation. With Attenuated Total Reflection (ATR) may achieve resolution approaching the wavelength. The table below shows practical resolution limits faced by conventional IR spectroscopy.
| IR Spectroscopy Method | Practical resolution
Limit
|
| Transmission FTIR | ~10-30 μm |
| ATR | ~3-10 μm |
With nanoIR, you can overcome these diffraction limits.
Overcoming resolution limits of infrared spectroscopy
The nanoIR system breaks through resolution limits in conventional IR spectroscopy by using the tip of an atomic force microscope probe to measure infrared absorption. The sample is illuminated by a tunable IR source. When IR radiation is absorbed by a region of the sample, the region heats up. The heat generates a rapid thermal expansion pulse that can be detected by the AFM cantilever tip. For more details, see The Science behind the Solution. This technique beats the "far field" optical diffraction limit because the absorbed radiation is measured by the tip in the extreme near field.
With the nanoIR system, the tip of an AFM is used to measure local thermal expansion resulting from absorption of IR light. Even though the focused spot of IR radiation is on the scale of many microns, the thermal expansion can be spatially resolved with the AFM tip on scales well below the optical diffraction limit.
Power & limits of AFM
Atomic force microscopy (AFM) has been enormously successful addressing problems in basic nanoscale research as well as applied problems in materials science and engineering. The AFM has also been widely credited with enabling the multi-billion dollar research investments in nanoscience and nanotechnology. A clear gap in AFM capabilities, however, is the ability to chemically characterize regions of the sample. In fact, the ability to identify material under the tip of an AFM has been identified as one of the "Holy Grails" of probe microscopy. While AFM can measure mechanical, electrical, magnetic and thermal properties of materials, it has lacked the robust ability to chemically characterize unknown materials.
Bringing chemical characterization to AFM
The ability to identify material under the tip of an AFM has been identified as one of the "Holy Grails" of probe microscopy. With the nanoIR instrument, Anasys Instruments brings robust chemical characterization to the AFM. The nanoIR uses infrared spectroscopy to provide chemical analysis of samples on the sub-micron length scale. Infrared spectroscopy measures the wavelength dependent absorption of radiation that results from excitations of specific molecular vibrations. The resulting absorption spectra provide rich information about the chemical content of material under the AFM tip.
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3. Humecki, H., ed. Practical Guide to Infrared Microspectroscopy. 1995, Marcel Decker: New York.
4. Chalmers, J.M., et al., FT-IR imaging of polymers: an industrial appraisal. Vibrational Spectroscopy 30(1): 43-52, 2002.
5. Kazarian, S.G. and K.L.A. Chan, FTIR Imaging of Polymeric Materials under High-Pressure Carbon Dioxide. Macromolecules 37(2): 579-584, 2003.
6. Snively, C.M. and J.L. Koenig, Application of Real Time Mid-Infrared FTIR Imaging to Polymeric Systems. 1. Diffusion of Liquid Crystals into Polymers. Macromolecules 31(11): 3753-3755, 1998.
7. Miller-Chou, B.A. and J.L. Koenig, FT-IR Imaging of Polymer Dissolution by Solvent Mixtures. 3. Entangled Polymer Chains with Solvents. Macromolecules 35(2): 440-444, 2001.
8. Snively, C.M. and J.L. Koenig, Fast FTIR imaging: A new tool for the study of semicrystalline polymer morphology. Journal of Polymer Science Part B: Polymer Physics 37(17): 2353-2359, 1999.
9. Bhargava, R., et al., FTIR Microspectroscopy of Polymeric Systems. Eds: pp 93-96, 2003.
10. Bhargava, R., et al., FTIR Imaging Studies of a New Two-Step Process To Produce Polymer Dispersed Liquid Crystals. Macromolecules 32(8): 2748-2760, 1999.
11. Martoglio Smith, P.A., Infrared microspectroscopy mapping studies of packaging materials: experiment design and data profiling considerations. Vibrational Spectroscopy 24(1): 47-62, 2000.
12. Gremlick, H. and B. Yan, eds. Infrared and Raman spectroscopy of biological materials. 2000, Marcel Decker: New York.
13. Wolkers, W.F., et al., A Fourier transform infrared microspectroscopy study of sugar glasses: application to anhydrobiotic higher plant cells. Biochimica et Biophysica Acta (BBA) - General Subjects 1379(1): 83-96, 1998.
14. Marcott, C., et al., FT-IR spectroscopic imaging microscopy of wheat kernels using a Mercury-Cadmium-Telluride focal-plane array detector. Vibrational Spectroscopy 19(1): 123-129, 1999.
15. McCann, M.C., et al., Fourier Transform Infrared Microspectroscopy Is a New Way to Look at Plant Cell Walls. Plant Physiol. 100(4): 1940-1947, 1992.
16. Carden, A. and M.D. Morris, Application of vibrational spectroscopy to the study of mineralized tissues (review). Journal of Biomedical Optics 5(3): 259-268, 2000.
17. Marcott, C., et al., Infrared Microspectroscopic Imaging of Biomineralized Tissues using a Mercury-Cadmium-Telluride Focal-Plane Array Detector. Phosphorus, Sulfur, and Silicon and the Related Elements 144(1): 417 - 420, 1999.
18. Mendelsohn, R., et al., Infrared Spectroscopy, Microscopy, and Microscopic Imaging of Mineralizing Tissues: Spectra-Structure Correlations from Human Iliac Crest Biopsies. Journal of Biomedical Optics 4(1): 14-21, 1999.
19. Paschalis, E.P., et al., FTIR Microspectroscopic Analysis of Normal Human Cortical and Trabecular Bone. Calcified Tissue International 61(6): 480-486, 1997.
20. Paschalis, E.P., et al., FTIR Microspectroscopic Analysis of Human Iliac Crest Biopsies from Untreated Osteoporotic Bone. Calcified Tissue International 61(6): 487-492, 1997.
21. Paschalis, E.P., et al., FTIR microspectroscopic analysis of human osteonal bone. Calcified Tissue International 59(6): 480-487, 1996.
22. Lasch, P., et al., FT-IR spectroscopic investigations of single cells on the subcellular level. Vibrational Spectroscopy 28(1): 147-157, 2002.
23. Wenning, M., et al., Fourier-Transform Infrared Microspectroscopy, a Novel and Rapid Tool for Identification of Yeasts. Appl. Environ. Microbiol. 68(10): 4717-4721, 2002.
24. Kansiz, M., et al., Fourier Transform Infrared microspectroscopy and chemometrics as a tool for the discrimination of cyanobacterial strains. Phytochemistry 52(3): 407-417, 1999.
25. Reich, G., Near-infrared spectroscopy and imaging: Basic principles and pharmaceutical applications. Advanced Drug Delivery Reviews 57(8): 1109-1143, 2005.
26. Chan, K.L.A. and S.G. Kazarian, Fourier Transform Infrared Imaging for High-Throughput Analysis of Pharmaceutical Formulations. Journal of Combinatorial Chemistry 7(2): 185-189, 2005.
27. Kazarian, S.G. and K.L.A. Chan, Applications of ATR-FTIR spectroscopic imaging to biomedical samples. Biochimica et Biophysica Acta (BBA) - Biomembranes 1758(7): 858-867, 2006.
28. Diem, M., et al., eds. Vibrational Spectroscopy for Medical Diagnosis. 2008, J. Wiley InterScience.
29. Wood, B.R., et al., FTIR microspectroscopic study of cell types and potential confounding variables in screening for cervical malignancies. Biospectroscopy 4(2): 75-91, 1998.
30. Lasch, P., et al., Imaging of colorectal adenocarcinoma using FT-IR microspectroscopy and cluster analysis. Biochimica et Biophysica Acta (BBA) - Molecular Basis of Disease 1688(2): 176-186, 2004.
31. MORDECHAI, S., et al., Possible common biomarkers from FTIR microspectroscopy of cervical cancer and melanoma. Journal of Microscopy 215(1): 86-91, 2004.
32. Fernandez, D.C., et al., Infrared spectroscopic imaging for histopathologic recognition. . Nat Biotechnol. 23: 469-474, 2005. |
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