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Topics Covered
Background
Introduction to Coatings and
Films
WITec CRM -
Combining Confocal Microscope with Raman Spectroscopy
Polymer Coating Used for this
Investigation
Results
WITec CRM - Ideal Tool for
Heterogeneous Layered Sample Analysis
Background
WITec is
a manufacturer of high-performance instrumentation for scientific and industrial
applications focused on new solutions for Optical and Scanning Probe
Microscopy.
Introduction to Coatings and Films
Coatings and films play an important role in many fields of application (drug
delivery coatings, coatings on medical devices, thin films for food protection
etc.), which makes an efficient technique for the investigation of these
materials essential. Confocal Raman Microscopy is a powerful tool for
non-destructively imaging the chemical composition of heterogeneous components
within a film or coating. The confocal setup not only provides the highest
spatial resolution, but also allows the acquisition of depth profiles ideally
suited to the three-dimensional characterization of polymer films and coatings
without sample preparation.
WITec CRM - Combining
Confocal Microscope with Raman Spectroscopy
The WITec
Confocal Raman Microscope alpha300 R combines a highly sensitive confocal
microscope and a high-transmission Raman spectroscopy system. With a resolution
down to 200 nm at each image pixel, a complete spectrum is typically acquired in
only 10 to 100 ms. The number of image points (spectra) is limited only by the
computer memory. A typical image consists of 10,000 (100 x 100) to 65 536 (256 x
256) spectra. An image is generated from this multi-spectrum file by integrating
over a specific Raman line or a region in all spectra. As all spectra are stored
in memory, a variety of properties such as peak-width, center of mass or peak
position of certain Raman lines can be calculated from a single measurement. For
depth profiling measurements, the focal plane can be moved in the z-direction
when performing either xz scans or generating x-y image stacks in the z
direction.
Polymer Coating Used for this Investigation
The inner polymer coating of an orange juice container was investigated in
this experiment with the alpha300 R by performing an x-z scan with a scan range of 50
ìm x 100 ìm at 200 x 120 pixels (= 24 000 spectra) using a 100x objective (NA=
1.25). For excitation, a 532 nm Nd:Yag laser was used. The acquisition time for
each spectrum was 50 ms.
Results
Within the acquired multi-spectrum file, four distinct spectra can be
observed (Fig.1 left). Each spectrum represents a specific chemical compound
within the polymer film. The distribution of each compound can be visualized
with the integrated software tools, by analyzing all acquired spectra. Fig. 1
(right) shows the resulting color-coded image, clearly revealing that the
coating consists of 5 different layers although only 4 components are involved.
The software also provides the ability to measure distances within the image,
indicating that all layers vary in thickness.
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Figure 1. Raman spectra (left) and Raman
image (right) of the inner coating of an orange juice container.
WITec CRM - Ideal Tool for Heterogeneous Layered Sample Analysis
The WITec
Confocal Raman Microscope alpha300 R is an ideal tool for the analysis of
heterogeneous layered samples on the sub-micrometer scale. As shown in the
example, different polymer layers in the film can be clearly resolved and
matched with their associated Raman-Spectrum. Detailed information on the
structure of multilayered polymer films or coatings can thus be attained using
the depth profiling capabilities of the Confocal Raman
Microscope.
Source: WITec
For more information on this source please visit WITec.