An improvised explosive device (IED) is the name given to explosive devices that are used in unconventional warfare by commandos or guerillas in a wide range of operations conducted by them. The components of an IED include a detonator, an explosive charge and an initiation device. IEDs are manufactured in a wide variety of designs and may comprise different types of detonators, initiators and explosive loads.
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In order to manage the electrical wiring, colored electric tape is normally used in the construction of IEDs. The analysis of this tape in both exploded and unexploded devices is done with the use of microspectroscopy. Comprehensive spectral data about the dyes and pigments used in tape coloring is obtained from the samples. The benefits of this method are that it is non-destructive and requires preparation of lower numbers of samples.
The 20/20 PV Microspectrophotometer
Craic Technologies offers the 20/20 PV microspectrophotometer, which is an ideal tool for the analysis of colored electric tape samples. The instrument design enables detection of slight spectral changes in microscopic samples in the ultraviolet (UV), near infrared (NIR) and visible regions of the electromagnetic spectrum.
Major Features
Key features of the 20/20 PV microspectrophotometer are as follows:
- Scientific-grade CCD array detector
- Thermo-electric cooling
- Long-term stability
- Minimal noise
- High spectral resolution
- Reflectance
- Ability to receive transmission
- Fluorescent spectra of samples to the scale of 1x1 µm
Analysis of Tape Samples
Five colored electrical tape samples were placed on a quartz slide and prepared for absorbance microscopy. The quartz slide was used since it provides an even, flat surface. The five colors include green, blue, yellow, white and red. The tape had a width of 1.2 cm and a thickness of 0.18 mm.
For every absorbance measurement using the 20/20 PV microspectrophotometer, 50 scans were averaged, the spectral range was 200 to 900nm and the sampling area was 10x10 µm. The reference was obtained through an open space on the quartz slide.
Results of the Experiment
Figure 1 clearly displays the absorbance spectra of the five colored samples.
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Figure 1. Overlay plot of the UV-Visible-NIR absorbance spectra of five colored electrical tape samples
Color Characteristics
Distinctive color characteristics in the visible wavelength range of 400 to 700nm are displayed by the green, blue, red and yellow spectra. For example, the red tape spectrum shows that it exhibits most light absorption in the visible region except the red end. Each of these four colors have the same type of spectral characteristics in the UV region below 400nm. In the same region, the white tape, however, shows a drastic increase in absorption levels which cannot be detected by the instrument below 370nm. This is almost the same as how glass absorbs most of the light below 350nm. The blue and green spectra display distinctive spectral peaks and valleys in the NIR region above 700nm whereas the other spectra show steadily decreasing absorbance values.
Conclusions
The 20/20 PV microspectrophotometer enables obtaining absorbance spectra from colored electrical tape non-destructively. The instrument produces superior quality UV, visible and NIR spectra that provides information about the pigments and dyes used in the tape. This is an excellent technique used to examine trace evidence from IEDs.
About Craic Technologies
CRAIC Technologies™ is the leading developer of superior instruments for UV-visible-NIR microanalysis. Spectra and images of sample features ranging from sub-micron to hundreds of microns can be analyzed. CRAIC Technologies products include UV and NIR microscopes, UV-visible-NIR microspectrophotometers, instruments to measure thin film thickness and colorimetry on the microscopic scale, Raman microspectrometers, automation solutions, traceable standards and more. Specialized systems have been developed for a number of fields including vitrinite coal analysis, protein crystals, forensic and semiconductor metrology.
This information has been sourced, reviewed and adapted from materials provided by CRAIC Technologies.
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