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from the how-long-till-they-start-tracking-us-with-it dept.
Technology based on the use of high-performance lasers and sensors for the generation and detection of infrared light promises to be one of the key technologies of the 21st century. Realization of this goal will require the use of dyes that absorb light specifically in the near-infrared region of the spectrum, and such compounds are therefore of special interest to both researchers and commercial firms.
One class of chemicals that show great potential in this area are the so-called peri-arylenes which, thanks to their excellent stability properties, are already being used in a wide range of technical applications. A research team led by LMU [Loyola Marymount University] chemist Professor Heinz Langhals now reports the synthesis of the first peri-arylene consisting of six basic subunits, whose absorption spectrum is almost entirely confined to the near-infrared (NIR) region. In other words, the substance appears colorless to the human eye, and this makes it suitable for use as an inconspicuous labeling agent. The findings appear in the Journal of Organic Chemistry.
[...] The 6-member derivative absorbs essentially only in near-infrared region, which lies "below the red" and is therefore invisible to the human eye. "Fabrics dyed with the new compound appear colorless but the dyestuff can be detected with a suitable sensor," Langhals explains. One conceivable application for such a marker lies in the recycling of expensive textiles, since the compound would greatly simplify the sorting process. But in addition to the end-product of the synthesis, the shorter members of the series are also of considerable practical interest. This is because they exhibit intriguing light-induced responses, which may make them suitable for use in fluorescent solar collectors. "One other advantage of the new substances lies in their environmentally benign character: They consist entirely of organic materials that are biodegradable and fully combustible," Langhals adds.
Finally, a way for your mom to label your underwear without embarrassing you about it.
Sexterrylenetetracarboxylic Bisimides: NIR Dyes (DOI: 10.1021/acs.joc.5b02092)
(Score: 2) by hankwang on Thursday December 24 2015, @08:42AM
I doubt that there are any pentachromats that are sensitive to 945 nm (wavelength mentioned in the study). Molecules that can be excited at such long wavelengths (low photon energies) tend to be damaged by short (blue) wavelengths.
A tetra/pentachromat will typically have extra receptor channels in the visible light range, causing them to perceive colors differently. But you can't print hidden messages for them. In daylight, a normal trichromat might not see the message, but under artificial light (line spectrum from a LED or HID lamp), the message would still show up.
I think there are plenty of pentachromatic women. About 3% of males have a mutated red receptor (protanopia); 3% have a green mutation (deuteranopia), so about 0.1% have both. A female child of such a father will have five different color receptors. Unfortunately, the wiring to the brain will not use this information, just like it suppresses the information from rod (night vision) receptors in color perception.
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(Score: 0) by Anonymous Coward on Thursday December 24 2015, @04:34PM
HID lamps use black-body radiation (just at a higher color temperature)
The real problem with GP's suggestion is that a large reward makes it practical to use specialized equipment to examine the poster. You would also have to control for the people at the print-shop knowing the message.
(Score: 1) by hankwang on Sunday December 27 2015, @11:25AM
Not really a black-body spectrum: https://upload.wikimedia.org/wikipedia/en/9/93/Metal_Halide_Lamp_Spectrum.jpg [wikimedia.org]
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(Score: 2) by Gravis on Thursday December 24 2015, @06:19PM
well i suppose they would be waiting a long time... until there actually is a proper pentachromat. ;)