In this edition, we examine the importance of using IR to prevent a new wave of high-price food counterfeiting, to detect explosives, to see the history of our universe and to understand ancient cultures.

1) Bone spectra from archaeological digs unearth information on past cultures

Our favourite story of the month was reported in Spectroscopy Europe, with infrared spectroscopy used as part of research undertaken on neolithic, copper age, Roman and medieval bone fragments, to understand funerary practices and also cooking techniques used by these cultures.

The research, led by Dr Fest at the Centro Fermi museum in Rome, showed how the infrared spectra of bone in humans and animals changed with heat. As the paper states: “burned bones are often found in archaeological sites as a result of fire or funerary practices and are often the only preserved human remains…” also stating that “bone mineral characteristics, such as crystallinity and carbonate/phosphate content vary as a function of age, sex, location in the skeleton, diet and pathological state of the person. With increasing burning temperature (> 200 °C), the bone matrix suffers structural and dimensional variations, usually leading to higher crystallinity. These are reflected in the vibrational spectra.”

Fig: Reproduced from Festa et al, Old burned bones tell us about past cultures

Findings show how the ability to effectively burn the body has improved over time, with data from the copper age (3500-2300 BCE) having spectroscopic signatures that “correspond to a burning temperature around 500 °C, virtually homogeneous … This temperature is compatible with an incomplete cremation in home fires.”

Whereas, for Roman bones, the spectra showed a range of temperatures for different bones, indicating the remains were of bodies burned in the grave, rather than being taken thereafter burning.

The full paper – and it’s worth a read – is available here

2) Mid infrared analysis of comet and asteroid dust

As equally wonderful as understanding human cultures is the chance to understand how asteroids and comets were formed and the conditions in which it happened. Research by Takahashi, et al, led out of the Japan Aerospace Exploration Agency does just that.

Interplanetary dust (IPD) is thought to be recently supplied from asteroids and comets. According to the paper, grain properties of the IPD can give information on the environment in the proto-solar system and can be traced from the shapes of silicate features seen in the zodiacal emission spectra.

The team used the infrared camera onboard the AKARI satellite to capture and analyse mid-IR silt-spectroscopic data of the zodiacal emission, taking shots from multiple angles. According to the paper, the IPD was found to typically include small silicate crystals, especially enstatite grains. The team also found the variations in the feature shapes and the related grain properties among the different sky directions. They concluded that the IPD in dust bands tends to have larger grains and show the indication of hydrated minerals. Whereas the spectra at higher ecliptic latitude showed a stronger excess, which indicates an increase in the fraction of small grains included in the line of sight at higher ecliptic latitudes.

The full paper, Mid-infrared spectroscopy of zodiacal emission with AKARI/IRC can be read here.

3) Tracking movements of explosives

Two items of news from this month highlight a major issue facing customs officials – how do you reliably track the use of contraband chemicals over state and national borders?

First, the Xinhua news agency reported on Bangkok’s bombing suspects who smuggled explosives over the Malaysia-Thailand border. Quoting a Thai army general, the report states two bombing suspects were seen carrying a sack, walking across the border ahead of the 2nd August bombings that killed four people.

Added to this is the Verge’s report on how Snapchat is being used to sell guns and explosives across state lines in the US.

And while dogs can be used to detect explosives there are several limitations, both on a moral capacity (is it appropriate to put the dog in danger?) and in terms of accuracy. As an article from the New Yorker following the Boston Marathon bombing points out, dogs noses aren’t always reliable: they take a long time to train, are subject to fatigue, can struggle when the environment is filled with many smells, and are trained to only detect a small handful of scents “a guava dog will pass right over T.N.T”.

Spectroscopy gives a quick, cost effective alternative, with low-cost handheld units able to give agents a spectra immediately. The big advantage comes as new chemicals become known, the databases can be immediately updated and spectras compared against them.

For the essential principles in developing such a spectroscopy system please see our white paper – here.

And this leads to one of our favourite graphics – the absorption spectrum of Semtex – reproduced from Howard el al’s 2015 paper on imaging of trace explosives.

4) Food fraud – targeting high-value foods

At the start of the month, food fraud involving adulterated saffron sold in the south of England led to the seizure of stock worth worth £750,000 in Alicante, Spain.

Gram for gram, saffron is more expensive than gold and typically sells for £6-£8 per gram, making adulteration with cheaper plan fibres highly profitable. The move follows a report in the Times suggesting fraudsters are now targeting the luxury food market, highlighting champagne and caviar, truffles and parmesan, wagyu beef and (as we’ve highlighted in a white paper on IR sensors for food counterfeit detection) manuka honey: “A rise in food fraud has included “beluga” caviar from fish besides sturgeon being sold in upmarket shops, fake Périgord truffles shipped from China, fake Moët made in Italy, Parmesan bulked out with wood pulp and fake olive oil proving to be sunflower oil mixed with chlorophyll and soya oil.”

The problem has also been highlighted in the US during August with the suicide of a farmer convicted of running the country’s largest ever organic food fraud scheme. And while it’s not the only method (see March 2019’s wonderful paper on testing for the use of inorganic fertiliser by looking at the stable isotope ratio of oxygen), infrared spectroscopy offers a cost-effective portable solution that enables the FDA/other regulatory bodies to act quickly.

See 2012’s paper on the fatty acid content of caviar from the Caspian Sea using infrared spectroscopy or 2013’s white paper on pesticide authentication by portable IR spectroscopy devices and our article on considerations in developing such a system.

And thankfully, for several of these food frauds, infrared spectroscopy is already being used to detect counterfeits before they’re a problem.

5) International conference on mid-infrared optoelectronic materials and devices

A date for the diary for all in the industry, the 15th International Conference on mid-infrared optoelectronic materials and devices will take place at the University of Surrey between the 1st and 4th of September 2020.

The conference looks at both recent progress and future trends in infrared optoelectronics and brings together both engineers and scientists from across the globe.

You can see more information here, as well as a summary of the 2019 conference just held, and the overview for the 2020 show is as follows:

  • Infrared optoelectronic materials development, growth, and characterization
  • Infrared optoelectronic devices, components, and systems
  • Infrared emitters and detectors
  • Interband and intersubband materials and devices
  • Novel architectures based on new materials and low-dimensional structures
  • Non-linear infrared optoelectronics
  • THz materials and devices.