Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Lasers Key to Handheld Gas and Liquid Sensors

08.08.2005


Terrorists have just laced the water supply of a major metropolis with a chemical so lethal that only small amounts are needed to kill thousands of people. But the chemical never reaches its targets. Tiny liquid phase sensors at strategic points in the city’s water mains detect the chemical as it passes and tell a computer to close down the affected pipes.



Current technology is too cumbersome for this kind of rapid detection and response. But new advances in liquid and gas phase chemical sensing being made at the Georgia Institute of Technology may lead to the development of palm-sized sensing tools that can provide the instant detection needed to stop such an attack.

Using small quantum cascade lasers, researchers at Tech, along with colleagues from Tel-Aviv University and OmniGuide Communications, have built and demonstrated a prototype handheld gas phase chemical sensing device and a liquid phase sensing device. The details appear in the July 15, 2005 issue of Analytical Chemistry and the May 9, 2005 issue of Applied Physics Letters.


The quantum cascade laser is the key to scaling down midinfrared chemical sensing tools to fit in the palm of the hand, said Boris Mizaikoff, associate professor in the School of Chemistry and Biochemistry at Georgia Tech.

"This diode laser light source emits midinfrared frequencies, operates at room temperature and is small – roughly the same size as the laser you use in a laser pointer or CD player,” said Mizaikoff.

Almost every organic molecule has a very distinctive absorption pattern in the midinfrared range (roughly between three and 20 microns) Illuminating molecules with a laser tuned to its fingerprint frequency will cause the molecules to vibrate as they absorb radiation at that frequency.

Detecting a chemical is as simple as illuminating a small volume of gas or liquid with a laser. If the laser is tuned to a characteristic absorption frequency of benzene, for example, and benzene is present, the molecules will vibrate and absorb an amount of radiation at its characteristic absorption frequency indicating its concentration.

"The quantum cascade lasers can be designed by bandstructure engineering to emit almost anywhere in the midinfrared band,” said Mizaikoff. “So, if the molecule you want to detect has an absorption at 11 microns, you design a laser that emits precisely at that frequency. With the concept of the quantum cascade laser, that’s possible for the first time.”

For the gas sensing modules, Mizaikoff and his student Christy Charlton use a photonic band gap hollow waveguide (developed by OmniGuide),essentially a hollow, flexible tube, to both contain very small amounts of the air being sampled and assist in sensing. The waveguide can be built to propagate only one wavelength of light very well. So when the laser illuminates the gas molecules inside the waveguide, the waveguide will propagate only the selected fingerprint frequency for detecting a specific molecule.

"In our paper, we’ve shown that if we take only one meter of photonic band gap hollow waveguide with an inner diameter of 700 microns coupled to a frequency-matched quantum cascade laser, we’ve been able to detect levels down to 30 parts-per-billion (ppb) of ethyl chloride,” said Mizaikoff. “In our opinion, it’s among the most sensitive measurement that’s been demonstrated in gas phase sensing in a hollow wave guide to date.”

Gas sensing done this way requires a sample of only one milliliter of gas, compared to few hundreds of milliliters for other techniques using regular multi-pass gas cells, he added.

One of the most promising applications for this technology is breath diagnostics, said Mizaikoff.

"A lot of diseases, like asthmatic conditions or acute lung injuries, have specific biomarkers that are contained in breath,” he said. “The problem is that you have a dramatic increase of these markers, but still at very low concentration levels, so you need extremely sensitive and reliable tools to detect these changes. We believe this is one way to develop a very compact sensing device, which could provide the sensitivities needed for breath diagnostics.”

Since the lasers are so small, devices could be made to sense multiple chemicals by simply adding more lasers.

For the liquid phase device, researchers use a planar silver halide waveguide, developed at Tel-Aviv University, to transmit the radiation. As with the gas devices, the quantum cascade lasers vastly increase the sensitivity of liquid phase chemical detection at the surface of this waveguide.

"By making the waveguide thinner and coupling the laser into that, we’re actually increasing the amount of energy transported in the so-called evanescent field, which means the sensitivity goes up,” said Mizaikoff.

Currently, there are only few techniques available that can provide an instant response at trace-levels in water monitoring. Usually, gas or liquid chromatography, which require collecting samples, is needed to detect such fine amounts.

"This might be the road to sensors that can continuously measure at ppb levels, with molecular selectivity, and instantaneously,” said Mizaikoff. “We believe this technology will be the inroad to single digit ppb water quality measurement.”

David Terraso | EurekAlert!
Further information:
http://www.icpa.gatech.edu

More articles from Life Sciences:

nachricht Warming ponds could accelerate climate change
21.02.2017 | University of Exeter

nachricht An alternative to opioids? Compound from marine snail is potent pain reliever
21.02.2017 | University of Utah

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Impacts of mass coral die-off on Indian Ocean reefs revealed

21.02.2017 | Earth Sciences

Novel breast tomosynthesis technique reduces screening recall rate

21.02.2017 | Medical Engineering

Use your Voice – and Smart Homes will “LISTEN”

21.02.2017 | Trade Fair News

VideoLinks
B2B-VideoLinks
More VideoLinks >>>