{"73903":{"#nid":"73903","#data":{"type":"news","title":"Lasers Key to Handheld Gas and Liquid Sensors","body":[{"value":"\u003Cp\u003ETerrorists 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\u0027s water mains detect the chemical as it passes and tell a computer to close down the affected pipes.\n\u003C\/p\u003E\n\u003Cp\u003ECurrent 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.\n\u003C\/p\u003E\n\u003Cp\u003EUsing 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.\n\u003C\/p\u003E\n\u003Cp\u003EThe 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.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022This 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,\u0022 said Mizaikoff.\n\u003C\/p\u003E\n\u003Cp\u003EAlmost 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.\n\u003C\/p\u003E\n\u003Cp\u003EDetecting 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.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022The quantum cascade lasers can be designed by bandstructure engineering to emit almost anywhere in the midinfrared band,\u0022 said Mizaikoff.  \u0022So, 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\u0027s possible for the first time.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EFor 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.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022In our paper, we\u0027ve 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\u0027ve been able to detect levels down to 30 parts-per-billion (ppb) of ethyl chloride,\u0022 said Mizaikoff. \u0022In our opinion, it\u0027s among the most sensitive measurement that\u0027s been demonstrated in gas phase sensing in a hollow wave guide to date.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EGas 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.\n\u003C\/p\u003E\n\u003Cp\u003EOne of the most promising applications for this technology is breath diagnostics, said Mizaikoff.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022A lot of diseases, like asthmatic conditions or acute lung injuries, have specific biomarkers that are contained in breath,\u0022 he said. \u0022The 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.\u0022\n\u003C\/p\u003E\n\u003Cp\u003ESince the lasers are so small, devices could be made to sense multiple chemicals by simply adding more lasers.\n\u003C\/p\u003E\n\u003Cp\u003EFor 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.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022By making the waveguide thinner and coupling the laser into that, we\u0027re actually increasing the amount of energy transported in the so-called evanescent field, which means the sensitivity goes up,\u0022 said Mizaikoff.\n\u003C\/p\u003E\n\u003Cp\u003ECurrently, 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.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022This might be the road to sensors that can continuously measure at ppb levels, with molecular selectivity, and instantaneously,\u0022 said Mizaikoff. \u0022We believe this technology will be the inroad to single digit ppb water quality measurement.\u0022\n\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":[{"value":"Ga Tech developing instant-response trace sensors"}],"field_summary":[{"value":"Tech researchers are using quantum cascade lasers to develop handheld gas and liquid phase sensors capable of providing instantaneous and continuous detection of trace elements. Potential applications include chemical weapon detection and diagnosing illnesses through breath.","format":"limited_html"}],"field_summary_sentence":[{"value":"Ga Tech developing instant-response trace sensors"}],"uid":"27310","created_gmt":"2005-08-04 00:00:00","changed_gmt":"2016-10-08 03:02:27","author":"David Terraso","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2005-08-04T00:00:00-04:00","iso_date":"2005-08-04T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"73904":{"id":"73904","type":"image","title":"Boris Mizaikoff and Christy Charlton","body":null,"created":"1449178028","gmt_created":"2015-12-03 21:27:08","changed":"1475894681","gmt_changed":"2016-10-08 02:44:41"}},"media_ids":["73904"],"related_links":[{"url":"http:\/\/asl.chemistry.gatech.edu\/","title":"Applied Sensors Laboratory"}],"groups":[{"id":"1214","name":"News Room"}],"categories":[],"keywords":[],"core_research_areas":[],"news_room_topics":[],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003E\u003Cstrong\u003EGeorgia Tech Media Relations\u003C\/strong\u003E\u003Cbr \/\u003ELaura Diamond\u003Cbr \/\u003E\u003Ca href=\u0022mailto:laura.diamond@comm.gatech.edu\u0022\u003Elaura.diamond@comm.gatech.edu\u003C\/a\u003E\u003Cbr \/\u003E404-894-6016\u003Cbr \/\u003EJason Maderer\u003Cbr \/\u003E\u003Ca href=\u0022mailto:maderer@gatech.edu\u0022\u003Emaderer@gatech.edu\u003C\/a\u003E\u003Cbr \/\u003E404-660-2926\u003C\/p\u003E","format":"limited_html"}],"email":["david.terraso@comm.gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}