Featured Research

from universities, journals, and other organizations

Naked jets of water make a better pollutant detector

Date:
October 3, 2013
Source:
The Optical Society
Summary:
When you shine UV through water polluted with certain organic chemicals and bacteria, the contaminants measurably absorb the UV light and then re-emit it as visible light. Many of today's more advanced devices for testing water are built to make use of this fluorescent property of pollutants; but the walls of the channels through which the water travels in these devices can produce background noise that makes it difficult to get a clear reading.

When you shine ultraviolet light (UV) through water polluted with certain organic chemicals and bacteria, the contaminants measurably absorb the UV light and then re-emit it as visible light. Many of today's more advanced devices for testing water are built to make use of this fluorescent property of pollutants; but the walls of the channels through which the water travels in these devices can produce background noise that makes it difficult to get a clear reading.

Reported today, in The Optical Society's (OSA) open-access journal, Optics Express, researchers in Italy have developed a pollutant detector that forgoes the channels in favor of a narrow stream of water unconfined by tubes or pipes. The naked jet of water doubles as both the sample and the collection equipment, providing a simple, cheap, and portable new tool to analyze liquids developed in the framework of the research project ACQUASENSE.

"The innovative aspect of this sensor is related to the simple and tricky way used to collect the light -- a water stream," says Gianluca Persichetti of the Institute for Electromagnetic Sensing of the Environment (IREA), National Research Council, (CNR) in Italy.

Typical microfluidic detectors rely on narrow channels to hold and control the water samples with their fluorescing organic compounds. But the laser light that illuminates bacteria and chemicals in the water also shines on the channel walls, where it scatters and obscures the distinction between the fluorescing contaminants and their background. Wear and tear on the walls also weakens the reliability of measurements made using these instruments.

To get around the problems caused by the channel walls, Persichetti and his colleagues of the group led by Romeo Bernini decided simply to do away with them. In their new technique, they pump the water sample through a nozzle at 1.4 meters per second, producing a narrow stream that is less than a millimeter in diameter. Then they shine a UV laser onto the exposed jet of water. The fluorescent light produced by the pollutants and bacteria bounces around and is trapped inside the jet, which acts as a waveguide, a tunnel that channels light through the stream.

The laser light itself is a source of a background noise that can cloud the signal, Perisichetti said, so the researchers minimize the amount of laser light that gets trapped in the jet by firing the laser beam at an angle perpendicular to the stream of water.

After traveling a total distance of 16 millimeters -- not much more than the width of your finger -- the jet enters a small pipe that contains an optical fiber, which collects the fluorescent light signals. The water is pumped back to recirculate through the nozzle, allowing the instrument to analyze even a small sample for an extended period of time.

The researchers tested their device with varying amounts of some of the main pollutants of ground water -- soil contaminants such as benzene, toluene, and xylene (together called BTX), and polycyclic aromatic hydrocarbons (PAH), which are hazardous, carcinogenic chemicals found in tar and petroleum. Persichetti and his colleagues found that the device was extremely sensitive: it could detect pollutant levels even lower than those allowed by the Environmental Protection Agency (EPA). The instrument could also sense Bacillus subtillus, a harmless bacterium similar to the one that causes anthrax.

The current device is fitted with an instrument called a spectrophotometer, which can measure the optical signatures of specific chemicals. To make the device even cheaper and smaller for future commercialization in water-safety testing, the researchers plan to replace the laser with a light-emitting diode (LED) and to replace the spectrophotometer with a simpler and less expensive set-up that would include a filter to remove unwanted background light, and a photodiode, which converts light into electricity, to detect the signal. In addition to water-safety applications, Persichetti says, future instruments can be designed with more sophisticated sensors to distinguish between a variety of chemicals or bacterial cells for biological and medical research.


Story Source:

The above story is based on materials provided by The Optical Society. Note: Materials may be edited for content and length.


Journal Reference:

  1. Gianluca Persichetti, Genni Gesta, Romeo Bernini. High sensitivity UV fluorescence spectroscopy based on an optofluidic jet waveguide. Optics Express, 2013; 21 (20): 24219 DOI: 10.1364/OE.21.024219

Cite This Page:

The Optical Society. "Naked jets of water make a better pollutant detector." ScienceDaily. ScienceDaily, 3 October 2013. <www.sciencedaily.com/releases/2013/10/131003162942.htm>.
The Optical Society. (2013, October 3). Naked jets of water make a better pollutant detector. ScienceDaily. Retrieved April 23, 2014 from www.sciencedaily.com/releases/2013/10/131003162942.htm
The Optical Society. "Naked jets of water make a better pollutant detector." ScienceDaily. www.sciencedaily.com/releases/2013/10/131003162942.htm (accessed April 23, 2014).

Share This



More Matter & Energy News

Wednesday, April 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Is North Korea Planning Nuclear Test #4?

Is North Korea Planning Nuclear Test #4?

Newsy (Apr. 22, 2014) South Korean officials say North Korea is preparing to conduct another nuclear test, but is Pyongyang just bluffing this time? Video provided by Newsy
Powered by NewsLook.com
China Falls for 4x4s at Beijing Auto Show

China Falls for 4x4s at Beijing Auto Show

AFP (Apr. 22, 2014) The urban 4x4 is the latest must-have for Chinese drivers, whose conversion to the cult of the SUV is the talking point of this year's Beijing auto show. Duration: 00:40 Video provided by AFP
Powered by NewsLook.com
Lytro Introduces 'Illum,' A Professional Light-Field Camera

Lytro Introduces 'Illum,' A Professional Light-Field Camera

Newsy (Apr. 22, 2014) The light-field photography engineers at Lytro unveiled their next innovation: a professional DSLR-like camera called "Illum." Video provided by Newsy
Powered by NewsLook.com
3 Reasons Why Harley Davidson Is Selling Tons of Epic Hogs

3 Reasons Why Harley Davidson Is Selling Tons of Epic Hogs

TheStreet (Apr. 22, 2014) Sales of motorcycles have continued to ride back from the depths of hell known as the Great Recession. Excluding scooters, sales of motorcycles increased 3% in 2013. In units, however, at 465,000 sold last year, the total remained about 50% below the peak hit in 2007. Industry leader Harley Davidson’s shareholders have benefited both by the industry recovery and positive headlines emanating from the company. Belus Capital Advisors CEO Brian Sozzi takes you beyond the headlines of the motorcycle maker. Video provided by TheStreet
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins