Lenox Laser Scholarship- “Evaluation of UV LEDs for detection of atmospheric NO2 by photolysis- chemiluminescence”

Lockheed WP-3D Orion. From NOAA website
Lockheed WP-3D Orion. From NOAA website


Evaluation of ultraviolet light-emitting diodes for detection of atmospheric NO2 by photolysis- chemiluminescence
by Ilana B Pollack, Brian M Lerner, and Thomas B Ryerson

This article was accepted to Journal of Atmospheric Chemistry in February of this year, and it details an atmospheric study done in May and June of 2010. Lenox Laser made a total of 3 parts for their studies of different LED detections systems of NO2. For some key background information if one is not familiar, I highly recommend reading this article first:
Flourescence detection of atmospheric nitrogen dioxide using a blue light-emitting diode as an excitation source by Yutaka Matsumi et al. It is much more readable and understandable.

Basically, detection of NO2 in the atmosphere relates to the ozone levels in the atmosphere. Thus, scientists of the field are interested in better, more accurate, and cheaper ways to measure NO2. One of the most recent trends to do so is to use commercially available UV-LEDs in their systems. The systems already often use a UV light source of some kind because in the chemistry of NO2 and related molecules, they will emit light in the process. Atmospheric scientists use this property, called chemiluminescence, to measure the NO2 molecules. Chemiluminescence detection is called P-CL.

In this article, the authors tested 3 UV-LEDs against each other in the P-CL system as shown in the diagram below:

Fig 1 from the paper- schematic of instrumental configuration
Fig 1 from the paper- schematic of instrumental configuration

I recommend reading the article itself to fully understand the diagram and the process. However, this is where Lenox Laser and our calibrated orifices come in. The red section where it says 700um orifice is where our first orifice was used. This is the bypass inlet, and was used to set the sample flow rate and cell pressure for the entire system. They found that the Nichia LEDs were the best overall.

So for the second part of the test, they took the Nichia LEDs on board the NOAA WP-3D aircraft with the P-CL for “on the job” training in the CalNex study. They replaced the more expensive and complicated mass flow controllers were replaced with our critical orifices and mass flow meters. In the diagram above the two places are indicated by arrows in the blue and black section. Replacing the parts in the system did improve the quality, and, as stated in the conclusion, they “eliminate mechanical components with complex flow paths that degrade time response. Replacing mass flow controllers with critical orifices and mass flow meters further simplifies the sample flow path in these laboratory test.”

The NOAA WP-3D aircraft is the plane that flies into hurricanes to monitor and gather information. It took part in CalNex – a study by several universities and institutions of air quality and climate change on the west coast. Our parts were used on board and tested with the UV-LED systems during the study. They even went with the plane as it was briefly diverted from the study to the Gulf of Mexico during the oil spill.

So in conclusion, this research paper incorporates optics, chemistry, and biology with flow technologies, atmospheric studies, and research planes all together, with Lenox Laser parts in the middle of it all!

As always, check out our main website www.lenoxlaser.com to see more of what we do, as well as the rest of this blog. If you have any questions or input, email me at archives@lenoxlaser.com

EDM of Reverse-Tapered Microholes
Spectrum of Industrial and Scientific Lasers