Evaluation of ultraviolet light-emitting diodes for detection of atmospheric NO2 by photolysis - chemiluminescence

• Published in: Journal of atmospheric chemistry Vol. 65; no. 2-3; pp. 111 - 125
• Main Authors: Pollack, Ilana B., Lerner, Brian M., Ryerson, Thomas B.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.04.2010; Springer; Springer Nature B.V
• Subjects: Air quality; Atmospheric Protection/Air Quality Control/Air Pollution; Atmospheric Sciences; Chemical composition and interactions. Ionic interactions and processes; Chemiluminescence; Climate change; Diodes; Earth and Environmental Science; Earth Sciences; Earth, ocean, space; Exact sciences and technology; External geophysics; Geophysics. Techniques, methods, instrumentation and models; Light sources; Luminescence; Meteorology; Nitric oxide; Nitrogen dioxide; Photolysis; Ultraviolet radiation; United States; California; Chemiluminescence; Photolysis; UV-LEDs; Nitrogen dioxide; Troposphere; sensitivity analysis; Reaction product; ultraviolet rays; North America; Light emitting diode; Measuring instrument; Atmospheric chemistry; Response time; Nitric oxide; Rate constant
• ISSN: 0167-7764; 1573-0662
• DOI: 10.1007/s10874-011-9184-3

Commercially available ultraviolet light-emitting diodes (UV-LEDs) are evaluated in the laboratory as a light source for photolysis of atmospheric nitrogen dioxide (NO 2 ) followed by chemiluminescence detection (P-CL) of the resulting nitric oxide (NO). Sensitivity, selectivity, and engineering simplicity of three UV-LED sources are compared. The most powerful source uses two 9-W Nichia LED modules and provides an NO 2 photolysis frequency ( j ) of 8.4 s −1 corresponding to a nine-fold improvement over a 100-W Hg arc lamp; this source provides the most sensitivity, but requires water cooling. A pair of Hamamatsu 0.25-W LED modules provides intermediate sensitivity with photolysis efficiency comparable to a 100-W Hg arc lamp. The Hamamatsu LEDs require no additional cooling and are a simple and inexpensive package, providing sensitivity and stability appropriate for long-term, unattended measurements at remote surface sites. A Droplet Measurement Technologies Blue-Light Converter (BLC) represents the most complete off-the-shelf system available for atmospheric measurements of NO 2 . The BLC provides the least sensitivity of the LED-based converters, but is less subject to interference from HONO. Implementing the Nichia LEDs into the NOAA WP-3D aircraft P-CL instrument, in conjunction with improved sample gas handling, improves instrument time response by a factor of eight and permits 1-Hz retrieval of ambient NO and NO 2 using a single detector simply by modulating the LEDs on and off. The performance and stability of the Nichia LEDs are further assessed during the CalNex (California Research at the Nexus of Air Quality and Climate Change) field study in May and June of 2010.