AlN Based 235nm and 255nm UV-C LEDs as Light Sources for Environmental Water Analysis

Collaborative Efforts to Improve Environmental Monitoring
Oral Presentation

Prepared by , J. Davis

Contact Information: toita@cisuvc.com; 518-271-7375


ABSTRACT

Ultraviolet light absorption spectra are often used to identify and quantify chemicals dissolved in water. Several chemical species that are important in environmental discussions have distinctive absorption peaks in the UV-C range (i.e., less than 280nm of wavelengths.) For example, NO3- (nitrate) that is a common cause of eutrophication and toxic algal blooms in lake, river or ocean coast has distinctive absorption peak in the UV-C range. Traditionally, deuterium, xenon or mercury lamps have been used as light sources in ultraviolet spectroscopy. However, systems using those vacuum lamps are fragile and generally expensive. Based on our high quality AlN (aluminum nitride) crystal substrate, we developed pseudomorphic LEDs with several wavelengths in UV-C range. LEDs are lighter, smaller and consume less power than conventional UV-C light sources. We propose to use the UV-C LEDs as light source in easy-to use, cost-effective absorption photometry for continuous water quality monitoring. In this paper, we will demonstrate performance of a UV-C LED-based continuous water monitoring probe and its application to continuous NO3- concentration monitoring in variety of environments including treated waste water. Nitrate concentration values obtained from comparison between absorption at 235nm and 255nm were in good agreement with chemically measured values. The LED based UV photometric sensors in water enable us to collect, analyze chemical concentration data in-situ, in real-time. Application to monitoring of several other chemical species in water, such as polyaromatic hydrocarbons (PAH) are also discussed.