Pollutant ions, optical sensing

Mesoporous Cage-Like Silica Monoliths for Optical Sensing of Pollutant Ions... 

The feasibility of an optical fiber system was demonstrated for the differential absorption analysis of the car pollutant nitrogen dioxide. It absorbs in the visible and can be "sensed" using an Ar-ion laser27. The yellow metabolite bilirubin has been monitored in blood via fiber optic spectrometry in serum28. The tip of a fiber optic cable was inserted into a injection needle so to reach the blood sample, and absorbance (and later fluorescence) was acquired of a sample contained in the cavity at the tip of the fiber or needle. 

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