Abstract
The chromo-fluorogenic detection of carbon monoxide in air has been achieved using a simple, inexpensive system based on ruthenium(II). This probe shows exceptional sensitivity and selectivity in its sensing behavior in the solid state. A color response visible to the naked eye is observed at 5 ppb of CO, and a remarkably clear color change occurs from orange to yellow at the onset of toxic CO concentrations (100 ppm) in air. Even greater sensitivity (1 ppb) can be achieved through a substantial increase in turn-on emission fluorescence in the presence of carbon monoxide, both in air and in solution. No response is observed with other gases including water vapor. Immobilization of the probe on a cellulose strip allows the system to be applied in its current form in a simple optoelectronic device to give a numerical reading and/or alarm.
Highlights
The development of electronic household detectors for harmful gases dates from the 1980s and 90s
Optical detection of carbon monoxide dates back to the late twentieth century when the presence of CO was revealed by a chemically infused paper that turned brown when exposed to the gas; only in the last few years has the number of chromogenic probes for CO detection based on new sensing concepts increased
Regardless of several advantages offered by chromogenic sensors, only a few probes for carbon monoxide detection using emission changes have been reported so far involving the use of iron10 and palladium11 complexes
Summary
The development of electronic household detectors for harmful gases dates from the 1980s and 90s. In some of these reported systems the modulations caused by the presence of carbon monoxide reveal particular shortcomings typically involving poor color or emission changes, sensing in solution but not in air and high detection limits which hamper the use of the probes as viable sensing systems. All these changes are consistent with a displacement of the BTD ligand by CO and the formation of complex [Ru(CH=CHPyr-1)Cl(CO)2(PPh3)2] (2) (Scheme 1).
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