Monolayer-based selective optical recognition and quantification of FeCl3 via electron transfer

Area of Science:

• Electrochemistry
• Analytical Chemistry
• Materials Science

Background:

• Accurate detection of iron(III) chloride (FeCl3) is crucial in various chemical processes.
• Existing methods for FeCl3 quantification can be complex and time-consuming.
• Development of selective and sensitive sensors is essential for real-time monitoring.

Purpose of the Study:

• To demonstrate a reagentless optical sensor for FeCl3 detection and quantification.
• To develop a sensor based on a redox-active Os(II)-chromophore monolayer.
• To validate the sensor's performance characteristics, including selectivity, reversibility, and stability.

Main Methods:

• Fabrication of an Os(II)-chromophore-based monolayer on glass.
• Optical monitoring of Fe3+-induced monolayer oxidation using UV/vis spectrophotometry.
• Reversibility testing by resetting the sensor with water.
• Selectivity assessment in the presence of various metal salts.
• Visual detection using 2,2'-bipyridyl.

Main Results:

• Successful reagentless optical recognition and quantification of FeCl3 in acetonitrile (CH3CN) down to parts-per-million (ppm) levels.
• The sensor demonstrated full reversibility and could be reset within one minute.
• High selectivity towards FeCl3 was observed, unaffected by common alkali, alkaline earth, and transition metal salts.
• Naked-eye detection of Fe3+ was possible with the addition of 2,2'-bipyridyl.
• Analytical validation confirmed sensitivity, reproducibility, stability, and a detection range of 0.5-162 ppm in CH3CN and 100-1000 ppm in water.

Conclusions:

• The Os(II)-chromophore monolayer serves as an effective reagentless optical sensor for FeCl3.
• The sensor exhibits excellent selectivity, reversibility, and stability for reliable quantification.
• This technology offers a promising approach for real-time monitoring of FeCl3 in various applications.