Fluorescent/ratiometric colorimetric dual-node sensor based on Fe/N co-doped carbon dots for nitrite detection

Area of Science:

• Analytical Chemistry
• Materials Science
• Food Science

Background:

• Nitrite (NO2-) is widely used in food preservation and coloration.
• Excessive nitrite intake poses significant health risks.
• Accurate and efficient nitrite detection methods are crucial for food safety.

Purpose of the Study:

• To develop a dual-mode sensor for sensitive and accurate nitrite detection.
• To synthesize blue fluorescent iron and nitrogen co-doped carbon dots (Fe/N-CDs) with peroxidase-like activity.
• To validate the sensor's performance in real food samples.

Main Methods:

• Synthesis of Fe/N-CDs via a one-step hydrothermal method using ferric chloride, EDTA, and DETA.
• Development of a dual-mode (fluorescent and colorimetric) sensing platform leveraging Fe/N-CDs' catalytic activity.
• Utilizing oxidation and diazotization reactions for nitrite detection, with smartphone-assisted RGB analysis for colorimetric quantification.

Main Results:

• Fe/N-CDs exhibited excellent peroxidase-like activity.
• The sensor demonstrated linear detection ranges of 2.5-75 μM (fluorescence) and 2.5-100 μM (colorimetric).
• Detection limits were as low as 0.68 μM (fluorescence) and 1.19 μM (colorimetric).
• Successful application in detecting nitrite in pickled vegetables and cured pork samples.
• Color change from blue to yellow correlated with increasing nitrite concentration, quantifiable via RGB analysis.

Conclusions:

• The developed Fe/N-CDs-based dual-mode sensor provides a sensitive and efficient method for nitrite detection.
• The platform is feasible for practical applications in food analysis.
• Smartphone-assisted colorimetric analysis offers a convenient quantitative approach for nitrite monitoring.