In Situ Turn-On Room Temperature Phosphorescence and Vapor Ultra-sensitivity at Lifetime Mode

Area of Science:

• Organic electronics
• Chemical sensing
• Luminescent materials

Background:

• Organic room temperature phosphorescence (RTP) systems for vapor sensing are challenging due to the need for both vapor permeability and phosphorescence ability.
• Existing methods predominantly use "turn-off" mode, which requires an oxygen-free environment and can be prone to interference.
• "Turn-on" mode offers superior anti-interference properties due to a lower initial signal, but is more difficult to achieve.

Purpose of the Study:

• To develop an in situ "turn-on" phosphorescence sensor for methamphetamine (MPEA) vapor detection.
• To overcome the limitations of existing RTP vapor sensing technologies.
• To enable highly sensitive and selective detection of MPEA vapor.

Main Methods:

• Formation of aromatic phenolic aldehyde-secondary amine ion pairs on a tri-formyl phenol (TFP) film.
• Utilizing the TFP film's conversion to a stable RTP state upon exposure to MPEA vapor.
• Characterization using nuclear magnetic resonance (NMR), mass spectrometry, and theoretical calculations.

Main Results:

• The TFP film exhibited a "turn-on" RTP response to MPEA vapor.
• Red-shifted absorption and emission spectra were observed.
• Enhanced emission intensity and a phosphorescence lifetime of 49.7 μs were recorded.
• Multi-modal sensing (chromaticity, fluorescence, phosphorescence) was achieved.
• The lifetime mode achieved a detection limit of 0.4 ppt, significantly lower than the intensity mode (20.3 ppb).

Conclusions:

• The developed system successfully realized "turn-on" RTP sensing for MPEA vapor.
• The ion-pair formation mechanism provides air-stable RTP performance.
• The sensor offers superior sensitivity and anti-interference capabilities for vapor phase detection.