Red Phosphorus: An Elementary Semiconductor for Room-Temperature NO₂ Gas Sensing.

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Sensing

Background:

• Black and blue phosphorus allotropes are explored for electronic devices and gas sensing.
• Amorphous red phosphorus (a-RP), a cost-effective allotrope, remains largely uninvestigated for electronic applications and gas sensing.

Purpose of the Study:

• To investigate the gas sensing properties of amorphous red phosphorus (a-RP).
• To explore the potential of a-RP as a room-temperature gas sensor, particularly for nitrogen dioxide (NO2).

Main Methods:

• Experimental characterizations of a-RP.
• Theoretical calculations, including density functional theory (DFT).
• Fabrication and testing of a-RP based gas sensors.

Main Results:

• a-RP demonstrates amphoteric gas sensing, detecting both reducing and oxidizing gases with resistance decreasing as gas concentration increases.
• a-RP sensors show high sensitivity, selectivity, and fast response/recovery for room-temperature NO2 detection.
• A unique sensing mechanism involving P-P bond expansion upon NO2 chemisorption was identified.

Conclusions:

• Amorphous red phosphorus is a promising material for developing highly sensitive and selective gas sensors.
• The identified P-P bond expansion mechanism provides insights into a-RP's gas sensing behavior.
• a-RP offers a cost-effective alternative for electronic gas sensing applications, especially for NO2.