Highly fluorescent g-C3N4 nanobelts derived from bulk g-C3N4 for NO2 gas sensing

Highlights: • A strategy to prepare fluorescent g-C₃N₄ nanobelts with tuneable PL was proposed. • g-C₃N₄ nanobelts with emission wavelength higher than its bulk were prepared. • A gas sensor for reversibly sensing of NO₂ gas at room temperature was designed. The fluorescent emission wavelengths of nanostructures derived from bulk graphitic carbon nitride were commonly lower than those of their bulk due to the quantum confinement effect, which are disadvantageous for bioimaging and sensing applications. Herein, a new strategy to engineer graphitic carbon nitride nanomaterials with tunable fluorescent wavelength and intensity was proposed via thermal treatment of bulk graphitic carbon nitride at high temperature and then hydrolysis in alkali solution. Highly fluorescent g-C₃N₄ nanobelts with emission peak at 494 nm, 19 nm higher than that of bulk graphitic carbon nitride and 23.6% quantum yield were successfully obtained by controlling the heating temperature at 750 °C for 2 h and the hydrolysis in 4 mol L⁻¹ NaOH solution for 8 h. Finally, a home-made portable gas sensor for reversibly sensing of toxic NO₂ gas at room temperature was designed by utilizing graphitic carbon nitride nanobelts as the fluorescent nanoprobe, which can overcome the disadvantages of high operation temperature or the interference of humidity resulting from the common chemiresistive sensors.