Nitrogen-doped carbon oxide quantum dots for flexible humidity sensor: Experimental and SCC-DFTB study

A flexible resistive-type humidity sensor based on N-type nitrogen-doped carbon oxide quantum dots (NCQDs) is presented. The NCQDs were synthesized by using simple hydrothermal method with reactions via citric acid and urea. The UV-vis, FE-TEM and XPS analysis confirm a successful doping of N atoms and existence of oxygencontaining functional groups into carbon quantum dots with the homogeneous spherical structure. The NCQDs humidity sensor exhibits high humidity response, good repeatability, and high stability as well as linear response to humidity in the range of 20-90% RH. The humidity sensing mechanism has been in-depth investigated by self-consistent charge density functional tight-binding (SCC-DFTB) including dispersion interaction. The SCC-DFTB reveals an important role of N doping with physisorption via direct charge transfer sensing mechanism.

Automated summary

A flexible resistive-type humidity sensor based on N-type nitrogen-doped carbon oxide quantum dots (NCQDs) exhibits high humidity response, good repeatability, and high stability. The study reveals the important role of N doping in the humidity sensing mechanism.