N-doped TiO2/rGO: synthesis, structure, optical characteristics, and humidity sensing applications.

In the current study, the effect of rGO ratio on the N- TiO2 has been synthesized through sol gel
method. The prepared N-TiO2/rGO composites were examined for humidity sensing applications.
The relationship between optical properties and the humidity sensing properties was studied. The
structure, morphology, and bonding interaction have been examined using XRD, FT-IR, PL and
HRTEM respectively. The average particle size as estimated from XRD and HRTEM was found
to be about 9nm. The optical properties have been studied using UV/ Vis. Spectroscopy. Further
optical parameters including refractive index and optical band gap energy have been estimated.
The humidity sensing behavior of the resultant composites were evaluated in a wide range of
humidity (7%-97% RH) at different testing frequencies. The optical band gap was found to be
decreased as the amount of rGO increase. Among all prepared samples, both the optical parameters
and humidity sensing experiments confirmed that the 0.5% rGO sample is the best candidate for
the humidity sensing applications. The best optimum testing frequency was demonstrated to be 50
Hz. The sensor demonstrates a fast response and recovery times of 13 s and 33 s with low hysteresis
and large sensitivity. The humidity sensing mechanism was studied using complex impedance
spectroscopy at different RH levels under testing frequency range from 50 Hz to 5 MHz and testing
voltage of 1VAC. The produced structure demonstrated a promising material for humidity
measuring devices.