An insight into electronic and optical properties of multilayer graphene quantum dots synthesized by hydrothermal approach

The carbonaceous small sized graphene quantum dots (GQDs) synthesized by hydrothermal route manifest the existence of band gap by cutting the graphene sheets into quantum dots (QDs). Consequently, the tuning of band gap from 0-3.2 eV occurs by decreasing the size of graphene owe to the quantum confinement effect. The small sized uniform particles corroborated from TEM analysis exhibits the excitation independent emission spectra in the UV excitation range. In addition, GQDs unveil the excitation dependent behavior by red shift in emission wavelength alongwith the decrease in intensity of photoluminescence upon excitation in the visible region. It happens due to the presence of varying size particles. The work function of GQDs was analysed by UPS spectroscopy and was found to be 4.48 eV. These electronic energy levels relies on the size and band gap of GQDs. The distinct optical and electronic properties leads to GQDs as an absorber, emissive and transport material in optoelectronic devices.