However, pristine graphene is a zero-bandgap material, where the energy bandgap can be manipulated for several applications, including photolytic activities and solar cells.
Certain optical and electronic properties of graphene, and modified graphene-based material, such as chemical stability, optical saturation, high charge carrier mobility, transparency, and intrinsic zero bandgap nature with tunable bandgap ability, enable graphene-based materials to perform efficiently for the development of forthcoming optoelectronic devices. In recent studies, certain extrinsic characteristics of chemically modified graphene have been investigated in several applications such as sensors, energy harvesting, supercapacitors, field-effect transistors, and solar cells. The bandgap tunability of GO in the visible range could allow it to be used in mid-IR photodetectors and ultrafast lasers as a saturable absorber, potentially outperforming graphene. The unique and stable physicochemical properties of graphene with a low-cost synthesis at a large scale make it the most promising material for future optical and electronic applications. The heteroatom atom doping of carbon-based nanomaterial, i.e., graphene, graphene oxide, and carbon nanotube, among others, has gained great attention in material science and research. The observed tunable optoelectrical characteristics of N-rGO make it a suitable material for developing future optoelectronic devices at the nanoscale. Besides, an enhanced n-type electrical conductivity in N-rGO was observed in Hall effect measurement. The UV/vis spectroscopic analysis confirmed the narrowness of the optical bandgap from 3.4 to 3.1, 2.5, and 2.2 eV in N-rGO samples, where N-rGO samples were synthesized with a nitrogen doping concentration of 2.80, 4.53, and 5.51 at.%. The properties of the synthesized N-rGO were determined using XPS, FTIR and Raman spectroscopy, UV/vis, as well as FESEM techniques. In this work, nitrogen-doped reduced graphene oxide (N-rGO) with tunable optical bandgap and enhanced electrical conductivity was synthesized via a microwave-assisted hydrothermal method. Graphene as a material for optoelectronic design applications has been significantly restricted owing to zero bandgap and non-compatible handling procedures compared with regular microelectronic ones.