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Graphene quantum dots (GQDs) containing N atoms were successfully synthesized using a facile, inexpensive and environmentally friendly hydrothermal reaction of urea and citric acid and the effect of the GQDs’ C–N configurations on their photoluminescence (PL) properties were investigated. High-resolution transmission electron microscopy (HR-TEM) images confirmed that the dots were spherical, with an average diameter of 2.17 nm. X-ray photoelectron spectroscopy (XPS) analysis indicated that the C–N configurations of the GQDs substantially affected their PL intensity. Increased PL intensity was obtained in areas with greater percentages of pyridinic-N and lower percentages of pyrrolic-N. This enhanced PL was attributed to delocalized π electrons from pyridinic-N contributing to the C system of the GQDs. On the basis of energy electron loss spectroscopy (EELS) and UV-Vis spectroscopy analyses, we …