Comment on "Synthesis, functionalization and bioimaging applications of highly fluorescent carbon nanoparticles" by Sourov Chandra et al., Nanoscale, 2011, 3, 1533.

A recent paper in this journal reported the synthesis of highly fluorescent crystalline carbon nanoparticles by microwave irradiation of sucrose with phosphoric acid. The emission wavelengths reported in this investigation are always twice the corresponding excitation wavelengths and the full widths at half maximum are extremely small (15-20 nm). We suggest that their results and discussions are questionable. Detailed analysis indicates that the fluorescence may not be real fluorescence, but the second order diffraction of excitation light.