Water Soluble Fluorescent Graphene Nanodots

Water soluble fluorescent graphene nanodots (GND) have been successfully prepared through a bottom up approach from brominated pyrene via alkaline hydrothermal condensation. FT-IR, UV-Vis, Raman, XRD, AFM, and TEM studies have shown the formation of −OH group rich nanodots having graphene features with an approximate size of 90 nm. Steady state and 3D fluorescence studies have shown efficient fluorescence emission with maximum at 540 nm upon excitation at 450 nm in pH≤7. Plasmid deoxyribonucleic acid (plasmid DNA) and bovine serum albumin (BSA) have shown their interaction with GND, which was studied via fluorescence quenching of GND and BSA, respectively. Selective quenching of the Förster resonance energy transfer (FRET) of BSA-GND conjugate via ascorbic acid (AA) has been used to construct a calibration curve for AA estimation with a linear range and limit of detection of 34.00–112.00 μmole/L and 31.343 μmole/L, respectively. GND has also shown concentration-dependent turn offchemosensing towards heavy metals like Pb²⁺, Cu²⁺, Hg²⁺ and Zn²⁺. In-vitromulticolor fluorescence imaging has been observed in GND-labelled HeLa (human cervical cancer) and NIH-3T3 (mouse embryonic fibroblast) cell lines with better uptake by HeLa cells. GND also has shown very high viability for both the cell lines up to the tested concentration of 300 μg/mL.