Heteroatoms co-doped graphene quantum dots for multi-photon imaging

Quantum dots (QD) are excellent nanosystems in light emitting applications, sensing, and medicine. Carbon based quantum dots (CQD) are cost effective and their fluorescence properties range from ultra-violet (UV) to near infrared (NIR). The disk-shaped nitrogen and sulfur co-doped graphene quantum dots (NS-GQD) and nitrogen doped carbon quantum dots (N-CQD) are developed using suitable chemicals. The non-covalent functionalization of NS-GQD with an organic dye leads to the development of nanohybrid of NS-GQD and rhodamine B (RB). The spectral overlap between the absorption spectrum of the RB and the PL spectrum of the NS-GQD indicates the feasibility of resonance energy transfer process. These developed nanohybrid suggests the capability as a dual wavelength probe in the field of sensing and optical nano-thermometry. Moreover, cell viability tests indicate that the NS-GQD fluorescent nanoprobe enhances the cell proliferation to a greater extent as compared to N-CQD. The 2-photon excitation (2PE) imaging analysis indicates that the NS-GQD is an active fluorescent probe while N-CQD is inactive.