Luminescent carbon quantum dots (CQDs) prepared from aqueous beetroot extract were developed as unique fluorescent nanomaterials for in vivo live animal imaging applications. Blue (B) and green (G) emitting environmentally benign CQDs (particle size of 5 nm and 8 nm, respectively) exhibited bright fluorescence in aqueous medium and were found to be biocompatible, photostable and non-toxic in animal models. The in vivo imaging and toxicity evaluation of both CQDs were performed for the first time in the Caenorhabditis elegans (C. elegans) model, which revealed consistent fluorescence in the gut tissues of the worms without exerting any sign of toxic effects on the nematodes. The in vivo bio-distribution of G-CQDs given by tail vein injection in live BALB/c mice showed optical signals in the lower abdominal regions, mainly in the intestine, and cleared from the body through faeces. The tremendous potential shown by these eco-friendly CQDs in the C. elegans and mice models advocates new hopes for greener CQD nanomaterials as diagnostic tools in the biomedical field.

A novel series of light emitting and thermally stable non-aggregating benzannulated quinolines and acridines were designed and prepared from ketene-S,S-acetal under mild conditions through C–C bond formation. Photophysical and electrochemical analyses of these bipolar N-heterocyclic compounds revealed intense solvatochromism due to the intramolecular charge-transfer character, exemplary for 9b, which covered PL ranging from blue (480 nm) to green (501 nm) to yellow (562 nm) to orange (589 nm) using aprotic solvents of varying polarity. Organic light emitting devices with a device configuration of ITO/PEDOT:PSS (40 nm)/NPB (20 nm)/(N-heterocyclic compound) (50 nm)/BCP (7 nm)/LiF (0.7 nm)/Al (200 nm) were successfully prepared. The optoelectronic properties of these compounds were altered by controlled tuning of donor–acceptor and aromatic π-conjugation in benzo[f]quinolines and benzo[a]acridines, which exhibited a low turn-on voltage with electroluminescence ranging from blue (6c: λ_EL 455 nm) to green (8a: λ_EL 496 nm) to yellow (11: λ_EL 545 nm) to red (9b: λ_EL 630 nm).

The discovery of an iron(III)-selective ratiometric fluorescent probe to detect and visualize endogenous labile iron pools in living organisms at the molecular level has been long awaited. Herein we report the first dual colorimetric and ratiometric fluorescent probe naphtho[2,1-b][1,10]phenanthroline NAP-3 for selective and ‘direct’ visualization of labile iron(III) pools in a multicellular organism, Caenorhabditis elegans.

We discovered a new type of nontoxic, highly fluorogenic and biocompatible probe AFN for selective staining of intracellular Lipid Droplets (LDs) in both fixed and live human cervical cancer cells (HeLa) and 3T3-L1 pre-adipocytes without any background artifacts.