Fluorescent carbon nanoparticles from laser-ablated Bougainvillea alba flower extract for bioimaging applications

The present study employed laser ablation to obtain fluorescent carbon nanoparticles (CNPs) using inexpensive and easily available Bougainvillea alba flower juice extract as the source. The laser ablation of flower juice extract was carried out using 355 nm wavelength of Nd: YAG pulsed laser for 60 min. HR-TEM studies showed the presence of both larger (about 60 nm) and smaller size (about 10 nm) CNPs and average particle size was found to be about 25 nm. Crystalline structure was also observed in CNPs, whose interplanar lattice spacing was 0.27 nm, indicating the contracted lattice spacing from usual graphitic structure. XRD and Raman analysis showed that the crystalline CNPs correspond to non-perfect graphitic carbon structure. Optical spectroscopic studies revealed the down-conversion of photoluminescence emission at 485 nm under the excitation wavelength of 400 nm. The average fluorescence lifetime of carbon nanoparticles was estimated as 1.1 ns from time-resolved spectroscopy. The CNPs were found to be non-toxic to human vein endothelial cells and internalized into the cells with high intensity up to 24 h. Two distinct PL emissions were observed with the large particles emitting at the longer wavelength localized predominantly in the cytosol and smaller particles emitting at the shorter wavelength concentrated on the nuclear membrane. The results suggest that the CNPs are biocompatible and have the potential for bioimaging applications.