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 355nm wavelength of Nd: YAG pulsed laser for 60min. HR-TEM studies showed the presence of both larger (about 60nm) and smaller size (about 10nm) CNPs and average particle size was found to be about 25nm. Crystalline structure was also observed in CNPs, whose interplanar lattice spacing was 0.27nm, indicating the contracted lattice spacing from usual graphitic structure. XRD and Raman analysis showed that the crystalline CNPs correspond tonon-perfect graphitic carbon structure. Optical spectroscopic studies revealed the down-conversion of photoluminescence emission at 485nm under the excitation wavelength of 400nm. The average fluorescence lifetime of carbon nanoparticles was estimated as 1.1ns 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 24h. 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.