Synthesis of water-soluble fluorescent carbon nanoparticles (CNPs) from nanosecond pulsed laser ablation in ethanol

Abstract

Traditionally, CNPs directly obtained from nanosecond pulsed laser ablation (ns-PLA) in an organic solvent like ethanol, isopropyl alcohol and acetone, possess toxic characteristics with excellent fluorescent properties. However, water-soluble CNPs are found to be non-toxic with weak fluorescent properties. In this study, a post-ablation method was utilized to achieve water-soluble fluorescent CNPs. Initially, the colloidal Eth-CNPs solution was obtained from ns-PLA of charcoal powder in the ethanol, which was subsequently dried at room temperature and then dispersed in water to achieve the final water-soluble CNPs (W-CNPs). The High-resolution Transmission Electron Microscopy (HRTEM) image analysis of W-CNPs shows quasi-spherical size particle distribution with an average particle size found to be around 21 nm. XPS studies of charcoal powder and W-CNPs confirm the creation of fluorescent emissive defects state on the surface of W-CNPs under laser ablation in ethanol. Photoluminescence studies of W-CNPs demonstrated the wavelength-dependent PL emission, with peak PL emission in the blue region of the visible spectrum. In vitro studies indicated the non-toxic nature of the W-CNPs at low and high concentration (1, 5 and 10% v/v) in human cardiomyocytes. Herein, the W-CNPs obtained from post-ns-PLA was found to exhibit both blue and green fluorescence in the cardiomyocytes and hence, it can be exploited as a fluoro probe in bioimaging applications.